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THE CHANGE OF CASEIN DURING STORAGE OF COOLED MILK AND ITS INFLUENCE ON THE QUALITY OF FERMENTED DAIRY PRODUCT


POLINA I. GUNKOVA, ALINA S. BUCHILINA *, ALEKSANDER L. ISHEVSKIY, ALEXEY S. FEDOROV
ITMO University, Faculty of Food Biotechnologies and Engineering, 49 Kronverksky Pr., Saint-Petersburg, 197101, Russia
*Corresponding author: alina.buchilina@yandex.ru

Issue:

SCSCC6, Volume XXI, No. 1

Section:

Volume 21, No. 1 (2020)

Abstract:

The duration of raw cooled milk storage until processing has a big influence on the properties and quality of fermented dairy products. Proteins undergo significant changes. At low temperatures, β-casein is removed from casein micelles to the milk plasma. As a result, the size of micelles decreases; under the enzymes` action, β-casein breaks down into γ-casein and components of the proteose-peptone fraction. The increase of γ-casein content and proteose-peptone fraction has a negative influence on the rate of proteins` acid coagulation, syneresis properties, milk heat resistance as well as other functional milk properties. Moreover, under the action of native and microbial proteinases in raw cooled milk during its prolonged storage, bitter peptides are formed, likewise amino acids break down into compounds with unpleasant putrid taste and odor, which can be transferred to fermented dairy products. This article shows the changes in the size of casein micelles during the refrigerated milk storage at temperature 4 ± 2 °С by 2 - 8 %; the concentration of casein γ-fraction by 23 - 25 %; milk heat resistance and total bacterial count. The results of the carried-out experiments let to sum up that the use of milk stored for 24 hours after acceptance decreases effective viscosity of a product by 27 - 31 %, water holding capacity by 30 - 32 %, together with the acquiring of off-flavor and bitterness by the final fermented dairy product.

Keywords:

milk heat resistance, milk storage, size of casein micelles, total bacterial count, γ-casein.

Code [ID]:

CSCC6202001V01S01A0007 [0005095]

Note:

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