| Hamimelon is a unique fruit in Xinjiang,and its unique climate and geographical conditions have made it "fragrant and sweet as honey".But because the ripe picking period of cantaloupe is relatively concentrated,it is also stored and transported unchanged.Every year,a large number of high-quality cantaloupes cannot be shipped to the inland market,causing waste.The non-thermal processing technology of ultrahigh pressure can keep the flavor and quality of original Hamimelon juice to the maximum extent and reach the hygienic standard.In this study we based fresh Hamimelon juice as the research object,which was a study of the essential enzyme activity(Alcoholdehydrogenase,ADH ? Acyltransferase,AAT ? Hydroperoxide Lyase,HPL?Lipoxygenase,LOX?Phospholipase A1,PLA-1?Phospholipase A2,PLA-2)in Hamimelon juice before and after the ultrahigh pressure processing.And amino acids automatic detector was adopted to test the ultrahigh pressure of Hamimelon juice amino acids analysis,explored the ultrahigh pressure processing after the changing rule of the amino acids content and composition in the Hamimelon juice.Using the principal component analysis to analyze the correlation between the condition of high pressure processing with essential enzymes,amino acids.In addition,the changes of quality were studied under different ultrahigh pressure treatment.The main results were as follows:(1)The ultrahigh pressure treatment has a passivation effect on ADH,AAT,HPL,LOX,PLA-1,and PLA-2.After 500 MPa,35 ?,15 min treatment the residual enzyme activity of 6 kinds enzymes respectively 0,0,3%,73%,3%,28.5%.At the same time,under 350 MPa and 400 MPa,45? and 55?,10 min and 15 min conditions 6 enzymes were activated by different degrees.There are two kinds of correlation in principal component analysis between the six enzymes activity and ultrahigh pressure conditions,respectively 35?,45? and 55?.Under the majority condition of 35?,400 MPa 6 kinds of enzyme residual activity can maintain a higher level.(2)The effect of amino acids by the different pressure contents was not obvious,and as the pressure increases the content of amino acids was maintained at a certain level.Under 350 MPa,400 MPa,450 MPa,500 MPa the total concentration of amino acids were 0.5 g/100 g,0.48 g/100 g,0.48 g/100 g,0.47 g/100 g.Under the35? and 55? total content were 0.535 g / 100 g,0.437 g / 100 g.Compared with normal temperature the total concentration was 0.422 g / 100 g.Proper heating can increase the content of amino acids in the melon juice,but in high temperature can make the amino acids decline.The change of total amino acids content almost ignored by the treatment time and the total amount were 0.43 g/100 g,0.41g/100 g,0.41 g/100 g,respectively under 400 MPa for 5 min,10 min and 15 min.The SRC value of amino acids were significantly different in the experiment conditions.450 MPa,35?,5 min is 71.9,500 MPa,15 min at room temperature is15.7.The RC value of the amino acids most were close to 1 under 450 MPa,45?.With the increase of time,the balance of amino acids in Hamimelon juice can be destroyed to a certain extent,and the nutrition was reduced.The SRC value of amino acids was only 39.0 under 500 MPa,55?,15 min.(3)Based on the principal component analysis,the amino acids extracted from Hamimelon juice can be extracted three principal components,and the cumulative contribution rate were 86.93%,which can basically summarize all amino acids information.The comprehensive score of amino acids were the highest in the 500 MPa,35?,15 min condition,the minimum under 450 MPa,15 min at room temperature.The overall score under 11 conditions were not significant.(4)After ultra-high pressure treatment of Hamimelon juice,soluble solids and pH values change were very small.500 MPa,55?,15 min were 10.4 and 6.22,respectively.The soluble solids and pH values under the different conditions influence will be a trend of rise or decrease,which was not very close to the original Hamimelon juice.The turbidity values after ultra-high pressure treatment were higher than theoriginal juice.Intensified as the test conditions turbidity value decreases,and 450 MPa,55?,15 min the turbidity value was 723.4 NTU.The colour of Hamimelon juice under the high pressure was tended to more bright.The L value under 450 MPa,55?,15 min was 34.81,compared with the original fruit juice increased by 2.95.The preservation of Vc was reduced under the high pressure treatment.In cooperation with the intermediate temperate Vc has maintained at a certain level,500 MPa,35?,5 min was 84.8%.The preservation of Vc in Hamimeom juice was damaged under high temperature,500 MPa,55?,15 min the preservation of Vc rate was 61.2%.At the same time,the vast majority of microbes in the Hamimelon juice were exterminated under the synergistic effect between the pressure and temperature,more than 450 MPa conditions bacterial colonies ?10,to ensure the safety of the melon juice. |
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