Effects Of Dehydration And Frozen Storage On Anthocyanin Content And Storage Quality Of Purple Potato

Purple sweet potato has a wide planting area and high yield,but it is seasonal and cannot meet the demand of year-round supply.The large-scale storage and processing capacity after production is limited.The existing storage methods cannot meet the demand for long-term storage.Therefore,this article proposes a method of dehydration and freezing to solve the problem of short storage period and deterioration of storage quality of purple sweet potato.This study used Vietnamese sweet potato roots as the test material to screen the most suitable dehydration and freezing conditions for purple sweet potatoes;compared direct freezing and quick freezing methods,and explored the effects of dehydration and freezing on the storage quality of purple sweet potatoes in terms of frozen storage quality and freeze-thaw quality.The types and contents of purple sweet potato anthocyanins in different dehydration treatment groups were studied,and the best way to store purple sweet potato for a long time with the purpose of retaining anthocyanins was found.The specific research results are as follows:1.The purple sweet potato is dehydrated at three different degrees of 15%,30%,and 45% through hot air drying.After dehydration,it is frozen and stored.The dehydration curve and freezing curve are measured,and the optimal degree of dehydration is selected according to energy consumption and cost.The results showed that the direct freezing and dehydration of 15% purple sweet potato did not achieve the quick-freezing effect.For 30% dehydrated and 45% dehydrated purple sweet potato,the time to pass the maximum ice crystal formation zone was less than 30 minutes,achieving the quick-freezing effect.The time required for dehydration of 45% and the cost of dehydration are 1.86 times and 1.85 times that of 30% dehydration.Therefore,from the perspective of achieving the effect of quick freezing and low energy consumption,30% dehydration is the optimal dehydration level for purple sweet potatoes.2.According to the optimal degree of dehydration,four methods of natural air drying,hot air drying,osmotic dehydration and vacuum freeze drying are used to dehydrate the purple sweet potato,and freeze storage for 6 months.The results showed that in terms of frozen storage quality,with the direct frozen storage treatment group as the control,the soluble sugar content of the osmotic dehydration treatment group was1.66 times that of the control group,and the total phenol content of the osmotic dehydration treatment group was 29.38% higher than that of the control group.The flavonoid content of the osmotic dehydration treatment group was 21.68% higher than that of the control group,the anthocyanin content of the osmotic dehydration treatment group lost 4.54%,the DPPH free radical scavenging ability of the osmotic dehydration treatment group lost 7.86%,and the total antioxidant capacity of the osmotic dehydration treatment group was 1.27 times that of the control group.Osmotic dehydration can better protect the quality of purple potato during frozen storage.3.The freeze-thaw index was measured,and the results showed that the appearance and color quality of purple sweet potato in the osmotic dehydration treatment group had the least influence.Compared with the direct frozen storage treatment group,it can maintain good texture quality,reduce the juice loss rate by 8.03%,increase the total phenol content by 47.67%,increase the flavonoid content by 32.34%,and increase the anthocyanin content by 126.5%.16.37% of peroxidase activity,69.79% of polyphenol oxidase content reduced,28.1% of DPPH free radical scavenging capacity,and 18.52%of total antioxidant capacity increased.Therefore,the osmotic dehydration freezing storage treatment is the best way to maintain the storage quality of purple sweet potatoes,and can significantly improve the quality of purple sweet potatoes after freezing and thawing.4.Use liquid chromatography tandem mass spectrometry to detect the full composition of purple potato anthocyanins.The anthocyanins of purple potato are mainly peony anthocyanins and cyanidins.In terms of anthocyanin loss,the total anthocyanin loss rate of the direct freezing treatment group was 68.93%,and the total anthocyanin loss rate of the osmotic dehydration freezing treatment group was 12.02%.Therefore,osmotic dehydration and freezing storage can better protect the anthocyanin content in samples after freezing and thawing.