PHYSICO-CHEMICAL CHANGES OF WATER AND HYDRATION OF PROTEIN COMPLEX WHEN FREEZING CHEESES

• Main Authors: Buaynov O.N., Buaynova I.V.
• Format: Article
• Language: Russian
• Published: Kemerovo State University 2015-12-01
• Series: Техника и технология пищевых производств
• Subjects: freezing; strongly bound moisture; low temperatures; cheeses; casein; hydrophilicity; frozen-out water
• Online Access: http://fptt.ru/stories/archive/39/2.pdf

The work deals with regularities and physical and chemical nature of the phase transition of water to ice and the condition of bound water when freezing semi-hard cheeses in the range of ultra-low temperatures from -20 deg. C to -50° deg. C, as well as the factors of cheese resistance to freezing and low temperature storage. The authors investigated three main subclasses of semi-hard cheeses with high and low temperatures of the second heating, which belong to high-fat or semi-fat chesses in terms of the mass fraction of fat in total solids. Studies on the experimental stand to obtain the basic laws of quick freezing at different modes of the air environment were conducted. The intensity of heat removing was determined by airflow rate in the cooling zone that was regulated up to 10 m/s. Samples of finely packaged cheese with the weight of 0.2 kg were frozen up to the specified temperature of -20 deg. C and -12 deg. C. The results of stage-by-stage phase turning of water to ice, depending on the values of low temperatures have been obtained. Analysis of the kinetics of the process showed a gradual transition of differently bound water into ice in accordance with its binding energy in descending order. Based on the analysis of the experimental data, phase diagrams of water condition depending on the final average temperature of frozen cheeses have been drawn and the data on the degree of hydration of the protein complex in the temperature range from -20 deg. C to -70 deg. C have been obtained.