Extraction,Purification And Composition Analysis Of Polyphenols From Kiwi Skin Residue

Kiwifruit is known to contain of fibre,carotenoids,vitamin C,and polyphenolic compounds.As is know,polyphenols have antioxidation,antiviral,antigenic,antimicrobial,anticancer properties,etc,and is also used in the treatment for cardiovascular disease.Which was selected as the potential antioxidant source rich in polyphenols.Kiwi skin residue is produced by industrial processing of kiwifruit products,if the abundance potential source of polyphenols in kiwi skin residue could be exploited,it will not only maximize economic value of kiwifruit but also protect the environment.In this study,polyphenols were extracted from kiwi skin residue by the method of ultrasound assisted extraction,then the extracted polyphenols were separated and purified by macroporous resin.The purified phenolic compounds were analyzed by HPLC.The aim of this study was to provide the theoretical basis for the actual production of polyphenols in kiwi skin residue.The research contents and results as follows:(1)This study investigated polyphenols extraction from kiwi skin residue by ultrasound,and the extraction process was optimized by response surface methodology.Taking polyphenols extract as the index,the effects of ultrasonic power,extraction time,extraction temperature and liquid to solid ratio on the total polyphenols yield were examined.On the basis of single factor experiment,the response surface test was designed by using Design Expert 8.0.6 software.The results showed that the optimal extraction conditions were ultrasonic powder of 383.94 W,extraction time of 30.00 min,extraction temperature of 64.81 ? and liquid to solid ratio of 23.10 mL/g for the maximum polyphenols extraction yield of 28.14 mg GAE/g.Under these conditions,the experimental polyphenols extraction yield was(28.10±0.38)mg GAE/g,which was well matched with the predicted values.(2)The static purification of polyphenols extracted by macroporous resin was studied.Firstly,the adsorption rate and desorption rate of 6 kinds of resins(NKA-9,NKA-?,HPD-100,HPD-400,AB-8,D-10)on polyphenolsextract were evaluated,and the results showed that NKA-? got better purification effect.Then,the effects of processing time,resin content,temperature and pH on the adsorption of polyphenols by NKA-? resin were investegated.Firstly,the optimum adsorption process was obtained with adsorption time 4.3 h,crude extract pH2.0,resin addition 1.40 g,temperature30 ?.Under these conditions,the theoretical value of the adsorption rate is95.69%,the adsorption rate of polyphenols was(94.89±0.08)%.Secondly,the mechanism of adsorption process was preliminarily studied,it was found that the Freundlich isotherm equation was more suitable to describe the adsorption of NKA-? resin on the polyphenols.Thermodynamic model showed that the adsorption process of polyphenols by NKA-? resin was an endothermic spontaneous reaction.According to the kinetic model,the pseudo-second-order model could simulate the adsorption process better than the pseudo-first-order model,and the adsorption process is heterogeneous surface.From the study of the static desorption time and eluent,the polyphenols were easily desorbed from the resin at desorption time of 2.5 h,ethanol volume fraction of 80%,and polyphenols purity was(33.2±0.08)%.Finally,High Performance Liquid Chromatography was used to analyse static purified polyphenols,and it was found that the main compounds of polyphenols were epicatechin(13.166 mg/100g),gallic acid(10.577mg/100g),catechin(10.805 mg/100g),chlorogenic acid(9.964 mg/100g)?(3)The selected optimal resin NKA-? was used for dynamic adsorption and desorption of polyphenols.Firstly,the effect of sample velocity on the dynamic adsorption was investigated,secondly,the elution velocity and elution volume were studied.The optimal velocity was obtained with elution velocity 1 mL/min,elution volume 50 mL.And the resin was subjected to operation not regeneration for 7 times under the optimum conditions of adsorption and desorption.The optimal condition of dynamic purification was verified,and the results showed that adsorption rate,desorption rate and polyphenols purity were(96.8±0.12)%,(98.01±0.06)%,(55.26±0.10)%,respectively.High Performance Liquid Chromatography was used to analysisdynamic purified polyphenols,it was found that the mian compounds of polyphenols were epicatechin(28.072 mg/100g),gallic acid(17.957mg/100g),chlorogenic acid(17.599 mg/100g),catechin(13.753 mg/100g).