Dairy products lactose

Lactic acid bacteria and bifidobacteria are preferred as protective and probiotic cultures, and have been used since the beginning of history as starter cultures. They have a long history of being safely used and consumed. LAB are widely used for fermentation of milk, meat, and vegetable foods. In fermentation of dairy products, lactose is metabolized to lactic acid. Other metabolic products, hydrogen peroxide, diacetyl, and bacteriocins may also play inhibitory roles and contribute to improving the organoleptic attributes of these foods, as well as their preservation (Messens and De Vuyst, 2002). 

In dairy products, lactose can be undesirable due to problems with lactose intolerance and p-galactosidases are therefore of commercial interest for processing lactose-rich dairy products. Several of the P-glucosidases reported above have good P-galactosidase activity. Eubacterial sources of p-galactosidase include... 

Whey has been used ia some substitute dairy products but aot as a source of proteia. Whey proteias have beea used ia dairy substitutes only siace the commercialisation of ultrafiltration (qv) technology. Membranes are used that retain proteia and permit water, lactose, and some minerals to pass through as permeate. Proteia coaceatrates are available from both acid and sweet whey and ia coaceatratioas of 35—80 wt % proteia. Whey proteia isolates are commercially available having proteia >90 wt%. The cost of these isolates is too high, however, to make them economical for substitute dairy foods. 

Galactose, a constituent of the disaccharide lactose found in dairy products, is metabolized by a patiiwav that includes the isomerization of UDP-galactose to UDP-glucose. where UDP = uridylyl diphosphate. The enzyme responsible for the transformation uses NAD+ as cofactor. Propose a mechanism. 

Lactose is mainly used as a fermentation substrate for lactic acid bacteria in dairy products, such as yogurt and cheese. These bacteria break down lactose into lactic acid, which solidifies the milk, and creates an acid environment that favors the benign lactic acid bacteria over those that are more harmful. 

Lactose intolerance is responsible for many cases of acute diarrhea, especially in patients of African descent, Asians, and Native Americans. Foods should be considered as possible causes, especially fat substitutes, dairy products, and products containing non-absorbable carbohydrates. 

Some individuals are unable to metabolise lactose and are lactose intolerant. This is because they lack the enzyme lactase that is needed to metabolise lactose. Lactose intolerance is common in those parts of the world where humans do not consume any dairy products after weaning. In practice this means in Asia, which means that most of the world s population might be lactose intolerant. It is possible to produce lactose removed skim milk. Another approach with lactose is to hydrolyse it to its constituent monosaccharides. As well as avoiding lactose intolerance this allows a syrup to be produced from cheese whey. These syrups are offered as an ingredient for toffees and caramels. 

Lactobacillus preparation is intended to replace colonic microflora. This supposedly restores intestinal functions and suppresses the growth of pathogenic microorganisms. However, a dairy product diet containing 200 to 400 g of lactose or dextrin is equally effective in recolonization of normal flora. 

The same functions used in agriculture can be applied to processed foods. In baked goods, wheat gluten, various additives, starch damage, and water absorption are just some of the parameters measured [21-24]. Dairy products are also important and often analyzed by NIR. Moisture, fat, protein, lactose, lactic acid, and ash are common analytes in the dairy industry [25-28]. 

On Ca +-form columns, some separation of monosaccharides is possible and, for the separation of galactose and glucose in dairy products, this is the column of choice. The separation of several disaccharides, such as sucrose plus maltose plus lactose, in sweetened dairy products cannot be accomplished on single-resin columns, however, and separation on amine-modified silica gel or on dual-resin columns " is recommended. These columns are capable of separating the five major food sugars, namely, D-glucose, D-fructose, sucrose, maltose, and lactose, but are subject to rapid degradation if proper precautions are not used (see Section II,2,a). 

By pre-treating milk with lactase, all adults can enjoy milk and a whole range of other lactose-free dairy products can be made such as ice cream and yogurt. In the production of ice cream, lactose hydrolysis can also be used to improve certain properties such as the texture, sweetness and tendency to crystallize. The increased sweetness is also advantageous in the manufacture of flavored milk products because less sugar needs to be added. 

The tendency of lactose to form supersaturated solutions that do not crystallize readily causes problems in many dairy products unless adequate controls are exercised. The problems are due primarily to the formation of large crystals, which cause sandiness, or to the formation of a lactose glass, which leads to hygroscopicity and caking (Figure 2.9). 

Glucose-galactose syrups are about three times sweeter than lactose (70% as sweet as sucrose) and hence lactose-hydrolysed milk could be used in the production of ice-cream, yoghurt or other sweetened dairy products, permitting the use of less sucrose and reducing caloric content. However, such applications have not been commercially successful. 

The properties of many dairy products, in fact their very existence, depend on the properties of milk proteins, although the fat, lactose and especially the salts, exert very significant modifying influences. Casein products are almost exclusively milk protein while the production of most cheese varieties is initiated through the specific modification of proteins by proteolytic enzymes or isoelectric precipitation. The high heat treatments to which many milk products are subjected are possible only because of the exceptionally high heat stability of the principal milk proteins, the caseins. 

The water sorption characteristics of dairy products (like those of most other foodstuffs) are governed by their non-fat constituents (principally lactose and proteins). However, in many milk and whey products, the situation is complicated by structural transformations and/or solute crystallization. 

The sorption behaviour of a number of dairy products is known (Kinsella and Fox, 1986). Generally, whey powders exhibit sigmoidal sorption isotherms, although the characteristics of the isotherm are influenced by the composition and history of the sample. Examples of sorption isotherms for whey protein concentrate (WPC), dialysed WPC and its dialysate (principally lactose) are shown in Figure 7.13. At low aw values, sorption is due mainly to the proteins present. A sharp decrease is observed in the sorption isotherm of lactose at aw values between 0.35 and 0.50 (e.g. Figure 7.13). This sudden decrease in water sorption can be explained by the crystallization of amorphous lactose in the a-form, which contains one mole of water of crystallization per mole. Above aw values of about 0.6, water sorption is principally influenced by small molecular weight components (Figure 7.13). 

Cooling solutions to below their freezing point results in the formation of ice. If solutions of sugars are cooled rapidly, non-equilibrium ice formation occurs. This is the most common form of ice in frozen dairy products (e.g. ice-cream). Rapid freezing of ice-cream mixes results in the freeze concentration of lactose and other sugars, resulting in supersaturated solutions if the temperature is too low to permit crystallization. The rapid cooling of lactose results in the formation of a supersaturated, freeze-concentrated amorphous matrix. 

Gould, I.A. (1945) Lactic acid in dairy products. III. The effect of heat on total acid and lactic acid production and on lactose destruction. J. Dairy Sci., 28, 367-77. 

Although < 12% of the species of yeast use lactose (see Table III), this utilization is of commercial interest, as /3-D-galactosidase (EC 3.2.1.23) from yeasts may be used to lower the lactose content of dairy products, such as whey from cheese-making (for example, see Ref. 359) or milk itself.380... 

Structural components of lactose Lactose is a disaccharide that consists of galactose and glucose. Milk and other dairy products are the dietary sources of lactose. 

Beebe, J. M. and Gilpin, R. K. 1983. Determination of a-and (3-lactose in dairy products by totally aqueous liquid chromatography. Anal Chim. Acta 146, 255-259. 

Perry, N. A. and Doan, F. J. 1950. A picric acid method for the simultaneous determination of lactose and sucrose in dairy products. J. Dairy Sci. 33, 176-185. 

Detailed studies on the growth rates of the individual faces of a-lactose crystals have appreciably increased our understanding of the crystallization process. All the habits of lactose crystals found in dairy products are crystallographically equivalent to the tomahawk form different relative growth rates on the crystal faces account for the var-... 

In dairy products, crystallization is more complex. The impurities (e.g., other milk components), as far as lactose is concerned, may interfere with the crystalline habit. As a result, the crystals tend to be irregularly shaped and clumped, instead of yielding the characteristic crystals obtained from simple lactose solutions. In some instances, the impurities may inhibit the formation of nuclei and thus retard or prevent lactose crystallization (Nickerson 1962). 

The crystallization principles previously discussed are applied in processing dairy products, such as sweetened condensed milk, instant milk powder, stabilized whey powders, lactose, and ice cream. 

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