Investigation Of Phytochemical And In-vitro Antioxidant Activity Of Puff Dried Chinese Dates(Ziziphus Jujuba Mill.) Using Near Infrared And Mid Infrared Spectroscopy

The Chinese dates(Ziziphus Jujuba Mill.)represent a healthy food choice for consumers.They are known for their rich nutritional profile with significant amounts of protein,minerals,polysaccharides,vitamin C and organic acids.It is also enriched with bioactive compounds of nutraceutical and nutritional values.Chinese dates have been used in traditional medicine and are claimed to prevent insomnia,epilepsy,cancer,hepatoprotection and cardiovascular diseases;a trait attributed to antioxidant compounds.The Chinese dates are perishable commodity and their quality may deteriorate within few days of harvest.Drying is one way to preserve the product while retaining desirable qualities with reduced volume and enhanced shelf life.The sun drying is the most common method used by the grower of Chinese dates.However,direct exposure to solar irradiation and variable drying parameters result in quality deterioration of Chinese dates.Resultantly,efficient drying retaining quality of the end-product is demanded by the growers of Chinese dates.Recently,the focus has been extended to the role of polyphenols,phenolics,anthocyanins,carotenoids and other antioxidant with human health and product quality.The phenolics and antioxidants have become major drivers of the quality characteristics and functional properties of Chinese dates.The traditional methods for the determination of these bioactive compounds mainly rely upon chromatographic and colorimetric techniques.These methods are destructive,timeconsuming,require extensive sample preparation,and involve large amounts of chemical reagents;leading to environmental issues.The near infrared(NIR)and mid infrared(MIR)spectroscopy are simple,rapid,non-destructive,non-invasive,readily available analytical techniques and offer great prospect to be used as an alternative to traditional wet chemistry;an aspect formulating major thrust of this work.To overcome the disadvantages of traditional wet chemistry,spectroscopic techniques(NIR,portable NIR and MIR)has been used to quantify the antioxidant properties and phenolic compounds in Chinese dates.The cardinal achievements realized from this study are summarized as follows:1.The Chinese dates were harvested at optimal ripeness in August 2017 from Hebei,Shandong,Shanxi,Xinjiang and Henan provinces of China.The acquired samples were subjected to convective hot air and puff drying system.The least significant difference test was used to differentiate the drying method and provinces.The drying methods significantly affected the 2,2-diphenyl-1-picrylhydrazyl radical(DPPH),total antioxidant capacity(TAC),total phenolic content(TPC),ferric reducing antioxidant power assay(FRAP),2,2?-azino-bis(3-ethylbenzothiazoline-6 sulfonate)diammonium salt(ABTS),total flavonoid content(TFC),total carotenoid content(TCC),total anthocyanin content(TANC),total sugar(TS),total acid(TA),ferrous chelating activity and phenolic compounds of Chinese dates.The mean comparison of drying methods indicated the superiority of puff drying in retaining antioxidant properties and phenolic compounds such as gallic acid,caffeic acid,phloridzin,rutin,cianidanol and L-epicatechin.Among the provinces,Xinjiang had highest content of DPPH,FRAP,TPC,TFC,TA,TS and phenolic compounds such as phloridzin and cianidanol,thereby yielding superior fruit.The environment friendly and commercially viable puff drying offered greater prospects for industrial processing of Chinese dates with considerably reduced drying time,higher phenolic compounds and antioxidant properties.2.NIR spectroscopy coupled linear discriminant analysis(LDA)and K-nearest neighbour(KNN)was used for discrimination of geographical regions.Besides,classical partial least squares(PLS)and variable selection algorithms;synergy interval(Si)-PLS,backward interval(Bi)-PLS and genetic algorithm(GA)-PLS were compared for optimal model development for antioxidant properties of puff dried Chinese dates.The performance of the built model was optimized by crossvalidation.Prior to building classification models,principal component analysis(PCA)was applied to evaluate the possibility of discrimination.The results showed that LDA model was superior to K-NN model with geographical discrimination rate of 100% and 93% in the calibration and prediction sets,respectively.The build prediction model based on variable selection algorithms excellently predicted the quantitation of DPPH,TAC,FRAP,ABTS,TFC,TCC,TANC and ferrous chelating activity.The correlation coefficient for the calibration(Rc)and prediction(Rp)sets and residual predictive deviation(RPD)of build model yielded 0.8503?Rc?0.9897,0.8463?Rp?0.9783,and 1.86?RPD?4.88.In comparison,Si-PLS model showed better accuracy for DPPH and TAC assay,Bi-PLS was found better for FRAP,ABTS,TFC and TCC,and GA-PLS showed better performance for TANC and ferrous chelating activity.The overall results revealed that NIR spectroscopy coupled with multivariate algorithms could be used for identification of geographical regions and quantification of antioxidant properties in Chinese dates.3.Integration of NIR and MIR spectroscopy was performed to quantify the polyphenols in puff dried Chinese dates.They are the foremost measure of phytochemical and offer numerous potential health benefits such as averting cancers,reducing the risk of coronary artery disease,diuretic activity,myocardial stimulant,coronary dilator and muscle relaxant.The polyphenols were quantified using an approach of Si-PCA-GA-PLS fusion model,using NIR and MIR spectroscopic data.The efficient spectral intervals were extracted by Si?PLS algorithm as input variables for fusion model.Subsequently,the selected spectral intervals from NIR and MIR techniques had high likelihood of containing information relevant to polyphenols along with some redundant information.To remove the unwanted information,PCA was applied at the selected intervals for the selection of top principal components(PCs).Thereafter,GA was used to construct the model based on NIR?MIR fusion data.The newly built model yielded Rc= 0.9621,Rp= 0.9451,RPD = 2.44,calibration set bias = 0.004 and prediction set bias = 0.061,computing only 15 variables.The findings revealed that integration of NIR and MIR is offer promising prospect for the prediction of polyphenols in puff dried Chinese dates.4.A low cost portable spectral analytical system was developed for the in-situ screening of phenolic compounds in puff dried Chinese dates.The individual phenolic compounds i.e.gallic acid,caffeic acid,L-epicatechin,phloridzin and cianidanol were identified and quantitated using high-performance liquid chromatography coupled with diode array detector(HPLC-DAD).The synergy interval partial least square with ant colony optimization(Si-ACO-PLS)approach was pursued to optimize and capture the informative variables for the prediction of these compounds.The Si-ACO-PLS build model yielded optimal performance,0.8540?Rc?0.9250,0.8582? Rp?0.9056,0.84? RMSEP?16.30 and 2.03? RPD ?2.26.The portable spectral analytical system coupled with Si-ACO-PLS proved to be simpler and cost-effective method to quantify the phenolic compounds in Chinese dates.The current study revealed that spectroscopic techniques(NIR,portable NIR and MIR)offer a cost-effective viable alternative to conventional wet chemistry for rapid and reliable quantification of bioactive compounds in Chinese dates.Additionally,NIR spectroscopy carry the same potential for discrimination of various Chinese dates harvested from different geographical regions.