Quality of low temperature heat-shocked green asparagus spears during short-term storage

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.