Effect of different storage methods on quantity and quality of potato

Potato (Solanum tuberosum) belongs to Solanaceae family and is a perennial plant which is herbaceous in nature. Potato is the world’s number one non-grain food commodity and 75% of the total production are being harvested in densely populated developing countries such as China and India, and thus alleviates the food crisis in third world countries. Potato is the most imperative and widely cultivated vegetable crop in Iran, per capita consumption in the country is more than 35 kg. Potatoes are the World’s most widely grown tubural crop and the fourth largest crop in terms of fresh produce after rice, wheat and maize. According to the National Policy on Potato Industry, the potato is an important food and cash crop that plays a major role in food security and is only second to maize in terms of utilization. Potato production is increasing due to the economic decline of competing cash crops such as maize, pyrethrum, and barley, and increasing demand from consumers and processors. Potato tuber undergoes physiological dormancy period during the postharvest storage. The length of the dormancy period is dependent on the varietal genetic profile, environmental factors and storage conditions. Commercial potato cultivars grown for the processing industry has shorter dormancy periods and associated with different storage disorders like sweetening, greening, toxicants, etc.; therefore it is vitally important to employ suitable storage conditions to ensure their continuous supply. Potato is semi perishable crop, however placed under low temperature storage to prevent them from sprouting and to ensure their regular supply whenever required. Low temperature potato storage is however, associated with low temperature sweetening and is specifically undesirable in processing potato varieties. The phenomenon is primarily associated with the potato storage under low temperature and as a result of which the insoluble starch is enzymatically hydrolyzed into soluble glucose, fructose and sucrose. Tuber sweetening deteriorates the tuber commercial quality and causes the fried products to turn brown and bitter in taste due to subsequent acrylamide formation. Packaging is an essential component of post harvest supply chain management in horticultural crops. In Iran and other developing countries, potatoes stored in polyethylene bags with a capacity of 40 to 80 kg that causes many problems during storage. Therefore, this study was conducted to evaluate the different potato packing methods for industry uses.
Material and Study was conducted in 2015-2016 at cold storage Ravand, in the Toos Industrial Zone, Mashhad, Iran in a completely randomized design with triplicate. Treatments including cold storage of potatoes, storage in a wooden box, kept in mesh bags, storage in polyethylene bags, and storage in punched polyethylene bags and kept in split polyethylene bags. Potato cultivar used in this study was Agria Picked up in the second half of October. Box weight was measured before storing tubers. Tuber store below six degrees Celsius and relative humidity between 85% and 90% were considered for all treatments. The amount of carbon dioxide during storage was set between 700 and 1000 ppm. Storage period took six months. After storage period, the number of healthy, sprouting and rotting tubers were counted and the sugar content, total phenol content and quality of chips, starch content, dry matter and tuber specific gravity were measured.
The results showed that the highest and the lowest loss percentage observed in mesh bags and polyethylene bags respectively. The difference between the two treatments was 2.4 percent. Tuber maintenance in polyethylene bags and polyethylene bag split showed the highest and lowest percentage of decay. Most sprouting tuber was observed in polyethylene bags and punched polyethylene bags, and the lowest sprouting tuber observed in a mesh bag and wooden box. The difference between the highest and lowest percentage of sprouting tuber in punched polyethylene bags and mesh bag was 16 percent. There were no significant differences observed in reducing sugars and total phenol component at different storage methods. The highest percentage of starch obtained in split polyethylene bags and mesh bag and the least amount of starch in punched polyethylene bags. Packing tubers in mesh bag showed the maximum and in split polyethylene bags showed the minimum brown color in chips. The difference between the highest and lowest specific gravity was two percent, however, in all treatments specific gravity was more than one. The highest of dry matter percentage observed in a mesh bag and split polyethylene bags with 24 percent and the lowest of dry matter percentage was observed in punched polyethylene bags. Tuber loss weight in polyethylene bags was lower than other treatments, but rotten tubers percentage was higher than the other treatments. In contrast, tuber weight loss in split polyethylene and punched bag's was equal to storage in wooden boxes and tuber decay in split polyethylene bags was lower than other treatments. Chips quality in split polyethylene bags was more than other treatments and equal to wooden boxes. Generally, wooden boxes, split polyethylene bags and punching bags are found suitable to reduce the percentage of rot and sprouting potato tubers and as effective way to store potatoes in storage room.