| Apple is nutritious,especially the polyphenols it contains many functional properties.Reports showed that they could be used as natural food or drug additives.For example free radical scavenging,antioxidant,cancer-preventing,blood pressure-lowering,heart disease-preventing,anti-caries,anti-allergic and anti-virus features.’Fuji’ apple was used as materials in this research.The stability of polyphenols in apple fruit flesh and correlation of other physicochemical parameters was investigated during the cold storage under 0℃±1℃.Simultaneously,the stability and antibacterial properties of polyphenols in apple peel,flesh and seeds under different conditions were studied to provide some reference to the future study of new types of safe food or drug additives.The main results were exhibited as follows:(1)With the extension of storage time,the pH value of ’Fuji’ apple flesh gradually increased;the contents of soluble protein,rutin,quercetin,catechinic acid and epicatechin also went up gradually;conversely,firmness and DPPH·scavenging activities of polyphenols experienced a gradual downward trend;the contents of malic acid,citric acid,titratable,water,total phenols,chlorogenic acid and phlorizin went down little by little;SSC increased first and then decreased;an adverse change was shown in the contents of fructose,glucose and sucrose;compared to all of these components,there was no significant change for the content of oxalic acid.(2)The total phenol content in apple flesh was stable during the storage period of 0～90 days,followed by a gradual degradation in the following 90～180 days and the DPPH·scavenging activities of apple polyphenols showed a positive correlation with the content of total phenolics,chlorogenic acid and phlorizin.In addition,during the cold storage,there was a sound correlation shown among the main quality parameters in apple.With principal component analysis and cluster analysis,the quality evaluation indicators of apple could be simplified as total soluble solid,hardness,solid acid ratio and moisture content.These results provided a theoretical basis to the fast evaluation of apple’s physicochemical properties.(3)When the polyphenol solutions of the peel and flesh of ’Fuji’ apple were exposed under different temperatures of 60℃,70℃ and 80℃,there was no significant difference among the changes of DPPH·scavenging activities caused by the content of total phenols,procyanidine and the total flavonoid.When the temperature was increased to 90℃,the DPPH·scavenging activities of the total phenols and procyanidine in polyphenol solutions of peel and flesh were both decreased with an extension of time.Under 90℃,the total flavonoid content increased and the polyphenol solution of flesh was more stable than the polyphenol solution of peel.When the pH value of the peel polyphenol solution was 8,there was no significant changes of the DPPH·scavenging activities of total phenols,procyanidine and the total flavonoid in the solution.When the pH values of the flesh polyphenol solutions were 6 and 8,there was no significant changes of the DPPH·scavenging activities of total phenols,procyanidine and the total flavonoid in the solution.Under dark conditions,the DPPH·scavenging activities of total phenols,procyanidine and the total flavonoid contents in both peel and flesh solutions were stable and the flesh polyphenol solution was more stable than the peel polyphenol solution.Therefore,the polyphenols in peel of ’Fuji’ apple should be stored or used under low temperature、weakly alkaline and dark conditions,while the polyphenols in flesh of‘Fuji’apple should be stored or used under low temperature、neutral or weakly alkaline or weakly acid pH and dark conditions.(4)With the increase of the concentration of sodium benzoate in the polyphenol solutions of apple peel or flesh,both of the total phenolic content and the total flavonoid content increased significantly,and procyanidine had no significant changes.The DPPH·scavenging activities caused by polyphenolic solution of peel decreased dramatically,while the DPPH·scavenging activities caused by polyphenolic solution of flesh first experienced an increase trend and then decreased.With the rising of the potassium sorbet concentration in peel polyphenolic solution,the content of total phenolic content and its DPPH·scavenging activities went down significantly,and the total flavonoid increased first and then decreased and there was no significant change for the content of procyanidine.The flesh polyphenolic solution was stable and with the increase of the concentration of Vc solution,the contents of total phenols and procyanidine and their DPPH·scavenging activities went up dramatically,but the content of total flavonoid showed a dramatic downward trend.With the increase of concentration of sodium sulfite,the content of total phenols increased significantly,and the content of total flavonoid and DPPH·scavenging activities decreased significantly,while procyanidine had no significant changes.With the increase of concentration of hydrogen peroxide in the flesh polyphenolic solution,the content of total phenolic and DPPH·scavenging activity decreased significantly,while the content of total flavonoid and procyanidine decreased significantly.Therefore,the polyphenolic solutions of apple from different sources should be stored and used under the consideration of the types of additives and their concentrations according to the purposes.(5)The total phenolic content in peel polyphenolic solution increased significantly with increase of the concentrations of K+,Ca2+and Cu2+,significantly decreased with the increase of the concentration of Mg2+,and first decreased and then increased with increase of the concentrations of Al3+.The total phenolic content in flesh polyphenolic solution was increased with the increase of the concentrations of Zn2+,Ca2+ and Cu2+,first increased and then decreased with the increase of the concentration of Na+.The total phenolic content in seed polyphenolic solution increased with the increase of the concentrations of K+,Mg2+and Zn2+,first increased and then decreased with increase of the concentration of Na+,and significantly increased with increase of the concentrations of Ca2+and Cu2+.The DPPH·scavenging activity of peel polyphenolic solution significantly decreased with the increase of the concentrations of Mg2+,Zn2+and Al3+,increased significantly with the increase of the concentration of Ca2+.The DPPH·scavenging activity of flesh polyphenolic solution significantly decreased with the increase of the concentrations of Mg2+andCu2+,and first increased and then decreased with the increase of the concentrations of Na+and Ca2+.The DPPH·scavenging activity of seed polyphenolic solution significantly decreased with the increase of the concentrations of K+,Ca2+,Zn2+and Cu2+,and increased significantly with the increase of the concentration of Na+.The content of procyanidine in peel polyphenolic solution increased with the increase of the concentrations of Na+,Zn2+and Cu2+,decreased with the increase of the concentrations of Ca2+ and Cu2+,and first increased and then decreased with the increase of the concentration of Mg2+.The content of procyanidine in flesh polyphenolic solution increased with the increase of the concentrations of Na+and Ca2+,and decreased with the increase of the concentrations of Zn2+,Al3+andCu2+.The content of procyanidine in seed polyphenolic solution decreased with the increase of the concentrations of Mg2+,Ca2+andCu2+,and increased with the increase of the concentration of K+and Na+.Therefore,the polyphenolic solutions of apple from different sources should be stored and used under the consideration of the types of metal ions and their concentrations according to the purposes.(6)The antibacterial effects of polyphenols in apple peel were better than those in apple seeds and flesh.Among all the tested bacteria,polyphenols showed the best antibacterial effects on Staphylococcus aureus.The minimal antibacterial concentration of peel polyphenols to Staphylococcus aureus MIC was 0.32 mg/mL and that for MBC was 2.55 mg/mL.The optimum pH range of the antibacterial effects of apple polyphenols was from 4 to 5 with the temperature below or equal to 65℃.The polyphenols in apple peel,flesh and seeds significantly decreased the decay rate and lesion diameter of Kiwi caused by dyed gray mold,which means that apple polyphenols could be used as a kind of edible coating during the freshing and storage period of Kiwi. |
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