This paper presents a study of the processing of collagen-containing raw material and its changes in the course of targeted complex processing by hydrolysis, including freeze-drying. The pH, chemical composition, penetration magnitude, and critical shear stress were determined. The dried samples were examined using Fourier-transform infrared spectroscopy, and their microstructures were characterized. The characteristic property of the product developed was determined to be the presence of a relatively homogeneous fibrillar structure that promotes the functional capacity of the proteinoid-forming fibres in the compositions of foods from different groups.

The research is devoted to the use of a cod skin hydrolysate as a component of citrus fruit beverages. It is demonstrated that the addition of a hydrolysate increases the content of protein in the beverage, slightly increases the viscosity of the beverage, and does not adversely affect its sensory characteristics. Hydrolysate is produced by enzymatic treatment of cod skin. The processing parameters allowing achieving the desired degree of destruction are determined. Physico-chemical parameters and sensory analyses of the obtained hydrolysate and its amino acid composition were analyzed. The influence of collagen hydrolysate on the physical and chemical composition of beverages, their structural and mechanical characteristics (pH and viscosity) and sensory analyses are estimated.

Initially the total antioxidant activity, the total flavonoid contents, the total phenolic contents and the ascorbic acid were measured in fresh fruits. Then samples for freezing and vacuum freeze-drying were frozen what led to a decrease in total antioxidant activity by 11% (persimmon)-28% (kiwi fruit), a reduction of total phenolic and total flavonoid contents for about 10% and the content of ascorbic acid decreases by 8% (kiwi fruit)-30% (apple). The remaining frozen purees were subjected to vacuum freeze-drying at the temperature plus 25-27 ºC and a chamber pressure of 80 Pa in the primary drying and the temperature plus 38-40 ºC and a chamber pressure of 80 Pa at the secondary drying. The total antioxidant activity of freeze dried samples in comparison with fresh fruit decreased by 20% (persimmon)-50-55% (apple), the total content of flavonoids and phenolic compounds decreased by 20-30%, reduction of the ascorbic acid ranged from 23-29% (apple and persimmon) to 55% (pear). The other part was subjected to convective drying and as a result the total antioxidant activity decreased by 46% (persimmon) to 68% (pear and apple), the total content of flavonoid contents compounds decreased by 42% (apple, kiwi, persimmon)-56% (pear). The total content of phenolic compounds in all samples decreased by 40-45% and the content of ascorbic acid reduced by 45-55%. The study results demonstrated that the antioxidant properties of the fruits studied in the following order: fresh fruit> frozen fruit> freeze-dried fruit> convective dried fruit.

Информация о статьеПоступила в редакцию 24.03

Fresh fermented milk products have a limited shelf life that can be extended by vacuum freeze-drying. Cryoprotectants are used to increase the survival of lactic acid microorganisms during freeze-drying. The most effective cryoprotectants are those of natural origin. Literature offers little information on the cryoprotective effects of fruit and vegetable purees. Therefore, we aimed to evaluate the effectiveness of fruit and vegetable purees in increasing the survival of lactic acid microorganisms during the freeze-drying and storage of fermented milk products. We studied bioyogurt samples containing pumpkin, fig, and banana purees. Rational modes of freezing and freeze-drying were established on the basis of thermal analysis. The cryoscopic temperature was determined by differential scanning calorimetry. The proportion of frozen moisture was calculated using the Nagaoka formula. Standard methods were employed to evaluate the sensory characteristics of bioyogurts and determine their protein, fat, and non-fat milk solids contents, as well as titratable acidity and microbiological indicators. The addition of pumpkin puree increased the cryoscopic temperature and reduced the freeze-drying stage and the total drying time by 13 h, depending on the amount of puree. However, the addition of sweet fig and banana purees decreased the cryoscopic temperature and increased the freeze-drying stage and the total drying time by 0.5–1.5 and 1.5–3 h, respectively. Based on the sensory evaluation of the freeze-dried bioyogurts, we selected the formulations with 15% of pumpkin and fig purees and 10% of banana puree. We found that the freeze-dried bioyogurts with puree had higher counts of lactic acid bacteria compared to the control. In the freeze-dried samples, the counts were higher at a storage temperature of 4 ± 2°C than at 20 ± 2°C. Pumpkin puree provided the best survival of lactic acid microorganisms during freeze-drying and storage.