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

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.

摘要：洋葱是全球第三大消费蔬菜，仅次于马铃薯与番茄。其贮藏保鲜效果受温度与湿度影响显著，由于仓储设施匮乏，采后损耗问题最为突出。本研究旨在评估立式贮藏筒仓（vertical silo）局部降温处理对愈伤洋葱鳞茎（cured onion bulbs）品种‘Bola Precoce’采后保鲜效果的影响。试验采用完全随机设计（completely randomized design），设置6次重复，采用裂区设计（split plot scheme）布局。主区包含两种贮藏条件：1号筒仓内室温贮藏的洋葱鳞茎（T1组），以及2号筒仓内人工降温贮藏的洋葱鳞茎（T2组）；副区为两个取样测定时期：贮藏0天与贮藏14天。本试验测定指标包括：采用彩度（C*）及内外明度（L*）表征的外皮颜色，鳞茎外皮与果肉的相对含水量（TRA），以及鲜质量损失率（PMF）。测定时间点为试验启动阶段，两组均于贮藏14天后取样，且T2组额外在贮藏21天时取样。两个筒仓的平均温度分别为30.4℃与16.4℃。T1组鳞茎的贮藏寿命为14天，T2组则为21天。贮藏初始时，T1组鳞茎外皮颜色更浅；贮藏14天后，T2组鳞茎外皮颜色变浅。就果肉颜色而言，两组果肉均随贮藏时间延长而颜色变浅；贮藏14天时，T1组果肉颜色较T2组更浅。贮藏初始时，两组内部彩度表现一致；贮藏14天后，T2组鳞茎的内外彩度均更高。仅T2组的果肉色调（hue）随贮藏时间延长而降低，且两次测定时其内部色调均更低。两次测定中，T1组的相对含水量均更高。鲜质量损失率随贮藏时间延长而升高，但两组间损失率无显著差异。与无冷藏贮藏相比，采用降温筒仓贮藏洋葱鳞茎可将其贮藏寿命延长7天。