Effects of heat treatment on atmospheric composition and color of peeled white asparagus in modified atmosphere packaging

Freshly harvested spears of white asparagus were subjected or not to heat treatment by immersion in a hot water bath at 55 degrees C for 3 min, then left unpeeled or were peeled before wrapping in 16 pm stretch film and stored at 3 degrees C for 6 days. During storage, the atmosphere within the packages was sampled for O-2, CO2 and C2H4 determination, while spear fresh weight, color and anthocyanin content at the 3 cm apical peel segments were determined before and after storage. The results showed that CO2 concentration in packages of white asparagus spears was not greatly influenced by peeling or heat treatment. On the other hand, a higher package O-2 depletion of treated (peeled or heated) spears was observed. Peeling also resulted in an increase of ethylene peak concentration, indicating wound-induced ethylene production, which was suppressed by heat treatment. The initial color of the whole spear was retained, while the appearance of a violet coloration on the spear tip was prevented by heat treatment in both unpeeled and peeled spears. Industrial relevance: Peeled white asparagus has drawn the attention of industry as a novel lightly processed product. The combination of heat treatment with modified atmosphere packaging (MAP) could be used to improve the storage life of this product. Moreover, both peeling and heat treatment cause changes in ethylene production and respiration rate of asparagus spears and this information could be useful for development of novel application to MAP design for lightly processed (peeled) white asparagus. (c) 2009 Elsevier Ltd. All rights reserved.