INVESTIGATION OF POTATO STORAGE QUALITY DEPENDING ON VARIETY PECULIARITIES

The aim of the research was to analyze an influence of variety peculiarities, different ripeness groups of potato of Dutch selection on storage quality. It has been established, that the output of commodity products in early varieties is in average 88.22±1.53 %, in middle-ripening ones – 96.87±1.09. Among the group of early-ripening varieties, there must be separated Kristina with the output of commodity products at the end of storage as 90.15 %. The lowest output of commodity products is in the variety of Tornado – 87.09. The variation coefficient of the commodity products output is 1.9 %, that is the commodity products output varies little. In the group of middle-ripening variety, higher storage quality was observed in varieties Elekta and Setanta. The commodity products output was 92.97 and 92.2 9 % respectively. Natural mass losses for the period of storage in tubers of all varieties were in average 4.2 %, among them 72.9 % at the expanse of moisture evaporation, and 27.1 % – at the expanse of breathing. In the group of early varieties, mass losses varied from 4.1 % Reports on research projects (2020), «EUREKA: Life Sciences» Number 6


Introduction
Potato is a very old crop. It was known just 14-15 thousand years ago at the territory of Southern America, where the population cultivated it from ancient times [1,2]. For today potato is the main food, fodder and technical crop. Tubers' food value is determined by high taste qualities and chemical composition, favorable for human health. Tubers contain from 14 to 22 % of starch, 1.5-3 % of proteins, 0.8-1 % of mineral substances, up to 1 % of cellulose. Potato starch is easily assimilated, and the biological value of its proteins is higher than one of other crops. Tubers contain many vitamins of the group В, РР, carotenoids. In winter periods potato is the main variety of vitamin C for humans. It is consumed for food boiled, fried, stewed [3,4]. 22 countries are considered main world producers of potato; 9 of them are situated in Europe, 5 -in Northern and Southern America, other -in the Asian-Pacific region [5]. The absolute leader is China. The gross harvest of potato exceeded 95 mln tons that were near one fourth of world indices [6].
As far as this crop is seasonal, the main mass of a newly collected harvest must be stored for a long time. Quality changes and mass losses take place at storage of potato. They depend on many factors, namely: weather conditions of the vegetation period, storage conditions, product quality parameters at the beginning of storage. It is necessary to note, that variety peculiarities and ripeness group are of great importance. We make a great mistake, storing tubers of early-ripening varieties. Even under ideal conditions potato is stored till November-December. Then it begins to sprout fast, losing its quality. It becomes unfit for food needs [7].
The correct choice of a variety mainly determines storage success. It is one of leading techniques in the complex of arrangements for organizing constant provision of the population with the "second bread".
Variety choice is the main factor for getting a high quality product. It has been established, that culinary properties, sensor indicators, flesh condition depend on variety peculiarities. The analysis of quality parameters of three potato varieties, cultivated in India, testifies that the higher quality parameters the less time of tubers boiling. Potato varieties Kufri Djoti and Kufri Badshakh absorb more water at boiling than tubers of the Pukhradj variety. The test for density renovation for boiled potato testifies that the Kufri Djoti and Kufri Badshakh varieties have higher density modules. The viscosity module of Kufri Djoti is higher than one of Kufri Badshakh and Pukhradj [8]. Byelorussian scientists produce chips and dry potato puree of the high quality (8-9 and 7 points respectively) of the varieties Bryansk delicates and Bryansk novinka [9].
It has been established, that technological conditions of potato in the period of storage depend on tubers' ripeness degree. Insufficient accumulation of reducing sugars at storage in a refrigerator allows to use potato without preliminary conditioning from September to March [12,13].
Tubers' storage quality depends on ripeness group. After seven months of storage the output of healthy tubers of early and middle-early varieties was 93.8 and 93.2 % respectively, middle-late and late -94.3 and 94.6 %.
At storage the content of dry substance, specific moisture, raw cellulose, potassium and phosphorus decreases. Among the studied varieties, the highest content of dry substance, specific moisture was obtained after storage in the Chala variety. The highest content of raw protein was in the Mashenadima variety. The results testify that tubers with high physical-chemical parameters preserve their properties longer [14,15].
Storage conditions are regulated for minimizing mass losses and ones of reducing sugars, ascorbic acid at a certain level, influencing further tubers' processing [16].
Based on methods and standards of their country, Czech scientists estimated the quality of 760 potato varieties, imported from different world countries. According to estimation criteria, the best were ones, created in France, FGR, Polish and Dutch varieties occupied the middle place. Varieties of the USA, Great Britain and CIS countries occupied the last place, connected with the essential darkening of flesh and mediocre taste [17].
So, a potato variety plays the main role in the total complex of techniques, conditioning the improvement of its storage quality.
At the present moment great attention must be paid to the question of storage quality of nutritive properties of tuber varieties in the storage period and revelation of best ones by the total complex of economic and consumption signs. The presented data demonstrate the necessity to study new potato varieties under storage conditions.
The aim of the research was to analyze an influence of variety peculiarities, different ripeness groups of potato of Dutch selection on storage quality. The research gives a possibility to decrease potato losses, to differentiate and to prolong its storage life.

Materials and methods for studying the intensity of natural mass losses of potato at storage
The storage was conducted with the early ripening potato varieties of Dutch selection: Banda, Kristina, Tornado, with middle-ripening: Setanta, Elekta, Savanna ( Table 1). The studies were conducted at PE "Potato of Poltava region" (v. Stavkove, Zinkivsky district) of the Forest-steppe of Ukraine.
The Dutch potato variety Kristina (Fig. 1) has the skin of an unusual dark-red color and cream flesh. It looks perfectly at shop shelves. It provides great interest and high popularity and also great success in final buyers. It also has high taste qualities. Due to the high content of starch and other nutritive substances, it is used for frying and salads [18]. The potato variety Savanna (Fig. 2) of Dutch selection has the perfect outlook and even skin, color of tubers is cream-white. It differs by even, massive tubers. It is one of best representatives of middle-ripening potato, provides high harvests [19].
The potato variety Tornado (Fig. 3) has the bright-engrained skin of bright-raspberry color. The flesh color is white. It provides great interest and high popularity and also great success in final buyers. The potato has a peasant taste. It is used for many dishes [20].  The Banba variety (Fig. 4) is a middle-ripening potato variety. Oval-oblong tubers with the dark-yellow skin. The flesh is light-yellow. The skin is even with fine eyes. It is a perfect variety for retail in super-markets. It has a pleasant taste. It is suitable for many dishes [21]. The Setanta variety (Fig. 5) is a middle-ripening potato variety. Tubers are even, of the oval form. The skin is even, of red color. The flesh is yellow. It differs by the high content of starch and dry substances. It is used for producing starch, chips, fried potato [22]. The potato variety Elekta (Fig. 6) of Dutch selection has tubers with a perfect outlook. The skin and flesh are of light-yellow coloration, even. The eyes' depth is small. Well-stored. It is used for many dishes [23].

Agricultural and biological sciences
Harvested potato was put in temporary storehouses with tidal-exhaust ventilation, covered with straw for a healing period at temperature 15…18 °С. In 2 weeks it was examined, sorted by hand, cleaned from soil, vegetable residues, fine, mechanically damaged, old tubers, injured by pests, ill were eliminated. Then potato was loaded in boxes and laid for storage in a stationary depository, equipped with mandatory ventilation. At the main storage period the temperature was kept within 3…5 °С and relative air humidity 90-95 %.  The experiments on potato storage were conducted according to "Methodical instructions for scientific-research works on vegetable storage" [24,25] Natural losses were determined by the formula Р=(Р 1 -Р 2 )×100/Р 1 , where Р 1 -mass at the beginning of storage, kg; Р 2 -mass after storage, kg.
Together with natural losses, there was determined technical spoilage, absolute spoilage, divided in losses at the expanse of sprouts and rotten.
The content of dry substances (dry mass) was determined by drying a potato batch to the constant mass at temperature 105 °С in a drying chamber according to [26].
At determining the chemical composition of tubers at the end to the determined storage term, the content of chemical substances was recalculated for the initial mass by the formula: where х -content of substances taking into account natural mass losses, %; а -content of substances at the end of storage, %; b -mass losses for the storage period, %.
The data, presented in the work, are the mean value of three measurements. The statistical analysis was conducted using Microsoft Excel 2007. Differences were considered statistically significant at the significance level α=0.05.

Results of studying the intensity of potato mass losses at storage
Storage as one of stages of commodity movement from a producer to a consumer provides quality and quantity preservation of a commodity with minimal losses, and also direct supply of a product to the population. Storage quality parameters are: standard product output, loss volume and storage term.
The potato mass at storage decreases. Natural losses take place at the expanse of dry substance decrease and water evaporation. Natural mass losses for the period of storage in tubers of all varieties were in average 4.2 %. At the expanse of dry substances -27.1 % .
In the group of early varieties, mass losses varied from 4.1 % in the Kristina variety to 5.1 % in the Banda one. There is the essential difference НІР 05 =0.31 % between the varieties by the mass Agricultural and biological sciences loss. Variation coefficient 7.4 % testifies to the small variation of mass loss in the studied potato varieties. The force of variety influence is 73 %.
In the group of middle-ripening varieties the mass loss varied with the middle force, variation coefficient -19.5 %. The lowest mass loss was observed in the potato variety Elekta as 3.28 % ( НІР 05 =0.55) % (Fig. 7). The standard product output and losses are reversely proportional that is the more losses the less output of standard products. Both storage quality parameters depend on conditions and terms of storage, variety peculiarities.
In average the commodity product output for all varieties for the storage period was 92.54 % of the initial mass ( Table 2). In the section of ripeness groups, the commodity product output in early varieties is in average 88.22±1.53 % (НІР 05 =1.78 %), in middle-ripening -96.87±1.09 (НІР 05 =0.72 %.) Each ripeness group contains varieties that demonstrated better output of commodity products. Among the group of early-ripening varieties, there must be separated Kristina with the output of commodity products at the end of storage as 90.15 %. The lowest output of commodity products is in the variety of Tornado -87.09. The variation coefficient of the commodity products output is 1.9 %, that is the commodity products output varies little. In the group of middle-ripening varieties, higher storage quality was observed in varieties Elekta and Setanta. The commodity products output was 92.97 and 92.29 % respectively. It has been established, that the commodity product output in early-ripening varieties of potato depends by 96 % on variety peculiarities, in middle-ripening ones -by 95 %.
Natural mass losses for the period of storage in tubers of all varieties were in average 4.2 %, among them 72.9 % at the expanse of moisture evaporation, and 27.1 % -at the expanse of breathing. In the group of early varieties, mass losses varied from 4.1 % in the variety Kristina to 5.1 % in the variety Banda. Variation coefficient 7.4 % testifies to the small fluctuation of mass losses in the studied potato varieties.
In the group of middle-ripening potato varieties, mass losses varied with the middle force, variation coefficient 19.5 %. The lower mass loss was observed in the potato variety Elekta as 3.28 %.
Losses were distributed in such a way: in the early varieties 39.6 % are natural losses, 34.4technical spoilage and 26 % -absolute spoilage (Fig. 8). In the group of middle-ripening potato varieties, there was observed the ratio of typical and total losses: natural losses were 47.3 %, technical spoilage 32.0 %, absolute spoilage 20.7 % (Fig. 9). 39  It has been established, that natural losses of the potato mass at storage in the structure of total ones prevail over other types of losses (39.6 and 47.3 %). In average 27-30 % of natural losses take place at the expanse of dry substance. The studies have established that dry substance losses decrease in varieties of the early group in average by 13.8 %, in ones of the middle-ripening group -by 3.7 % of the initial content ( Table 3).
The least losses of dry substances among the studied varieties were in the variety Setanta -3.7 % comparing with the initial content.
Most labile components of tubers at storage are sugars, vitamin C and starch. The continuous process of sugars transformation in starch and vise versa takes place in tubers. Under conditions of optimal storage temperatures there is observed a certain predominance of starch transformation in sugars over starch synthesis of them, influencing their ratio, decreasing in average by 8.8 % of the initial level in the group of early-ripening potato varieties and by 5 % in the middle-ripening ones.

Conclusions
It has been established, that the variety peculiarities and ripeness group of potato of Dutch selection influence storage quality. The output of commodity products in early varieties is in average-88.22±1.53 %, in middle-ripening ones -96.87±1.09. Among the group of early-ripening varieties, there must be separated Kristina with the output of commodity products at the end of storage as 90.15 %. The lowest output of commodity products is in the variety of Tornado -87.09.
In the group of middle-ripening variety, higher storage quality was observed in varieties Elekta and Setanta.
The commodity products output was 92.97 and 92.2 9 % respectively. In the group of early varieties, mass losses varied from 4.1 % in the variety Kristina to 5.1 % in the variety Banda. In the group of middle-ripening potato varieties, mass losses varied with the middle force, variation coefficient 19.5 %. The lowest mass loss was observed in the potato variety Elekta as 3.28 %.