Effect Of ?-Polylysine And High-Temperature Instant On Nfc Blood Orange Juice Sterilization Process And Storage Quality

Not from concentrate?NFC?juice is favored by consumers because of its sweet and sour flavor,pleasant sensory and rich nutrition.The processing technology and mechanism of NFC juice in China were poorly studied and the juice quality changes during storage were not analysed comprehensively,compared with the best NFC juice in the world.Therefore,there were some problems,e.g.,the product quality was not up to the standard and the nutrients were seriously lost during processing and sterilization.The nutritional and commercial value of blood orange were much higher than other orange species.Therefore,Tarocco blood oranges were used as the experimental material to prepare NFC juice and three sterilization methods?the non-thermal sterilization-?-polylysine,high temperature instant sterilization,and synergistic sterilization?were applied to NFC juice.Meanwhile,the sterilization effect and quality change during storage of NFC blood orange juice were mainly studied.By optimizing the processing technology and studying the storage quality and sterilization effect,it would provide theoretical basis and technical support for the processing and storage of NFC blood orange juice.The main research contents were as follows:Firstly,the preparation process of NFC blood orange juice was optimized.The homogenization and sterilization conditions of NFC blood orange juice were optimized by single factor experiment and response surface analysis,taking the stability coefficient as the response value.The best homogenization conditions of NFC blood orange juice were:homogenization pressure was 28 MPa,homogenization times was twice,feed temperature was26?.The sterilization conditions of?-polylysine group,high temperature instant sterilization group and synergistic sterilization group were optimized by single factor and orthogonal experiments,taking sterilization rate as the response value.The best sterilization conditions were:?-polylysine group:?-polylysine concentration was 200?g/mL,temperature was 26?,pH was natural.High-temperature instant sterilization group:sterilization temperature was121?,sterilization time was 4 s,pH was natural.Synergistic sterilization group:sterilization temperature was 96?,sterilization time was 4 s,?-polylysine concentration was 150?g/mL,pH was natural.The dosage of the?-polylysine in synergistic sterilization group was 25%lower than the dosage of the?-polylysine group.The sterilization temperature was 25?lower than the temperature of high-temperature instant sterilization group,but the sterilization time was both 4 s.Secondly,the storage quality of NFC blood orange juice was studied.Under the best homogeneous conditions,four groups of NFC blood orange juice?unsterilized group,?-polylysine group,high-temperature instant sterilization group,synergistic sterilization group?were prepared.The quality of NFC blood orange juice during the storage period was evaluated using the physicochemical indicators,sensory indicators,nutritional ingredients,flavor substances,rheological properties,antioxidant active ingredients and antioxidant activities as indicators.The results showed that any microorganisms were not exceeded the standard in synergistic sterilization group during a short shelf life of 15 days and sterilization effect was good.The physicochemical properties and nutritional components of synergistic sterilization group were not changed.While synergistic sterilization group had bright color and excellent flavor.The loss rate of Vitamin C,total phenol,total flavonoids was 45.34%,32.40%,24.20%lower than unsterilized group,respectively.DPPH and ABTS free radical scavenging rates and FRAP total antioxidant capacity was 39.02%,43.56%,25.29 mg/100 m L,respectively.The comprehensive evaluation of synergistic sterilization group was highest,followed by?-polylysine group,and high-temperature instant sterilization group was lowest.Finally,the sterilization effect of three sterilization methods was explored.The sterilization effect of?-polylysine sterilization group??-polylysine concentration was 200?g/mL?,high-temperature instant sterilization group?sterilization temperature was 121?and sterilization time was 4 s?and synergistic sterilization group??-polylysine concentration was 150?g/mL,sterilization temperature was 96?and sterilization time was 4 s?were analysed,selecting Saccharomyces cerevisiae and Alicyclobacillus acidoterrestris as the typical spoilage microorganisms of NFC blood orange juice.Three sterilization methods could reduce the electronegativity of S.cerevisiae and A.acidoterrestris.Synergistic sterilization had a greater effect on cell membrane permeability than other sterilization methods,showing the fluorescence value of OD₆₀₀ was 6.41 times and 7.55 times that of the control group.While?-polylysine sterilization?inhibition?and high-temperature instant sterilization was 1.60 times and 2.34 times,2.78 times and 5.90 times,respectively.The electrostatic interaction of?-polylysine sterilization?inhibition?could result in the cell wall and membrane damages of S.cerevisiae and A.acidoterrestris.Protein was denatured by the high temperature during high-temperature instant sterilization,showing the transformation of?-helix to?-fold or?-rotation.Furthermore,electrostatic interaction and high temperature denatured protein both played roles in the synergistic sterilization mechanism,which led to stronger destruction strength.In addition,the above sterilization methods could reduce the contents of Adenosine-triphosphatease?ATPase?,Peroxidase?POD?,Catalase?CAT?,Succinate dehydrogenase?SDH?and Malate dehydrogenase?MDH?.Thus it directly affected the internal energy conversion of the typical spoilage microorganisms and the tricarboxylic acid cycle.