Study On Quality Change During Processing And Storage Of Preserved Strawberry Fruit

Strawberry(Fragaria×ananassa Duch),known as the "Queen of Fruits",has high nutritional value and is widely grown in China.Preserved strawberry,a new type of partially dehydrated fruit product,is rich in nutrition components and liked deeply by consumers because of its glutinous taste and heart-shaped.In this paper,the factors(raw materials,processing technology,and storage environment)that affect the preserved strawberry fruit quality were studied and quality properties(nutritional components,color,and texture parameters)were determined.It provides the theoretical basis for strawberry preserved fruit processing and also provides a reference for improving the quality of strawberry preserved fruit.The main research contents and results were as follows:(1)Through analyzing nutritional components,color,and texture parameters of Monterey,Sweet charlie,and Hongyan strawberry with three ripening stages(pink stage,semi-red stage,and red ripe stage).Results showed that the contents of chlorophyll,total phenols,hardness,malic acid,and citric acid of three varieties all declined,while the contents of anthocyanin,Vc(vitamin C),water,glucose,fructose,sucrose,and brix were increased during strawberry ripening.The content of other amino acids gradually decreased with the increase of maturity,except Asp(aspartic acid).Furthermore,the VC,anthocyanins,total phenols,color,texture parameters,and other nutritional components of strawberry preserved fruit with different maturity and variety were measured.It was found that the nutrient content loss rate of Monterey semi-red strawberry preserved fruit was the lowest(VC is 68.93%;anthocyanin is 72.48%;total phenol is 15.75%),the brightness value L*,the elasticity,and the sensory comprehensive score was the highest.(2)The effects of solid osmotic dehydration(SSD),liquid osmotic dehydration(LOD),constant temperature hot air drying,gradient hot air drying,sucrose concentration,maltose addition,and citric acid addition on the quality of strawberry preserved fruit during processing were studied.At the same time,nutritional components,color,texture parameters,and microstructure were compared.Results showed that the retention rate of strawberry anthocyanin and VC after SSD was 1.53 times and 1.15 times of LOD;The content of VC and total phenol,elastic force,L*,a*,b*,and sensory comprehensive score in gradient hot air drying was higher than constant temperature drying.Under SSD conditions,sucrose concentration had a significant effect on the quality of preserved strawberry fruit,when the addition amount of sucrose was 40%of the mass of the strawberry,the sensory comprehensive score and color were high,and the texture parameter was waxy and tough.However,sugar crystallization still appeared in preserved strawberry fruit during storage.Added 0.5%citric acid and 10%maltose could delay the preserved strawberry fruit crystallization,at the same time the sensory comprehensive score was the highest.(3)The effects of temperature,packaging method and storage time on the quality of strawberry preserved fruit were studied.The preserved strawberry fruit prepared by the optimized process was packaged in different methods(vacuum lightproof packaging,vacuum transparent packaging,non-vacuum lightproof packaging,and non-vacuum transparent packaging).The changes of color and nutritional components of strawberry preserved fruit stored at 4?,25?,37?,and 55? were analyzed.The results showed that with the increase of storage time,the color and nutritional components showed different degrees of decline.And the higher the temperature,the faster the decline.The contents of amino acids,free sugars,VC,total phenolic content,and color in strawberry preserved fruit decreased slowly under vacuum lightproof packaging.However non-vacuum transparent packaging falls fast.It was found that the quality of strawberry preserved fruit packaged in vacuum lightproof packaging was the most stable during storage at 4?.