Milk and Dairy Products Lecture Notes PDF

Milk and dairy products 4 th lecture Dr. Mohamed Elsaadany 1 Milk Dr. Mohamed Elsaadany 3  Introduction Caw milk The lacteal secretion, practically free from colostrum, obtained by the complete milking of one or more he...

Milk and dairy products 4 th lecture Dr. Mohamed Elsaadany 1 Milk Dr. Mohamed Elsaadany 3  Introduction Caw milk The lacteal secretion, practically free from colostrum, obtained by the complete milking of one or more healthy cows The term milk is also used for white colour, non-animal beverages resembling milk in colour & texture such as soy milk, rice milk, almond milk, & coconut milk. Dr. Mohamed Elsaadany 4  Composition of Milk Water: 87-88% Carbohydrate: (approx. 5% ) mainly fermentation In heated milk products, e.g., in condensed milk, there is also lactulose which is a little sweeter’ Fat: 3-4% in whole milk contains fat soluble vitamins, pigment carotene & Xanthophylls; cholesterol (33 mg in a cup of whole milk) & phospholipids but is primarily TGs(95%) It also contains 2.1% linoleic acid, 0.5% linolenic acid & 0.14% Arachidonic acid. Dr. Mohamed Elsaadany 5  Composition of Milk Protein: (3-4%) including The casein (80% of milk protein) is arranged in super-structures called micelles, which consist of protein together with phosphate, citrate and calcium. The casein micelles also may be coagulated by addition of the enzyme rennin. Whey proteins (20% of milk protein) include Include lactalbumin, lactoglobulin & immunoglobulin more hydrated than casein and are denatured and precipitated by heat rather than by acid. Other protein components include enzymes such as lipase, protease, & alkaline phosphatase, which hydrolyses TGs, proteins, & phosphate esters, respectively. Dr. Mohamed Elsaadany 6  Composition Vitamins of & Minerals: Milk Vitamins Vitamins A, B6, B12, C, D, K, E, thiamine, niacin, biotin, riboflavin, folates, and pantothenic acid. Vitamin A is naturally in the fat component of whole milk andmore may be added prior to sale. whole milk is generally fortified with vitamin D because it is naturally present only in small amounts. Low-fat and non-fat milk are fortified with both of these fat-soluble vitamins because milk fat is reduced or absent. Minerals Ca & P approx. 1% of milk Other minerals present are chloride, magnesium, potassium, sodium, and sulfur. Dr. Mohamed Elsaadany 7  Composition Vitamins of & Minerals: Milk Dr. Mohamed Elsaadany 8  Physical Vitamins Properties & Minerals: Acidity: fresh milk pH is 6.5-6.7 at 25°C Viscosity: depends on the amount of fat, size of fat globules & extent of clustering of globules. Homogenisation & ageing the viscosity Freezing point: -0.55°C Boiling point: 100.2°C Dr. Mohamed Elsaadany 9  Color and Vitamins flavor & Minerals: Compounds Color Factors that contribute to the color of milk are fat, colloidally dispersed casein and calcium complexes, and riboflavin (B2). They give the light ivory color. The amount of carotene provide the yellowish tinge of butter. Flavor The flavor of milk is mild & slightly sweet. The characteristic mouth-feel is due to the presence of emulsified fat, colloidally dispersed proteins, the carbohydrate lactose, & milk salts. Fresh milk also contains acetone, acetaldehyde, methyl ketones, & SFAs that provide aroma. Dr. Mohamed Elsaadany 10  Terminology Vitamins & Minerals: Pasteurization Pasteurization is a process in which foods are treated with mild heat, usually to less than 100 °C (212 °F), to eliminate pathogens and extend shelf life. Pasteurization destroys 100% of pathogenic bacteria, yeasts, and molds and 95 to 99% of other, nonpathogenic bacteria. Inactivation of alkaline phosphatase is used as an indication of pasteurization Dr. Mohamed Elsaadany 11  Terminology Vitamins & Minerals: Ultrapasteurization A process in which a milk product is heated at or above 280°F (138°C) for at least 2 seconds. Ultrahigh-temperature (UHT) milk Milk that has been pasteurized using very high temperatures, is aseptically sealed, and is capable of being stored unrefrigerated for up to 3 months. Homogenization A mechanical process that breaks up the fat globules in milk into much smaller globules that do not clump together and are permanently dispersed in a very fine emulsion. Coagulate To clot or become semisolid. In milk, denatured proteins often separate from the liquid by coagulation. Dr. Mohamed Elsaadany 12 Types of Milk Dr. Mohamed Elsaadany 13 TYPES &OF Vitamins MILK Minerals: Dr. Mohamed Elsaadany 14  Types of Vitamins milk & Minerals: Fresh milk Whole milk Must contain 3.25% milk fat and at least 8.25% milk solids-not-fat (MSNF) The milk is usually fortified with vitamins A and D, but this is optional Reduced-Fat and Low-Fat Milk These milks have had some of their fat removed so that milk fat levels are decreased to 2.0 and 1.0%, respectively, Fat-Free or Nonfat Milk Nonfat is synonymous with fat-free. Removing as much fat as possible Fat-free milk should contain no more than 0.5% milk fat. Fresh Fluid Milks from Animals Other Than Cows milks from other animals such as Goat, Sheep, and Other Animal Goat’s milk is low in folate and vitamins D, C, and B12 Dr. Mohamed Elsaadany 15  Types of Vitamins milk & Minerals: Favored milk Flavored milk is created by adding a flavoring agent plus sugar to milk, thereby making the product more appetizing to customers. Ex. fruit, chocolate, vanilla, coffee, caramel, cappuccino, peanut butter, root beer, and vegetable Eggnog milk a traditional rich holiday beverage made with eggs, cream or milk, nutmeg, and often spirits. It is sold predominantly during Christmas Dr. Mohamed Elsaadany 16  Types of Vitamins milk & Minerals: Dry milk: made with whole milk or skimmed milk dehydrated to about 97% by spray drying & vaccum drying. Good shelf life. Highly hygroscopic & can be reconstituted to fluid milk. Instant Milk Instant milk is different from regular nonfat dried milk. It is manufactured by exposing nonfat dried milk to steam, after which it is redried. Cultured Milk Products have the potential to benefit human health. All cultured milk products had bacterial cultures in order to ferment their lactose into lactic acid. When microbial food cultures are naturally present in a food, they are not listed on the label When cultures are added the term “cultured” followed by the name of the substrate should listed Yogurt in the U.S. regulatory state that the culture must include Lactobacillus bulgaricus and Streptococcus thermophilus Dr. Mohamed Elsaadany 17  Types of Vitamins milk & Minerals: Buttermilk originally is the liquid left over after fresh cream had been chilled and churned to produce butter. Now, most commercially available buttermilk is cultured by adding Streptococcus lactis bacteria to pasteurized nonfat, reduced-fat, or low-fat milk. Yogurt Yogurt is produced by mixing two types of bacteria, Lactobacillus bulgaricus and Streptococcus thermophilous, and adding them to pasteurized, homogenized milk the mixure then held at a warm temperature (108°F–115°F/42°C–46°C) Acidophilus Milk Acidophilus milk is a cultured milk created with the assistance of Lactobacillus acidophilus. These bacteria break down lactose to glucose and galactose, resulting in twice as many sugar molecules. Dr. Mohamed Elsaadany 18  Types of Vitamins milk & Minerals: Kefir Kefir is a yellowish white, acidic, viscous, and slightly alcoholic dairy beverage, originated in Russia and it is defined as the yogurt of the 21st century. Kefir is a type of fermented milk produced by a mixed flora consisting of yeasts, various LAB, and acetic acid bacteria contains about 1% alcohol and a little carbon dioxide results by fermentation Sour Cream Cream can be soured by Streptococcus lactis bacteria or some other acidifying agent. Creams and Substitutes Creams come in a variety of different fat percentages and these can also be replaced by various cream substitutes. Cream Cream is a collection of fat droplets that floats to the top of non-homogenized whole milk. The heavier and thicker the cream is, the higher the fat content will be. Creams vary in their milk fat content, ranging from a low of 18% to a high of 36%. Dr. Mohamed Elsaadany 19  MILK PRODUCTS Vitamins IN FOOD PREPARATION & Minerals: Whipped Milk Products Liquid milk products such as cream, evaporated milk, and reconstituted nonfat dried milk can be made into a foam by whipping air into the liquid. Whipped Cream Cream expands two to three times its volume when whipped. Fat Content The higher the fat content of the cream, the more stable the whipped cream will be. Temperature Cooling cream increases its viscosity or firmness and its tendency to clump. Sugar increases the stability of whipped cream, but it should be added gradually, Overbeating for even a few seconds over the peak point turns whipped cream into butter and whey. Dr. Mohamed Elsaadany 20  MILK PRODUCTS Vitamins IN FOOD PREPARATION & Minerals: Butter fat content is generally about 80%. Made from sweet or sour cream. Butter is a concentrated form of fluid milk produced through churning of pasteurized cream. Churning involves agitation that breaks fat globule membranes so the emulsion breaks, fat coalesces, and water (buttermilk) escapes. The original 20/80 oil-in-water type of emulsion of milk becomes a 20/80 water- in-oil emulsion. Butter may have a yellow color due to the fat-soluble animal pigment, carotene, or an additive. Butter spoil as a result of hydrolysis of TG molecules releasing free butyric & caproic acids. Ghee, A type of clarified butter, is prepared by simmering butter and removing the residue. The texture, colour, and taste of ghee depend on the quality of the butter and the duration of the boiling. Dr. Mohamed Elsaadany 22  STORAGE& OF Vitamins MILK PRODUCTS Minerals: Refrigerated All fluid milk except unopened, aseptic packages of UHT pasteurized milk and certain canned milk products should be stored in the refrigerator. One should never drink milk directly from the container, because bacteria in the mouth can wash back into the product. Storing milk in proper opaque containers will reduce its exposure to light, which can trigger oxidation, resulting in off -flavors and the loss of riboflavin (B2). Milk. No more than 3 weeks. Yogurt. Best consumed within the first 10 days, but can last up to 3 to 6 weeks. If it separates, simply stir the liquid back into the curd before serving. Buttermilk. Best when used within 3 to 4 days after purchase, because it will continue to sour, but it can last up to 3 or 4 weeks. Sour cream. Unopened, up to 1 month, but is best when used within a few days. Dr. Mohamed Elsaadany 23  STORAGE& OF Vitamins MILK PRODUCTS Minerals: Dry storage Dry milk, ultrapasteurized milk, evaporated milk, and sweetened condensed milk are stored at or slightly below room temperature (72°F/22°C). Unopened cans of evaporated and sweetened condensed milks will keep up to a year in dry, ventilated areas, but double that if refrigerated Ultrapasteurized milk can be stored unopened at room temperature for up to 3 months. Once opened, all these milks must be treated like fresh milks and refri gerated. Dr. Mohamed Elsaadany 24 2 Cheese Dr. Mohamed Elsaadany 25  Classification of Cheeses Cheeses classified according Semi-hard. 40 to 50% to their moisture content: moisture. Fresh. Moisture content is Hard. The moisture content over 80%, and they are not ranges from 30 to 40%. aged. Cheddar and Swiss are Soft. Water content ranges examples. from 50 to 75% and are Very hard. Water content of aged for just a short time.. approximately 30% and are aged the longest.. Dr. Mohamed Elsaadany 26  Cheese Production The basic steps common to produce cheese include: – Milk selection – Coagulation – Curd treatment – Curing – Ripening The yield from 10 pounds of milk is approximately 1 pound of cheese and 9 pounds of whey. Dr. Mohamed Elsaadany 27  Cheese Production Milk selection has the greatest influence on classification of cheese. Any mammal’s milk can be made into cheese. Coagulation Cheese-making starts with the coagulation of the casein protein in milk. The type of method used determines many of the characteristics of the resulting cheese. The two main methods to aid coagulation are the action of: – Enzymes – Acid Dr. Mohamed Elsaadany 28  Cheese Production Curd treatment The curd produced by acid has a soft and spongy texture. This texture is influenced by pH, becoming more solid and compact as the acidity increases. Dr. Mohamed Elsaadany 29  Cheese Production The curd may be treated to remove more whey by: – Cutting – Heating – Salting – Further optional treatment includes knitting and/or pressing Dr. Mohamed Elsaadany 30  Cheese Production Curing: To expose cheese to controlled temperature and humidity during aging. Ripening: The chemical and physical changes that occur during the curing period. Processed cheese: A cheese made from blending one or more varieties of cheese, with or without heat, and mixing it with other ingredients. Dr. Mohamed Elsaadany 31  Purchasing Cheese Grading USDA-defined U.S. Grades AA, A, B, and C. Graded cheeses are evaluated based on their: – Variety – Flavor – Texture – Finish – Color – Appearance Dr. Mohamed Elsaadany 32  Food Preparation with Cheese Selecting a Cheese Some of these functional The chemical properties include: composition of a cheese – Shredability determines its – Meltability functional properties – Oiling off and dictates how it will – Blistering be used in food – Browning preparation. – Strechability Dr. Mohamed Elsaadany 36 Storage of Cheese Cheese must be Processed cheese stored properly to products can be stored prevent deterioration. in a cool, preferably Most cheeses should dark, cupboard until be refrigerated. ready for use... – Though refrigeration Some can even be more effectively retains frozen. desirable qualities. Dr. Mohamed Elsaadany 37