Fluid milk production components

Nutritional Value of Milk Products. Milk is considered one of the principal sources of nutrition for humans. Some people are intolerant to one or more components of milk so must avoid the product or consume a treated product. One example is intolerance to lactose in milk. Fluid milk is available in which the lactose has been treated to make it more digestible. The consumption of milk fat, either in fluid milk or in products derived from milk, has decreased markedly in the 1990s. Whole milk sales decreased 12% between 1985 and 1988, whereas the sales of low fat milk increased 165%, and skimmed milk sales increased 48% (35). Nutritionists have recommended that fat consumed provide no more than 30 calories, and that consumption of calories be reduced. Generally, a daily diet of 2000—3000 cal/d is needed depending on many variables, such as gender, type of work, age, body responses, exercise, etc. Further, there is concern about cholesterol [57-88-5] and density of fat consumed. Complete information on the nutritive value of milk and milk products is provided on product labels (36) (see also Table 4). 

The process for cholesterol removal from anhydrous milkfat was patented by General Mills (41). Fractionment Tirtiaux also disclosed the development of a vacuum steam distillation system called the LAN cylinder (38). The steam distillation process (Figure 2) was commercialized, producing a 90-95% cholesterol reduction in anhydrous milkfat with a 95% yield that was reconstituted into 2% fat fluid milk (42). The major disadvantage to the process is that it strips or removes most all volatile flavor components from the fat. These flavor components must be captured (i.e., vacreation) before the distillation process to attempt to reproduce the delicate flavors so desired for reconstitution into a butter product. 

Although in fluid milk the phospholipid fraction is more susceptible to oxidation than the triacylglycerol fraction, in dry milk products, the triacylglycerol fraction is more susceptible to oxidation and the phospholipids act as antioxidants. Thus, solvent-extracted milkfat containing phosphohpids is much more stable to oxidation than milkfat free of phospholipids, obtained by melting churned butter (also called butter oil). The susceptibility of milk phospholipids to oxidation appears to be dependent on whether they are suspended in water or fat. This difference of oxidahve stability influences the development of different flavor defects in various dairy products. With butter, which is a water-in-oil emulsion system containing an aqueous phase of phospholipids dispersed in fat, the phosphohpids oxidize more readily than the triacylglycerol components. 

The volatile carbonyl compounds developed from milk fat oxidation are detectable at extremely low levels (parts per bilhon). Flavor compounds are less volatile and mainly retained by the fat component. These compounds are thus much more easily perceived in milk, where they have much lower threshold values (0.004-0.1) than in oil systems (0.1-2.5). Because flavor compounds are very easily perceived in milk products, they can be detected at extremely low levels of oxidation. Fluid milk becomes rancid at peroxide values less than one. 

An active substance, although initially released from its dosage form (and dissolved), may become unavailable for absorption due to reactimis with other medicines or food components [4]. An example is the formation of insoluble complexes of tetracycline with calcium or aluminium ions from antacids or milk products. Interaction (chelation or binding) with iron ions leads to a reduced absorption for a variety of active substances such as doxycycline, penicillamine, methyldopa and ciprofloxacin. The absorption of active substances showing pH-dependent dissolution behaviour may be influenced by medicines that influence the gastric pH, such as H2-antagonists, proton pump inhibitors and antacids. Antimycotic active substances such as ketoconazole or itraconazole dissolve better in acidic fluids. Therefore their bioavailability may be increased by the concomitant use of an acidic drink like cola, whereas the concomitant use of antacids or proton pump inhibitors is likely to reduce the bioavailability. Concomitant use of milk may increase the dissolution of acidic active substances, whereas fats from food may increase the bioavailability of lipophilic active substances like albendazole and griseofulvin. 

In the food production and OTC (Over the Counter) Drug industries, like milk, soups, cough syrup, and juices, outside balanced seals are quite popular. Their design permits easy cleaning of the equipment without pump disassembly. These seals are prominent in the chemical processing industry because all metal components in the seal are located outside the fluid. This avoids problems of galvanic eorro.sion. 

The nature of competition in multi-protein systems is a question of great interest which is touched on by a considerable number of the papers in this volume. Such interest is understandable in that many of the areas of application involve adsorption from complex media for example blood, plasma or serum, tear fluid and other body fluids, soil, milk, and food products generally. The information normally sought concerns the concentration profile of the proteins on the surface and how this is related to the concentration "profile" in the bulk phase. In general there is a redistribution of proteins in the surface phase, resulting in an enrichment of some components and an impoverishment of others relative to the bulk phase. The redistribution may also be time dependent and the kinetics as well as the equilibrium aspects are of interest. 

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