The study objects were the Republic of Kazakhstan selection apple sorts: “Baiterek”, “Sarkyt” and “Saya”, also pear sorts: “Syilyk”, “Zhazdyk” and “Nagima”. Study of the process of moisture evaporation within vacuum drying of the fruits has essential value in the nutritional value saving. Basically, the product evaporative capacity is characterized by the evaporation resistance coefficient ‒ µ. Also during moisture removal, thermodynamic state of moisture changes that is described by water activity indicator ‒ aw. Experimental determination of these parameters allows for the analyzing moisture evaporation during vacuum drying process. Studies have established the following evaporation resistance coefficients: µ=2.03±0.07 for apple sorts and µ=2.3±0.05 for pear sorts. Either water activity decreases from 1.0 to 0.62±0.01 for apple sorts and from 1.0 to 0.65±0.04 for pear sorts. Two drying periods are discovered. The first drying period: 5.45–6.10 h for apple sorts; and 6.12–6.25 h. for pear sorts. The second drying period duration: 4.15–3.50 h for apple sorts; and 4.35–4.48 h for pear sorts. The critical humidity value: 27.1±2.1 % for apple sorts; and 30.1±2.5 % for pear sorts. Comparative analysis of calculated and experimental data shows maximum deviations 22.5 % for apple sorts and 23 % for pear sorts. The proposed equation for the calculating a moisture evaporation rate, considering the product properties and the hygroscopic parameters of air, can be used in practice to study the moisture evaporation dynamics from the product surface. The study results allow for the selecting an optimal mode for vacuum drying of apples and pears sorts in order to safe nutritional value and to produce biologically active additives for the food industry
The article develops a methodology for conducting experimental studies on vacuum drying of varieties of apples, pears and raspberries growing in the southern regions of the Republic of Kazakhstan. Experimental studies and analysis of the influence of regime parameters on the drying process of selected products have been carried out, depending on the height of the layer of the dried material, the degree of grinding of raw materials, the degree of heating of the dried material and the pressure of the medium in the evacuated chamber.The analysis of the obtained drying curves for apples, pears and raspberries, in the initial state having a liquid paste-like mass, at the pressure in the vacuum chamber of 0.008 MPa, the loading height of 3, 4 and 5 mm, the degree of heating of the dried material - about 40 ° C, previously selected for research, shows that they have a similar character - all drying curves have quite clearly defined segments: the period of establishing regime parameters or the period of the beginning of drying, the period of constant drying rate and the period of decreasing drying rate.The results of experimental studies are generalized and based on them, equations describing the dynamics of moisture evaporation from the surface of products in the form of fourth-degree polynomial equations are obtained.
Relevance. In general, phenolic compounds are aromatic compositions, where a benzene ring is associated with one or more hydroxide groups. All phenolic compounds are divided into groups by structure and fragment’s type. There are more 10 000 types of different phenolic compounds structures that are found in plants raw materials and food products. The studies covered in the article are relevant, both from the point of view of scientific novelty, and to substantiate the benefits of consuming cherries of new varieties of Kazakhstan breeding.The purpose of the study is to analyze the content of polyphenols and flavonoids in the cherries of Kazakhstan selection.Research objectives: to collect theoretical data, apply research methods to determinethe content of polyphenols and flavonoids in the laboratory, to draw relevant conclusions.Methods. For the study of physico-chemical and chemical indicators of the total polyphenols and total flavonoids contents, following sweet cherry varieties of the Kazakhstan selection were considered: Aigerim, Lyazat and Merei. Following physico-chemical indicators were studied: solids content, total sugars and titratable acidity. It was found that among the considered sweet cherry sorts, the highest values had variety Lyazat, specifically in the chemical indicators: sugar-acid index, ascorbic acid (vitamin C) content, total polyphenols and total flavonoids contents.Results. By the total polyphenols and flavonoids contents varieties Aigerim (866 μg/mL and 275 μg/mL), Lyazat(885 μg/mL and 290 μg/mL) and Merei (865 μg/mL and 255 μg/mL) are close to each other. In the considering relatively Lyazat, the Total polyphenols content, Aigerim and Merei have lowest data by 0.05% and 0.13%, respectively. Total flavonoids content of varieties values for Aigerim and Merei 0.05% and 0.22% — were also identified. In general, a review of all obtained data with the known values shows that indicators of the total polyphenols and flavonoids contents are with in the acceptable variations.
Relevance. Fruits and vegetables are an excellent source of substances with antioxidant and healthy properties. Such substances include polyphenols, carotenoids and triterpenoids. Phenolic compounds have strong antioxidant, anti-inflammatory, antiviral and anti-carcinogenic properties. Pear is the main fruit crop of regions with mild climate and have growing cultivation scales. Pear flavonoids contribute to the coloring of fruits, protect them against pathogens and are healthy ingredients of fruits. The purpose of the research is to analyze the content of flavonoids in pears of Kazakhstan selection.Methods. The methods used in the study are as follows: determining solids content (the found value is expressed in units of the mass fraction of sucrose in an aqueous solution of sucrose, which under given conditions has the same refractive index as the analyzed solution, in %) titratable acidity (determination of the mass concentration of titratable acids in terms of malic, tartaric or citric acids (μg/mL) was carried out using potentiometric titration with sodium hydroxide solution to pH = 8.1), total sugars (the permanganate method is based on the ability of sugar carbonyl groups to reduce copper (II) oxide to copper (I) oxide in an alkaline medium), sugar-acid index, ascorbic acid (vitamin C) content, total phenolic compounds content, total flavonoids content.Results. The comparison analyses shows Syilyk and Zhazdyk varieties have the highest values of studied traits,. Specifically, physico-chemical indicators: solids content, total sugars and titratable acidity. Also the best indicators are shown in biological active compounds: sugar-acid index, ascorbic acid (vitamin C) content, total phenolic content and total flavonoids content. The polyphenols content in all pear varieties have high values in the range 107–124 μg/mL. Extracts of Syilyk and Zhazdyk pears have highest values of biologically active substances, and might be recommended for the development of technology in order to obtain concentrates and to enrich the compositions of the food products.
Studies have established that various drying periods are observed during the drying process: for example, for apple varieties, the first drying period is 5.45...6.10 hours, and for pear varieties 6.12 ...6.25 hours. The duration of the second drying period for apple varieties is 4.15...3.50 hours, and for pear varieties 4.35...4.48 hours. The analysis of the drying curve showed that the boundary between the periods of constant and falling land velocity, i.e. the critical humidity for apple varieties is on average 27 ± 2.1%, and for pear 30.1 ± 2.5%. An analysis of the kinetics of moisture evaporation shows that in an apple during the first four hours of drying, on average, 2.71 g evaporates, and for the next two hours it decreases monotonically to 2.31 g. The same picture of moisture evaporation dynamics is also observed for pears: for the first four hours, on average, 3.41 g evaporates, and for the next two hours, the evaporation dynamics decreases to 2.78 g. Studies have established that the coefficient of evaporation resistance for apple varieties: Baiterek, Sarkyt and Saya is µ = 2.03 ± 0.07, for pear varieties: Sylyk, Zhazdyk and Nagima is µ = 2.3± 0.05.
The article studied the patterns of changes in water activity during vacuum drying of apple varieties: Baiterek, Sarkyt and Saya and pear varieties: Syilyk, Zhazdyk and Nagima. Studies have established that in all the studied varieties of apple and pear, the following pattern is observed: in the first four hours of the drying time, the water activity indicator decreases monotonously, and the subsequent drying time drops sharply. This pattern is explained by the fact that after four hours of drying time, part of the remaining weakly bound moisture is gradually removed from the product, and then the bound moisture. Studies have shown that dehydration of fruits, the water activity characterizing the qualitative properties of the product decreases: for apple varieties from 1.0 to 0.62 ± 0.01, for pear varieties this indicator decreases from 1.0 to 0.65 ± 0.04. On the basis of mathematical processing of experimental data, a power-law dependence of water activity on the duration of drying was established. The established pattern of changes in water activity from the duration of drying in subsequent works will be used to determine the optimal drying mode for apples and pears in order to produce high-quality dry powders for the food industry.
As the drying zone deepens, outer surface layer of the product does not have time to be moistened, due to a small amount of moisture coming from the inside. It becomes dry, its temperature rises. The intensity of moisture transfer from the inner layers of the product depends on many parameters, including a moisture diffusion coefficient. The study aim is to create a methodology for determining the moisture diffusion coefficient within vacuum drying of fruits, by taking into account cracks, channels and capillaries formed in the dry layer of the product through the resistance coefficient to evaporation. The work essence consists in the determining of the moisture diffusion coefficient as a driving force, a difference between water activity and air humidity, by considering the resistance coefficient to evaporation, characterizing the effect of hydrodynamic resistance of the dried dry layer of the product. This approach was used to determine the moisture diffusion coefficient during vacuum drying of the Baiterek apple sort and the Zhazdyk pear sort of Kazakhstani selection. It was established that in the first period of drying the moisture diffusion coefficient decreases on average from 24,4∙10‒7 m2/s to 13,2∙10‒7 m2/s. The critical humidity for pear is 37.4 %, and for apple 35.1 %. As result of the formation of dry layer on the surface and subsequent layers, the moisture diffusion coefficient gradually decreases. In the second drying period, the moisture diffusion coefficient decreases from 5,42∙10-8 m2/s to 2,12∙10‒8 m2/s. The work practical significance is related with the application of the obtained results in the determination of the optimal drying regime with maximum preservation of the product original quality. The proposed methodology can be used in the practice to study the moisture diffusion coefficient within vacuum drying of fruits, by considering the product properties and the hygroscopic parameters of the drying matter
Relevance. Apples and apple juices are healthy food products with a large amount of biologically active substances. The polyphenols contained in them are powerful natural antioxidants. They prevent the development of many chronic heart diseases and have many pharmacological properties. Thus, polyphenols increase the resistance of blood vessels, improve blood circulation, protect elastin and collagen fibers, and serve as fundamental elements supporting skin tissues. Apples contain such practically valuable substances as pectins. At the same time, in fresh apples, protopectin prevails over soluble pectin and makes up 52.3– 97.0% of the total amount.Methods. The objects of the study were the fruits of apple varieties: Voskhod, Talgar Bayterek, Sarkyt and Saya, as well as pear varieties: Bostandyk, Nagima, Sylyk, Zhazdyk. The fruits of apples and pears were harvested from September to mid-October 2021 in Saryagash district, in the farm "Tenge". Experimental data were obtained in the laboratory of the South-Kazakhstan University named after M. Auezov. At the first stage of the study, the quality of apples was determined in accordance with the requirements of GOST R 54697–2011. At the second stage, physico-chemical parameters were determined according to standard methods. The content of soluble solids was determined by the refractometric method using a refractometer, at ambient temperature 20±0.5 °C, The mass fraction of dry substances was determined by the refractive index. The sum of sugars — according to the Bertrand method.Result. Studies have established that the fruits of all studied varieties of apples and pears grown in Kazakhstan, according to organoleptic and physico-chemical indicators, contain high levels of chemicals and phenolic compounds, but the most valuable source of biologically active substances were apples of variety Baiterek and pears of variey Zhazdyk.
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