Set Yogurt Production process PDF

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Summary

Yogurt Production Table of Contents List of Figures .............................................................................................................................................. II List of Figures .........................................................................................

Description

Yogurt Production

Table of Contents List of Figures .............................................................................................................................................. II List of Figures .............................................................................................................................................. II 1.

Introduction ...................................................................................................................................... - 1 1.1

Background .............................................................................................................................. - 1 -

1.2

Objective of the review work ................................................................................................... - 2 -

2.

3.

Ingredient used in yoghurt production ......................................................................................... - 3 -

2.1

Dairy Products ......................................................................................................................... - 3 -

2.2

Stabilizers................................................................................................................................. - 4 -

2.3

Sweeteners ............................................................................................................................... - 5 -

2.4

Fruit for Flavoring Yogurt ....................................................................................................... - 6 -

2.5

Starter Culture .......................................................................................................................... - 7 -

Set Yoghurt Manufacturing Processes ............................................................................................. - 8 3.1

Milk Receiving and Pretreating ............................................................................................... - 8 -

3.2

Heat Treatments ..................................................................................................................... - 10 -

3.3 Homogenization ........................................................................................................................... - 14 -

4.

5.

6.

3.3

Cooling and Inoculating ......................................................................................................... - 15 -

3.4

Packaging and Incubation ...................................................................................................... - 16 -

3.5

Storage and Distribution ........................................................................................................ - 17 -

Packaging Materials for Yogurt ..................................................................................................... - 18 4.1

Paper and Paper Board ........................................................................................................... - 18 -

4.2

Metals..................................................................................................................................... - 18 -

4.3

Glass....................................................................................................................................... - 19 -

4.4

Plastic and Polymers .............................................................................................................. - 19 -

Microbial and Chemical Defects and Prevention Mechanisms for yogurt .................................... - 20 5.1

Microbial Defects and their Prevention Mechanisms ............................................................ - 21 -

5.2

Prevention Mechanisms ......................................................................................................... - 22 -

Quality Control and Safety Management for Set Yogurt............................................................... - 24 6.1

Quality Control and Safety Management before Production ................................................. - 24 -

6.1.1

Quality Control before Production ................................................................................. - 24 -

6.1.2

Safety Management before Production .......................................................................... - 25 -

6.2

Quality Control and Safety Management during Production ................................................. - 26 -

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Yogurt Production 6.2.1

Quality Control during Production ................................................................................ - 26 -

6.2.2

Safety Management during Processing .......................................................................... - 27 -

6.3

7.

Quality Control and Safety Management after Production .................................................... - 28 -

6.3.1

Quality Control after Production.................................................................................... - 28 -

6.3.2

Safety Management after Production ............................................................................. - 28 -

Summary and Recommendations................................................................................................... - 29 7.1

Summary ................................................................................................................................ - 29 -

7.2

Recommendations .................................................................................................................. - 30 -

References .............................................................................................................................................. - 31 -

List of Figures Figure 1: Process flow sheet of set yogurt production .............................................................................. - 8 Figure 2: Milk Receiving and Pretreating ................................................................................................. - 9 Figure 3: Engineering flow sheet of set yoghurt production................................................................... - 11 Figure 4: Plate Heat Exchanger .............................................................................................................. - 13 Figure 5: Homogenizer ........................................................................................................................... - 15 Figure 6: Yogurt Packaging .................................................................................................................... - 16 Figure 7: Yogurt Transporting Truck with Temperature Regulator made by Alabaman Company ....... - 17 Figure 8: Illustration of a structure for recipes on enterprise and control levels according to ANSI/ISAS88 standard. ........................................................................................................................................... - 26 -

List of Figures Table 2: Typical chemical composition and nutrient profile of yogurt.................................................... - 1 Table 3: Some ingredients which can be used during the manufacture of yoghurt .................................. - 5 Table 4: Some common defects of yoghurt; indication of some possible causes; and remedies. ........... - 20 Table 5: Microbiological Standard of Yoghurt ...................................................................................... - 22 -

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Yogurt Production

1. Introduction 1.1 Background Yogurt is a semisolid fermented product made from a standardized milk mix by the activity of a symbiotic blend of Streptococcus salavarius subsp. thermophilus and Lactobacillus delbruechii subsp. bulgaricus cultures. For the sake of brevity we shall term the yogurt culture organisms as ST and LB. Milk of various mammals is used for making yogurt in various parts of the world. However, most of the industrialized production of yogurt uses cow's milk. It is common to boost the solids-not-fat fraction of the milk to about 12% with added nonfat dry milk or condensed skim milk. The increased protein content in the mix results in a custard like consistency following the fermentation period (Hui, 1992). The typical composition and nutrient profile of yogurt are shown in Table below. In general, yogurt contains more protein, calcium, and other nutrients than milk, reflecting extra solids-notfat content. Table 1: Typical chemical composition and nutrient profile of yogurt

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Yogurt Production Communities in the Middle East and Asia are widely acknowledged as having introduced fermented milks such as yoghurt into their diet almost as soon as man began to domesticate animals. Some fermented milks did, of course, become popular with local populations in regions like Scandinavia and Russia, but it was thousands of years later that sections of the general public in Europe and North America began to take a serious interest in fermented milks. One of the reasons for this limited uptake was that natural yoghurt can taste extremely acidic to Western palates unless accompanied by another dish, and it was not until the various forms of sweetened and fruit-flavoured yoghurt went on sale that the market for yoghurt really expanded (Tamime, 2006). Today, yoghurt remains a milk-based fermented milk that is presented to the consumer in either a gel form (set yoghurt) or as a viscous fluid (stirred yoghurt) but, as figures for consumption have risen, so manufacturers have expanded the market by introducing an ever wider range of fruit flavours and/or changing the image of the product, e.g. by raising the total solids and fat contents of a standard stirred yoghurt to give a product with a luxury image. Nevertheless, despite these and other innovations, the method of manufacture is still based on the system employed by nomadic herdsmen many centuries ago. For example, the majority of yoghurts consumed worldwide are manufactured with cultures of bacteria with growth optima of 37–45ºC, and this characteristic derives from the fact that the species in question, namely Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus, evolved in the Middle East where the ambient temperature in the summer months is often well in excess of 35ºC. Similarly, the universal method of manufacturing a satisfactory yoghurt is based on the traditional process expanded (Tamime, 2006).

1.2 Objective of the review work The main objective of this review work is to give insight knowledge about the production of yogurt; to discuss the main ingredients, main unit operation and equipment‟s used in yogurt production. The microbial and chemical defects of yogurt and prevention mechanisms will also cover in this review work. Moreover quality and safety of yogurt: before process, during process and after process will touch and described in this review work.

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Yogurt Production 2. Ingredient used in yoghurt production Yogurt is the food produced by culturing one or more of the optional dairy ingredients with a characterizing bacterial culture that contains the lactic acid-producing bacteria, Lactobacillus bulgaricus and Streptococcus thermophilus. One or more of the other optional ingredients described below may also be added. All ingredients used are safe and suitable. Yogurt, before the addition of bulky flavors, contains not less than 3.25% milkfat and not less than 8.25% milksolids- not-fat, and has a titratable acidity of not less than 0.9%, expressed as lactic acid (Hui, 1992).

2.1 Dairy Products Fresh bovine (cow) milk is usually the base material for making yoghurt in the Western world, although ovine, caprine or buffalo milks can also be employed. The fat content of bovine milk tends, depending on breed of cow and diet, to be in the range 3.0–3.5 g 100 mL–1, and this value has to be reduced by separation or supplemented with cream according to consumer taste and/or market demand; the fat content of most retail yoghurts lies in the range 1.0–4.5 g 100 mL–1. However, the critical feature of the milk is the level of solids-non-fat (SNF), which, in bovine milk, varies from 8.5–9.0 g 100 mL–1 according to the season of the year, with around 4.5 g being lactose, 3.3 g being protein (2.6 g casein and 0.7 g whey proteins) and the balance being minerals (Tamime, 2006). Yogurt is generally made from a mix standardized from whole, partially defatted milk, condensed skim milk, cream, and nonfat dry milk. In rare practice, milk may be partly concentrated by removal of 15 to 20% water in a vacuum pan. Supple- mentation of milk-solidsnot-fat with nonfat dry milk is the preferred industrial procedure. All dairy raw materials should be selected for high bacteriological quality. Ingredients containing mastitis milk and rancid milk should be avoided. Also, milk partially fermented by contaminating organisms and milk containing antibiotic and sanitizing chemical residues cannot be used for yogurt production (Hui, 1992).

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Yogurt Production 2.2 Stabilizers The primary purpose of using a stabilizer in yogurt is to produce smoothness in body and texture, impart gel structure, and reduce wheying off or syneresis. The stabilizer increases shelf life and provides a reasonable degree of uniformity of the product. Stabilizers function through their ability to form gel structures in water, thereby leaving less free water for syneresis. A good yogurt stabilizer should not impart any flavor, should be effective at low pH values, and should be easily dispersed in the normal working temperatures in a dairy plant. The stabilizers generally used in yogurt are gelatin; vegetable gums such as carboxymethyl cellulose, locust bean, and Guar; and seaweed gums such as alginates and carrageenans (Hui, 1992). Gelatin is derived by irreversible hydrolysis of the proteins collagen and ossein. It is used at a level of 0.3 to 0.5% to get a smooth shiny appearance in refrigerated yogurt. Gelatin is a good stabilizer for frozen yogurt. The term Bloom refers to the gel strength as determined by a Bloom gelometer under standard conditions. Gelatin of Bloom strength of 225 or 250 is commonly used. The gelatin level should be geared to the consistency standards for yogurt. Amounts above 0.35% tend to give yogurt of relatively high milk solids a curdy appearance on stirring. At temperatures below 100C, the yogurt acquires a puddinglike consistency. Gelatin tends to degrade during processing at ultrahigh temperatures and its activity is temperature dependent. The yogurt gel is considerably weakened by a rise in temperature (Hui, 1992). The most active stabilisers are hydrocolloids chosen for their ability to absorb water, and gums of plant origin, e.g. guar gum and locust bean gum, provide a stirred product with a very favourable mouth-feel. Gelatin gives a distinct, shiny appearance to stirred yoghurts, and a gellike structure that melts cleanly in the mouth; it is also effective in controlling the migration of moisture. Low methoxyl pectins provide an alternative source of viscosity in stirred yoghurts, or stabilise the fruit preparation in Swiss-style yoghurts, and some sources of dietary fibre added for alleged nutritional reasons (e.g. polydextrose) may affect viscosity as well. Other types of stabiliser that have been used in yoghurt making include carboxymethyl cellulose, locust bean gum, alginates, carrageenan, starch and modified starch (Tamime, 2006).

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Yogurt Production 2.3 Sweeteners Nutritive carbohydrates used in yogurt manufacture are similar to the sweeteners used in ice cream and other frozen desserts described by Arbuckle. Sucrose is the major sweetener used in yogurt production. Sometimes corn sweeteners may also be used, especially in frozen yogurt mixes. The level of sucrose in yogurt mix appears to affect the production of lactic acid and flavor by yogurt culture. A decrease in characteristic flavor compound (acetaldehyde) production has been reported at 8% or higher concentration of sucrose.1 Sucrose may be added in a dry, granulated, free- flowing, crystalline form or as a liquid sugar containing 67% sucrose. Liquid sugar is preferred for its handling convenience in large operations. Commercial yogurts have an average of 4.06% lactose, 1.85% galactose, 0.05% glucose, and pH of 4.40 (Hui, 1992). Sweetening agents, such as sucrose, high-fructose corn syrup or honey, are usually added to stirred yoghurts to mask the acidity for acid-conscious consumers and, perhaps, produce a firmer texture. However, since sugars increase the osmotic pressure of the milk base, the addition of excessive levels (> 10 g 100 mL–1) prior to fermentation can inhibit starter activity; for this reason, sugars may be added with the fruit to stirred yoghurts just before filling. Some brands of fruit yoghurt employ artificial sweeteners (e.g. aspartame or sucralose) as a means of lowering the calorie content, but some people have expressed reservations about this practice. However, sugar and sweeteners can influence the microstructure of yoghurt; the former caused the casein micelles to form clusters, while aspartame caused the casein micelles to form double longitudinal polymers (Tamime, 2006). Table 2: Some ingredients which can be used during the manufacture of yoghurt

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Yogurt Production 2.4 Fruit for Flavoring Yogurt The fruit preparations for blending in yogurt are specially designed to meet the marketing requirements for different types of yogurt. They are generally present at levels of 10 to 20% in the final product. A majority of the fruits contain natural flavors. Flavors and certified colors are usually added to the fruit-for-yogurt preparations for improved eye appeal and better flavor profile. The fruit base should meet the following requirements.  It should exhibit true color and flavor of the fruit when blended with yogurt,  It should be easily dispersible in yogurt without causing texture defects, phase separation, or syneresis.  The pH of the fruit base should be compatible with yogurt pH.  The fruit should have zero yeast and mold population in order to prevent spoilage and to extend shelf life. The fruit flavors vary in popularity in different parts of the country and during different times of the year. In general, more popular fruits are strawberry, raspberry, blueberry, peach, cherry, orange, lemons, purple plum, boysenberry, spiced apple, apricot, and pineapple. Blends of these fruits are also popular. Fruits used in yogurt base manufacture may be frozen, canned, dried, or combinations thereof. Among the frozen fruits are strawberry, raspberry, blueberry, apple peach, orange, lemon, cherry, purple plum, blackberry, and cranberry. Canned fruits are pineapple, peach, mandarin orange, lemon, purple plum, and maraschino cherry. The dried fruit category included apricot, apple, and prune. Fruit juices and syrups are also incorporated in the bases. Sugar in the base of fruit is uses in protecting fruit flavor against loss by volatilization and oxidation. It also balances the fruit and the yogurt flavor. The pH control of the base is important for fruit color retention. The color of yogurt should represent the fruit color in intensity, hue, and shade. The base should be stored under refrigera...