Yogurt production

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I. GENERAL DESCRIPTION:


1. Definition
(Dairy science and Technology, University of Guelph, http://www.foodsci.uoguelph.ca/dairyedu/home.html)

Yogurt is a semi-solid fermented milk product. Most of the industrialized yogurt production uses cow's milk. Whole milk, partially skimmed milk, skim milk or cream may be used. Other yogurt ingredients may include some or all of the following: other dairy products (concentrated skim milk, nonfat dry milk, whey, lactose, these products are often used to increase the nonfat solids content), sweeteners (glucose or sucrose, high-intensity sweeteners e.g. aspartame), stabilizers (gelatin, carboxymethyl cellulose, locust bean Guar, alginates, carrageenans, whey protein concentrate), flavours and fruit preparations (including natural and artificial flavouring, colour).


2. General Flowsheet


Yoghurt production.jpg


Figure 1: Yogurt production LITERATURE: BAT for Food, Drink and Milk Industries, June 2005


3. Description of techniques, methods and equipment

(Dairy science and Technology, University of Guelph, http://www.foodsci.uoguelph.ca/dairyedu/home.html and BAT for Food, Drink and Milk Industries, June 2005)

  • General:
The milk is clarified and separated into cream and skim milk, then standardized to achieve the desired fat content. The fat and non-fat solids content of the milk is first increased by the addition of milk powders. Stabilizers may be added at this stage. The various ingredients are then blended together in a mix tank equipped with a powder funnel and an agitation system.
The milk is then homogenized at a temperature of around 55oC and pasteurized at 80-90oC for 30min in a batch process, or 90-95oC for 5min in a continuous process.
The heat treated milk is then cooled to around 40-43oC and seeded with two starter organisms. Fermentation takes about 4 hours. At the end of the process, the product is cooled to 15-20oC, using either tank cooling coils or, more commonly, tubular or plate heat exchangers. Fruit and flavour may be incorporated at this time, then packaged. The yogurt is then cooled to less than 5oC, to slow down the physical, chemical and microbiological degradation, and filled into pots ready for storage and distribution.
  • Other yogurt products:
  • Plain yogurt: There are two types of plain yogurt:
1)stirred style yogurt and
2)set style yogurt.
The above description is essentially the manufacturing procedures for stirred style. In set style, the yogurt is packaged immediately after inoculation with the starter and is incubated in the packages.
  • Fruit-on-the-bottom style: fruit mixture is layered at the bottom followed by inoculated yogurt, incubation occurs in the sealed cups.
  • Soft-serve and Hard Pack frozen yogurt
  • Continental, French, and Swiss: stirred style yogurt with fruit preparation
  • Yogurt beverages: Drinking yogurt is essentially stirred yogurt which has a total solids content not exceeding 11% and which has undergone homogenization to further reduce the viscosity, Flavouring and colouring are invariably added. Heat treatment may be applied to extend the storage life. HTST pasteurization with aseptic processing will give a shelf life of several weeks at 2-4°C, which UHT processes with aseptic packaging will give a shelf life of several weeks at room temperature.


4. Temperature ranges and other parameters
(Dairy science and Technology, University of Guelph, http://www.foodsci.uoguelph.ca/dairyedu/home.html and BAT for Food, Drink and Milk Industries, June 2005)


Yoghurt production2.jpg


5. Benchmark data


Yoghurt production3.jpg


II. NEW TECHNOLOGIES:

See information for dairies.


III. SOLAR SYSTEMS INTEGRATION:

Pasteurization is a heat intensive process. In this case the temperature level of the process can be reachable by using solar systems. Due to the fact that large amounts of hot water or steam may be required, auxiliary boilers can be used additionally to solar collectors (Joanneum Research).


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