BACK    Non-refrigerated storage

Refrigerated storage:

Refrigerated storages are generally used for long-term storage of seed and table potatoes. This is essentially done in commercial cold storages since potatoes harvested in February-March have to be stored until October or so for 6-8 months.

Storage at 2-4°C:

There are roughly 5000 cold storages in India and of the total capacity of cold stores, approximately 80% is used for storage of potatoes alone. Low temperature storage is the most common method of potato storage in the country. Low temperature storage is effective because at storage temperature of 4°C and below, sprout growth does not take place in most of the varieties. Further, the metabolic processes are slowed down therefore; losses caused by respiration are the minimum. In India, cold stores were developed mainly for the storage of seed potatoes but the present utilization pattern of cold storage space in different parts of the country shows that about 60% of the cold storage space is being used for the storage of ware potatoes and 40% for the storage of seed potatoes. Since the primary purpose of storage at 2-4°C is to check sprout growth, storage of seed potatoes at 2-4°C in cold store is ideal. But storage of ware potatoes at 2-4°C is not desirable since low temperatures induce accumulation of large amounts of sugars making the tubers sweet and therefore, less suitable for consumption; Besides, the cold stored potatoes are unfit for processing as high level of reducing sugars causes browning in potato chips, even the keeping quality of cold stored potatoes deteriorates quickly once they are removed from the cold store as tubers begin to sprout fast and marketing of cold stored potatoes is also a problem, due to their poor keeping quality. The high sugar content of potatoes stored at 2-4°C can be reduced to some extent by reconditioning at 20°C for 6 weeks. However, reconditioning can not restore the sugars to the initial levels. Therefore, it is recommended that 2-4°C storage be used for potato seed only and the potatoes meant for table and processing should be stored at higher temperatures either under elevated temperatures of 10-12°C for long-term (6-8 months) or under non-refrigerated conditions for short-term (3-4 months). For seed storage, it is recommended that after proper skin curing, sorting and grading, the seed should be treated with a solution of 3% boric acid and after shade drying, be stored under cold storages.

Elevated temperature storage at 10-12°C:

Potatoes for ware and processing purposes are generally stored at 8-10°C in the developing world. This storage temperature does not allow excessive sugar accumulation, therefore, potatoes are not sweet in taste. Since sugar level is within the acceptable limit, the potatoes are also suitable for processing. But this temperature does not slow down sprout growth at the release of dormancy and therefore, some sprout suppressant has to be used for checking sprout growth. CIPC (isopropyl N (3-chlorophenyl) carbamate) is the most common sprout suppressant used on potatoes. It is a mitotic inhibitor and checks sprout growth by inhibiting cell division. This chemical was registered for use in India only in 1998, and at present about 450 cold stores in the country are using this chemical on potatoes stored at 10-12°C. The details of the treatment and recommendations have already been described in previous section.