| Royal jelly is a kind of heat-sensitive functional food.It has high moisture content and is difficult to preserve.It is prone to spoilage and deterioration.Currently,vacuum freeze-drying is commonly used in industrial processing to produce royal jelly dry powder,which has the disadvantages of large energy consumption and so on.Therefore,it is very important to explore a new energy-efficient processing method to produce royal jelly dry powder.In this study,the dry powder of royal jelly was prepared by microwave vacuum drying method.The optimum process parameters for the production of royal jelly dry powder by microwave vacuum drying method were determined by response surface analysis,research the secondary structure changes of royal jelly water soluble protein and its effect on the life span of bees and related gene expression levels.The main research contents and results are as follows:Process optimization of producing royal jelly dry powder by microwave vacuum drying:According to Box-Behnken’s center combination experimental design principle,combined with the results of single-factor experimental analysis,with heating temperature Xi,microwave power X2 and material thickness X3 as independent variables,water content Yi and solubility Y2 as response values,a three-factor and three-level response surface was designed using Design Expert 8.0 software to optimize the process parameters for the production of royal jelly dry powder by microwave vacuum drying.The results were analyzed to obtain the water content Y1 and the solubility Y2 model regression equation:Y1=50.267-1.746X1-0.047X2-1.136X3+4.5E-5X1X2+2.234E-16X1X3+3.75E-4X2X3+0.0215X12+5.523E-5X22+0.126X32 Y2=-35.186+5.1 95X1+0.076X2+3.291X3+3.9E-4X1X2-0.020X1X3-1.25E-4X2X3-0.066X12-1.128E-4X22-0.30X32 The analysis of variance of the regression equations of water content and solubility showed that the Prob>F values were<0.01 in both models,indicating that the model reached a very significant level,the degree of fit was better,and the missing parameters were not significant.Optimize the regression equation and the optimum process parameters for producing the royal jelly dry powder:heating temperature X1=40.05,microwave power X2=399.54,material thickness X3=4.01,at this time the moisture content of royal jelly dry powder was 3.56%,the solubility was 90.44%.Study on the secondary structure of water soluble protein from royal jelly:Extraction of water-soluble proteins in fresh royal jelly and dry powder,detection of MRJPs by SDS-PAGE and Native-PAGE,contrast bands,found no significant difference in molecular weight.Determination of fourier transform infrared spectra of fresh royal jelly and dry powder,the infrared spectrum of fresh royal jelly as a standard map,which shows that the main chemical components of freeze-dried powder and microwave vacuum drying powder do not change significantly.The a-helical structure content in the amide I band(1600-1700 cm-1)is greater than the β-sheet and p-tum.Determination of secondary structure in water-soluble protein of royal jelly dry powder by circular dichroism,the results showed that the contents of a-helix,β-sheet,β-turn and irregular structure in fresh royal jelly MRJPs were 28.2%,21.4%,19.0%and 31.5%,respectively.The content of various secondary structure in freeze-dried powder DRJs is basically similar to that of fresh royal jelly,however,the contents of α-helix and β-turns in microwave vacuum dried MRJs increased,β-sheet decreased,and the irregular structure remained unchanged.Effects of royal jelly dry powder and MRJPs on bee lifespan and related gene expression:Using Italian worker bees as a model,50%sucrose solution as basic food,fresh royal jelly(RJ),royal jelly freeze-dried powder(DRJ),royal jelly microwave vacuum drying powder(MRJ),water-soluble protein of fresh royal jelly(RJs),water-soluble protein of freeze-dried powder(DRJs)and water-soluble protein of microwave vacuum drying powder(MRJs)as supplementary food to feed bees,study the effect of royal jelly powder and MRJPs on the life span of worker bees.The results showed that both the royal jelly dry powder group and the MRJPs group significantly improved the survival rate of bees(P<0.05),and the royal jelly group was superior to the MRJPs group,the microwave vacuum drying powder group had no significant difference compared with freeze-dried powder and fresh royal jelly.The expression of AmILP1,AmILP2,AmAKH and Vg genes related to longevity of bee heads in each experimental group was detected by fluorescent quantitative RT-PCR.The results showed that compared with the sucrose group,the AmILP1 gene in each group had an upward trend,but the effect was not significant,and the expression level in the MRJPs group was relatively higher than that in the royal jelly group.AmILP2 gene expression was not significantly different in each group.Compared with the sucrose group,the AmAKH gene was significantly down-regulated in each experimental group(P<0.05),the RJ group,DRJ group and DRJs group showed extremely significant levels(P<0.01).The Vg gene in the bee head was significantly upregulated in each experimental group(P<0.05),RJ and MRJ group showed extremely significant levels(P<0.01).The relative expression of royal jelly group was significantly higher than that of MRJPs group,the relative expression of Vg gene in the sucrose control group is extremely low.The results showed that the royal jelly and MRJPs groups could significantly affect the expression of AmAKH and Vg genes,and the royal jelly group had better prolongation of honeybee life than the MRJPs group. |
