| Green asparagus (Asparagus officinalis L.) is one of the most popular vegetables in China. It is a good source of nutrients and contains many elements which contribute to both nutrition and fitness. However, asparagus is also one of the few vegetables that is a highly perishable and deteriorates rapidly after harvesting. Moreover, it is difficult to maintain the freshness of asparagus due to its high fragile mechanical and physiological properties. To extend the shelf life of asparagus, we have used measures from cleaning, sterilization, preventing decay, preservation and packaging by measuring the quality, antioxidation and polyamine during storage. The result will be beneficial for providing a theoretical basis and practical guidance for postharvest asparagus.1. The changes of quality, antioxidant activity and polyamines of green asparagus (Asparagus officinalis L.) between bud and buttom segments were investigated during storage at 18±2℃. The results indicated that quality, antioxidant activity arid polyamines of the bud segment were significant higher than that of the buttom segment. The content of ascorbic acid decreased following the storage, and the changes of the total phenolic compounds, flavonoids, and total antioxidant capacity of asparagus increased before 6 days and then decreased, while the flavonoids trend of bud segment decreased during the storage. Significant correlations were found between the three materials and antioxidant activities. Free putrescine (Put) increased over three days and decreased over the following period, free spermidine (Spd) and spermine (Spm) content decreased across all periods of 12 days. There were significant correlations between free and conjuaged Put, and free and conjugated Put were also significantly correlated with those of free and conjugated Spd and Spm.2. The changes of quality, antioxidant activity and polyamines of green asparagus between bud and buttom segments were investigated during storage at 2±2℃. The results indicated that quality, antioxidant activity and polyamines of the bud segment were significant higher than that of the buttom segment under low temperature. The changes of the total phenolic compounds,flavonoids,total antioxidant abilities of asparagus were first decreased and then increased, while the flavonoids of bud segment and ascorbic acid trend decreased during the storage. There were significant correlations between the three materials and antioxidant activities.Free polyamines decreased over the following period, while conjugated polyamines changes differently for asparagus segment and polyamines types. Free and conjugated Put were also significantly correlated with those of free and conjugated Spd and Spm.3. The experiment was studied to examine the effect of ultrasonic wave (frequency 20kHz,60kHz,100kHz) on color, hardness, weight loss, total phenolic content, ascorbic acid, antioxidant activities, bacterial count, mold counting and polyamines of asparagus. The results indicated that ultrasound wave reduced the number of bacteria, mould and weight loss, kept its hardness,delayed the content of ascorbic acid, promoted accumulation of total phenolics and its antioxidant activities in the middle stage of storage,but had no obvious effects on color. Ultrasound wave cut down the content of free Put and Spm, kept free Spd content, promoted conjugated polyamines.4. The effects of salicylic acid (SA) on the quality, antioxidant activity and polyamines of asparagus stored at 18±2℃were investigated by analyzing the color, shear force and the activity of antioxidant compounds and polyamines (PAs). The results showed that SA improved the color, maintained the chlorophyll, phenolic, flavonoid and ascorbic acid content of asparagus. High concentrations of SA caused a deterioration in asparagus would harm to color and had no effect on shear force within 6 days. SA induced the maximum concentration of phenolics in post-harvest asparagus, promoted the increase in total flavonoids before 6-9 days, affected the antioxidant activity positively as indicated by the resultant increase in FRAP concentration.SA retarded free Put peak, kept Spd and spermidine (Spm) content, reduced conjugated polyamines.5. In order to determine the impacts of natamycin on postharvest asparagus, respiratory rate, color, shear force, weight loss, polyamines, bacterial and mold count were examined under low temperature. The results indicated that the natamycin treatments reduced respiratory rates of asparagus,inhibited the increases of weight loss and putrescine content, cut down the total molds of 1-3 orders of magnitude effectively. The peaks of spermine and spermidine appeared earlier in natamycin treatments and their contents are increased. Moreover, the asparagus with natamycin had better appearance and texture.6. To determine the impacts of active packaging (oxidant absorber, oxidant absorber plus 1-Methylcyclopropene, oxidant absorber plus 1-Methylcyclopropene and cinnamon oil) on postharvest asparagus, color, shear force, weight loss, bacterial and mold count, and polyamines were examined under low temperature. The results indicated that asparagus with active packaging had better color, inhibited the increasing of hardness, kept antioxidant meterials and activities, the decreasing of ascorbic acid, Spd and Spm, retarded the Put peak, cut down the total molds of magnitude effectively. |
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