Vegetable crops deformation assays for package height definition: a new approach

Abstract

In the present work one determined the threshold pile height below which cracking and other deformations do not occur in products with low apparent density such as lettuce, collard greens and bell pepper. Initially the threshold pile height was sought applying decreasing compression stresses equivalent to pile loads of 160, 120 and 80 cm, with four replicates in four hour assays. The safe threshold pile height which protects the products against cracking rupture in these three commodities were of 80 cm. In a complementary study, plastic and elastic deformations induced by this safe pile threshold height were measured. The irreversible deformation, plastic deformation component, were lower in bell pepper (3.8 %), medium in lettuce (4.23 %) and had the higher values in collard greens (10.2 %). The reversible deformations, the elastic component, was also the lower in bell pepper (4.14 %), medium in lettuce (7.41 %) and the higher in collard greens (8.17 %). Considering these modest plastic deformations, the safe pile threshold heights were accepted and the safe package heights were defined as the pile threshold height multiplied by a factor of 0.5. This safety factor incorporates protection against accelerations of impact and vibration which occur during handling and transportation, as it was previously used for the development of packages for compact fruits and vegetables with higher apparent density. According to the method used the maximum package height should be of 40 cm, for the low density model products of this study.Index terms: Brassica oleraceae acephala, Capsicum annuum, Lactuca sativa, pile height, post-harvest. RESUMONeste trabalho, determinou-se a altura limiar de pilha, altura abaixo da qual não ocorrem rachaduras e outras deformações que são prejudiciais em alface, couve e pimentão, três produtos de baixa densidade aparente. Primeiramente, determinou-se a altura da pilha abaixo da qual não ocorrem rachaduras. Para isso os tratamentos foram compressões decrescentes. Essas compressões decrescentes foram 160, 120 e 80 cm de pilha, aplicadas com 4 repetições, durante 4 horas. A altura limiar de pilha estática que protege contra rachaduras nesses três produtos foi 80 cm. Em seguida, estudaram-se as deformações elásticas e plásticas causadas por essa altura de pilha limiar e observou-se que a parte irreversível da deformação, componente plástico, foi menor em pimentão (3,8 %), média em alface (4,23 %) e maior em couve (10,2 %). As deformações reversíveis ou elásticas também foram menores em pimentão (4,14 %), médias em alface (7,41 %) e maiores em couve (8,17 %). Tendo-se em vista as modestas deformações plásticas aceitou-se a altura limiar das pilhas e definiu-se a altura das embalagens como a altura limiar dividida por dois, para incorporar proteção contra acelerações de impacto e vibração durante o manuseio e o transporte, da mesma maneira anteriormente para frutas e hortaliças compactas e de maior densidade aparente. Desse modo para essas três hortaliças modelo, de baixa densidade aparente, i...

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