Drying time and post-harvest quality of onion bulbs submitted to artificial curing

Abstract

RESUMO Drying time and post-harvest quality of onion bulbs submitted to artificial curingAfter harvest, onion bulbs are submitted to curing, whose objective is to provide loss of moisture in leaves and drying of outer layers (peel) of bulbs, reaching attractive external coloration and reduction in the intensity of rottenness. The objective of this study was to use an air treatment unit (ATU) -known as heat pump -as an alternative drying method, and to evaluate drying time and preservation of the chemical and physical characteristics. The experiment was carried out in a complete random design with ten replicates and three treatments, which were the following: T 1-(control) natural curing in shed; (2) T 2-(aeration with air artificially heated by propane burning); and (3) T 3-(aeration with artificially dehydrated and heated air using ATU). Curing completion time, relative water content (RWC) of the skin and inner layers, pulp color and skin coloring, total titratable acidity (TTA), total soluble solids (TSS), visual index of dormancy breaking (VID), and fresh weight loss (FWL) were evaluated in this study. No significant difference (p < 0.05) were found for TTA, TSS, VID, FWL, and pulp color among treatments. It can be concluded that T 3 promoted a faster curing (12 hours) of bulbs, which provided bulbs with drier skin and intense yellow color. Tempo de secagem e qualidade pós-colheita de bulbos de cebola submetidos à cura artificialApós a colheita da cebola, realiza-se a cura cuja finalidade é proporcionar a perda da umidade das folhas e secagem das películas externas (casca) dos bulbos, alcançando coloração externa atrativa e redução da intensidade de podridões. Objetivou-se com este trabalho utilizar uma unidade de tratamento de ar (UTA), conhecida como bomba de calor, como método alternativo de secagem e avaliar o tempo de secagem e a preservação das características químicas e físicas dos bulbos de cebola após a cura. O experimento foi conduzido no delineamento inteiramente casualizado com dez repetições e três tratamentos que consistiram em: T 1 -(Testemunha) cura natural realizada em galpão. T 2 -(aeração com ar aquecido artificialmente pela queima de propano) e T 3 -(aeração com ar aquecido e desidratado artificialmente por meio da UTA). Avaliou-se o tempo de finalização da cura, teor relativo de água (TRA) da casca e películas internas, coloração da casca e polpa, acidez total titulável (ATT), sólidos solúveis totais (SST), índice visual de superação da dormência (IVD) e perda de massa fresca (PMF). Não houve diferença significativa (p < 0,05) para a ATT, SST, IVD, PMF e coloração da polpa entre os tratamentos estudados. Conclui-se que o T 3 permitiu a cura dos bulbos de forma mais rápida (12 horas), proporcionando bulbos com casca mais seca e coloração amarelo intenso.Palavras-chave: Allium cepa; características químicas e físicas; métodos de secagem; ar aquecido.Drying time and post-harvest quality of onion bulbs submitted to artificial curing Rev. Ceres, Viçosa, v. 63, n.6, p. 822-828, nov/dez, 2016

Effect of controlled atmospheres on the quality of white onion (Allium cepa L)

“…The control onions had a greener color than those treated in a CA. Similar results were obtained by Cardoso et al (2016) in ''Bola Precoce'' onions, who reported that this parameter is affected by curing, obtaining a higher value (a* = -2.32) for onions that were cured in the field than for those that were cured with artificial hot air (a* = -2.05) and with artificially heated and dried air (a* = -1.76). In another study, Trujillo et al (2016) reported higher values than those obtained in the present work in ''Roja Ocañera'' (a* = 20.24), ''Peruana Inca Alto del Pozo'' (a* = 21.85), ''Peruana Inca Abrego'' (a* = 22.50) and ''Peruana Inca La Playa'' (a* = 21.75) onions.…”

“…Other authors have reported lower results in ''Crioula Roxa'' purple onions (Berno et al 2014) and in ''Roja Ocañera'', ''Peruana Inca Alto del Pozo'', ''Peruana Inca Abrego'' and ''Peruana Inca La Playa'' red onions (Trujillo et al 2016). Cardoso et al (2016) also reported lower values of superficial L* in ''Bola Precoce'' onions (L* = 67.96 on average) to those obtained in the present work, reporting that curing had no effect on this parameter. The onions stored in CA kept their luminosity practically constant throughout the conservation time.…”

“…These values correspond to more neutral colors, according to Cardoso et al (2016) who pointed out that the chroma defines the intensity of color, taking values close to zero for neutral colors and around 60 for bright colors. According to Petropoulos et al (2015), the chroma depends on the variety and type of tissue of the onion.…”

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

“…Significant difference between T1 (103.04%) and T2 (19.89%) on day zero was verified, and after 14 days of storage, the values of 55.95% and 11.10% for T1 and T2, respectively, were obtained (Table 2); this occurred due to the passage of cooled air under the onion bulbs, removing moisture from the external leaves, resulting in drying these layers. According to Cardoso et al (2016), ventilation and heat allow the external leaves of the bulbs to be dried offering more effective protection against water loss in inner layers. Treatments T1 and T2 showed significant fresh weight loss over 14 days of storage (0.14 and 1.06%), as observed in Table 2.…”

“…After natural cure in a shed (Cardoso et al, 2016), bulbs were selected, defective and rotten bulbs were removed.…”