Comparison Of Effects Of Ultra-high Pressure Treatment And Heat Treatment On Qualities Of Tropical Fruit Juices

Fresh juice is popular because of containing the fruit frangrance and flavor matter, but asthe presence of micro organisms, not only these qualities of fresh juice easily are damagedand also the nutritional content of the juice has been broken down. These consume thenutritional content, make the storage period shorter and decrease the safety of juice.Nowadays, the food safety is more concerned, it becomes hot off the press in the field of foodscience how to effectively control the harmful microorganisms in fruit juices and at the sametime probably preserve the quantity of nutrients and flavor ingredients.Ultra high pressure(UHP) technology is considered to be one of the most potential and promising nonthermalpreservation techniques in food industry.Comparison of effects of ultra high pressure and heat treatment on qualities of tropicalfruit juices were researched in this paper.Sensory quality, nutrient components andphysicochemical properties of three different fruit juices (pineapple juice, mango puree,lychee juice) were studied as well, based on achievement of commercial sterilizationrequirements by UHP treatment and heat treatment separately.The main contents andconclusions obtained were introduced as follows.(1)Sensory quality, nutrient components and physicochemical properties of pineapplejuice were studied, based on achievement of commercial sterilization requirements by UHPtreatment and heat treatment separately. The results showed that total number of bacteriadeclined with the increase of pressure (300~500 MPa) and arrived commercial asepsis at 400MPa for 10min. Besides, the sterilization was at the same level by heat treatment (85℃for5min); pH value, total acid, total sugar, soluble solid content of pineapple juice had nosignificant change in both UHP treatment and heat treatment(P>0.05); the system of juicewas stable by UHP treatment; the color of juice by UHP was better than that of heat treatment,while the value of L*, a* and b* changed significantly (P<0.05) after UHP treatment; theretention of antitype ascorbic acid appeared to be 94.92%, which was much higher than thatof the heat treatment; the results of quantitative descriptive analysis (QDA) showed that thepineapple juice after UHP treatment was more closer to control sample than that under heattreatment in color, flavor and taste.(2)Sensory quality,nutrient components and physicochemical properties of mangopuree were studied, base on achievement commercial sterilization requirements by UHPtreatment and heat treatment separately. The results showed that total number of bacteriadeclines with pressure (300~500MPa) increase and arrived commercial asepsis at 450MPa for 20min. Besides, the sterilization were at the same level by heat treatment(85℃for 10min);pH value, soluble solid content of mango puree have no significant change in both UHPtreatment and heat treatment (P>0.05);the color of mango puree by UHP was much betterthan heat treatment,while the value of L* and b* were changed significantly (P<0.05)afterUHP treatment,except of the value of a*;the retention of antitype ascorbic acid was appearedto 91.18%,which is much higher than the heat treatment;the results of QDA showed that themango puree after UHP treatment was more close to control sample than the heat treated incolor, flavor and taste.It is concluded that UHP treatment can effectively inactivate themicrobe and maintain the flavor and quality of mango puree.(3)In order to investigate the effects of UHP on the activities of peroxidase (POD) andpolyphenol oxidase (PPO) in freshly squeezed lychee juice,UHP treatment(300~450MPa,10~40min) and the combined treatment of UHP(450MPa,20min) and temperature(10~60℃)are conducted on fresh lychee juice.Besides, physicochemical properties and Sensory qualitywere studied to explore the quality of lychee juice.The results showed that the POD wasactivated when the UHP treatment on the lychee juice was carried out under the temperature28℃,the dwell time 20min and the pressure between 300~450 MPa.The POD activity reachedthe maximal level under pressure of 300Mpa.The PPO residual activity was rapidly decreasedwith the increasing of pressure,and reached 45.5% at the pressure of 450MPa. Lychee PODwas more pressure resistant than PPO.The residual activity of PPO and POD was rapidlydecreased with the increasing of dwell time at the pressure of 450 Mpa.Combined treatmentof UHP and temperature had certain synergistic effect for POD and PPO inactivation,and thesynergistic inhibition effect would be more obvious with higher temperature.The pH valueand soluble solid content of lychee juice have no significant change in the combined treatmentof UHP and temperature (P>0.05);The retention of antitype ascorbic acid was decreased withthe increasing of temperature.L* value of juice after being conducted by the combinedtreatment of UHP and temperature increased significantly and the color of juice isimproved,but△E* value between the deal samples and control sample changed significantlywith the synergizing temperature increased.The results of QDA showed that the lychee juiceafter temperature of 10℃or 28℃synergizing UHP treatment was more close to controlsample than other treatments in color, flavor and taste. Sensory quality was declined when thesynergizing temperature was increased.It is concluded that UHP treatment can effectively inactivate the microbe and maintainthe flavor and quality of pineapple juice, mango puree and lychee juice.