Термостатный способ производства кисломолочных продуктов: Как делают йогурт на предприятии: два способа

4. Технология производства кисломолочных продуктов

При производстве кисломолочных напитков применяются два способа: термостатный и резервуарный. При термостатном способе производства кисломолочных напитков сквашивание молока и созревание напитков производится в бутылках в термостатных и хладостатных камерах.

При резервуарном способе производства заквашивание, сквашивание молока и созревание напитков происходит в одной емкости.

Кисломолочные напитки, выработанные резервуарным способом, после созревания и перемешивания разливают в стеклянную или бумажную тару, поэтому сгусток у них по сравнению с термостатным способом нарушенный – имеющий однородную сметанообразную консистенцию.

Чтобы получить продукт с плотной однородной консистенцией необходимо поддерживать температуру сквашивания, оптимальную для данного продукта. Продолжительность сквашивания молока зависит от вида получаемой кисломолочной продукции и колеблется в пределах от 4 до 16 часов. Окончание сквашивания определяют по характеру сгустка и по кислотности, которая должна быть немного ниже кислотности готового продукта.

Охлаждение и созревание осуществляют при температуре не выше 6 в течение нескольких часов (6–8). За это время происходит набухание белков молока, что ведет к образованию более плотного сгустка, ослабевает или полностью прекращается молочнокислый процесс.

При производстве продуктов смешанного брожения во время охлаждения и созревания приостанавливается развитие молочнокислых микроорганизмов, но развиваются дрожжи, в результате чего в этих кисломолочных напитках накапливаются спирт, углекислота.

Готовую продукцию контролируют на наличие бактерий группы кишечной палочки и по микроскопическому препарату от одной-двух партий не реже одного раза в 5 дней.

Особого внимания требует оборудование, непосредственно соприкасающееся с продуктом в процессе, производства. Перед началом технологического процесса следует провести тщательную санитарную обработку такого оборудования. При ухудшении санитарных показателей готового продукта осуществляют тщательный анализ и дополнительный контроль хода технологического процесса для установления причин вторичного обсеменения продукта, проверяют качество закваски, а также санитарно-гигиеническое состояние цеха.

Кисломолочные продукты выпускают также с плодово-ягодными наполнителями и витаминизированные. Контроль готовой продукции проводят по методам, принятым для кисломолочных напитков с плодово-ягодными наполнителями. При производстве кисломолочных напитков с наполнителями нужно быть особенно внимательными во избежание выработки продукции негарантированного качества [5].

Резервуарный способ производства кисломолочных продуктов

Описание общих операций технологического процесса.

Приёмка молока осуществляется согласно ГОСТ Р 52054–2003. Молоко охлаждается до 4 °С с целью предотвращения развития микрофлоры и порчи молока. Резервирование молока не должно продолжаться более 12 часов. Перед очисткой молоко подогревают до 40…45 °С. Нормализация молока по массовой доли жира осуществляется в потоке или смешением. Нормализованное молоко гомогенизируют с целью исключения отстоя жира, получения продукта с однородной консистенцией. Пастеризация проводится при температуре 90…95 °С с выдержкой от 2 до 8 мин. Пастеризованную нормализованную смесь охлаждают до температуры заквашивания. Заквашивание осуществляется специально подобранными заквасками из термофильных или мезофильных молочнокислых бактерий, бифидобактерий. В зависимости от вида продукта и закваски продолжительность сквашивания составляет 4…12 часов, температура сквашивания – 20…43 °С.

Для кефира, в состав которого входят дрожжи, необходимо дополнительное созревание в течение 12–14 часов, в течение которых происходит формирование специфического вкуса продукта. Готовый продукт охлаждают и направляют на розлив [6].

Производство кисломолочных диетических продуктов – кефира, ацидофилина, ацидофильного молока, ацидофильно-дрожжевого молока, напитков «Снежок», «Южный, йогурт и других – увеличилось в десятки раз.

Наиболее популярен у населения кефир, поэтому он занял доминирующее положение в производстве кисломолочных напитков, выпускаемых в Казахстане. Родиной кефира является Северный Кавказ, где его долгое время изготовляли в бурдюках или в деревянных кадках. Технология его изготовления в аулах простая–кефирные грибки заливают парным молоком, охлажденным до 18–20» С, в процессе сквашивания и созревания продукт периодически взбалтывают. При созревании кефира вследствие усиленной аэрации активно развиваются дрожжи, что влияет на вкус и консистенцию продукта: консистенция становится жидкой, сметанообразной, вкус – специфическим, кислым, приобретает остроту.

В России кефир вырабатывался еще в 1866–1867 гг. кустарным способом на грибках, привезенных с Кавказа в сухом виде. Кефирные грибки оживляли в кипяченом охлажденном обезжиренном молоке и использовали для приготовления заквасок. Молоко для кефира подогревали до 16–23° С и заквашивали закваской, непосредственно слитой с грибков. После получения сгустка бутыли взбалтывали для ускорения процесса образования напитка и выдерживали в помещении при температуре 14 – 16° С в течение суток, а иногда и более продолжительное время.

По той же технологии вырабатывали кефир на городских молочных заводах, при этом применяли пастеризацию молока и розлив напитка в бутыли с герметической укупоркой. В результате длительности технологического процесса, трудоемкости многих операций выпуск кефира был ограничен и спрос у населения на него не удовлетворялся поэтому технологию кефира изменили: его стали выпускать, ускоренным способом, получившим впоследствии наименование термостатного.

Молоко, идущее на выработку кефира, стали сквашивать при высоких температурах в термостатах без встряхивания и соответствующего накопления продуктов дрожжевого брожения. В результате изменения технологии вместо мягкого но консистенции полужидкого напитка с характерным освежающим вкусом заводы стали выпускать продукт с плотным сгустком, по вкусу похожим на простоквашу.

В результате ряда научно-исследовательских работ ВНИМИ разработал резервуарный способ производства кефира, являющийся в настоящее время общепризнанным прогрессивным способом, который широко внедряется в молочную промышленность.

Основными этапами технологического процесса являются следующие:

– тепловая обработка и гомогенизация молока, идущего на выработку кефира;

– сквашивание молока, охлаждение и созревание кефира в резервуарах;

– розлив напитка повышенной вязкости в бумажные пакеты и стеклянные бутылки.

При производстве кефира резервуарным способом молоко пастеризуют при 85С и выдерживают. С увеличением температуры пастеризации продолжительность выдержки уменьшается. Обязательной операцией является гомогенизация молока: она препятствует отстою сыворотки в готовом продукте и придает ему однородную сметанообразную консистенцию. Молоко гомогенизируют под давлением не ниже 125 ат, оптимальное давление гомогенизации 175 ат. Сквашивают молоко при температуре 20–25°С в двустенных танках-резервуарах, специально сконструированных для производства кисломолочных напитков. Закваску вносят в потоке или любым другим способом при непрерывном перемешивании молока в резервуаре. Конец сквашивания определяют по достижении кислотности сгустка 85–90° Т. В межстенное пространство танка для охлаждения сгустка до температуры созревания подают воду температурой 1–3 °С, а затем включают мешалку для размешивания его и оставляют в покое для созревания.

В процессе созревания кефир приобретает специфический вкус, отличный от вкуса, присущего простокваше.

Способ охлаждения зависит от схемы технологического процесса, принятой на данном предприятии.

При производстве кефира большое значение имеет перемешивание и охлаждение его при подаче на розлив. Мешалка должна не взбалтывать, и не резать его на пласты и кубики, а плавко и равномерно перемешивать всю массу кефира. Частичное перемешивание или резка сгустка приводит к отделению сыворотки (синерезису) так же как взбалтывание кефира мешалкой приводит к пенообразованию, что влечет за собой образование отстоя сыворотки. Для сохранения качества кефира нельзя пользоваться насосами, вспенивающими кефир и разбивающими продукт. Охлажденный кефир расфасовывают в мелкую тару (бутылки и бумажные пакеты). Перед выпуском в торговую сеть готовый продукт охлаждают в камере до 6–8° С.

Ниже приводится основная технологическая схема производства кисломолочных напитков резервуарным способом (в двух вариантах – с охлаждением в резервуарах и охлаждением в потоке на пластинчатом теплообменнике), разработанная ВНПЛШ и предусматривающая механизацию и автоматизацию основных и вспомогательных операций.

По этой схеме молоко подается насосами по трубам, а расфасованный готовый продукт–внутризаводским транспортом (цепными и ленточными транспортерами и т.д.).

В теплообменниках молоко и напитки подвергают термической обработке (нагреванию и охлаждению) до заданной температуры. От механических примесей молоко очищается в сепараторах-очистителях в потоке и для получения соответствующей дисперсности жира и улучшения вязкости напитка обрабатывается в гомогенизаторах.

Напиток в резервуаре перемешивается приводной мешалкой. Расфасовывают напиток в бутылки или бумажные пакеты на разливочных машинах и автоматах. Трудоемкие процессы мойки оборудования выполняются с помощью устройств оросительного и реактивного действия.

Контроль технологического процесса и управление им автоматизированы.

Особенность такой схемы заключается в том, что кефир после сквашивания и достижения заданной кислотности перемешивается и охлаждается в одном и том же резервуаре, после чего поступает на розлив и подается в камеру для доохлаждения.

Процесс охлаждения сквашенного кисломолочного напитка в двустенном резервуаре длится 3,5 – б ч. При производстве кисломолочных продуктов на термофильных культурах повышается кислотность очень быстро. Для приостановки бурного нарастания кислотности после достижения 85–90° Т продукт с помощью тихоходного насоса подают из резервуара на пластинчатый охладитель, где продолжительность процесса охлаждения снижается до 1 ч.

Другой вариант основной схемы технологического процесса производства кисломолочных напитков резервуарным способом с охлаждением в потоке приведен на рис. 2.

Особенностью этого технологического режима является то, что молоко сквашивается в двустенном резервуаре или в обычном молокохранильном танке 13, оборудованном приводными трубчатыми «мешалками, а по достижении кислотности 85–90° Т напиток с помощью тихоходного насоса 14 из танка 13 поступает на охладитель 15. Напиток охлаждается в тонком слое очень быстро. Далее он поступает в промежуточный танк 16, а затем самотеком направляется на машины типа «Юдек», ОР-6У, И2-ОРК-6, И2-ОРК-3 для расфасовки в стеклянные бутылки или на автомат типа АП-1Н, АП-2Н для расфасовки в бумажные пакеты. Расфасованный напиток транспортером подается в камеру хранения для дальнейшего охлаждения.

Преимущества производства кисломолочных напитков резервуарным способом следующие:

– почти полностью исключается ручной труд в результате механизации и автоматизации технологического процесса;

– повышается квалификация рабочих, обслуживающих линию; снижаются затраты труда и повышается его производительность:

– снижается стоимость 1 т продукта на 4 р. 46 к.; сокращаются производственные площади, так как готовый продукт созревает и охлаждается в тех же танках, в которых приготовляется, а не в термостатных помещениях; снижается расход тепла и холода.

Практика эксплуатации оборудования для резервуарного способа получения напитков показала, что линии, скомплектованные из машин и аппаратов, специально сконструированных для резервуарного способа производства кисломолочных напитков, в эксплуатации рентабельны и обеспечивают выпуск продуктов высокого качества.

Если в линиях производства кисломолочных напитков резервуарным способом используется оборудование для производства питьевого молока, то оно работает с перебоями.

В настоящее время серийно выпускаются все основные машины и аппараты для комплектации типовой линии (теплообменники типа ОПЛ-5 и ОПЛ-10, гомогенизаторы A1-ОГМ, автоматы АП-1Н, АП-2Н, двустенные танки-резервуары и линии розлива И2-ОЛ2–6 и И2-ОЛ2–3. Линия производства кисломолочных напитков, скомплектованная из двустенных танков, является универсальной, так как на ней можно вырабатывать напитки по двум вариантам технологической схемы после внесения в нее насоса и пластинчатого пастеризатора [7].

Термостатный способ производства кефира

Технологический процесс производства кефира термостатным способом состоит из следующих операций:

• приемка и подготовка сырья;

• нормализация молока;

• очистка и гомогенизация молока;

• пастеризация и охлаждение молока;

• заквашивание молока;

• розлив, упаковка и маркировка;

• сквашивание молока;

• охлаждение и созревание молочного сгустка.

Приемку и подготовку сырья, нормализацию молока, очистку и гомогенизацию, пастеризацию и охлаждение молока производят также, как и при выработке кефира резервуарным способом. Допускается выработка кефира термостатным способом из негомогенизированного нормализованного молока.

Заквашивают молоко в резервуарах после охлаждения его до температуры 18-21 ⁰С летом и 22–25 ⁰С зимой. Вносят 1–3% грибковой (сливов с кефирных грибков) или 3–5% производственной кефирной закваски. Заквашенное молоко тщательно перемешивают в течение 15 мин, а затем направляют на розлив.

Розлив одного резервуара заквашенного молока должен быть закончен не позже, чем через 2 ч во избежание образования хлопьев свернувшегося белка. Заквашенное молоко разливают в потребительскую тару при непрерывном перемешивании для предотвращения оседания закваски.

Тару с заквашенным молоком немедленно направляют в термостатную камеру для сквашивания. Сквашивание проводят от 8 до 12 ч. Температуру в термостатной камере устанавливают 18–21 ⁰С летом и 22–25 ⁰С зимой. Окончание сквашивания определяют по образованию сгустка кислотностью от 75 до 80⁰Т (рН от 4,85 до 4,75). По окончании сквашивания тару с молочным сгустком направляют в холодильную камеру и охлаждают до температуры (4±2) ⁰С.

Сгусток оставляют в покое для созревания в течение 8–13 ч. По окончании процесса созревания технологический процесс считается законченным и продукт готов к реализации.

Кумыс

Кумыс: кисломолочный продукт смешанного молочнокислого и спиртового брожения, изготовляемый сквашиванием кобыльего молока заквасочными микроорганизмами болгарской и ацидофильной молочнокислых палочек и дрожжей, при этом содержание молочнокислых микроорганизмов в готовом продукте в конце срока годности составляет не менее 10⁷ КОЕ в 1 г продукта, а дрожжей не менее 10⁵ КОЕ в 1 г продукта.

Этот кисломолочный напиток издавна известен у кочевых народов России своими лечебными свойствами.

Основные показатели, характеризующие качество продукта, даны в табл. 2.5.

Из всех кисломолочных напитков кумыс обладает наиболее ценными диетическими и ярко выраженными терапевтическими свойствами. Содержащиеся в нем молочная кислота, спирт и диоксид углерода, воздействуя на желудок и поджелудочную железу, стимулируют выделение пищеварительных соков, усиливают перистальтику желудка и кишечника. Белки кумыса находящиеся в частично пептонизированном и мелкодисперсном состоянии, легко всасываются и усваиваются. В кумысе микрофлора вырабатывает антибиотик низин, синтезирует витамины группы В и в несколько раз больше, чем в коровьем молоке, витамин С.

Физико-химические показатели кумыса

Продукт	Показатели и нормы
	Кислотность °Т, не более	Массовая доля спирта, %, не более
Кумыс из коровьего молока 1,5% жирности
слабый	95	0,6
средний	110	1,1
крепкий	130	1,6
Кумыс натуральный 1% жирности
слабый	70-80	1,0
средний	81-100	1,5
крепкий	101-120	3,0

Кумыс оздоравливает пищеварительный тракт, поднимает тонус организма, нормализует скорость оседания эритроцитов, увеличивает содержание в крови гемоглобина, подавляет развитие туберкулезной палочки, способствует излечиванию заболеваний верхних дыхательных путей, хронических бронхитов и пневмоний. Кобылье молоко, по сравнению с коровьим, содержит значительно больше молочного сахара, меньше жира и белков, при этом казеин и альбумин в нем находятся в равных количествах. Поэтому при сквашивании белок кобыльего молока не образует сгусток, а выпадает в виде рыхлых, мелких, почти неощутимых хлопьев, которые не образуют осадка, консистенция продукта остается жидкой.

Для заквашивания молока применяют специальную кумысную закваску, в состав которой входят молочнокислые палочки, в небольшом количестве стрептококки и молочные дрожжи. Так как производство кумыса очень часто носит выраженный сезонный характер (3–5 месяцев в году), обычно материалом для закваски служит кумыс прошлого года. Казахи, киргизы сохраняют ее годами, оставляя с осени промытый и высушенный осадок кумыса, в котором микроорганизмы не теряют своей жизнеспособности до следующего кумысного сезона. Башкиры обычно весной готовят новую закваску, используя для этой цели катык (кислое коровье молоко). Специально приготовленный катык методически в течение нескольких дней разбавляется в количестве 1:1 сырым кобыльим молоком (переквашивается). Параллельно с увеличением доли кобыльего молока происходит перестройка микрофлоры смеси. Готовой закваску считают тогда, когда кумысное брожение хорошо развилось, и катыковая микрофлора заменилась кумысной. Кумысная микрофлора является специфической микрофлорой, выращиваемой на сыром кобыльем молоке при определенных условиях температуры и аэрации. Кислотность такой закваски 150-160 °Т. Для производства кумыса из кобыльего молока используют парное молоко от здоровых кобыл. Оно должно быть чистым, без посторонних привкусов и запахов, кислотностью не выше 7 °Т. В парное молоко вносят закваску в количестве 15–30%, тщательно перемешивают 15 минут и выдерживают 3–5 ч при температуре 25–28 °С для развития молочнокислого брожения. Когда кислотность поднимается до 65–70 °Т, заквашенное молоко вымешивают в течение 1 ч, разливают в тару и плотно укупоривают. Тару с кумысом ставят в холодильную камеру при температуре 6–10 °С для развития спиртового брожения (созревания). В зависимости от продолжительности созревания кумыс подразделяют на слабый, который созревает 1 сутки, средний – 2 и крепкий – 3 сут. Кумыс имеет своеобразный кислый вкус и запах, жидкую консистенцию. Цвет – молочно-белый с голубоватым оттенком. Кислотность слабого кумыса 70–80 °Т, среднего – от 81 до 100 °Т, крепкого –от 101 до 120 °Т; спирта содержится, соответственно, 1,0; 1,5 и 3%.

Там, где кобыльего молока производится мало или оно вообще отсутствует, вполне можно организовать получение кумыса из коровьего молока. Использование коровьего молока для производства кумыса имеет большое преимущество: оно в несколько раз дешевле, чем кобылье, его получают во всех зонах страны в течение всего года. Кумыс вырабатывают из пастеризованного коровьего молока, в которое предварительно добавляется до 5% сахара. Закваска вносится в количестве 10%. В состав закваски входят молочнокислые палочки и молочные дрожжи. Температура сквашивания 26–28 °С. При постоянном перемешивании продукт сквашивается около 5 ч до кислотности 85–90 °Т. Продолжительность созревания при 16–18 °С составляет 1,5–2 ч. Во время созревания через каждые 15–20 минут производят перемешивание. Кислотность готового кумыса из коровьего молока 100–150 °Т. В трехсуточном кумысе накапливается до 1% спирта.

Технология приготовления кумыса из коровьего обезжиренного молока следующая. В свежее коровье обезжиренное молоко добавляют 20% сыворотки и 3% сахара в виде сиропа. Смесь пастеризуют при температуре 92–95 °С, выдерживают 20 минут, охлаждают до 30 °С и заквашивают заранее приготовленной комбинированной закваской. Кумыс из коровьего молока готовят на культуре, выделенной из кумыса, полученного из кобыльего молока. В состав закваски входит смесь дрожжей и болгарской палочки. Заквашенное молоко находится в двустенных емкостях с мешалками до полного сквашивания, при этом его постоянно перемешивают. При получении сгустка продукт охлаждают до 16–18 °С и выдерживают при этой температуре 15–20 ч. Затем продукт разливают в тару, герметически укупоривают и хранят при температуре 4–6 °С. Перед употреблением тару с кумысом необходимо встряхивать. Слабый кумыс должен иметь кислотность 100–120 °Т, средний – от 120 до 140 и крепкий – от 140 до 150 °Т, массовая доля спирта, соответственно 0,1–0,3; 0,2–0,4; 1%.

Модуль 2

Лекция 9

90000 Dairy product | Britannica 90001 90002 Nutrient composition 90003 90004 Although milk is a liquid and most often considered a drink, it contains between 12 and 13 percent total solids and perhaps should be regarded as a food. In contrast, many «solid» foods, such as tomatoes, carrots, and lettuce, contain as little as 6 percent solids. 90005 90004 Many factors influence the composition of milk, including breed, genetic constitution of the individual cow, age of the cow, stage of lactation, interval between milkings, and certain disease conditions.Since the last milk drawn at each milking is richest in fat, the completeness of milking also influences a sample. In general, the type of feed only slightly affects the composition of milk, but feed of poor quality or insufficient quantity causes both a low yield and a low percentage of total solids. Current feeding programs utilize computer technology to achieve the greatest efficiency from each animal. 90005 90004 The composition of milk varies among mammals, primarily to meet growth rates of the individual species.The proteins contained within the mother’s milk are the major components contributing to the growth rate of the young animals. Human milk is relatively low in both proteins and minerals compared with that of cows and goats. 90005 90004 Goat milk has about the same nutrient composition as cow milk, but it differs in several characteristics. Goat milk is completely white in colour because all the beta-carotene (ingested from feed) is converted to vitamin A. The fat globules are smaller and therefore remain suspended, so the cream does not rise and mechanical homogenization is unnecessary.Goat milk curd forms into small, light flakes and is more easily digested, much like the curd formed from human milk. It is often prescribed for persons who are allergic to the proteins in cow milk and for some patients afflicted with stomach ulcers. 90005 90004 Sheep milk is rich in nutrients, having 18 percent total solids (5.8 percent protein and 6.5 percent fat). Reindeer milk has the highest level of nutrients, with 36.7 percent total solids (10.3 percent protein and 22 percent fat). These high-fat, high-protein milks are excellent ingredients for cheese and other manufactured dairy products.90005 90004 The major components of milk are water, fat, protein, carbohydrate (lactose), and minerals (ash). However, there are numerous other highly important micronutrients such as vitamins, essential amino acids, and trace minerals. Indeed, more than 250 chemical compounds have been identified in milk. The table shows the composition of fresh fluid milk and other dairy products. 90005 90016 90017 Nutrient composition of dairy products (per 100 g) 90018 90019 90020 90021 dairy product 90022 90021 energy (kcal) 90022 90021 water (g) 90022 90021 protein (g) 90022 90021 fat (g) 90022 90021 carbohydrate (g) 90022 90021 cholesterol (mg) 90022 90021 vitamin A (IU) 90022 90021 riboflavin (mg) 90022 90021 calcium (mg) 90022 90041 90042 90043 90020 90045 * Fortified with vitamin A.90046 90041 90020 90045 ** Low moisture, part skim. 90046 90041 90020 90045 Source: U.S. Department of Agriculture, Composition of Foods, Agriculture Handbook no. 8-1. 90046 90041 90056 90057 90020 90059 fresh whole milk 90046 90061 61 90046 90061 88 90046 90061 3.29 90046 90061 3.34 90046 90061 4.66 90046 90061 14 90046 90061 126 90046 90061 0.162 90046 90061 119 90046 90041 90020 90061 fresh low-fat milk * 90046 90061 50 90046 90061 89 90046 90061 3.33 90046 90061 1.92 90046 90061 4.80 90046 90061 8 90046 90061 205 90046 90061 0.165 90046 90061 122 90046 90041 90020 90061 fresh skim milk * 90046 90061 35 90046 90061 91 90046 90061 3.41 90046 90061 0.18 90046 90061 4.85 90046 90061 2 90046 90061 204 90046 90061 0.140 90046 90061 123 90046 90041 90020 90059 evaporated milk 90046 90061 134 90046 90061 74 90046 90061 6.81 90046 90061 7.56 90046 90061 10.04 90046 90061 29 90046 90061 243 90046 90061 0.316 90046 90061 261 90046 90041 90020 90059 evaporated skim milk * 90046 90061 78 90046 90061 79 90046 90061 7.55 90046 90061 0.20 90046 90061 11.35 90046 90061 4 90046 90061 392 90046 90061 0.309 90046 90061 290 90046 90041 90020 90059 sweetened condensed milk 90046 90061 321 90046 90061 27 90046 90061 7.91 90046 90061 8.70 90046 90061 54.40 90046 90061 34 90046 90061 328 90046 90061 0.416 90046 90061 284 90046 90041 90020 90059 nonfat dry milk * 90046 90061 358 90046 90061 4 90046 90061 35.10 90046 90061 0.72 90046 90061 52.19 90046 90061 18 90046 90061 2,370 90046 90061 1.744 90046 90061 1,231 90046 90041 90020 90059 butter 90046 90061 717 90046 90061 16 90046 90061 0.85 90046 90061 81.11 90046 90061 0.06 90046 90061 219 90046 90061 3,058 90046 90061 0.034 90046 90061 24 90046 90041 90020 90059 ice cream (vanilla) 90046 90061 201 90046 90061 61 90046 90061 3.50 90046 90061 11.00 90046 90061 23.60 90046 90061 44 90046 90061 409 90046 90061 0.240 90046 90061 128 90046 90041 90020 90059 ice milk (vanilla) 90046 90061 139 90046 90061 68 90046 90061 3.80 90046 90061 4.30 90046 90061 22.70 90046 90061 14 90046 90061 165 90046 90061 0.265 90046 90061 139 90046 90041 90020 90059 sherbet (orange) 90046 90061 138 90046 90061 66 90046 90061 1.10 90046 90061 2.00 90046 90061 30.40 90046 90061 5 90046 90061 76 90046 90061 0.068 90046 90061 54 90046 90041 90020 90059 frozen yogurt, nonfat 90046 90061 128 90046 90061 69 90046 90061 3.94 90046 90061 0.18 90046 90061 28.16 90046 90061 2 90046 90061 7 90046 90061 0.265 90046 90061 134 90046 90041 90020 90059 buttermilk 90046 90061 40 90046 90061 90 90046 90061 3.31 90046 90061 0.88 90046 90061 4.79 90046 90061 4 90046 90061 33 90046 90061 0.154 90046 90061 116 90046 90041 90020 90059 sour cream 90046 90061 214 90046 90061 71 90046 90061 3.16 90046 90061 20.96 90046 90061 4.27 90046 90061 44 90046 90061 790 90046 90061 0.149 90046 90061 116 90046 90041 90020 90059 yogurt, plain, low-fat 90046 90061 63 90046 90061 85 90046 90061 5.25 90046 90061 1.55 90046 90061 7.04 90046 90061 6 90046 90061 66 90046 90061 0.214 90046 90061 183 90046 90041 90020 90059 yogurt, fruit, low-fat 90046 90061 102 90046 90061 74 90046 90061 4.37 90046 90061 1.08 90046 90061 19.05 90046 90061 4 90046 90061 46 90046 90061 0.178 90046 90061 152 90046 90041 90020 90059 blue cheese 90046 90061 353 90046 90061 42 90046 90061 21.40 90046 90061 28.74 90046 90061 2.34 90046 90061 75 90046 90061 721 90046 90061 0.382 90046 90061 528 90046 90041 90020 90059 Brie cheese 90046 90061 334 90046 90061 48 90046 90061 20.75 90046 90061 27.68 90046 90061 0.45 90046 90061 100 90046 90061 667 90046 90061 0.520 90046 90061 184 90046 90041 90020 90059 Cheddar cheese 90046 90061 403 90046 90061 37 90046 90061 24.90 90046 90061 33.14 90046 90061 1.28 90046 90061 105 90046 90061 1,059 90046 90061 0.375 90046 90061 721 90046 90041 90020 90059 cottage cheese 90046 90061 103 90046 90061 79 90046 90061 12.49 90046 90061 4.51 90046 90061 2.68 90046 90061 15 90046 90061 163 90046 90061 0.163 90046 90061 60 90046 90041 90020 90059 cream cheese 90046 90061 349 90046 90061 54 90046 90061 7.55 90046 90061 34.87 90046 90061 2.66 90046 90061 110 90046 90061 1,427 90046 90061 0.197 90046 90061 80 90046 90041 90020 90059 mozzarella cheese ** 90046 90061 280 90046 90061 49 90046 90061 27.47 90046 90061 17.12 90046 90061 3.14 90046 90061 54 90046 90061 628 90046 90061 0.343 90046 90061 731 90046 90041 90020 90059 Parmesan cheese, grated 90046 90061 456 90046 90061 18 90046 90061 41.56 90046 90061 30.02 90046 90061 3.74 90046 90061 79 90046 90061 701 90046 90061 0.386 90046 90061 1,376 90046 90041 90020 90059 Emmentaler (Swiss) cheese 90046 90061 376 90046 90061 37 90046 90061 28.43 90046 90061 27.54 90046 90061 3.38 90046 90061 92 90046 90061 845 90046 90061 0.365 90046 90061 961 90046 90041 90586 90587 .90000 Dairy production and products: Milk composition 90001 90002 Milk provides essential nutrients and is an important source of dietary energy, high-quality proteins and fats. Milk can make a significant contribution to the required nutrient intakes for calcium, magnesium, selenium, riboflavin, vitamin B12 and pantothenic acid. Milk and milk products are nutrient-dense foods and their consumption can add diversity to plant-based diets. Animal milk can play an important role in the diets of children in populations with very low fat intakes and limited access to other animal source foods.90003 90002 The species of dairy animal, its breed, age and diet, along with the stage of lactation, parity (number of parturitions), farming system, physical environment and season influence the colour, flavour and composition of milk and allow the production of a variety of milk products: 90003 90006 90007 90008 Cow milk: 90009 Fat constitutes approximately 3 to 4 percent of the solid content of cow milk, protein about 3.5 percent and lactose 5 percent, but the gross chemical composition of cow milk varies depending on the breed .For example, the fat content is usually higher in 90010 Bos indicus 90011 than 90010 B. taurus 90011 cattle. The fat content of milk from 90010 B. indicus 90011 cattle can be as much as 5.5 percent. 90016 90007 90008 90008 Buffalo milk 90009 90009 has a very high fat content, which is on average twice as high as that of cow milk. The fat-to-protein ratio in buffalo milk is about 2: 1. Compared with cattle milk, buffalo milk also has a higher casein-to-protein ratio. The high calcium content of casein facilitates cheese making.90016 90007 90008 90008 Camel milk 90009 90009 has a similar composition to cow milk but is slightly saltier. Camel milk can be three times as rich in vitamin C as cow milk and represents a vital source of this vitamin for people living in arid and semi-arid areas, who often can not obtain vitamin C from fruits and vegetables. Camel milk is also rich in unsaturated fatty acids and B vitamins. Milk from Bactrian camels has a higher percentage of fat than milk from dromedaries, but levels of proteins and lactose are similar.Generally, camel milk is consumed raw or fermented. 90016 90007 90008 Sheep milk 90009 has higher fat and protein contents than goat and cow milk; only buffalo and yak milk contain more fat. Sheep milk also generally has a higher lactose content than milk from cows, buffaloes and goats. The high protein and overall solid contents of sheep milk make it particularly appropriate for cheese and yoghurt making. Milk from sheep is important in the Mediterranean region, where most of it is processed into cheeses such as pecorino, caciocavallo and feta.90016 90007 90008 Goat milk 90009 has a similar composition to cow milk. In Mediterranean countries and in Latin America, goat milk is generally transformed into cheese; in Africa and South Asia, it is usually consumed raw or acidified. 90016 90007 90008 Yak milk 90009 tastes sweet and has a fragrant, sweetish smell. Yak milk has between 15 and 18 percent solid content, 5.5 to 9 percent fat and 4 to 5.9 percent protein. It therefore has higher solid, fat and protein contents than cow and goat milk, and resembles buffalo milk.Raw milk is used mainly by herders and their families in milky tea. Yak milk can be processed into a variety of milk products including butter, cheese and fermented milk products. 90016 90007 90008 Equine milk: 90009 Horse and donkey milk have very similar compositions. Equine milk, like human milk, is relatively low in proteins (particularly caseins) and ashes and rich in lactose. Compared with that of other dairy species, equine milk contains low levels of fat and protein. Most equine milk is consumed fermented and it is not suitable for cheese making.90016 90045 90006 90007 Water is the principal constituent of milk. The water contents of milk from different dairy species — cattle, buffaloes, yaks, sheep, goats, horses and donkeys — range from 83 percent in yaks to 91 percent in donkeys. 90016 90045.90000 RECOMBINED MILK PRODUCTS | Dairy Processing Handbook 90001 90002 Milk is a perishable commodity, and therefore scarce in many countries with little or no dairy production of their own. In such countries raw milk is replaced partly or fully by milk powder as raw material. 90003 90002 Recombination is an alternative method of supplying a product that closely resembles fresh dairy milk to markets where the genuine article is not available. The manufacture of recombined milk and milk products has been well established in many countries around the world, and a variety of processes and equipment have been developed for this purpose.90005 The principles of the processes are much the same. The initial applications were fluid milk, but this was followed by production of recombined evaporated milk and sweetened condensed milk. Today recombination also includes yoghurt, butter and cheese. 90005 The processes have been developed over the years from simple batch operations to sophisticated systems with high capacities. 90003 90002 The main processes in the basic reconstitution and recombining operations are: 90003 90010 90011 Raw material handling 90012 90011 Weighing and mixing 90012 90011 Filtration, homogenization and heat treatment 90012 90017 90018 Definitions 90019 90002 The following definitions are given as a guide to clarify certain expressions used in the industry.90005 Reconstituted milk is the liquid milk obtained by adding water to skim milk powder (SMP), whole milk powder (WMP) or their mix. 90005 Recombined milk is the liquid milk obtained by adding water to SMP and adding milk fat separately in such a quantity that the desired fat content is achieved. 90005 90024 Reconstituted milk 90025 products are the products resulting from addition of water to the dried or condensed form of product in the amounts necessary to re-establish the specified water / solids ratio.90005 90024 Recombined milk 90025 products are manufactured by mixing milk fat and milk solids-non-fat (MSNF), with water. This combination must be made so as to re-establish the specified fat to MSNF ratio and dry matter (DM) to water ratio. 90005 90024 Recombined modified milk 90025 and 90024 milk 90025 products are products made from dairy-product ingredients with compositions other than normal dairy products, e.g. flavoured products, butter from fractionated fat, or dietary evaporated or condensed milk.90005 90024 Filled milks 90025 and 90024 milk 90025 products are «semi-dairy» products in which the milk fat is replaced by vegetable oils, e.g. liquid milk, evaporated milk, condensed milk or cheese. Alternative terms could be called «imitation» or «substitute» milk products. 90005 90024 Fortified milk 90025 is made from fresh milk, reconstituted milk or recombined milk with the addition of one or more ingredients of dairy products. 90005 90024 Toned milk 90025 is fresh milk mixed with reconstituted or recombined skim milk in order to prepare normal composition milk or modified milk from high-fat milk, by adjusting the MSNF.90005 90024 Anhydrous milk 90025 fat (AMF) is a pure dairy fat product obtained from fresh milk, cream or butter to which no neutralizing substances have been added. 90005 90024 Anhydrous butter oil 90025 is an all-fat product made from cream or butter of unspecified age. 90005 90024 Butter oil 90025 is a product made from cream or butter of unspecified age which may have a lower fat content. 90005 90024 Vegetable oils 90025 are refined, bleached, deodorized oils, preferably coconut, palm and soybean oils.90003 90002 Reconstituted milk is the liquid milk obtained by adding water to skim milk powder or whole milk powder. 90003 90002 Recombined milk is the liquid milk obtained by adding water to skim milk powder and adding milk fat separately in such a quantity that the desired fat content is achieved. 90003 90018 Raw material 90019 90064 Milk powder 90065 90002 Non-fat solids for recombined milk are usually supplied in the form of skim milk powder. This is made by skimming the fat from the whole milk in centrifugal separators and then removing the water from the skim milk by evaporation and drying.The powder can be stored for months, or even years, without being spoiled, and dissolves easily in water to form reconstituted skim milk. 90005 The most commonly used method of classifying skim milk powder (SMP) is to refer to the heat treatment, to which the skim milk has been exposed prior to evaporation and spray drying. 90005 During the heat treatment of milk, the whey proteins are denatured to different degrees, depending on the temperature / time relationship. The degree of denaturation can be classified according to the Whey Protein Nitrogen Index (WPNI), which was discussed in Chapter 17.90005 The different recombined milk products usually require skim milk powder of various types of heat classification, (see Table 18.1). 90005 Milk powder is typically supplied in 25 kg plastic-lined laminated bags. 90005 In smaller plants, the powder is often emptied by hand, direct from the bags into the mixing system, but in the larger plants, the bags are emptied automatically. Even more sophisticated is the use of silo tanks to which the powder from the emptied bags is transferred pneumatically.90005 There are also rational methods for transporting milk powder to recombining plants in bulk bins containing 200 — 1,000 kg. The size of the containers is limited by the handling facilities in the locality receiving the powder. 90003 90002 Table 18.1 90003 90002 Skim milk powders for reconstituted and recombined products 90003 90078 90079 90080 90081 Typical powder qualities 90082 90083 90083 90083 90083 90083 90083 90089 90090 90091 90080 90093 90094 Type and characteristics 90095 90096 90093 90094 Extra low heat Ext ra LH <70 ° C / 15s 90095 90096 90093 90094 Low heat LH 70 ° C / 15s 90095 90096 90093 90094 Medium heat MH 85-90 ° C / 20-30s 90095 90096 90093 90094 Medium high heat MHH 90-124 ° C / 0-30s 90095 90096 90093 90094 High heat HH 110-135 ° C / 30 90095 90096 90093 High heat High stability HHHS ** ~ 135 ° C / 30 s 90096 90089 90080 90093 WPNI * mg / g 90096 90093 - 90096 90093> 6.0 90096 90093 5.9 — 4.5 90096 90093 4.4 — 1.5 90096 90093 <1.4 90096 90093 <1.4 90096 90089 90080 90137 90137 90137 90137 90137 90137 90137 90089 90080 90093 90094 Recombined product 90095 90096 90093 X 90096 90093 X 90096 90137 90137 90137 90137 90089 90080 90093 Hard cheese 90096 90093 X 90096 90093 X 90096 90137 90137 90137 90137 90089 90080 90093 Semi hard cheese 90096 90093 X 90096 90093 X 90096 90137 90137 90137 90137 90089 90080 90093 White / Feta cheese 90096 90093 X 90096 90093 X 90096 90093 X 90096 90137 90137 90137 90089 90080 90093 Fresh cheese 90096 90137 90093 X 90096 90093 X 90096 90137 90137 90137 90089 90080 90093 Pasteurized milk 90096 90137 90093 X 90096 90093 X 90096 90093 X 90096 90137 90137 90089 90080 90093 UHT milk 90096 90137 90093 X 90096 90093 X 90096 90093 X 90096 90137 90137 90089 90080 90093 Sterilized milk 90096 90137 90093 X 90096 90093 X 90096 90093 X 90096 9013 7 90137 90089 90080 90093 Sweetened condensed milk 90096 90137 90093 X 90096 90093 X 90096 90137 90137 90137 90089 90080 90093 Evaporated milk 90096 90137 90093 X 90096 90093 X 90096 90093 X 90096 90093 X 90096 90093 X 90096 90089 90080 90093 Cultured milk 90096 90137 90093 X 90096 90093 X 90096 90093 X 90096 90137 90137 90089 90080 90093 Standard ice cream 90096 90137 90093 X 90096 90093 X 90096 90093 X 90096 90093 X 90096 90137 90089 90080 90137 90137 90137 90137 90137 90137 90137 90089 90080 90093 * IDF 162: 2002 / ISO 11814 90096 90137 90137 90137 90137 90137 90137 90089 90080 90093 ** High heat high stability powder from specially selected milk 90096 90137 90137 90137 90137 90137 90137 90089 90080 90137 90137 90137 90137 90137 90137 90137 90089 90339 90340 90064 Dissolving of milk powder 90065 90002 The dissolving properties of milk powders are very important for the recombined product quality and are affected by the following factors: 90003 90010 90011 Wettability 90012 90011 Ability to sink 90012 90011 Dispersability 90012 90011 Solubility 90012 90017 90002 Analytical methods for these properties are given in: 90003 90010 90011 Standards for Grades of Dry Milk, Including Methods of Analysis, American Dairy Products Institute, Inc., USA 90012 90011 ISO / IDF standard methods 90012 90017 90363 Wettability 90364 90002 The degree of wettability is very much a function of the particle volume, and especially of the capillarity. 90005 Agglomerated powders have improved capillarity, resulting in increased wettability. Increased particle size (130 - 150 μm) also results in improved wettability. Good wettability is less than 30 seconds. 90003 90363 Ability to sink 90364 90002 The ability to sink is a function of specific volume and particle size.Agglomerated powders normally have the best ability to sink. 90003 90363 Dispersability 90364 90002 Good dispersability is obtained when powders added to the water are distributed as single particles, leaving no lumps. The structure of the powder particles, as well as the configuration of the protein molecules, is of importance. A powder with a high content of denatured proteins is very difficult to disperse. A dispersability of at least 90% is normal for milk powders for recombination. 90003 90363 Solubility 90364 90002 This property describes how well the powders dissolve and measures the amount of nondissolving protein.How good the solubility is depends very much on the technology used for production of the powder. 90005 A good solubility index should be as low as 0.25 ml undissolved sediment in 50 ml recombined milk. 90003 Factors affecting the dissolving of milk powder are: 90005 90010 90011 Wettability 90012 90011 Ability to sink 90012 90011 Dispersability 90012 90011 Solubility 90012 90017 90064 Fats and oils 90065 90002 Unsalted butter can be used in the manufacture of recombined milk products, but it must be kept under refrigerated storage.90005 The most common source of milk fat for recombination is anhydrous milk fat (AMF), which does not require such storage. It is typically packed in 90005 19.5 kg cans or 196 kg drums. Provided that care is taken in the manufacture of the product, and that air is excluded by packing the product under inert gas (nitrogen), AMF will keep for 6 - 12 months even at elevated ambient temperatures of 30 - 40 ° C. 90005 Milk fat packed in cans can be melted by immersion in hot water at 80 ° C for 2 - 3 hours.Drums of AMF, however, require longer melting times. The normal method is to store the drums in a hot room at 45 - 50 ° C for 24 - 28 hours before use, or to use a steam chest or tunnel which can melt the contents of the drums in about 2 hours. Once melted, the AMF should be transferred to a jacketed holding tank with facilities for maintaining the temperature. 90005 Similar handling systems can also be employed when non-liquid vegetable oils are used in production of recombined "filled" milk products.90003 90064 Water 90065 90002 Water is a raw materials in all types of reconstituted and recombined milk products. It must be of good drinking quality, free from harmful microorganisms and of acceptably low hardness, expressed as calcium carbonate (CaCO 90403 3 90404) and should be below 100 mg / l, corresponding to about 5.5 ° dH. As only "distilled" water is removed in the production of milk powder, the water used for reconstitution or recombination must also be pure; an excessive mineral content will jeopardize the salt balance and heat stability of the reconstituted or recombined product, which in turn will cause problems in pasteurization, not to mention sterilization or UHT treatment.90005 Too much copper or iron in the water may cause off-flavours, due to oxidation of fat. 90003 90002 The maximum levels recommended are therefore: 90003 90010 90011 Cu (copper), mg / l 0.05 90012 90011 Fe (iron), mg / l 0.1 90012 90017 90002 See also Chapter 6.11, Table 6.11.1 regarding specifications for water. 90003 90064 Additives 90065 90002 Dry additives such as sugar, stabilizers and emulsifiers can be handled in the same way as the milk powder, i.e. they are dumped from the bags either directly into the mixing vessel or into the mixing system.90003 90018 Recombination of milk products 90019 90064 Temperature and hydration time 90065 90002 The solubility of milk powder increases when the water temperature increases from 10 to 50 ° C. There is no increase between 50 and 100 ° C. Low-heat powder is easier to dissolve than high-heat powder. It is important that the proteins obtain their normal state of hydration, which takes less than 20 minutes at 40 - 50 ° C. 90005 As a rule fresh, high-quality powder requires the shortest hydration time.Insufficient hydration time may lead to a "chalky" defect in the final product. Recombined milk for cheese manufacture should be given two hours 'hydration time. 90005 It is possible to reconstitute at 10 ° C and then store the milk at this temperature overnight to obtain maximum hydration. However, more powder particles remain undissolved at a mixing temperature of 10 - 20 ° C compared to 35 - 45 ° C, even if the mix is ​​kept for 24 hours. In milk with 8% dry solids, the difference is very small. The proportion of undissolved powder in milk that is heated to at least 40 ° C after reconstitution is very small, even in a mix with 26% dry solids.90005 The air content of reconstituted milk increases at lower mixing temperatures. 90005 The fat must be added at a temperature above its melting point. To assure this, AMF must be added at above 40 ° C. The recombined milk should not be kept at this high mixing temperature for more than two hours because of risk for bacterial growth. 90003 90002 The air content of reconstituted milk increases at lower mixing temperatures. 90003 90064 Fat addition and emulsification 90065 90002 Incorporation of fat into recombined products has always been a relatively 90005 difficult operation.The fat has to be properly dispersed and emulsified, and this places certain requirements on the processing equipment and process parameters. 90005 Traditionally, the melted fat is metered into the line during continuous operation, followed by thorough mixing in a static or mechanically operated mixer before entering a homogenizer. 90005 In modern systems using high-shear mixing devices, fat can be dosed directly into the mixing vessel of the unit. The dispersion of fat is sufficient to create a stable emulsion, which allows eliminating homogenization at this stage of the process.Later on, the recombined products will be finally homogenized during pasteurization or UHT processing. 90005 In small scale batch production, fat is sometimes added to the milk in a mixing tank. To ensure that the composition of the product is uniform when it is pumped to downstream processing, the milk has to be thoroughly agitated, often with a high-shear agitator. Even when a homogenizer is integrated into the system, it is important that the fat in the feed is uniformly distributed. 90005 An emulsifier is sometimes added to facilitate and improve the emulsification of milk fat.90005 Recombined cream can be made from skim milk powder or buttermilk powder and anhydrous milk fat to a fat content of about 40%. The stability is improved by addition of emulsifiers and stabilizers. 90003 90064 Air content 90065 90002 Skim milk powder normally contains a total of about 40% air by volume, consisting of occluded and interstitial air. The mixing equipment may also cause air addition if not properly operated and maintained. 90005 Tests indicate that the air content in reconstituted skim milk, dissolved at 50 ° C and with 14 to 18% dry solids, is the same as in normal skim milk.At a mixing temperature of 30 ° C, the air content is 50 - 60% higher even after a holding time of one hour. With 41% dry solids, the air content of the mix was 10 times higher than in normal skim milk. 90003 90002 Too much air in the recombined milk has the following disadvantages: 90003 90010 90011 Foaming 90012 90011 Burning-on in the heat exchanger 90012 90011 Cavitation in the homogenizer 90012 90011 Whey formation in cultured-milk products 90012 90011 Increased risk of oxidation of fat 90012 90017 90002 As recombination is accompanied by foaming, the volume of the mixing tank (s) should be about 20% larger than the volume of the batch, to avoid foam forcing its way out of the manhole.90005 Some mixing equipment make it possible to recombine products under vacuum. By constantly extracting air from the mixing vessel, a certain vacuum is maintained, which reduces foaming to a minimum. 90003 90064 Powder handling 90065 90002 Proportioning of skim milk powder is based on the simple rule that the weight of the powder is one tenth of the weight of milk produced. For small plants, manual emptying of a calculated number of sacks of a given weight into the mixing tank is the easiest and most practical solution, but production can be mechanized for higher capacities.90005 Milk powder handling creates a lot of dust. Large-scale sack-emptying therefore requires special equipment, including a dust collecting unit, as seen in Figure 18.1. 90005 Powder can also be supplied in containers. In this case, suitable equipment comprises a variable-speed screw feeder, which takes powder from the bottom of the container and discharges it into the mixer. The container can be lifted into position by a tilting rack, (Figure 18.2), or by a hoist. 90005 In highly mechanized plants, the powder is supplied in bulk.It is stored in bulk silos and transferred pneumatically to a day bin, from which it is batched into the process via a weighing hopper and a screw feeder. The system in Figure 18.3 also includes a unit for central dust collection. 90005 When a vacuum mixing system is used, the powders are sucked into the mixing vessel from specially designed powder silo tanks. It is also possible to prepare mixtures of different dry ingredients in these silos before dissolving takes place. 90003 Fig.18.1 90002 Equipment for handling powder in sacks. 90003 90475 90011 Dust collecting unit 90012 90011 Sifter 90012 90011 Sack elevator 90012 90482 Fig. 18.2 90002 Tilting rack for powder container. 90003 90018 Design of recombination plants 90019 90002 Recombination plants are built for capacities of up to 20,000 l / h. In larger plants, parallel lines are installed to meet higher capacity requirements. 90005 The sequence in a large plant is essentially the same as in a small one, except that it requires more tanks for storage and melting of fat, mixing, and buffer storage of the finished product.The degree of mechanization may also differ as described above. 90005 In large plants, it is necessary to use weighing tanks for fat dosage, in order to achieve the necessary accuracy. In a smaller plant, the weighing tank can often be replaced by a proportioning pump. 90003 90002 Fig. 18.3 90002 Equipment for bulk powder handling in large plants. 90003 90475 90011 Silo for powder 90012 90011 Blower 90012 90011 Day bin 90012 90011 Weighing hopper 90012 90011 Hopper 90012 90011 Screw feeder 90012 90011 Dust filter 90012 90482 90003 90064 Deaeration 90065 90002 In small plants, where mixing of material in a processing tank is just enough, the product will be naturally and satisfactorily deaerated if a reconstitution temperature of approx.40 ° C has been maintained and, when all powder has been dissolved, the resultant solution is allowed to stand for 20 minutes with the agitator switched off. 90005 The same procedure should also be applied in large-scale production. To maintain uninterrupted production, however, it is advisable to deaerate the product by vacuum treatment in connection with heat treatment. 90003 90064 Heat treatment 90065 90002 The design of the plant is influenced not only by its capacity, but also by the method of heat treatment of the recombined milk.Three alternative methods are used: 90003 90002 • Pasteurization at a temperature of at least 72 ° C for 15 seconds 90005 followed immediately by cooling to 4 ° C. 90003 90002 • UHT treatment by direct or indirect heating to 132 - 149 ° C 90005 for a few seconds, followed by cooling to approximately 90005 20 ° C prior to aseptic packing. 90003 90064 Small-scale production 90065 90002 In very small-scale production, 1,000 - 2,000 l, batch processing is most common. Mixing and processing are carried out in a jacketed mixing tank with a two-speed shearing agitator and with heating and cooling facilities.The plant is shown in Figure 18.4. However, such low production capacities are more and more unusual. 90005 After a suitable volume of water has been measured into the tank and heated to 43 - 49 ° C, powder is added steadily and agitation applied until all the powder has dissolved. The resulting solution should be allowed to stand for 20 minutes with the agitator switched off. At the end of this time, the agitator is restarted and the temperature is raised to 54 - 65 ° C, before milk fat is added.This has previously been liquefied by being held in a warm room at 38 - 45 ° C. If processing is to be continued in the tank, the agitator is switched to high speed for several minutes to disperse the fat. The agitator is then switched to the stirring position, and the process concludes with pasteurization and homogenization followed by cooling to packing temperature. 90003 90002 Fig.18.4 90002 Recombination plant for batch processing. 90003 90475 90011 Mixing tank with heating / cooling jacket 90012 90011 High-shear two-speed agitator 90012 90011 Thermometer 90012 90011 Emptying pump 90012 90011 Flow meter 90012 90482 90003 90064 Large-scale production 90065 90002 Figure 18.5 shows a large recombination plant for continuous operation, where the fat is dosed into the vessel of the mixer. 90005 Water of food quality is metered into one of the mixing tanks (4). On the way, it is heated in a plate heat exchanger, as the skim milk powder dissolves more easily in warm water than in cold. 90005 The circulation pump is started when the tank is half full and water flows through a bypass line from the mixing tank to a high-shear mixer (3). 90005 In the high-shear mixing unit shown in Figure 18.6, the dry ingredients and fat are added to a mixing vessel filled with water at a rate determined by the size of the selected module. Anhydrous milk fat is added from the fat storage tank (1). 90005 The heart of the mixing system is the mixing head (Figure 18.6), which is located at the bottom of the mixing vessel. It consists of a rotor and perforated stator, and is designed for three functions; mixing, pumping and dispersing. The ingredients and the liquid are sucked down into the mixing unit by a pump wheel and pressed out through the holes in the perforated ring by impeller wings underneath the pump wheel.When passing the perforated stator, high shear forces will effectively dissolve and disperse the added ingredients. As the outlet of the mixer is positioned after the mixing unit, all added ingredients have to pass through the mixing unit at least once. 90005 The agitator in the mixing tank (4) is started at the same time as the circulation pump. Water continues to flow into the tank while mixing is in progress until the specified quantity has been supplied. 90005 When all the powder has been added, the agitator and the circulation loop are stopped and the contents of the tank are given a certain resting interval for hydration of the proteins.This will take about 20 minutes at a temperature of 35 - 45 ºC. At the end of this period, the agitator is restarted. 90005 When all the ingredients have been added to the first batch, the process is repeated in the next tank. 90005 The skim milk / fat mixture is drawn from the full mixing tank by the pump, which forwards the mixture through duplex filters (6) where any foreign objects such as pieces of string or sacking are trapped. After being pre-heated in the heat exchanger (7), the product is pumped to the homogenizer (9), where the dispersion of fat globules is completed.90005 During the powder-mixing operation, the product may pick up large volumes of air, which can cause burning-on in the pasteurizer as well as homogenization problems. A vacuum deaerator vessel (8) can be installed in the line before the homogenizer to eliminate this. The product is pre-heated to 3 ° C above homogenization temperature before being flashed in the deaerator, where the vacuum is adjusted so that the outgoing product has the correct homogenization temperature, typically 65 ° C. 90005 The homogenized milk is pasteurized and chilled in a plate heat exchanger (7) before being pumped to storage tanks (10) and further to packaging or to UHT treatment.90005 When the fat can not be added in the mixing step, the fat has to be added through an in-line injector just before homogenization. All steps are the same as in Figure 18.5, except that the liquid fat is continuously metered into the flow by a positive displacement proportioning pump. A static mixer completes the blending downstream the injector and before entering the homogenizer. 90003 90002 Fig.18.5 90002 Recombination plant with fat supply to mixing vessel. 90003 90475 90011 Tank for fat 90012 90011 Insulated pipe for fat 90012 90011 Mixer with high-shear mixing unit 90012 90011 Mixing tanks 90012 90011 Water heater 90012 90011 Filters 90012 90011 Plate heat exchanger 90012 90011 Vacuum deaerator 90012 90011 Homogenizer 90012 90011 Storage tanks 90012 90482 90003 90002 Fig.18.6 90002 High-shear mixer with mixing unit positioned underneath a waterfilled vessel. 90003 90003 90064 Vacuum mixing 90065 90002 In some mixing equipment, mixing under vacuum is possible. In Figure 18.7 a recombination plant with a vacuum mixer is shown. Since vacuum is applied in the mixing vessel, very little air will be incorporated in the product during the mixing process, and foaming will also be minimized. When using vacuum during mixing, the ingredients are sucked into a vessel filled with water (2) at a point below the liquid surface.The wetting of the powders is thus improved and the risk of floating powder lumps on the surface is eliminated. Another benefit of vacuum mixing is that it facilitates automatic powder addition, as the powders are sucked directly from silo tanks (5) into the mixing vessel (2). This also makes it possible to organize the handling of the dry ingredients in a separate room, and to have the mixer and mixing plant in the processing hall. 90003 90002 Fig. 18.7 90002 Recombination plant with vacuum mixing.90003 90475 90011 Vacuum mixer (within dotted line) 90012 90011 Vessel filled with water 90012 90011 Mixing unit 90012 90011 Circulation pump 90012 90011 Silo tanks for powder 90012 90011 Circulation tanks 90012 90482 90003 90064 Milk handling 90065 90002 It is necessary to consider the handling of the recombined milk in 90005 conjunction with the planning of the plant. This ensures that the product reaches the consumer in good condition. 90003 90064 Storage 90065 90002 Recombined milk normally flows directly from the production line to packing.A buffer tank may be needed to compensate for temporary stoppages in the production or packing lines. In the case of sterilized milk, this tank must be of aseptic design (Figure 18.8), to avoid the risk of reinfection. 90005 Once sterile milk has been packed, it can be stored in any conditions provided that the packages are intact. Pasteurized milk must be kept in cold storage rooms. UHT-treated and sterilized milk are to be preferred in markets where the refrigeration chain is absent or incomplete.90003 90002 Fig. 18.8 90002 An aseptic tank eliminates the risk of reinfection. 90003 90003 90064 Packing 90065 90002 The milk should be packed as soon as possible after production. UHT-treated milk must flow in a closed aseptic system to the aseptic carton filling machine. 90005 Pasteurized milk can be packed in paper or plastic packs or glass bottles. If bottles are used, they should be of dark glass, which prevents the flavour of the milk from being spoiled by exposure to light.90005 The package must always be airtight to protect the milk from oxidation. It should also be strong enough for stacking in crates or boxes. 90003 90064 Distribution 90065 90002 Since UHT treated and sterilized milk can be stored in ambient temperature the whole distribution chain is more simple than for pasteurized milk, which need to be refrigerated all the time. UHT-treated milk can, for example, be transported on an ordinary lorry for long distances and exposed for sale in a shop with no refrigeration facilities where people come to buy perhaps once a week.Pasteurized milk, on the other hand, requires a refrigeration chain of insulated distribution vans, chilled counters in the shops, daily shopping and, preferably, home refrigerators. 90003.90000 COLLECTION AND RECEPTION OF MILK 90001 90002 The milk is brought from the farm (or collecting centre) to the dairy for processing. All kinds of receptacles have been used, and are still in use, throughout the world, from 2 - 3 litre calabashes and pottery to modern bulk-cooling farm tanks for thousands of litres of milk. 90003 90002 Formerly, when dairies were small, collection was confined to nearby farms. The microorganisms in the milk could be kept under control with a minimum of chilling, as the distances were short and the milk was collected daily.Today the trend is towards progressively larger dairy units. There is a demand for a higher production and increased quality of the finished product. Milk must be brought from farther away and this means that daily collection is generally out of the question. Nowadays, collection usually takes place every other day, but the interval can sometimes be three days and even four. 90003 90006 Keeping the milk cool 90007 90002 The milk should be chilled to + 4 ° C immediately after milking and be kept at this temperature all the way to the dairy.90009 If the cold chain is broken somewhere along the way, e.g. during transportation, the microorganisms in the milk will start to multiply. This 90009 will result in the development of various metabolic products and enzymes. Subsequent chilling will arrest this development, but the damage will already 90009 be done. The bacteria count is higher and the milk contains substances that will affect the quality of the end product. 90003 90013 DESIGN OF FARM DAIRY PREMISES 90014 90002 The first steps in preserving the quality of milk must be taken at the farm.Milking conditions must be as hygienic as possible; the milking system designed to avoid aeration, the cooling equipment correctly dimensioned. To meet the hygienic requirements, dairy farms have special rooms for refrigerated storage. Bulk cooling tanks are also becoming more common. These tanks (Figure 5.1) with a capacity of 300 to 30 000 litres, are fitted with an agitator and cooling equipment to meet certain stipulations - for example 90009 that all the milk in the tank should be chilled to +4 ° C within two hours after milking.Larger farms, producing large quantities of milk, often install separate plate coolers for chilling the milk before it enters the tank (Figure 5.2). This saves mixing warm milk from the cow with the already chilled contents of the tank. The milk room should also contain equipment for cleaning and disinfecting the utensils, pipe system and bulk cooling tank. 90003 Fig. 5.1 90002 Bulk cooling tank with agitator and chilling unit. 90003 Fig. 5.2 90002 The milk flow in an instant cooling system from cow to cooling tank.90003 90013 DELIVERY TO THE DAIRY 90014 90002 The raw milk arrives at the dairy in insulated road tankers. The milk must be kept well chilled, free from air and treated as gently as possible. For example, tanks should be well filled to prevent the milk from sloshing around in the container. 90003 90026 BULK COLLECTION 90027 90002 When milk is collected by the tanker, it must be possible to drive all the way to the farm milk room. The loading hose from the tanker is connected to the outlet valve on the farm cooling tank (Fig.5.3). The tanker is usually fitted with a flow meter and pump so that the volume is automatically recorded. Otherwise, the volume is measured by recording the level difference which, for the size of the tank in question, represents a certain volume. In many cases, the tanker is equipped with an air-eliminator. Pumping is stopped as soon as the cooling tank has been emptied. This prevents air from being mixed into the milk. The tank of the bulk collection vehicle is divided into a number of compartments to prevent the milk from sloshing around during transportation.Each compartment is filled in turn, and when the tanker has completed its scheduled round, it delivers the milk to the dairy. 90003 90002 Fig. 5.3 90002 Bulk collection at the farm. 90003 90003 90013 Testing milk for quality 90014 90002 Milk from sick animals and milk which contains antibiotics or sediment must not be accepted by the dairy (Fig. 5.4). Even traces of antibiotics in milk can render it unsuitable for the manufacture of products which are acidified by the addition of bacteria cultures, e.g. yoghurt and cheese. Normally, only a general assessment of the milk quality is made at the farm. The composition and hygienic quality is usually determined in a number of tests on arrival at the dairy. The outcome of some of these tests has a direct bearing on the compensation to the farmer. The most common tests carried out on milk supplies are detailed below. 90003 90002 Fig. 5.4 90002 Milk from animals treated with antibiotics must be kept separate from other milk. 90003 90003 90026 Taste and smell 90027 90002 In the case of bulk collection, the driver takes a sample of the milk at the farm for testing at the dairy.Milk that deviates in taste and smell from normal milk receives a lower quality rating. This affects the payment to the farmer. Milk with significant deviations in taste and smell should be rejected by the dairy. 90003 90002 Fig. 5.5 90002 Analysing milk samples. 90003 90003 90026 Cleaning checks 90027 90002 The inside surfaces of farm tanks are carefully inspected. Any milk residue is evidence of inefficient cleaning and will result in a deduction in accordance with a quality payment scheme.90003 90026 Hygiene or Resazurin Tests 90027 90002 The bacteria content of the milk is a measure of its hygienic quality. The Resazurin Tests are used frequently. Resazurin is a blue dye which becomes colourless when it is chemically reduced by the removal of oxygen. When it is added to the milk sample, the metabolic activity of the bacteria present has the effect of changing the colour of the dye at a rate which bears a direct relationship to the number of bacteria in the sample. 90009 Two hygiene tests use this principle.One is a quick-screening test, which may form the basis for the rejection of a bad churn supply. If the sample starts to change shade immediately, the consignment is considered unfit for human consumption. 90009 The other test is a routine test and involves storage of the sample in a refrigerator overnight, before a Resazurin solution is added. The sample is then incubated in a water bath and held at 37,5 ° C for two hours. 90003 90026 Somatic cell count 90027 90002 A large number (more than 500,000 per ml of milk) of somatic cells in the milk indicates that the cows are suffering from udder diseases.The cell content is determined with specially designed particle counters (e.g. a Coulter counter). 90003 The common tests carried out on milk supplies are: 90009 90065 90066 Taste and smell 90067 90066 Cleaning 90067 90066 Hygiene 90067 90066 Somatic cell count 90067 90066 Bacteria count 90067 90066 Protein content 90067 90066 Fat content 90067 90066 Freezing point 90067 90082 90026 Bacteria count 90027 90002 A simplified form of bacteria count can also be used to assess the bacteria content.In this, the Leesment method, the bacteria are cultivated at 30 ° C for 72 hours in a 0.001 ml milk sample with a nutritive substrate. The bacteria count is determined with a special screen. 90003 90026 Protein content 90027 90002 Many dairies pay farmers according to the protein content of the milk. This is analysed by means of instruments operating with infrared rays. Up to 300 analyses per hour can be performed. 90003 90026 Fat content 90027 90002 Various methods can be used to determine the butterfat content.The Gerber test is the most widely used method for whole milk. 90003 90026 Freezing point 90027 90002 Many dairies check the freezing point of the milk to determine whether or not it has been diluted with water. Milk of normal composition has a freezing point of -0.54 to -0.59 ° C. The freezing point will rise if water is added to the milk. Special instruments are used for this check. 90003 90006 Milk reception 90007 90002 Dairies have special reception departments to handle the milk brought in from the farms.The first thing done at reception is to determine the quantity of the milk. The quantity is recorded and entered into the weighing system that the dairy uses to weigh the intake and compare it with the output. 90009 The quantity of the intake can be measured by volume or by weight. 90003 90013 Tanker reception 90014 90002 Tankers arriving at the dairy drive straight into a reception hall, often large enough to accommodate several vehicles. 90009 The milk is measured either by volume or by weight.90003 90002 Fig. 5.6 90002 Measuring milk intake in a tanker reception hall. 90003 90003 90026 Measuring by volume 90027 90002 This method uses a flowmeter. It registers the air in the milk as well as the milk, so the results are not always reliable. It is important to prevent air from entering with the milk. Measuring can be improved by fitting an air-eliminator before the flowmeter (Figure 5.7). 90009 The tanker outlet valve is connected to an air-eliminator and from this the milk - free from air - is pumped through the flowmeter, which continuously indicates the total flow.When all the milk has been delivered, a card is placed in the meter for recording the total volume. 90009 The pump is started by the control equipment, which senses when the milk in the air-eliminator has reached the preset level for preventing air from being sucked into the line. The pump is stopped as soon as the milk level drops below a certain level. 90009 After measuring, the milk is pumped to a storage (silo) tank. 90003 90002 Fig. 5.7 90002 Measuring by volume. 90003 90123 90066 Air-eliminator 90067 90066 Pump 90067 90066 Filter 90067 90066 Metering device 90067 90132 90003 90026 Measuring by weight 90027 90002 Bulk-collected milk can be measured in in two ways: 90003 90123 90066 Weighing the tanker before and after unloading and then subtracting one value from the other (Figure 5.8). 90067 90066 Using special weighing tanks with load cells in the feet (Figure 5.9). In the first alternative, the tanker is driven onto a weighbridge at the dairy. 90067 90132 Fig. 5.8 90002 Tanker on a weighbridge. 90003 Fig. 5.9 90002 Milk reception via a weighing tank. 90003 90002 Operation may be manual or automatic. If manual, the operator records the weight against the driver's code number. Where operation is automatic, the necessary data are recorded when the driver places a card in a card scanner.Before being weighed the tanker normally passes a vehicle washing station. This is of special importance when the weather is bad. 90009 When the gross weight of the tanker has been recorded, the milk is delivered into the dairy. This may take place in line with a de-aerator but not a flowmeter. When empty, the tanker is weighed again and the tare weight is deducted from the previously recorded gross weight. 90003 90002 When the weighing-tank method is used, the milk is pumped from the tanker into a special tank with load cells built into the feet.The cells supply an electric signal that is always proportional to the weight of the tank. The strength of the signal increases with the weight of the tank as the milk enters the tank. The weight of the contents in the tank can be recorded when all the milk has been delivered. After this the milk is pumped to a silo tank. 90003 90013 Tanker cleaning 90014 90002 Tankers are cleaned every day, as a rule at the end of a collection round. If the tanker makes several rounds a day, cleaning should take place after each round.Cleaning can be carried out by connecting the tanker to a cleaning system while in the reception area, or by driving it to a special cleaning station. 90009 Many dairies also clean the outside of their tankers every day so that they always look clean when they are on the road. In more and more countries new rules are introduced about disinfection of tankers to avoid spreading animal diseases. 90003 90013 Chilling the incoming milk 90014 90002 Normally, a temperature increase to slightly above + 4 ° C is unavoidable during transportation.Therefore, the milk is usually cooled to below + 4 ° C in a plate heat exchanger, before being stored in a silo tank to await processing. 90003 90013 Raw milk storage 90014 90002 The untreated raw milk - whole milk - is stored in large vertical tanks - silo tanks - which have capacities from about 100,000 litres up to 500,000 litres. Smaller silo tanks are often located indoors while the larger tanks are placed outdoors to reduce building costs. Outdoor silo tanks are of double-wall construction, with insulation between the walls.The inner tank is of stainless steel, polished on the inside, and the outer wall is usually of welded sheet metal. 90003 90026 Agitation in silo tanks 90027 90002 These large tanks must have some form of agitation arrangement to prevent cream separation by gravity. The agitation must be very smooth. Extreme agitation causes aeration of the milk and fat globule disintegration. This exposes the fat to attack from the lipase enzymes in the milk. Gentle agitation is therefore a basic rule in the treatment of milk.The tank in Figure 5.10 has a propeller agitator, often used with good results in silo tanks. In very high tanks it may be necessary to fit two agitators at different levels to obtain the required effect. 90009 Outdoor silo tanks have a panel for ancillary equipment (Fig. 5.11). The panels on the tanks all face inwards towards a covered central control station. 90003 Fig. 5.10 90002 Silo tank with propeller agitator. 90003 Fig. 5.11 90002 Silo tank with alcove for manhole, indicators, etc.90003 90123 90066 Agitator 90067 90066 Manhole 90067 90066 Temperature indicator 90067 90066 Low-level electrode 90067 90066 Pneumatic level indicator 90067 90066 High-level electrode 90067 90132 90026 Tank temperature indication 90027 90002 The temperature in the tank is indicated on the tank control panel. Usually, an ordinary thermometer is used, but it is becoming more common to use an electric transmitter, which transmits signals to a central monitoring station. 90003 90026 Level indication 90027 90002 There are various methods available for measuring the milk level in a tank.The pneumatic level indicator measures the static pressure represented by the head of liquid in the tank. The higher the pressure, the higher the level in the tank. The indicator transmits readings to an instrument. 90003 90026 Low-level protection 90027 90002 All agitation of milk must be gentle. The agitator must therefore not be started before it is covered with milk. An electrode is often fitted in the tank wall at the level required for starting the agitator. The agitator stops if the level in the tank drops below the electrode.This electrode is known as the low-level indicator (LL). 90003 90026 Overflow protection 90027 90002 A high-level electrode (HL) is fitted at the top of the tank to prevent overfilling. This electrode closes the inlet valve when the tank is full, and the milk supply is switched to the next tank. 90003 90026 Empty tank indication 90027 90002 During an emptying operation, it is important to know when the tank is completely empty. Otherwise, any milk remaining when the outlet valve has closed will be rinsed out and lost during the subsequent cleaning procedure.The other risk is that air will be sucked into the line if emptying continues after the tank is dry. This will interfere with later treatment. Consequently an electrode, lowest low level, (LLL) is often located in the drainage line to indicate when the last of the milk has left the tank. The signal from this electrode is used to switch to another tank or to stop emptying. 90003.