Study On The Interaction Between Persimmon Tannins And Pectins

Persimmon's tannin?PT?has many biological functions,such as antioxidant activity,detoxification,anti-hyperlipidemic and anti-bacterial activities.However,due to the poor organoleptic and poor properties in food processing,such as astringency,poor solubility and easily oxidizable,it can be hardly added into foodstuffs.Interactions between the hydrophilic polysaccharide and polyphenol may improve the poor processing properties of polyphenols,which can also broaden the scope of its application as functional food ingredients in food matrix.Therefore,the mathematical model of the combination of sensory evaluation with electronic tongue,fluorescence spectrum and nephelometry,and dynamic light scattering?DLS?methods were used to investigate the interactions between persimmon tannin with average degrees of polymerization?DP26/5?and different degree esterification of pectin?HM/LM?,and the effect on the astringency tastes of persimmon tannin.Additionally,the rheological assays,scanning electron microscopy?SEM?,confocal laser scanning microscopy?CLSM?were used to investigate the influence of the persimmon tannin-pectin interactions on the pectin rheological and gel properties.Meanwhile,the mode of interaction between persimmon tannins and pectins was further analyzed by isothermal titration calorimetry?ITC?,fluorescent probes,DLS,Zeta potential and TEM.The main research results were as follows:1.Effects of the persimmon tannin-pectin interactions on the tannins astringencyBased on the mathematical model of sensory combined with the electronic tongue(E_value=276.135ZZ-276.135-276.135BB+0.164CA)evaluation we established before,the influence of persimmon tannin-pectin interactions on astringency strength of persimmon tannin was investigated.The results showed that HM/LM pectin significantly reduced the astringency intensity of persimmon tannin?DP26/5??p<0.05?.Especially,astringency intensity remarkably diminished?p<0.05?when the ratio of tannin:pectin reached 1:5?wt/wt?.DSC analysis indicated that the persimmon tannin-pectin interactions could enhance the thermal stability of complexes,and the decrease of the thermal denaturation temperature whereas increase in denaturation enthalpy suggested the stable tannin-pectin complexes were formed.Additionally,nephelometery,DLS,fluorescence spectrum results further demonstrated that ternary complexes "persimmon tannin-pectin-mucin" might develop by their interactions,and thus reducing astringency of persimmon tannin.2.Influence of the persimmon tannin-pectin interactions on the rheological properties of pectinThe effects of the persimmon tannin?DP26/5?on the flow behavior and the dynamic rheological of pectins?HM/LM?were investigated under various shear rates and temperature.The flow behavior results indicated that persimmon tannin did not significantly affect the flow type of HM/LM pectins,which presented a non-Newtonian shear-thinning behavior,and was well described by Cross Model?R²>0.99?.Tannin-pectin complexes system showed that the weakest viscosity-temperature dependence,and fitted to the Arrhenius equation.Besides,the tannin-HM pectin complex viscosity higher than that of tannin-LM pectin complex viscosity values?p<0.001?.Similarly,with the increasing of pH,viscosity of tannin-pectin complexes increased slightly.But the degrees of polymerization of persimmon tannin did not pronounce impact on the viscosity of pectin.In addition,the dynamic rheological results indicated that the presence of persimmon tannin could improve the onset point?gelation time and tempraure?of HM/LM pectin.3.Influence of the persimmon tannin-pectin interactions on the gel properties of pectinThe effects of persimmon tannin?DP26/5?on the rheological and microstructural properties of pectin?HM/LM?gel were investigated by large-deformation,dynamic rheological,SEM and CLSM measurements.The large-deformation results demonstrated that persimmon tannins could significantly enhance the strength of HM/LM pectin gels?p<0.05?.Besides,the rheological results indicated that the addition of persimmon tannins,especially DP5 tannins improved the gelling ability of the HM/LM pectin gels with the increasing of persimmon tannins concentration?except for low concentration of tannins,0.05%??p<0.05?.Higher concentration of persimmon tannins led to higher storage modulus of tannin-pectin complex gels,and the higher the gelation speed of gels.Meanwhile,the tannin-LM pectin gel strength was stronger?G?⁵000?than that of tannin-HM pectin gel?G?¹000??p<0.05?.Furthermore,SEM and CLSM analyses revealed the heterogeneous and aggregated network of the pectin gels containing persimmon tannins.Under constant Ca²⁺and sucrose condition,the intermolecular cross-linking between the carboxyl groups of LM pectin molecule and the phenolic hydroxyl groups of tannins through hydrogen bonds might stabilize the pectin gels junction zone and further improved the gel strength of LM pectin.For HM pectin gels,interaction of persimmon tannin with HM pectin through hydrogen bonds and hydrophobic improved HM pectin junction zone and thus resulting in a higher complex gel strength.4.Analysis of the interactions between persimmon tannins and pectinsThe interactions between DP26/5 persimmon tannin and HM/LM pectin were explored by UV-Vis,DLS,TEM,ITC and pyrene fluorescence methods.ITC results illustrated that persimmon tannins were spontaneously bound to pectin,and related to exothermic interaction,which drove mostly by enthalpy due to the hydrogen bond association.Meanwhile,Pyrene fluorescence probe analysis indicated that hydrophobic effect was also involved in non-covalent interactions.In contrast,electrostatic interactions,which was involved charging molecules generally,played no dominant role.Additionally,UV-Vis,DLS,TEM methods displayed that pectins showed strong effects on the self-aggregation of persimmon tannin and improved the homogeneity of condensed tannin aggregates.Stronger association was observed with the high-polymerisationtannins?DP26?with high-methoxyl pectin?DE74?(Ka=?8.50±3.0?×10³ M^-1)than with low-methylated pectin?DE30?(Ka=?3.62±1.92?×10³ M^-1).However,environmental factors including temperature,pH,SDS and urea could impact on the interactions of persimmon tannin with pectin.These results further revealed that the interactions between tannins and pectins might result from hydrogen bonding and hydrophobic interactions;5.Application of the persimmon tannin-pectin mixtures on the breadThe application of persimmon tannin-pectin complexes in bread was evaluated using environmental scanning electron microscopy?ESEM?,lage and small deformation rheometry.The results showed that the influences of low concentration of persimmon's tannin on dough and bread qualities were not obvious,while high concentration persimmon tannins?up to1%?resulted in the inhibition of dough formation and significantly reduced bread volume?p<0.05?.However,the tannin-pectin complexes significantly alleviated the negative effect of persimmon tannin on dough and bread qualities,such as decreases of bread hardness,chewiness and restoring force,as well as the significant increases in the storage modulus?G'?,the loss modulus?G''?,the complex modulus?G*??p<0.05?.Moreover,the results of TPC,DPPH^·,ABTS^+·,ORAC assays showed that a significantly higher antioxidant capacity complexes fortified bread than the control one.These results demonstrated that persimmon tannin-pectin incorporation may not only reduce the negative effects resulting from tannins on dough and bread qualities,but also increase the antioxidative potential of bread,suggesting that supplement with persimmon tannin might enhance the nutritional value of bread.Therefore,this study provided theoretical information that persimmon tannin-pectin complexes could be recognized as functional ingredients delivering system in the future.