Sunday, April 13, 2014

ROLE OF MILK COMPONENTS USED AS INGREDIENTS IN NON-DAIRY FOODS

INTRODUCTION

Milk is a white liquid produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals before they are able to digest other types of food. Early-lactation milk contains colostrum, which carries the mother's antibodies to the baby and can reduce the risk of many diseases in the baby. It also contains many other nutrients.

Milk is an emulsion or colloid of butter fat globules within a water-based fluid that contains dissolved carbohydrates and protein aggregates with minerals. Because it is produced as a food source for a neonate, all of its contents provide benefits to the growing young. The principal requirements of the neonate are energy (lipids, lactose, and protein), biosynthesis of non-essential amino acids supplied by proteins (essential amino acids and amino groups), essential fatty acids, vitamins and inorganic elements, and water.

Generally, fat and protein content of milk are positively correlated within a population of dairy cattle; however, different breeds of cattle vary in average component levels. Holsteins have the lowest fat and protein content, while Jersey and Guernsey breeds have the highest. Because Holsteins produce more milk, they generally have a higher total yield of fat and protein than other breeds.

Breed
% Fat
% Protein
F:P
Ayrshire
3.86
3.18
1.21
Brown Swiss
4.04
3.38
1.20
Guernsey
4.51
3.37
1.34
Holstein
3.65
3.06
1.19
Jersey
4.60
3.59
1.28
Average fat and protein content of milk produced by different breeds.
(F:P -ratio of fat to protein)

MILK LIPID COMPONENTS

Milk fat can be modified to improve its functionality and expand its usage for traditional and nontraditional applications. The triglyceride, diglyceride, monoglyceride, and individual fatty acid components of milk fat determine functionality. Milk fat functionality is expressed through crystallization and melting behaviors, surface-active properties, and nutritional properties.

Methods that are available to modify the functional properties of milk fat include fractionation by melt crystallization and supercritical fluid extraction, blending, texturization, interesterification, and glycerolysis. The selection of modification procedures is often driven by the requirements of the application.

Modification of selected functionalities can expand the opportunities for milk fat as nontraditional ingredients in traditional applications, such as the use of milk fat fractions in chocolate and bakery products. New applications include the use of intact milk fat and milk fat fractions in the production of structured lipids, sucrose polyesters, edible films, emulsifiers, and cosmetics. Other nontraditional functionality associated with milk lipid components includes the antioxidant and anticarcinogenic properties of conjugated linoleic acid and the antimicrobial properties of lauric acid.

The functional attributes that milk fat imparts to a food system are very dependent upon the application. For example, butter is used for its shortening properties in cookies to yield a tender crumb, but is used in pastries for its layering properties, which promotes the characteristic flakiness of croissants and puff pastry.

The complex chemical composition and broad melting range of milk fat provide many opportunities for the production of milk fat ingredients with improved functionality. Modification of milk fat functionality can be accomplished by a variety of processes, yielding different characteristics in the finished ingredient. The functional requirements of ingredients based on milk fat are driven by the needs of the application, which should be of primary consideration when milk fat is modified.

Applications of Intact Milk Fat Triglycerides

1)     Structured Lipids and Medium-Chain Triglycerides

Structured lipids and medium-chain triglycerides are lipid food ingredients that are increasingly used in high energy foods for people with special nutritional needs and as frying oils and confectionery and bakery fats. The desired chemical and physical properties of structured lipids are dependent upon the final application. Structured lipids and medium-chain triglycerides are produced by random transesterification of a blend of fatty acid reservoirs that have been selected for their chemical and physical properties.

The primary functionality of milk fat in structured lipids is their use as a reservoir of C8 and C10 fatty acids. Structured lipids made with blends of milk fat, commercially available medium-chain triglycerides, and vegetable oils exhibit a range of metabolic and physical functionalities. The use of milk fat fractions with increased concentrations of the C8 and C10 fatty acids may increase the potential value of milk fat as a fatty acid reservoir in the production of structured lipids.

2)     Sucrose Polyesters

Sucrose polyesters are fat substitutes that provide the flavor and physical functionalities of fat, but that are not absorbed by the body and provide no caloric value. The flavor and physical properties of sucrose polyesters are influenced by the fat blend used as the fatty acid source. Sucrose polyesters are another application of the use of milk fat as a fatty acid reservoir in the production of structured food ingredients.

Sucrose polyesters are produced by transesterification reactions between sucrose and fatty acid methyl esters. Sucrose polyesters made with milk fat have been investigated to a limited extent, and results have shown that milk fat may be a suitable source for the production of sucrose polyesters. The physical properties of sucrose polyesters made with milk fat are dependent upon the properties of the milk fat and, thus, sucrose polyesters with a range of physical properties may be produced by modification of the physical properties of the starting milk fat material (e.g., milk fat fractions).

3)     Infant Formulas

The fatty acid and triglyceride composition of current infant formulas differs from human milk, and an infant formula that more closely resembles human milk is desirable. Milk fat has been reported to be a suitable fatty acid reservoir for the production of infant formulas that more closely resemble human milk fat. Infant formulas are produced by interesterification of a fat blend selected for its fatty acid composition. The use of an immobilized 1,3-specific lipase as the catalyst in interesterification reactions allows more accuracy in creating an infant formula with a fatty acid composition and positional distribution that is similar to human milk fat.

Applications of Milk Fat Fractions

1)     Laminated Pastries

Laminated pastries include croissants, Danish, and puff pastries. Milk fat, in the form of butter, is commonly used as a roll-in fat for premium laminated pastries because of its desirable flavor properties. The roll-in fat is spread or extruded onto the dough surface, and the dough is folded to form layers of dough separated by layers of fat. The layering process results in the characteristic flaky texture associated with pastries. The desired physical attributes of a laminated pastry fat include firmness, plasticity, and layering properties.

The degree of firmness required is dependent upon the finished product. For example, a puff pastry is characteristically very flaky and crisp and requires a fat with a melting point of 38 to 42°C, but a Danish pastry has a more tender texture and requires a fat with a melting point of 30 to 32°C. Regardless of the final melting point, the fat must be solid enough to maintain a thin barrier layer between dough layers without melting and becoming incorporated into the dough, but must be plastic enough to be repeatedly folded and rolled without cracking.

2)     Chocolate

Milk fat is used in chocolate manufacture because it imparts desirable flavor and textural properties to chocolate, is compatible with cocoa butter, provides anti bloom properties in dark chocolate, is legally allowed in chocolate, and is less expensive than cocoa butter. The ability to use more milk fat to replace some of the cocoa butter in chocolate is limited by the inhibition of crystallization as the level of incorporation increases.

The use of milk fat results in softening of the product, which is easily illustrated by the difference in firmness and snap of dark chocolate compared with those of milk chocolate. Milk fat components inhibit the crystallization of cocoa butter by two mechanisms: the low melting fraction dissolves cocoa butter crystals, and the middle melting fraction forms eutectics with cocoa butter at replacement greater than 30%. The high melting fraction of milk fat does not cause softening and contributes to the anti bloom properties associated with milk fat.

The isolation of a high melting milk fat fraction creates a unique ingredient that improves the desired functionalities of milk fat while it simultaneously decreases undesired attributes. Blending of fractions offers further diversity and flexibility to meet the requirements of individual customers. Milk fat ingredients for use in chocolate are melted prior to incorporation, and therefore, texturization is not necessary.

3)     Edible Films

Edible films are used in the food industry as barriers to gases and water vapor, as protective coatings for ingredients that are susceptible for oxidation, as a means of reducing the migration of lipids in foods or improving the structural integrity of foods, and as packaging materials. High melting lipids and waxes are often added to edible films to improve their water vapor properties. Edible films made with high melting milk fat fractions exhibited good water vapor barrier properties and may also benefit from the flavor functionality of milk fat. The production of wax monoesters from milk fat using lipase-catalyzed synthesis is technically feasible. Wax monoesters made from milk fat may provide good functionality in edible films.

Applications of Milk Fat Monoglycerides and Diglycerides

1)     Emulsifiers

Monoglycerides are the most commonly used emulsifiers in foods. The use of milk fat-based monoglycerides and diglycerides may provide both emulsification properties and flavor properties to foods. The production of monoglycerides and diglycerides from milk fat using lipase-catalyzed glycerolysis has been reported to be feasible. Emulsification properties have generally been attributed to the monoglyceride component of monoglyceride and diglyceride mixtures. Monoglyceride and diglyceride mixtures made from butter oil with concentrations of 50 to 55% monoglycerides have been obtained by lipase-mediated glycerolysis.

MILK PROTEINS

Major protein components of milk,

Casein

  • α-, β-, and К-casein and casein-related compounds, including casomorphine compounds

Soluble Milk Proteins (Whey Proteins)
  • α-Lactalbumin
  • β-Lactoglobulin
  • Bovine serum albumin
  • Immunoglobulins
  • Lactoferrin
  • Lactoperoxidase

NPN

  • Polypeptides and proteose-peptones
  • Free amino acids
  • Urea
  • Glyco- and macropeptides

Commercial utilization of individual soluble milk proteins


Component
Properties
Uses
α-Lactalbumin (with bovine serum albumin and immunoglobulins)
Nutrition

Infant formula

Lactoferrin
Antibacterial
Infant formula
Lactoperoxidase
Anticaries
Toothpaste
Growth factor
Stimulates mammalian
cell growth
Growth of human skin
and lung cells

Possible commercial utilization of individual soluble milk and whey proteins


Component
Properties
Uses
β-Lactoglobulin

Gelling

·         Restructured meats and fish.
·         Clear sports and dietetic beverages.
Immunoglobulin and
bovine serum albumin

Solubility and nutrition
Anticancer
Enhanced immunity

·         Cancer prevention and treatment.
·         Diets for persons who are. HIV positive, have AIDS, or otherwise compromised immune systems.
·         Diets for athletes.

MILK SUGARS

Natural oligosaccharides exist in milk in very minor concentrations. These oligosaccharides are not yet commercially available. In a discussion of milk sugars, lactose cannot be ignored even though it is a major, not minor, component of milk.

Commercial utilization of selected lactose derivatives


Component
Properties
Uses
Lactulose

Bifidobacteria enhancement
Laxative
Oxygen uptake, ammonia reduction in blood
Suppresses ammonia production in intestine
Ammonia reduction in blood
Infant formula
Laxatives
Diet for athletes

Drug against chronic portal systemic encephalopathy
Drug against hepatic encephalopathy
Lactitol

Bifidobacteria enhancement
NoncaIoric sweetener
Infant formula
Chewing gum
Lactobionic acid

Bifidobaeteria enhancement and other health-related uses
Various
Oligosaccharides

Bifidobaeteria enhancement
Infant formula, baby foods, other foods (yogurt, etc.)

MILK SALTS


Commercial utilization of milk salts


Component
Properties
Uses
Mixture of milk salts recovered
from whey UF permeate
Flavor
Nutrition
Table salt substitute
Health drinks


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