Effects of thawing methods on quality characteristics of three quick-frozen citrus pulp
The three citrus pulp from Zigui navel orange,Yichang mandarin,and Ponkan tangerine was treated with six methods including refrigerator thawing,natural thawing,flowing water thawing,warm water thawing,ultrasonic thawing,and microwave thawing to study the effects of thawing methods on the quality characteristicsof the quick-frozen citrus pulp.The thawing time,loss rate of juice,conventional quali-ty indexes,color,hardness,total phenolic content,antioxidant activity,and changes in sensory of quick-fro-zen citrus pulp were measured.The results showed that the effects of different thawing treatments on the quality of citrus pulp from Zigui navel orange,Yichang mandarin,and Ponkan tangerine were significantly different(P<0.05).The time of microwave thawing for Zigui navel orange,Yichang mandarin,and Ponkan tangerine was the shortest,being 0.82 min,0.89 min,and 0.81 min,respectively.The loss rate of juice in microwave thawing for Zigui navel orange,Yichang mandarin,and Ponkan tangerine was the lowest,being 0.25%,0.16%,and 0.15%,respectively.The conventional quality indexes of microwave and ultrasonic thawing were well preserved.The microwave thawing had the least effect on color with ΔE of 8.48,7.52,and 4.71,and the least loss of hardness with reductions of 36.1%,52.03%,and 36.48%,respectively.The content of total phenol and antioxidant activity in microwave thawing were relatively high,and the sensory profile was closest to that of fresh flesh samples.Compared to the other five thawing methods,microwave thawing can thaw the flesh within 1 minute,and effectively slow down the changes in color and the hard-ness loss of pulp,and better preserve the edible and nutritional qualities of the quick-frozen citrus pulp.
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