Artificially cooling of onion bulbs stored in brickwork-patterned vertical silos

Abstract

ABSTRACT Onion is the third most consumed vegetable worldwide, such as potatoes and tomatoes. Its conservation is influenced by temperature and humidity, and greatest losses occur at postharvest due to lack of storage infrastructure. Thus, the aim of this study was to evaluate the effect of partial cooling in vertical silo on postharvest conservation of cured onion bulbs cultivar Bola Precoce. The experimental design was completely randomized, with six replicates, arranged in split plot scheme. Plots consisted of two storage conditions: onion bulbs stored in silo 1 at room temperature (T1) and bulbs stored in silo 2 with artificial cooling (T2). Subplots were two periods of bulb removal from storage (0 and 14 days). We evaluated peel color, using chroma (C*) and internal and external luminosity (L*); relative water content (TRA) of peel and pulp of bulbs and fresh mass loss (PMF) when the experiment was installed and after 14 days for both experiments and at 21 days for T2. The average temperatures obtained in both silos were 30.4 and 16.4°C, respectively. Bulbs of T1 had 14 days shelf life whereas, bulbs of T2 had a shelf life of 21 days. Bulbs of T1 showed lighter peel on day zero. The 14-day storage made the bulbs lighter in T2. In relation to pulp color, storage period made pulp lighter in both treatments. On day 14, bulbs of T1 showed lighter pulp color comparing to bulbs of T2. Both treatments showed similar behavior on day zero for internal chroma. After 14 days storage, internal and external chroma was higher in bulbs of T2. Storage period reduced internal hue only in bulbs of T2 which showed lower internal hue in both evaluation periods. TRA was higher in T1 in both evaluation periods. PMF was higher according to storage period; however loss did not differ between treatments. Storage of onion bulbs in cooled silos increased their viability in 7 days, in relation to storage without refrigeration.