Effect Of Ultra-High Pressure Treatment On Quality Characteristics Of Royal Jelly

Royal jelly,secreted by the hypopharyngeal and mandibular glands of nurse worker bees,is a kind of milky white or yellowish pulp.It has many functional properties.However,the pulp-like texture of royal jelly and its physical and chemical properties such as heat sensitivity have special requirements for processing.Ultra-high pressure treatment can reduce the impact of temperature on food,and can change the texture,color,flavor and certain ingredients of food.In order to expand the application field of royal jelly,royal jelly was used as the material,and different ultra-high pressure treatments were used（pressures were 300,400,and 500MPa,and the holding time was 5,10,and 15min）.Study the effects of ultra-high pressure on its color,volatile compounds,active ingredients（proteins,free amino acids,fatty acids,sugars）,bacteriostatic effects,in vitro digestion degree of hydrolysis,and product oxidation resistance.The aim of this study is to provide a basis for ultra-high pressure processing of royal jelly.The research results are as follows:1.Influence of volatile compounds.A headspace（HS）/solid phase microextraction（SPME）method was developed to accurately determine the profiles of volatile compounds from royal jelly.Based on the single-factor tests of extraction temperature and time,sample size,saturated NaCl solution addition.The optimization of the extraction conditions was carried out by response surface methodology.The analytical conditions of the optimized HS-SPME method were:extraction temperature62°C,extraction time 60min,2g royal jelly,1 mL saturated NaCl solution.Under this condition,the average value of the total peak area can reach 3.24799×10¹⁰,and the extraction and separation effect is good.A total of 46 compounds were detected in the untreated group.The 400MPa,15min,500MPa,10min and 500MPa,15min treatment groups were 42,39,and 37,respectively.The types of volatile compounds in other treatment groups did not change much compared with the untreated group.The content of volatile compounds in the treatment groups of 400MPa,15min and500MPa,10min and 15min increased significantly compared with other treatments,among which the types and contents of acidic substances were the highest.The content of acids in the 500MPa,10min and 15min treatment groups was much higher than that of the other treatment groups（p<0.01）,which were 46.40±3.17μg/μL and47.82±4.95μg/μL respectively.They were significantly increased compared with29.49±0.61μg/μL in the untreated group.The 500MPa,5min treatment group had the highest alcohol content,which was 2.76 times that of the untreated group.The500Mpa,10min treatment group had the highest content of esters,ketones,and aldehydes.They were 4.56±0.44μg/μL,5.05±0.09μg/μL,5.58±0.28μg/μL,which was2.70,2.13 and 2.11 times that of the untreated.Cluster analysis found that 400Mpa,15min treatment and 500MPa treatment groups had a greater impact on royal jelly volatile compounds,while 300MPa treatment groups had less effect on volatile compounds.2.Color effect.Under ultra-high pressure treatment at different pressures and times,the b^*values changed significantly.Compared with the untreated group’s17.20±0.97,the b^*value of the 400MPa,10min and 500MPa,5min treated groups increased to 23.57±0.14 and 22.60±0.18,respectively.At the same time,theΔE changed greatly.In the change ofΔE,the treatment group of 500MPa,10min had the least influence on it.3.Influence of rheological properties.The results show that royal jelly is a pseudoplastic non-Newtonian fluid.The shear-thinning behaviour of royal jelly was also retained after Ultrahigh pressure treatment,but high pressure treatment changed its viscosity.Among them,the treatment groups of 400MPa,15 min and 500MPa all increased the viscosity of royal jelly,which was increased by 1.43,1.28,6.42,11.75Pa.s compared with the untreated group.At the same holding time,the viscosity and shear stress gradually increase with the increase of pressure.When the pressure is less than 500MPa,the storage modulus G′of each treatment group increases with the increase of pressure,while the treatment group of 500MPa decreases.The loss modulus G″gradually increases with increasing pressure.4.The influence of protein structure and active ingredients.At the same pressure,the content ofα-helix andβ-sheet decreases and the content ofβ-turn increases with the increase of the holding time.The total amount of free amino acids in the treatment group with the same pressure for 15 minutes was significantly lower than that in the5min,10min treatment group and the untreated group.At the same pressure holding time,the content of 10-HAD increases with increasing pressure.The relative content of total free fatty acids increased under the conditions of 400MPa and 500MPa for15min,and other treatments decreased to varying degrees.The antibacterial effect was highly correlated with the relative content of 10-HDA and total free fatty acids.The sucrose content of all treatment groups was lower than that of the untreated group.The total sugar content was lower than that of the untreated group except each treatment group of 500MPa.5.In vitro digestion effects.Ultrahigh pressure treatment increased the degree of hydrolysis of royal jelly,and the degree of hydrolysis of pepsin and trypsin continuous enzymolysis solution was higher than that of the untreated group.The 300MPa,10 min treatment group had the highest degree of hydrolysis,8.57±0.26%,which was 49.04%higher than the untreated group.The DPPH clearance rate of the pepsin hydrolysate was higher than that of the samples after continuous digestion,and DPPH clearance rate was the highest when the treatment condition was 300Mpa and10min,75.20±2.23%,which was 17.59%higher than that of the untreated group.After continuous digestion,the treatment group with 300MPa and 15min had the strongest total antioxidant capacity and the highest FRAP value was 0.51±0.01mmol/L FeSO4,which was higher than that of the untreated group by 27.50%.