Study On Mass Transfer And Quality Of Flavor Syrup For Jasmine Extracted By Solid Osmosis At Low Temperature

In recent years,Chinese sugarcane industry has been suffering from increasingly serious industry-wide losses due to high raw material cane production costs,single product,and weak market competitiveness,etc.The development of diversified high-value products from sugarcane resources has become an effective way for the industry to improve economic efficiency.With the development of specialized,nutritious and functional products in downstream markets such as food and beverages,the market demand for syrups rich in functional ingredients such as flowers,fruits and vegetables or berries and dates with health benefits is increasing.However,at present,flavored syrups are mainly produced by thermal concentration technology,which leads to the loss of nutritional,healthy and aromatic substances.In view of this,in this paper,jasmine flowers and brown rock sugar were used as raw materials to prepare syrup with jasmine flavor and nutrients by ultrasound-assisted solid osmotic dehydration（SOD）at low temperature,the solid osmosis process and mass transfer kinetics of the imbibition process were investigated,as well as the physicochemical properties and functional characteristics of the flavored syrup.The main research contents and results are as follows:（1）Study on the process of preparing jasmine flavor syrup by solid osmotic dehydration at low-temperature and syrup quality attributes.The effects of different process parameters（sugar dose and sugar size）on the water loss,solid gain,syrup yield and quality of jasmine during SOD at low temperature were investigated,and it was found that the water loss and solid gain of jasmine SOD reached the maximum after 168 h at a higher sugar dose of 120%（w/w）and moderate sugar size of 6-20 mesh,which were 36.42 and 36.74 g/100 g,27.52and 27.72 g/100 g,respectively,and the highest syrup yield,which increased by28.15-149.53%and 8.41-9.65%relative to the conditions of other process parameters.The SOD was effective in extracting most of the aromatic compounds and active components such as polyphenols and flavonoids from jasmine,but the process parameters did not have a significant effect on the extraction of the main volatile substances（p>0.05）.Total phenols,total flavonoids contents and DPPH of the syrup were highest at lower sugar dose of 40%（w/w）,reaching 297.25 mg GAE·kg^-1 dw,347.59 mg RU·kg^-1 dw and 421.90 mg Tx·kg^-1 dw,respectively.（2）Effect of ultrasound on mass transfer and quality of jasmine flavor syrup prepared by solid osmotic dehydration at low-temperature.Three ultrasonic treatments were performed at SOD 48 h,60 h and 84 h to study the effects of ultrasound on water loss,solid gain,syrup yield and quality of jasmine by solid osmotic dehydration at low-temperature.It was found that ultrasonication significantly promoted the leaching of water,sugar,organic acids,polyphenols,flavonoids and antioxidant activity of jasmine flowers,thus improving the yield and antioxidant activity of syrup.The promotion effect of ultrasound on the leaching of water,polyphenols,flavonoids and antioxidant activity of jasmine flowers was enhanced with the increase of ultrasound time,and after ultrasonic treatment for 120 min,the water loss,solid gain and syrup yield of jasmine flowers were increased by 14.52%,17.47%and 14.73%,respectively.（3）Process kinetics of jasmine flavor syrup preparation by solid osmotic dehydration:Azuara model,Weibull model,Crank model and first-order kinetic equations were used to study the mass transfer kinetics of the solid osmotic dehydration process.higher R² values（0.9675-0.9995）and lowerχ²（0.0008-0.3843）,RMSE（0.0056-0.8820）of the Azuara and Weibull models indicated a good description of the SOD for jasmine’s water and solute transfer patterns,indicated that the water and solute mass transfer patterns of jasmine SOD could be better described.When the sugar dose was 120%（w/w）and the sugar size was6-20 mesh,the SOD of jasmine had the fastest mass transfer rate and the most water loss and solute uptake.Ultrasonication significantly increased the rate of SOD for jasmine’s mass transfer and promoted the diffusion of solutes such as water,sugar and organic acids in jasmine.When the sonication time was 120 min,the equilibrium water loss rate and equilibrium solid increase rate of jasmine increased by 8.50%and 11.01%,and the water diffusion coefficient and solute diffusion coefficient increased by 4.20%and 3.90%,respectively,which was due to the fact that sonication could destroy the tissue structure of jasmine petals,and microscopic channels and pores were formed on the petal surface,thus promoting mass transfer of jasmine.（4）Appropriate amounts of succinic acid,malic acid and glucose were added to the solid osmotic dehydration system of jasmine at low temperature to study their effects on mass transfer and syrup quality of solid osmotic dehydration at low temperature,understanding the effect of jasmine flower composition on the yield and quality of syrup.It was found that glucose and malic acid significantly increased the water and solute diffusion rate,syrup yield and antioxidant activity of jasmine.twofold glucose system DG2 and fivefold malic acid system DM5syrup yield increased by 5.33%and 19.36%,and the DPPH of syrup increased by8.56%and 22.31%,respectively.This was due to the fact that the osmotic pressure of both DG2 and DM5 system syrups was significantly greater than D0,Moreover,malic acid softens the tissue of jasmine,which promotes the material transfer in the process of solid osmotic dehydration for jasmine.