Quality Control Of Pomelo Juice

The pomelo produced locally in Guangdong was used as raw material,and the quality of pomelo juice was improved by two treatment methods: Using ultra-high pressure treatment and adding aspergillus niger solid-state fermentation product.Above processes could simulate the effects of ultra-high pressure on polyphenol oxidase and peroxidase enzyme inactivation kinetic equation.Response surface experiment was used to optimize the fermentation conditions of aspergillus niger solid-state,which could apply on pomelo juice debittering and depectinizing with pomelo peel.In addition,the simultaneous determination of four flavonoid glycosides in pomelo by high performance liquid chromatography was studied.The main research results of the determination method of limonin and limonin are as follows:(1)After different UHP treatment conditions,the activities of PPO and POD in pomelo juice conformed to the first-order kinetic enzyme inactivation law;Under the treatment conditions of600 MPa/18 min,the inactivation rate of PPO reached 94.68%,and that of POD reached 90.78%.The activities of these two enzymes decreased by more than one logarithmic cycle.(2)The dominant bacterium in pomelo juice was Pantoea,and the abundance of Pantoea in pomelo juice without UHP treatment accounted for 98%;As the increase of processing pressure,the total amount of bacteria in pomelo juice decreased,and the absolute abundance of each type of bacteria decreased;The pressure tolerance of Pantoea was lower than that of other bacterium,and its relative abundance gradually decreased along with the increase of UHP treatment intensity;However,it is still the dominant strain in pomelo juice.Under the highest-intensity high-pressure treatment conditions(600 MPa/14 min),the proportion of Pantoea in pomelo juice still accounted for more than 60%.(3)The response surface Box-Behnken test was used to acquire the optimal culture conditions of the fermentation of solid Aspergillus niger pomelo peel: The solid-liquid ratio was1:2.5,fermentation time was 64 h,and the inoculation amount was 2.5%.Under this optimal condition,the enzymes produced by fermentation are used for debittering and clarification of pomelo juice.The removal rate of naringin,limonin,pectin was 93.18%,34.37%,95.68%,respectively.(4)The high performance liquid chromatography for determing the amount of rutinnaringin,naringin,hesperidin,neohesperidin and limonin in pomelo was optimized.Column: Bio-Bond 5?m C18(4.6 mm × 250 mm);Injection volume: 10 ?L;Detection wavelengths of flavonoid glycosides and limonin were 283 nm and 220 nm;Mobile phase: Acetonitrile(A)and water(B),gradient elution: 0 min,22 % A;8 min,22% A;10 min,95% A;16 min,95% A;18 min,22% A;20 min,22% A,flow rate was 1 m L/min.Under this determination condition,the above five components were well separated;The correlation coefficients of the standard curves were all beyond 0.999 7,the detection limit was 0.69?1.72 mg/L,the limit of quantification was 1.51?3.15 mg/L,and the relative standard deviation was less than 2%.The sample recovery rates were all beyond 98%,and the relative standard deviations of the sample recovery rates were all less than 2%.Under the above determination conditions,the contents of rutinnaringin,naringin,hesperidin,neohesperidin and limonin in young pomelo fruits were determined to be 8.49%,8.05%,1.30%,and 1.31%,1.46%,respectively.The contents of rutanaringin,naringin,hesperidin,neohesperidin and limonin contained in pomelo juice were 1.41%,2.63%,0.23%,0.16%,0.78%,respectively.