Ultrasonic Assisted Preparation Of Prebiotic Low Sugar Strawberry Preserves

Strawberry is a kind of fruit with rich nutritional value.It is rich in vitamin C,sugar,minerals and other nutrients,and has the health care functions of item and digestion promotion.It can improve the commodity rate and economic value of strawberries,and alleviate the situation that the supply of fresh strawberries exceeds the demand in mature season.Strawberry preserves are also popular among consumers because of their unique flavor and taste,strong original fruit taste and other characteristics.In this paper,frozen strawberry was used as raw material to optimize its thawing process,sugar solution formula,ultrasonic assisted sugar permeation process and drying process,to prepare strawberry preserved fruits with healthy nutrition and high sensory quality,and to analyze the quality of the products and predict the shelf life.The main research results are as follows:1.The best defrosting technology of frozen strawberry is:Thawing of 100 g strawberry under 195 W microwave power for 14 minutes,at this time,the juice loss rate of strawberry is the least,the content of soluble solids is higher,and the appearance quality is better.2.Using functional oligosaccharide to replace part of sucrose to prepare low sugar strawberry preserved fruit,and improving the plumpness of preserved fruit by adding edible gum.First,the kinds of edible gum and functional oligosaccharide in the sugar permeation solution were screened,and then the carrageenan and isomaltol were optimized by single factor experiment.The optimal formula was obtained as follows:the addition amount of soft white sugar was 30%,the addition amount of isomaltol was 10%,the addition amount of carrageenan was 0.4%,the addition amount of citric acid was 0.5%,the addition amount of carmine was 0.1%,and the material liquid ratio was 1:2（w/w）,the sensory quality of strawberry preserved fruit prepared by this formula is the highest,and the addition of functional substances also improves the nutritional value of the preserved fruit.3.Ultrasonic assisted osmotic technology was used to promote the mass transfer rate in the process of sugar permeation.Through response surface test,the ultrasonic power（A）,ultrasonic time（B）and sugar soaking time（C）were optimized.The optimal processing parameters were:ultrasonic power 200 W,ultrasonic time 66 min,sugar soaking time 26 h.At this time,the comprehensive score of preserved fruit was the highest（0.7499）.The regression equation of comprehensive score（Y）to A,B and C was established:Y=0.65+0.088A+0.043B+0.14C+0.030AB+2.325×10^-3AC+0.020BC-0.20A²-0.10B²-0.14C²4.The technological parameters of hot air microwave combined drying were as follows:first,hot air drying at 65℃for 10 hours,then turning to 3 W/g microwave power density for 80 minutes.This drying method saves time and energy,and the quality of preserved fruit is better.5.The results of quality analysis of strawberry preserved fruit after optimization:water content is 20.65%,water activity is 0.613,preserved rate is 34.63%,total sugar is 59.57g/100g,total acid is 1.51 g/100 g,vitamin C is 7.46 mg/100 g,protein is 1.13g/100 g,fat is 0.41 g/100 g,dietary fiber dimension is 5.87 g/100 g,total energy is1113.66 k J,glucose is 17.88 g/100 g,fructose is 14.90 g/100 g.Sucrose<0.2 g/100g,total phenolis 46.85 mg/100 g,flavone is 14.79 mg/100 g,anthocyanin is6.12mg/100g,DPPH clearance is 95.27%,rich in nutritional value,low in sugar and calories,with antioxidant effect.6.The shelf life of strawberry preserved fruit was 40 days at 35℃and 15 days at 45℃by ALST method.It was predicted that the shelf life of strawberry preserved fruit was 106 days at room temperature.