Study On Polyphenol Oxidase Characterization Of Banana And Inhibition Of Browing In Banana Wine

Banana is one of the fruits with best economy in the world and has excellent nutritionaland health value. But banana is usually used for fresh due to the processing problems, andthere are few products made by bananas, especially for the drinks and fruit wines. Enzymaticbrowning takes place in banana processing, which easily make the products quality bad andhave a bad influence on marketing. Further research banana enzymatic browning of factorsand controlling technology play an important role in promoting the development of theprocess technology and the quality of banana. In this article, Baxi banana (Musa AAACavendish cv Baxi) was used as the main material to discuss the enzymology characteristicsof PPO in banana. Simultaneously, several common browning inhibitors were selectedaccording to the inhibition effect on PPO and storage quality, and the composite inhibitioneffect and conditions were analysised. The main results were as follows:The changes of indexes in processing of banana mature in two storage temperatures:Stored respectively at18℃and24℃, hardness, content starch, tannin and pectin content ofbanana were all gradually reducing, while the content of MDA and reducing sugar graduallyincreased. At the two temperatures, variation trend of all the indexes stayed the same, but theindex rate at higher temperature changed faster.The enzyme activity change of PPO, POD and CAT in banana maturation: The enzymeactivity of banana’s PPO, POD presented higher at first and then declined with the increasingof maturity. What’s more, they were significant positive correlations and the correlationcoefficient of them was0.9739(P<0.01). When the storage temperature was18oC, theenzyme activity of PPO was significant negative correlation with the hardness (-0.8756;P<0.05), starch content (-0.9201; P<0.01) and pectin content (-0.8959; P<0.01). The enzymeactivity of POD was significant negative correlation with the hardness (-0.8917; P<0.05),starch content (-0.9773; P<0.01), tannin content (-0.9002; P<0.05) and pectin content (-0.9605; P<0.01). What’s more, the enzyme activity of POD was significant positivecorrelation with the reducing sugar (0.9145; P<0.05). The same, the enzyme activities of PPOand POD were significant positive correlations with the reducing sugar content and thecorrelation coefficient of them were0.8471(P<0.05),0.9709(P<0.01) when the storagetemperature was24oC. The enzyme activity of PPO was significant negative correlation withstarch content (-0.8467; P<0.05) and pectin content (-0.9177; P<0.01). The enzyme activity ofPOD was significant negative correlation with starch content (-0.8779; P<0.05), tannincontent (-0.9228; P<0.01) and pectin content (-0.9605; P<0.01). There was no correlation with MDA. Enzymatic activity of CAT changed more, but the whole trend still increasedfirstly and then decreased, and there was no relationship between the change of enzymeactivity and indexs.The enzymology characteristics of banana PPO: the optimum pH of PPO was6.5, whilethere was higher enzyme activity in the nearly neutral condition, and it will appeared two rushhours in pH5.5and6.5. Between them, the PPO activity was the largest in the6.5andanother peak time was at the pH5.5. There appearing the double phenomena due to the PPOisozyme. The best temperature for the enzyme live of banana’s PPO was30oC. The thermalstability was poorer and in the60oC, PPO enzymatic activity inhibition was23.95%. But from60~75oC, the inhibition rate rised more slowly. When the temperature reached80oC, enzymeinhibition rate was up to50.34%, and it was doubled than60oC inhibition rate. But when thetemperature reached90oC, the inhibition rate increased sharply, reached up to91.73%. Whenthe temperature reached100oC, PPO was almost completely inactivation, and inhibition ratereached99.46%.The commonly used inhibitors on banana PPO inhibition effect: we explored theinhibition effect which was influenced by different consistences through the three inhibitors,such as citric acid, sulfur dioxide and ascorbic acid. The study revealed that in all inhibitors,the ascorbic acid had the best inhibition effect, adding the range of0.1~0.5g/kg, and thesuppression ratio could be up to97.5%~98.35%. The next was sulfur dioxide (0.10~0.15g/kg),and the inhibition effect was11.85%~16.77%in the add range. But the citric acid(1.0~5.0g/kg) inhibition effect was the worse, only could be reach1.07%~9.04%. If we onlyused the ascorbic acid as a separate inhibitor, the best inhibition effect was the8th~10thhourafter treatment. If we used the sulfur dioxide as inhibitor, the effect appeared at the10th~18thh.The best effect in the treatment of collaborative inhibition (add dose of VCis0.2g/kg and SO2is0.12g/kg) was the12th. What’s more, the best inhibit enzymes activity pH was4.0.The research of process parameters on banana PPO inhibition: If the single factor wasused for the response surface optimized combination, the model showed the highersignificance, R2=0.900. The X3(pH) and X2(VCconcentration) in linear item had thesignificant influence on the PPO enzyme activity (P<0.01). The next was X4(dealing time)(P<0.05), but the X1(SO2concentration) had no influence (P>0.05). But the square andinteractive items were very significant (P<0.01). The central combination design resultshowed that SO2concentration was0.12g/kg, and ascorbic acid was0.2g/kg. The pH value ofenzyme action was3.83and the process-time was12.6h. In this condition, the PPOenzymatic activity was just92.05(u/min·g) and the inhibition rate was up to96.98%. The test was used to verify the technological parameter, and the result showed that the real enzymeactivity was92.27(u/min·g) on average and inhibition rate reaches96.62%. Compared toprediction theory (92.05u/min·g), the relative error was about0.37%.The application of technological parameters of PPO enzyme activity inhibition in thebanana fruit wine: The technological parameters (SO2concentration was0.12g/kg, ascorbicacid was0.2g/kg, pH value of enzyme action was3.83and the process-time was12.6h) wereapplied to the color protection treatment of banana pulp, the result showed that banana pulpcolor was lighter and only few appeared browning. But banana pulp by the conventional colorprotection treatment (SO2concentration was0.06g/kg) appeared browning seriously and90%of the surface turned black brown. Yeasts of71B, L45, W15and EC1118were selected toferment banana wine after color protection. Using the new color protection technology, thebanana wines fermented with different yeasts appeared light yellow, and the wine color valueswere between0.118and0.138. But using the conventional color protection technology, thecolors of wines were deeper, and the color values were between0.174and0.198. What’s more,the color values of wines fermented with same yeast but different color protection technologyhad significant differences (P<0.01). Meanwhile, after the determination and analysis of thegeneral physical and chemical indicators in wines which are treated separately by the new andconventional color protection treatment, it showed that the new color protection technologyhad no significant influence on the capacity of the yeast fermentation. After sensoryevaluation, the yeast EC1118was selected as the most suitable for banana wine fermentation.