Study On The Effect Of High Pressure Homogenization Treatment On Quality Of Cloudy Peach Juice

This paper studied the effect of high pressure homogenization(HPH)treatment combined with bio-bacteriostatic agent and steam blanching on the quality of cloudy peach juice.the effects of HPH treatment combined with Nisin and Lysozyme on the physical and chemical properties,such as pH,soluble solids,color and other nutrients such as total phenols,flavonoids,Vc,monosaccharides and antioxidant activity were studied;the effect of HPH combined with steam blanching on the color,total phenols,flavonoids,Vc,monosaccharides,and antioxidant activity of cloudy peach juice were studied.This study provided a theoretical basis for the application of HPH treatment to the processing and application of cloudy peach juice.The main conclusions of the experiment are as follows:(1)The effect of HPH treatment combined with bio-bacteriostatic agents on the microorganisms in cloudy peach juice was studied.Adding 200 IU/mL Nisin and 1000IU/mL Lysozyme to cloudy peach juice followed by HPH treatment could significantly improve the inactivation effect.As compared with single HPH treatment(60?/190 MPa),the total bacterial count in cloudy peach juice after HPH(60?/190 MPa)combined with Nisin were reduced by 0.77 log CFU/mL,respectively.Those values of cloudy peach after HPH combined with Lysozyme were reduced by 0.11 log CFU/mL,respectively.No synergistic effect was found for Nisin and Lysozyme when cloudy peach juice treated by HPH.Therefore,the treatment of HPH(60°C/190 MPa)with addition of the bio-bacteriostatic agent could reduce the microorganisms in the cloudy peach juice.At 4?and room temperature storage conditions,the total bacterial count in cloudy peach juice with a single HPH(60?/190 MPa)were kept less than 2 log CFU/mL during 63 days of storage,and the mold and yeast was less than 20 CFU/mL;However,it was slightly higher than cloudy peach juice after same HPH with bio-bacteriostatic agent.(2)The effect of HPH treatment combined with bio-bacteriostatic agent on the quality of cloudy peach juice was evaluated.In terms of physicochemical properties:HPH treatment with or without addition of bio-bacteriostatic agents to cloudy peach juice,the pH values were both decreased,and the soluble solid content were both increased.In terms of color:HPH treatment with or without the addition of bio-bacteriostatic agents in cloudy peach juice,the L~*values were both significantly reduced,the a~*values were significantly increased,and the b~*values were not significantly changed.When the inlet temperatures was 45?and 60?,the PPO activity after HPH treatment was reduced by 18.42%and97.38%.As compared single HPH treatment,the HPH treatment combined with the addition of bio-bacteriostatic agents significantly decreased the PPO activity in the cloudy peach juice.In terms of nutritional quality:there were no significant changes in total phenols and flavonoids content in the cloudy peach juice after a single HPH treatment.There was no significantly change in sorbitol,glucose,sucrose,and fructose after HPH treatment with or without the addition of a bio-bacteriostatic agents to the cloudy peach juice.(3)The effect of HPH treatment combined with steam blanching on cloudy peach juice quality was studied.As compared with single HPH treatment,HPH treatment combined with stream blanching both significantly increased the L~*and b~*values of couldy peach juice,while decreased the a~*value.The residual PPO activity of cloudy peach juice were significantly decreased to less than 5%after HPH combined with steam blanching.Thus,the blanching treatment was beneficial for reducing the activity of PPO and inhibiting the browning of cloudy peach juice.As compared with single HPH treatment,the content of flavonoids and total phenols in cloudy peach juice significantly increased,quinic acid,citric acid,and malic acid were also significantly increased.While,the Vc content didn't change significantly by HPH treatment with steam blanching.Therefore,HPH treatment(60°C/190MPa)combined with steam blanching for 3 min can provide the cloudy peach juice with a good color and nutrition.