Study On The Technology Of Preparing Jasmine Flower Syrup By Low-Temperature Dry Impregnating With Solid Sugar

The demand for flavor syrups has been increasing in recent years and the research of flavor syrup are receiving more and more attention.Developing high-value and diversified products of solid sugar and promoting the growth of industrial consumption of solid sugar have become the new trend of development at present.Low-temperature dry impregnation of solid sugar was used to prepare jasmine flavor syrup to develop a flavor syrup with good quality,high nutritional value,unique flavor,natural,no exogenous additions,and no boiling.This will improve the comprehensive utilization of jasmine flowers and promote industrial development.In this study,jasmine flavor syrup was prepared by low-temperature dry impregnation using solid sugar(including yellow multicrystal rock sugar,polycrystalline white ice,single crystal white rock sugar,white granulated sugar)and jasmine flower as raw materials.The process conditions of impregnation process were optimized by response surface experiment,and the mass transfer analysis of impregnation process was carried out by different dynamic models to determine the optimal model.On this basis,the sterilization effect of different ultra-high pressure treatment conditions on jasmine flavor syrup was studied.The technological parameters of ultra-high pressure sterilization were optimized by response surface methodology(RSM),and the physical and chemical indexes and nutritional components were determined.At the same time,the jasmine flavor syrup after ultra-high pressure sterilization was stored at 5℃,25℃and 35℃for 35 days,and the storage period was studied.Microbial analysis and physical and chemical indexes were determined during the storage process.The main conclusions are as follows:(1)To clarify the effect of solid sugars on the yield of jasmine flavor syrup,the jasmine flavor syrup was prepared by low-temperature dry impregnation of solid sugar,and the change of yield of jasmine flavor syrup during the process was analyzed.Through single factor test,it was found that yellow multicrystal rock sugar impregnated jasmine flower got the highest rate of flavor syrup.With the increase of impregnation time,the yield of jasmine flavor syrup increased rapidly from 0 to 96 h,and then slowly increased.With the increase of flower sugar mass ratio(g/g),the yield of jasmine syrup increased firstly and then decreased slowly,and the yield was higher at 1:1.2 g/g.There was no single correlation between the impregnation efficiency and the number of brown-ice sugar mesh.The yield of jasmine flavor syrup increased rapidly with the increase of yellow multicrystal rock sugar mesh from 6 to 20 mesh.The yield of jasmine flavor syrup decreased significantly after 20 mesh,and the yield of flavor syrup was relatively high at 20 mesh.On the basis of single factor experiment results,response surface analysis method was used to determine the optimal processing conditions for the preparation of flavor syrup:impregnation time 130.0 h,mass ratio of flower sugar 1:1.2 g/g,yellow multicrystal rock sugar 21 mesh.Under these conditions,the maximum yield of jasmine flavor syrup is 39.82%.RSM was used to predict the effects of various factors on the yield of jasmine flavor syrup in the following order:impregnation time、number of yellow multicrystal rock sugar mesh、mass ratio of jasmine sugar.(2)Four kinetic models including Page,Weibull,Azuara and Peleg were used to accurately describe the mass transfer kinetics of impregnation between solid sugar and jasmine flower.The model with the maximum coefficient of determination(R~2)and the minimum root mean square error(RMSE)and mean absolute percentage error(MAPE)was selected to evaluate the matching results of experimental values and p redicted values.The model fitting results showed that Page could be used to describe the mass transfer kinetics of water loss rate of jasmine flower impregnated with yellow multicrystal rock sugar.Weibull can be used to describe the mass transfer kinetics of solid growth rate of jasmine flower impregnated with yellow multicrystal rock sugar.Both Page and Weibull can be used to describe the mass transfer kinetics of water loss rate of jasmine flower impregnated with single crystal white rock sugar.Azuara has a good fitting effect on the mass transfer process of solid gain rate impregnated with single crystal white rock sugar.(3)The effect of pressure,pressure holding time and cycle times on total bactericidal rate of jasmine flower flavor syrup was studied.The bactericidal rate of ultra-high pressure on jasmine flavor syrup is proportional to pressure,holding time and cycle times.The optimum process parameters of ultra-high pressure sterilization were optimized by RSM as follows:pressure 600 MPa,pressure holding 10 min,circulation 4 cycles.Under this process condition,jasmine flavor syrup achieved good bactericidal effect,and the bactericidal rate reached 98.64%.The effects of ultra-high pressure on the physicochemical index and nutrient composition of jasmine flavor syrup were studied.After pressure treatment,there was no significant difference in soluble solids content among samples,while turbidity and viscosity decreased significantly.The contents of total phenol,total acid and total flavone had no significant change,while the contents of sucrose decreased,and the contents of fructose and glucose increased.(4)The storage period of jasmine flavor syrup after ultra-high pressure treatment at different temperatures(5℃,25℃,35℃)was studied,and the microbial indexes(total number of colonies,escherichia coli and yeast)and physical and chemical indexes(p H,soluble solid content,viscosity,turbidity and color)were measured.During the storage period of 35 days,no molds,yeasts and escherichia coli were detected,and under the storage conditions of 5℃and 25℃,indicating that the storage temperature had an important effect on inhibiting the growth of microorganisms.The number of microorganisms showed a downward trend,always in line with the safety and health standards.Under the storage conditions of 35℃,the total number of bacteria increased rapidly.The soluble solids of jasmine flavor syrup remained in the range of 62.9°Brix to 63.6°Brix during storage,and did not change significantly.At different storage temperatures,p H changed significantly(p<0.05),p H remained between 5.03 and 5.19,viscosity decreased,turbidity first decreased and then gradually increased,color difference increased rapidly with storage time,and the higher the storage temperature,the faster the color change.