بررسی میزان قند ارقام مختلف سیب زمینی در حین برداشت

Introduction
Potato with the scientific name (Solanum tuberosum. L.) is a plant that is cultivated as an important product in all countries and is known as a source of carbohydrates, proteins, and vitamins in the human diet. This is a native product of South America and its origin is from Peru. After wheat, rice and corn, potato is the fourth product in people's food basket, which in Iran sometimes takes the place of rice and takes second place, which shows its importance in meeting people's food needs. According to the reports of the Food and Agriculture Organization of the United Nations, the area under potato cultivation in Iran in 2019 was more than 164 thousand hectares and the harvested product from this area was about 32.5 million tons. In the food industry, this product is transformed into various products such as baked potatoes, fried potatoes, potato chips, potato starch, dry fried potatoes, etc.
Since the expectations for food products with appropriate quality and safety standards have increased, it seems necessary to determine the characteristics of food products. In the meantime, in the potato product, quality evaluation after the harvest stage is necessary to provide a reliable and uniform product to the market, because potatoes, like many other products, have uneven quality and handling in It is the harvesting stage. At the same time, the safety and desirability of food play an important role in the food industry and are directly related to people's health. Potatoes for the processing industry must have some requirements such as low sugar content, high dry matter and specific weight, high antioxidants, light skin color and no sprouting. Stored potatoes may suffer from sweetening, rotting, water loss and sprout growth during storage. Storage conditions after harvesting can cause changes in the chemical composition and quality of the product. Therefore, the management of potato tubers in all stages of production and storage is very important.
The quality of this product and its processed products depends on the variety and environmental conditions (both during the growing season and during the storage period). By analyzing the relationship between chips color, dry solids, sucrose, reducing sugar, ascorbic acid, protein and storage temperature data, Meza showed that dry solids, reducing sugar and sucrose in determining the color of fresh potato chips and reducing sugar, tuber temperature and sucrose content are very important in determining the color of stored tuber chips and the relative importance of each of these parameters changes with the type of tuber variety and storage.
The amount of potato sugar significantly depends on the variety and storage temperature and it happens quickly in cold weather. In potato tubers during the storage period, starch is gradually hydrolyzed and turned into sugar (glucose). In unripe tubers and potatoes that are stored for a long time at low temperatures, there are more amounts of glucose, this feature is considered an anti-quality feature for the potato product in the industry, why? The increase of regenerating sugars causes the produced chips to turn brown and bitter. Storing potatoes for more than 7 months can cause ageing or old sweetness, and storage at a temperature of fewer than 10 degrees Celsius can cause sweetness caused by cold. Although potato storage at low temperatures can have beneficial results such as reducing respiration rate, reducing physiological ageing, inhibiting germination, reducing evaporative water loss and reducing microbial pathogens. But sugars accumulate when the balance between starch degradation and breakdown is not established and there is carbohydrate respiration. Therefore, potatoes that are kept at a lower temperature have a lot of sugar. Researchers reported that when potatoes are stored at zero degrees Celsius, there will be a complete stop in the accumulation of sugar.


Methodology
First, 5 different varieties of fresh potatoes (Spirit, Agria, Sante, Jelli and Marfona) were prepared from Ardabil Agricultural Research Center (Arallo District). It should be noted that these potatoes were prepared immediately after harvesting so that there are no changes in the amount of sugar due to the time interval after harvesting.
The amount of sugar in each sample was measured in three replicates using a liquid refractometer model BPTR100 (Middle East Control System Company, brand name Prisma Tech, made in Iran) available at Mohaghegh Ardabili University (Figure 1). For this, first, some water was taken from the samples and after pouring it into a microtube, it was placed inside a refrigerated centrifuge (top speed) of the LISA France model, and after rotating at a speed of 1800 rpm for 2 minutes, the impurities at the bottom settled and separated the pure liquid (pure potato juice). After reaching the ambient temperature, the said liquid was placed on the refractometer and its sugar content was read in terms of Brix.

Conclusion

The results of the analysis of the variance of cultivar effect on potato sugar content are shown in Table 1. According to the analysis of the variance table, the effect of variety on potato sugar level was significant at 1% probability level. You can see the changes in the amount of sugar of different potato cultivars in Figure 2. The difference in the amount of sugar in different cultivars is due to the difference in their starch hydrolysis (the main compound of potato-potato tubers) which occurs as a result of the respiration of the product, and it is in this way that the higher the amount of starch in If one variety is less, that variety has less sugar, and it is important to note that the chemical composition depends on the potato variety, soil, climate, and agricultural factors. In general, it can be said that potatoes with more sugar are suitable for the chips industry, and potatoes with medium sugar are suitable for frying. According to Figure 2, the highest amount of sugar is related to the Esprit variety and the lowest amount is related to the Jelly variety. The reason for the difference in the amount of sugar between different cultivars is mainly related to the type of soil, fertilizer and poison used. According to the data and the results of the research, it was observed that the amount of sugar in different varieties of potato is different, in the meantime, the jelly variety generally has a lower amount of sugar at the time of harvesting, and the variety of Esprit has the highest amount of sugar at the time of harvesting. Was. It is recommended to choose a more suitable variety according to the conditions according to the type of consumption and the importance of quality characteristics for consumption and processing, of course, physical characteristics are also involved in this relationship, which should be taken into consideration.