STORAGE OF ONIONS IN FARM SCALE VENTILATED SILOS

Onion is the third most popular vegetable commercialized in Brazil. But despite of its importance there only a few studies dealing with the storage of the bulb without refrigeration. In this research 400 kg of cured onions were stored in a 1.0 m in diameter by 1.5 m in height silo, ventilated at rate of 25 m³/h every day during the night period (12 h). As control treatment, the onions were put in 20 kg bags of interlaced threads polyethylene. Total soluble solids, titratable acidity, length of sprouting leaf, alliinase activity and loss fresh weight. The onions stored in the silo were discarded after 90 days, at this time 80% of bulbs rotten were determined at 15 days intervals and 0.5% were sprouted. The bagged bulbs were discarded at 45 days of storage showing, 86% were rotten onions and 1% of sprouted bulbs. There was an increase in the total soluble solids in the onions stored in the bags, while in the silo there was an increase followed by a continuous drop at later stages of storage. The length of the sprouting leaf during storage increased by 6.1-fold on the bagged onions and by 4.5-fold on the silo ventilated. The pungency increased during storage in both treatments, due to an increase in alliinase activity. In the control treatments and bagged onions, the rates of fresh weight was 0.069%/day and 0.055%/day. The ventilated silo is a viable sustainable alternative given the cost of tube storage technique compared to the traditional bagging method.