Abstract
The present study evaluated the effects of heat-shock treatment (washing in 48°C distilled water for 5 min) on quality of green asparagus spears stored at 25 or 4°C for 7 days. The results showed that the quality characteristics including toughness, lignin and cellulose contents, and phenylalanine ammonia-lyase, cinnamyl alcohol dehydrogenase and peroxidase activities were increasing in both heat-shocked and control spears stored at 25°C; however, the heat-shocked spears exhibited lower degrees of increases than control spears. Similar increasing trends but with even smaller magnitudes in these characteristics were obtained from the heat-shocked spears stored at 4°C. Heat-shocked spears stored at 25 or 4°C also demonstrated lesser proliferations of total mesophilic aerobes, Escherichia coli and mold than their respective controls. Thus, a combination of 48°C heat-shock treatment and 4°C cold storage can be used to conserve the quality of stored green asparagus spears. Key words: Green asparagus, heat-shock, lignification, microbial load, storage.
Highlights
Green asparagus (Asparagus officinalis L.) spear is a healthy but highly perishable vegetable, which has a very short shelf life with normal post-harvest handling at ambient temperature
The toughness of green asparagus spears is reported to be related to the degree of lignification in their tissues, which is regulated by enzymes Phenylalanine Ammonia-Lyase (PAL), cinnamyl alcohol dehydrogenase (CAD) and peroxidase (POD)
These results indicate that the 48°C heat-shock treatment prior to storage could retard the lignin increases in green asparagus spears during seven days of storage at 25°C
Summary
Green asparagus (Asparagus officinalis L.) spear is a healthy but highly perishable vegetable, which has a very short shelf life (generally three to five days) with normal post-harvest handling at ambient temperature. Many physical and chemical changes such as the loss of water and the increase of toughness that reduce the quality of green asparagus spears occur during harvesting, handling and storage (Rodriguez-Arcos et al, 2002; Liu and Jiang, 2006). Among these changes, the increase of toughness is an important factor in de-grading the quality of green asparagus spears and decreasing their market value. The increased microbial load would further reduce the quality of green asparagus spears and shorten their shelf life (Sothornvit and Kiatchanapaibul, 2009). Many methods have been developed to ensure microbial safety and extending shelf life of green asparagus spears
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