Effects of Osmotic Dehydration of Calcium Salt Combined with Sugar Solution on the Quality of Four Small Berries after Repeated Freeze-thawing

In order to explore the effects of osmotic dehydration freezing treatment of calcium salt combined with sugar solution on the quality of different small berries after repeated freezing-thawing, strawberry, blueberry, wolfberry and sea buckthorn were selected as the research objects. The normal slow freezing at -20 ℃ was set as the control group,the osmotic dehydration treatment of calcium salt combined with sugar solution and the freezing at -20 ℃ after sugar solution osmotic dehydration were set as the treatment group. The color, texture and bioactive substance indexes of four kinds of small berries were determined regularly after three freeze-thawing cycles. The results showed that the four kinds of small berries were not resistant to repeated freeze-thawing, and more than two freeze-thawing cycles would seriously damage the edible processing quality of small berries. The osmotic dewatering treatment with calcium salt in sugar solution significantly reduced the cell membrane permeability and juice loss of the four small berries, improved the fruit hardness significantly, and preserved the fruit color and appearance quality better. The osmotic dewatering treatment of calcium salt combined with sugar solution had a better protective effect on the bioactive substances such as ascorbic acid in fruits, and significantly increased the total phenol content of strawberry, blueberry and sea buckthorn during the first two freeze-thaw cycles. Calcium salt combined with sugar solution can also inhibit the activities of polyphenol oxidase and peroxidase of the four small berries, reduce the browning phenomenon caused by oxidation during freeze-thaw process, and protect the quality of the berries. Compared with the normal slow freezing at-20 ℃, the osmotic dehydration of sugar solution also had a certain protective effect on the related texture and quality of small berries, but its effect was weak calcium salt combined with the osmotic dehydration of sugar solution.