YOGHURT AND CHEESE Dimple s1 RV 11 BT

YOGHURT AND CHEESE Dimple. s(1 RV 11 BT 018) Sindhushree (1 RV 11 Bt 053) Vani. B. Sri(1 RV 11 BT 058) RVCE Yashaswini. B. N(1 RV 11 BT 062)

Yoghurt Production and Processing HISTORY Yogurt has a long history, especially in Eastern Europe. It is generally believed that this fermented milk product became popular after Issac Caruso, who was born in what to-day is part of Greece, started industrial production of yogurt in Spain in 1919 under the name Danone has since become a multi-national food producer, now centred in France. Yogurt is the most popular probiotic food worldwide. The production of yogurt requires the action of two bacteria - Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus on milk. The action of the bacteria, lowers the p. H of the milk, which in turn thickens it, and results in the sour taste characteristic of natural yogurt. Microbial Biotechnology

What is the composition of yogurt? • Yogurt, a fermented dairy product whereby milk is inoculated with bacteria cultures, is an example of a mixed pure culture fermentation. That is, a controlled mixture of known cultures of bacteria used in the fermentation process. • A. Yogurt is the product of fermentation, a slow decomposition process of organic substances induced by microorganisms or enzymes. Food fermentation is the study of microbial activity, usually anaerobic, on suitable substrates under controlled or uncontrolled conditions. To produce yogurt, lactose, a compound sugar found in milk known as lactin or milk sugar, is fermented by two different species of bacteria: Lactobacillus and RVCE Streptococcus

• B. Yogurt is commercially produced by adding to milk a 2– 4% nonfat dry milk powder that has been inoculated with a 5% combination of Lactobacillus bulgaricus and Streptococcus thermophilus (1: 1 ratio). The milk mixture is then incubated at 45 degrees C for 3 to 6 hours. The product must be chilled immediately. • C. The fat content of yogurt varies from 0 -3. 5%; most yogurt is low fat and contains 1– 1. 5% fat. • D. Lactic acid, the end product of anaerobic metabolism of glucose, provides the tart flavor of yogurt, as well as the formation of a gel structure. The major flavor components of yogurt are carbonyl compounds; among these, acetaldehyde is the most important and gives the yogurt its green apple or nutty flavor. Yogurt quality is based on color, appearance, body, texture, and flavor. RVCE

• E. Ropy (slime-producing) lactic acid bacteria produce polysaccharides that are released into the yogurt where they increase viscosity and improve water retention. Viscosity is the resistance of a fluid to flow. Yogurt has a high moisture content of 82– 86%. • F. Milk SNF (solids-not-fat) content of yogurt varies from 9– 16%. SNF can be increased by adding milk powder, and by other means. Increased SNF levels are needed to increase protein content, which helps to increase product viscosity to desired levels. • G. Frozen yogurt is manufactured by mixing varied amounts of fermented yogurt with ice milk containing sweeteners, stabilizers, etc. RVCE

How are fermentation and anaerobic respiration needed to create the yoghurt product • A. Aerobic respiration is the total oxidative degradation of glucose that must have oxygen to take place. Fermentation is an example of anaerobic respiration, which takes place in the absence of oxygen and consists essentially of the early stages of aerobic respiration. During this type of respiration, glucose is converted to a variety of end products, such as lactic acid. • Since acids produce a sour taste, the result is a sourtasting dairy product. The increased acidity (lowered p. H) of the milk causes milk protein to coagulate and become more viscous. The bacteria Streptococcus also produces other compounds that have an effect on final flavor. RVCE

• B. Lactic acid bacteria are gram-positive, non-spore forming bacteria that produce lactic acid as the major product of fermentation. These bacteria are very important in pickling, cheese making, fermented dairy products, and other technologies. • C. Milk proteins have the unique ability to curdle (form a gel). Curdling is induced by proteolytic enzymes, lactic acid, heat, and other means. Each milk gel has a solid structure consisting of a protein matrix and other components. This gel matrix has the ability to immobilize the liquid phase of milk. By modifying this ability, it is possible to manufacture stable milk products with a high water content (i. e. yogurt). RVCE

• D. Milk to be used in yogurt production is usually heated to increase the total solids content in order to make a firm end product. An end product is the final compound or substance resulting from a chemical reaction. Heating causes the micelles in the milk to interconnect in chains to form the gel matrix. • E. Cooling of the yogurt after incubation (fermentation) stops bacterial fermentation. • F. If cows are receiving antibiotic treatments, their milk is usually discarded for a specific period of time. Otherwise, residual effects from the antibiotics in the milk could inhibit the growth of desirable bacteria necessary for yogurt production. RVCE

Preparation • Yogurt is produced through the fermentation of milk by lactic acid bacteria, usually lactobacillus bulgarius and. Streptococcus thermophilus. • The milk is firstly heat treated, homogenised and is then cooled to allow the addition of bacteria or starter culture. • Given the right conditions, i. e. correct temperature and moisture, the bacteria are able to ferment the milk sugar (lactose), producing lactic acid. • The milk proteins then coagulate and set, to form yogurt. • A colourless liquid called acetaldehyde is also produced during fermentation and gives yogurt its distinct flavour. • Yogurt can be made from different types of milk, including skimmed, semi-skimmed, whole, evaporated or powdered RVCE

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Varieties of yogurt • The market now offers a vast array of yogurts to suit all palates and meal occasions. They come in a variety of textures (e. g. liquid, set, smooth), fat contents (e. g. luxury, low-fat, virtually fat-free) and flavours (e. g. natural, fruit, cereal), can be consumed as a snack or part of a meal, as a sweet or savoury food and are available all year-round. • Fermenting milks with different micro-organisms has also provided an opportunity to develop a wide range of products with different flavours, textures, consistencies and, more recently, health attributes. These include: • Live yogurts, which contain harmless bacteria that are added to the milk and are still present and alive. • Probiotic yogurts, which contain live probiotic micro-organisms that are suggested to be beneficial to health. • Bio yogurts, which are very popular and are made using bifido bacterium bifidum (bifidobacteria) and/or lactobacillus acidophilius. Bio yogurt has a milder, creamier flavour which is less acidic than some other varieties and has shown to aid RVCE digestion and promote good health.

Types of Yogurt • Set Yogurt- this type of yogurt is incubated and cooled in the final package. Firm “jelly like” texture. • Stirred Yogurt- incubated in a tank and final coagulum is broken by stirring before cooling. Less firm then set yogurt (like a thick cream). A little reformation of coagulum will occur after packaging. RVCE

• Drinking Yogurt- also has coagulum broken before cooling. Very little reformation of coagulum will occur. • Frozen Yogurt- Incubated like stirred yogurt. Cooling is achieved by pumping through a freezer like ice cream. Has a texture like ice cream. RVCE

• Concentrated Yogurt- incubated like stirred yogurt. After coagulum is broken, some water is boiled off. Produces rough and gritty textures. • Flavored Yogurt- Flavors are added just before yogurt is poured into pots. Add in usually contain about 50 % sugar. RVCE

10 Reasons Yogurt is a Top Health Food… 1. 2. 3. Easier to digest then milk Contributes to colon health Increases the absorption of other nutrients such as calcium 4. Boosts immunity 5. Aids in healing process after infections in the intestines 6. Decreases yeast infections 7. A rich source of calcium 8. Good source of protein 9. Lowers cholesterol 10. It is a “grow food” meaning iy helps children to grow RVCE

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INTRODUCTION • Cheese making is the craft of making cheese, which dates back at least 5, 000 years. The production of cheese, like many other food preservation processes allows the nutritional and economic value of a food material, in this case milk, to be preserved. It allows the consumer to choose (within limits) when to consume the food rather than have to consume it straight away, and it allows the product to be altered which gives it higher value. The job of the cheese maker is to convert milk into cheese. The milk may be from a cow, goat, sheep or buffalo, although worldwide cow's milk is most commonly used. The cheese maker applies craft and skill to the practice of cheese making, intending to produce a product with specific characteristics and organoleptic requirements (appearance, aroma, taste, texture) that are consistent every time it is made. Some cheeses may be deliberately left to ferment from naturally airborne spores and bacteria; this generally leads to a less consistent product but one that is highly valuable in a niche market for exactly that reason, no two are ever quite the same. RVCE

preparation • Cheese production has three steps: curd formation, curd treatment and curd ripening. • 1. Curd formation can use mare, ewe, cow or goat milk to produce “sour” or “sweet” curd. Sour curd is produced by fermentative lactic acid bacteria as mentioned above. Sweet curd is produced by adding an enzyme called renin instead of bacteria to curdle the milk. The curd is separated from the whey by draining. The curd can be used directly to make unripened cheeses such as ricotta or cottage cheese or can undergo RVCE further processing to make a ripened cheese.

• 2. Curd treatment consists of condensing and squeezing to form dense, hard curd. It is then molded into the desired shape, salted and mixed with different types of secondary microflora. RVCE

• 3. Secondary microflora ripen the cheese and will determine the final texture and aroma of each type of cheese. For hard ripened cheeses such as Cheddar, curds are further compressed and the bacteria particular for the cheese is added. The Cheddar is wrapped in wax or plastic to prevent contamination and then incubated to allow the bacteria to do its work. For soft ripened cheeses such as Camembert and Limburger, a microbe, usually mold, is added to the surface of the cheese that produces a protein-digesting enzyme. This enzyme breaks apart the curds and causes the cheese to become creamy and spreadable. RVCE

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• MICROBIAL TECHNOLOGY AS APPLIED TO CHEESE MAKING: • Acidifying (souring) milk helps to separate the curds and whey and control the growth of undesirable bacteria in cheese. Usually special ‘starter’ bacteria are added to milk to start the cheesemaking process. These bacteria convert the lactose (milk sugar) to lactic acid and lower the milk’s p. H. • There are two types of bacteria used for this process: • Mesophilic bacteria thrive at room temperature but die at higher temperatures. They are used to make mellow cheeses, such as Cheddar, Gouda and Colby. • Thermophilic bacteria thrive at higher temperatures, around 55 °C, and are used to make sharper cheeses such as Gruyère, Parmesan and Romano. RVCE

• Some cheeses are curdled only by acidity. For example, paneer cheese is made using lemon juice to curdle the milk and cottage cheese is made using mesophilic bacteria. However, for most cheeses, rennet is also added to the milk after a starter bacteria. Rennet is a mixture containing the active enzyme chymosin. Rennet speeds up the coagulation of casein and produces a stronger curd. It also allows curdling at a lower acidity, which is important for some types of cheese. RVCE

Functional Food Preparation Properties of Cheese • • – Shredability – Meltability – Oiling off – Blistering – Browning Strechability 4 oz. Usually = 1 cup of shredded cheese. Melting: higher fat=greater meltability and blendability. Processed cheeses don’t tend to separate out the fat, melt, & blend more easily due to added water and emulsifiers. Low fat cheeses separate and higher protein conte t makes them toughen as heated. Oiling: high fat cheeses release free fat and glistens on the surface Browning; Maillard reaction RVCE

CHEESE PRODUCTION • Cheese making is the controlled process of removing water from milk. This process concentrates the milk’s protein, fat and other nutrients and increases its shelf life. Cheese making involves coagulating the casein protein in milk and then separating the milk into solid curds and liquid whey. The liquid whey is drained away, and the curds are salted, shaped and left to ripen in a controlled environment. • Microorganisms are used in each step of this process and determine the flavor and texture of the final cheese. RVCE

• The microbes important for dairy product manufacturing can be divided into two groups: 1. primary and 2. secondary micro flora. Products undergoing fermentation by only primary micro flora are called unripened and those processed by both primary and secondary micro flora are called ripened. Primary micro flora are fermentative lactic acid bacteria which cause the milk to curdle. Primary micro flora consists of certain kinds of Lactococcus, Lactobacillus and Streptococcus that are intentionally added to pasteurized milk and grown at 30°C or 37°C (temperature depends on the bacteria added). Secondary micro flora include several different types of bacteria (Leuconstoc, Lactobacillus, and Propionibacterium), yeasts and molds; they are only used for some types of surface ripened and mold ripened cheeses. The various combinations of micro flora determine what milk product you will end up with. RVCE

TYPES OF CHEESE Fresh type This cheese does not ripe. It resembles yoghurt. However, it is different in the fact that it has more moisture content than ordinary cheese. It is a origin of cream cheese. The main kinds cheese Cuttage, mozzarella, ricotta, Boursault, fromage blanc etc. RVCE

White mold type White mold covers the surface of cheese. It is cheesy to eat. The main kinds cheese Camembert, Coulommiers, capricciodue, Baraka etc. RVCE

Blue mold type It says blue cheese. It makes like white mold cheese. The main kinds cheese Blue, Gorgonzola, Stilton, Roquefort etc. RVCE

Washed type When ripe cheese, salt water and so on are sprayed on the surface of cheese. This cheese is soft. The main kinds cheese epowas, Mondor, Munster. RVCE

Chevre type • This cheese made from the milk of a goat. This cheese is dry comparatively. The main kinds cheese Saintes mall, varance RVCE

• Semi hard type It is most visible to cheese. Milk is hardened. The curd is cut. It is put into a frame. Pressure is applied. And it ripens. The main kinds cheese Gouda, mimolette, raclette etc. RVCE

Hard type Pressure stronger than semi hard type cheese. RVCE

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