EFFECT OF HARVESTING TIME AND CURING TEMPERATURE ON SOME PROPERTIES OF IRANIAN WHITE GARLIC

Improper drying causes the most serious postharvest loss of garlic cultivation. So, to determine the best conditions for garlic curing, garlic was harvested in three stages. The first stage was when 70% of the tip of the leaves turned yellow, while the second part began when whole leaves became yellow and eventually the last harvesting was ensued by getting dry, brown leaves falling over the field. After harvesting, bulbs with the same size were divided into four groups before storing for 6 months at ambient temperature. The first group was dried in natural conditions in the shade at 24±2°C and the other groups were treated by heating at 35, 45 and 55°C respectively. The results of two years showed that after harvesting, yield, pyruvate and firmness of garlic bulbs at three stages of harvesting varied slightly. Drying time in natural conditions of the first stage of harvesting was longer than the heat treating process time as well as the other harvesting stages. For temperatures higher than 45°C some cloves turned yellow, soft and sticky especially at the early stages of harvesting. The drying process was stopped in both methods when the humidity of cloves, clove skins and stems reached 641, 202 and 154% respectively. After the curing in all stages, the pyruvate content in natural curing was almost constant but in the heat treating method, pyruvate showed a significant reduction by increasing the temperature. An increment of pyruvate and softness was observed within 30-180 days of storage. During the heat treatment the weight loss and spoilage of garlic bulbs increased in terms of the drying time and reduced in the first stage by drying at 35°C and the second stage of harvesting by drying at 35 and 45°C as compared to other treatments.