Influence of different acids on pH changes of heat-treated skim milk with formed complex casein/whey protein
2000
Macej, O.D. | Jovanovic, S.T. | Vukicevic, D.M. | Denin, J.D. (Poljoprivredni fakultet, Beograd - Zemun (Yugoslavia))
The skim milk has been subjected to high heat treatment (95 deg C during 20 min) to form chemical complex between casein and whey proteins (coaggregates of milk proteins). Influence of the addition of two organic (lactic and acetic) and two inorganic (HCl and H2SO4) acids on the rate of pH changes of heat-treated skim milk and formation of co-precipitates have been investigated. Addition of 7 ml HCl and about 7.2 ml H2SO4, respectively, reduces pH of heat-treated skim milk to 4.6. The buffer capacity of skim milk is lower in relation to these acids, when pH decreased below 4.5. On the other hand, lactic and acetic acids indicated significantly slower pH reduction of heat-treated skim milk. The milk buffer capacity to these acids is particularly significant below pH 5.0. At pH below 4.85 buffer capacity is greater to acetic than to lactic acid. Titration curves become parallel with abscise with further pH reduction below 4.40 for acetic, and 4.05 for lactic acid, which indicates that the milk buffer capacity is greatest in this pH region of these acids. For production of co-precipitates, all four acids can be used, but when HCl is used, produced coprecipitates have two most important parameters necessary for application of co-precipitates, the smallest level of calcium and the best solubility.
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