The possibility of using protein concentrates and isolates instead of milk solids-not-fat (MSNF) in the production of ice cream with a high mass fraction of milk fat (12%) and increased mass fraction of protein was investigated and justified in this article. The ice cream samples with use of milk protein concentrates (MPC), whey protein concentrates (WPC), milk protein isolates (MPI) and native whey protein isolates (NWPI) were made according to classical technology. Ice cream samples were analyzed by their quality indices. Viscosity and texture of samples were studied by the rheological methods; the overrun was calculated. The microstructural properties, such as dispersion of ice crystals and air bubbles were investigated by the light microscopy. The sensorial properties were analyzed by 6 certified panelists. The reduction in viscosity by 9-74% with use of MPC, WPC and MPI and the increase by 96% with use of NWPI were noted. It was found that replacement of MSNF reduced the overrun by 36-67%. Study of microstructure showed that with use of protein isolates, mean size of ice crystals was reduced and with use of protein concentrates was increased. The increasing in mean size of air bubbles with use of NWPI was established. The studied textural parameters were increased with use MPC and MPI. The hardness and adhesiveness with use of NWPI were increased. The sensorial properties of samples with replacement of MSNF were not worse than with use of MSNF. It has been established that the replacement of MSNF with concentrates and isolates of milk and whey proteins can be an effective way to increasing the protein content in ice cream while maintaining or improving its sensory properties.

The present work aimed to investigate the effect of a newly proposed mixture of quinoa seeds and tiger nuts (QTM) (1:1) on low-fat beef patties. The chemical composition, vitamins, minerals, and antioxidant activity of QTM were determined. The chemical composition, water-holding capacity, cooking loss, and sensory evaluation of low-fat beef patties prepared with 10% QTM as a partial fat replacer were also studied. Microbiological quality of frozen minced meat semi-finished products (burger patties, at -18°C) for 126 days was also determined. Based on the results, QTM contained 14.35% lipid, 9.37% protein, and 11.38% dietary fibre. Moreover, QTM also contained good amount of minerals and vitamins. The antioxidant activity of QTM was 20.41 mg/g. Results also showed that the addition of QTM had a positive effect on the sensorial quality of beef patties. Chemical composition, water-holding capacity, cooking loss, and pH profiles of newly formulated burger patties significantly improved following the addition of 10% QTM as a partial fat replacer. During the storage of semi-finished products, thiobarbituric values showed that the newly formulated beef patties had a lower level of lipid oxidation as compared to control. With lower microbial loads and lipid oxidation, the shelf life of the newly formulated beef patties also significantly increased as compared to control. As the conclusion, QTM could be applied as a functional component in meat products.

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A BST R ACTThe results of studies of physical changes of the structure of milk ice cream at fat content of 4.0 % -6.0 % and frozen whipped fruit desserts at different degree of overrun with/without addition of whey and whey protein concentrate are given in the paper. It is shown that the storage temperature affects the dispersion of structural elements of frozen whipped fruit desserts. An average size of air bubbles of frozen whipped desserts stored at minus 18 °C is 1.2 -1.4 times larger than the size of the bubbles of the samples stored at minus 25 °С. The average size of ice crystals increased 1.4 times after 9 months of storage at minus 18 °C. The average size of air bubbles of ice cream at 4 % fat content increased 1.5 times after 6 months of storage, and the ice crystals size increased 1.1 times. It is recommended to use the storage temperature below minus 25 °С to keep the quality of ice cream and frozen whipped desserts. Milk ice cream and frozen fruit desserts are recommended to be stored at minus 18 °С during not more than 6 months.FOR CITATION: Sitnikova P.B., Tvorogova A.A. Physical changes in the structure of ice cream and frozen fruit desserts during storage. Food systems. 2019; 2(2): 31-35.

The determination of the technological functionality of milk fat particles in terms of their effect on the nucleation in ice cream plombir with a mass fraction of milk fat of at least 15% was the aim of the study. this work was carried out to justify the possibility of producing ice cream without emulsifiers — components that stabilize the air phase. It has been established that milk fat, with content of at least 15% in the ice cream, as a structural element of the system, positively influences the effective viscosity, which optimal value is necessary for the distribution of structural elements in ice cream. Besides the particles of milk fat in plombir are partially demulsified and there-fore are involved in the stabilization of the air phase because of their presence in a higher quantity if to compare with other types of ice cream due to its fragile protein-lipid shell. It promotes also the nucleation of ice crystals, thus ensuring their high dispersity. As stabilizers of the structure the products of physical modification are used, which firmly hold water in the structure, including after temperature fluctuations. the practical importance of the research was found in the development of ice cream plombir technology without the use of emulsifiers — a product without food additives or with a limited use of them.