Study On Microwave Vacuum And Freeze Drying Technology Of Blue Honeysuckle Berry Chips

Blue Honeysuckle(BHB)berries are rich in anthocyanin,vitamins,and other nutrients,which are beneficial for food and medicine.However,the moisture content of fresh berries exceeds 80%,which is hard to be stored and kept fresh.Meanwhile,the taste of fresh berry is bitter and astringent,and there are few deep-processing products of BHB.The above-mentioned problems affect the application of the nutrition and edible value of BHB.Drying is an effective means to extend the shelf life of berries and increase their value.Because the working principle of freeze-drying is to dehydrate the material at low temperature by reducing the vacuum under the condition of material frozen,which not only keeps the original shape and color of the product,but also improves the retention rate of nutrients,which is the most suitable drying method for processing heat sensitive and high value-added materials.However,single vacuum freeze-drying is time-consuming and costly,which limits its industrial application and promotion.To improve the taste of BHB food and ensure the nutritional quality,improve the processing efficiency of the berry freeze-drying.In this study,BHB was used as raw materials,supplemented by yogurt and fructose syrup as flavoring agents.The combination of single factor experiment and numerical simulation was employed to deterimine the ratio of each component in the formula of BHB yogurt chips was determined.The drying characteristics of the concentrated BHB mixed pulp by using different drying methods,hot air drying,microwave drying,and microwave vacuum drying,were explored,and factors such as temperature,microwave intensity,and microwave vacuum degree were used to determine the color and anthocyanin content of the concentrated mixed pulp.According to the analysis of the influence of changes,microwave vacuum drying is selected as the most suitable drying method for concentrated BHB mixed pulp.The effect of different moisture content conditions on the internal microstructure of BHB yogurt chips puffed by freeze-drying was studied.According to the test results,it is proposed that the combined microwave vacuum-freeze drying can improve the sensory quality of BHB yogurt chips.According to the central combination test method,the optimal process parameter combination of the combined drying program is optined,which provides a theoretical basis for the industrialization of the combined drying of fruits and vegetables such as BHB.The results and discussion are as follows:(1)The single factor test method was used to study the influence of the addition amount of each component(Yogurt,BHB pulp,Fructose syrup)of the BHB yogurt crisp formula on the temperature of eutectic point,co-melting point,texture quality and color quality of the BHB mixed pulp.Combined with numerical simulation,the heat and mass transfer mechanism of the freeze-drying process was verified.The results show that: the range of the additional amount of each component in the formula of Blue Honeysuckle yogurt compound crisp as the amount of yogurt added of 90 g to 100 g,the amount of BHB pulp added of 32 g to 64 g,the amount of yogurt added of 8g to 16 g.According to the production requirement,the dosage of each component can be appropriately adjustment according to the ratio of Yogurt: BHB pulp: Fructose syrup = 6:3:1.The shape of the BHB yogurt composite chip is well maintained,the internal pores are uniform and dense,the taste is moderately sweet and sour,and there is no unpleasant taste such as bitterness and astringency.At the same time,the crispy snacks are rich in fruit flavor and have a yogurt aroma.At the same time,the crispy flakes are rich in fruit flavor and have the aroma of yogurt.The product has a acceptable texture and crisp taste,and the anthocyanin content is higher than that of the BHB products on currently sale,ensuring the rich nutritional value of the product.(2)Through comparative test methods,the drying characteristics of BHB mixed pulp under three different concentration methods: in hot air drying,microwave drying,and microwave vacuum drying.Were investigaged The effects of temperature,microwave power,and microwave vacuum degree on the color and anthocyanin content of BHB mixed pulp were studied.The results indicated the hot air had the longest drying time with the obvious difference of color for the concentration of mixed pulp in dark red,accompanied by serious surface conjunctiva and the worst sensory quality and the lowest anthocyanin retention rate.In the process of microwave concentration to the target moisture content(1.22g/g),the dehydration rate presents a rapid increase first and then a uniform changing trend.Moreover,the microwave power is positively correlated with the temperature of the mixed pulp during the drying process.Under the microwave power of 320 W to 480 W,the material temperature rises significantly,which accelerates the drying rate and also significantly degrades BHB anthocyanin.At the same time,it was found that the protective effect of shortening the drying time on anthocyanin is better than the damaging effect of temperature increase on anthocyanin.Microwave vacuum concentration of BHB mixed pulp combines the advantages of microwave and vacuum,while ensuring the shortest drying time,it also satisfies the highest anthocyanin retention rate and the smallest color difference.The freeze-drying time of the concentrated BHB mixed pulp is shorter than the drying time of the unconcentrated pulp,with high texture quality after drying is better.After drying,the internal microstructure of the crispy chip is complete and uniform.Therefore,a microwave vacuum-vacuum freezing combining drying process of BHB yogurt snack was proposed.(3)During the combined drying process,the central combined test method was used to study the influence of the moisture content of the transition point,the thickness of the chips,and the analytical drying temperature on the drying time of the BHB yogurt chips and the sensory quality after drying.The experimental results and response surface analysis show that: the suitable moisture content of the material transfer point can not only shorten the freeze-drying time,but also have a positive effect on the sensory quality of BHBY chips.The surface color of crisp chips is closely related to the analytical drying temperature.The optimized combination of microwave vacuum and freeze-drying process parameters for BHB yogurt chips is as the critical point moisture conversion from concentration to dehydration at is 65.4%(1.89g/g),fresh chip thickness of 13 mm,and the analytical drying temperature of 36.9?.