Cheese heated milk

Kebary, K.M.K., El-Sonbaty, A.H. and Badawi, R.M. (1999). Effects of heating milk and accelerating ripening of low fat Ras cheese on biogenic amines and free amino acids development, Food Chem., 64, 67. 

Gels prepared from heated milk synerese poorly (assuming that the milk does coagulate). Such reduced syneresis properties are desirable for fermented milk products, e.g. yoghurt (milk for which is severly heated, e.g. 90°C x 10 min) but are undesirable for cheese. 

Hillier, R. M. and Lyster, R. L. J. 1979. Whey protein denaturation in heated milk and cheese whey. J. Dairy Res. 46, 95-102. 

Casein or Caseinogen. A white phosphoprotein occurring as a colloidal suspension in milk. It can be pptd by heating milk with an acid or by other methods. Casein is the principal ingredient of cottage or other cheeses. It is also used in manuf of plastics, paints, paper, synthetic fibers, etc... 

In cheese making, milk is initially heated to kill bacteria and then cooled. A starter culture of Streptococcus bacteria is then added, which coagulates the milk into curds and whey (Figure 7.21). The curds are put into steel or wooden drums and pressed and allowed to dry. 

The Karl Fischer method is applied in a multitude of substances from finished products (butter, cheese, dried milk sugar, etc.) to solvents and other industrial products (paper, gas, petroleum, plastic films, etc.). Solids and not soluble samples must, prior to the measurement, either be ground into powders, extracted with anhydrous solvents, eliminated as azeotropes or heated to evaporate the water in special accessories. The only difficult cases are encountered with strongly acidic or basic media since they denature reactants as well as ketones and aldehydes which perturb the titration through formation of acetals (special reagents must be used for these instances). 

Huppertz, T., Hinz, K., Zobrist, M.R., Uniacke, T., Kelly, A.L., and Fox, PR 2005. Effects of high pressure treatment on the rennet coagulation and cheese-making properties of heated milk. Innovative Food Science and Emerging Technologies 6 279-285. 

The control of the quality of milk delivered at a cheese factory is as important as any part of the process of cheese making of the factory. Milk control at the cheese factory is even more important than at the creamery as pasteurization which has become so useful to the creamery-man has not been so satisfactorily applied to the making of cheese. This is on account of the off flavors caused by making cheese from heated milk and the effect of heat on curd-forming. 

Milk Proteins. As some milk proteins will gel on heating and others can be modified to make whipping agents it has long been thought that milk proteins could be used as whole or partial substitute for egg proteins. Purified whey proteins were regarded as a suitable raw material as whey is a low value by-product from cheese making. Early... 

The predominant amines found in cheese are tyramine, cadaverine, putrescine and histamine (Table 6.6) (Stratton et ah, 1991 Silla Santos, 1996 Novella-Rodriguez et ah, 2002 Novella-Rodriguez et al., 2003). Biogenic amine levels may vary between types of cheese as well as within the varieties themselves. The differences within a variety of cheese may be due to a number of factors, including manufacturing processes, bacterial counts in the milk, heat treatments used, use of starter cultures, and the duration and conditions of the ripening process (Stratton et al., 1991 Pinho et al., 2001 Novella-Rodriguez et al., 2003). 

Effect of milk heating on peptide formation during cheese ripening... 

The book assumes a knowledge of chemistry and biochemistry but not of dairy chemistry. As the title suggests, the book has a stronger biochemical orientation than either Principles of Dairy Chemistry or Dairy Chemistry and Physics. In addition to a fairly in-depth treatment of the chemistry of the principal constituents of milk, i.e. water, lactose, lipids, proteins (including enzymes), salts and vitamins, various more applied aspects are also covered, e.g. heat-induced changes, cheese, protein-rich products and the applications of enzymes in dairy technology. The principal physical properties are also described. 

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. 

Traditionally, milk was paid for mainly on the basis of its fat content but milk payments are now usually based on the content of fat plus protein. Specifications for many dairy products include a value for protein content. Changes in protein characteristics, e.g. insolubility as a result of heat denaturation in milk powders or the increasing solubility of cheese proteins during ripening, are industrially important features of these products. 

Acid phosphomonoesterase Hydrolysis of phosphoric acid esters Reduce heat stability of milk cheese ripening... 

Cathepsin D (EC3.4.23.5). It has been known for more than 20 years that milk also contains an acid proteinase, (optimum pH ss 4.0) which is now known to be cathepsin D, a lysozomal enzyme. It is relatively heat labile (inactivated by 70°C x 10 min). Its activity in milk has not been studied extensively and its significance is unknown. At least some of the indigenous acid proteinase is incorporated into cheese curd its specificity on asl- and / -caseins is quite similar to that of chymosin but it has very poor milk-clotting activity (McSweeney, Fox and Olson, 1995). It may contribute to proteolysis in cheese but its activity is probably normally overshadowed by chymosin, which is present at a much higher level. 

The strength of the rennet-induced gel is also adversely affected by heat treatment of the milk, again presumably because the whey protein-coated micelles are unable to participate properly in the gel network. Gels from severely heat-treated milk have poor syneresis properties, resulting in high-moisture cheese which does not ripen properly. Syneresis is undesirable in fermented milks, e.g. yoghurt, the milk for which is severely heat-treated (e.g. 90°C x 10 min) to reduce the risk of syneresis. 

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