Cheese-making properties

K-casein also contains two Cys residues per monomer subunit and is thus capable of interacting with the whey proteins, e.g., mainly g-lactoglobulin, via the disulfide interchange mechanism at temperatures at or above 65°C. This latter phenomenon is believed to be important in providing colloidal stability to the milk casein micelle system, as well as to the whey proteins, in high temperature processed milk products. It has also been postulated that this latter interaction with g-lactoglobulin may alter the availability of K-casein in the micelle, and thus has a detrimental effect upon the cheese making properties of milk (4). 

Lopez-Fandino, R., Carrascosa, A.V., and Olano, A. The effects of high pressure on whey protein denaturation and cheese-making properties of raw milk, /. Dairy Sci, 79, 929,1996. 

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. 

Enzymes are the catalysts evolved in nature to achieve the speed and coordination of a multitude of chemical reaction necessary to develop and maintain life. Chemical reactions are far too slow to be effective under the conditions prevalent in normal living systems - aqueous environments with neutral pH values and temperatures between 20 and 40 °C. Even catalysts developed in the chemical industry fall short enzymes in comparison achieve up to 107 - fold faster reaction rates. Mankind has utilized enzymes empirically since ancient times for the conservation or production of food, e. g. in cheese making or brewing. A historical background is given in Table 1-1. The catalytic properties of enzymes were recognized long before their chemical nature was known. We stil. use acceleration of reaction rate to search for unknown enzymes as well as to measure and quantify enzyme activity. 

Despite the many studies characterizing the biochemical nature of starter growth, there is a dearth of information on the nature and importance of the various cheese making techniques, and yet these are clearly essential for the definition of desirable starter properties. 

It is necessary here to consider the type of research which these methods may be used for. Historically, techniques for building models, both physical and mathematical, to relate biologicsd properties to chemical structure have been developed in pharmaceutical and agrochemical research. Many of the examples used in this text are derived from these fields of work. There is no reason, however, why any sort of property which depends on chemical structure should not be modelled in this way. This might be termed quantitative structure-property relationships (QSPR) rather than QSAR where A stands for activity. Such models are beginning to be reported recent examples include applications in the design of dyestuffs, cosmetics, egg-white substitutes, artificial sweeteners, cheese-making, and prepared food products. I have tried to incorporate some of these applications to illustrate the methods, as well as the more traditional examples of QSAR. 

In a sense, propionic acid bacteria are domesticated bacteria. They might have been used for cheese making as early as 9000 years BC. In the last 40 years their practical uses have expanded to include vitamin Bn and propionic acid production, bread baking, starters for ensilage and some pharmaceutical preparations. New prospects for their future uses are also emerging, based on the useful properties recently discovered. 

Changes in the composition, structure and properties of milk proteins (caseins and whey proteins) occur during pasteurisation, sterilisation and especially during fermentation, drying and thickening of milk and in cheese making. 

Salts. Rochelle salt is used in the silvering of mirrors. Its properties of piezoelectricity make it valuable in electric oscillators. Medicinally, it is an ingredient of mild saline cathartic preparations, eg, compound effervescing powder. In food, it can be used as an emulsifying agent in the manufacture of process cheese. 

Citrate salts have long been used in the processed cheese industry as "emulsifying salts," and there is still interest in the mechanism of their action. Shirashoji et al. (2006) examined the effects of trisodium citrate on the properties of processed cheese. Increasing concentration of sodium citrate decreased the size droplets of the cheese. This effect is typical when emulsifying properties of a system are improved. This is expected as the complexation of calcium by citrate causes dissociation of the casein micelle, making the casein more available for emulsifying fat droplets. This possibly contributed to the reinforcement of the structure of the processed cheese. 

---