Study On The Interaction Between Rice Starch And Food Derived Polyphenols

Polyphenols in grains play an important role in the prevention of chronic diseases such as diabetes and cancer,which is attributed to their diverse bioactivities such as anti-oxidation.Cereal food processing often leads to the release of intracellular and extracellular compounds,and the released endogenous polyphenols come into contact and interact with starch,which would change the physical and chemical properties of starch,and affect the nutritional value and quality of food.Therefore,studying the effect of polyphenols on the structure and physicochemical properties of starch and exploring interaction mechanism between them can provide theoretical guidance for the application of polyphenols in starch-based functional foods.This paper studied that effects of three representative polyphenols（ferulic acid,gallic acid and quercetin）with different water solubility and hydroxyl numbers on the physicochemical and structural properties of rice starch,and the digestive properties and the release of polyphenols from complexes were studied.The contents and results of the research were as follows:（1）The effects of three different polyphenols on physicochemical properties of rice starch were studied,including retrogradation and pasting properties,freeze-thaw stability,solubility,gelatinization and rheological properties.The results showed that three polyphenols could inhibit the retrogradation of starch,and QC had the greatest effect among them.GA could significantly inhibit the formation of sponge-like structures during freezing and thawing,and QC could significantly reduce the syneresis rate of starch and improve the freeze-thaw stability.FA and GA significantly increased the solubility and reduced the viscosity value of starch during gelatinization,while the addition of QC had the opposite effect.FA and GA significantly decreased the gelatinization temperature;while QC had slight but no significant effect on the gelatinization temperature of starch and significantly reduced the gelatinization enthalpy of starch.The mixture systems of polyphenols and rice starch presented a typical pseudoplastic fluid,and possessed the shear-thinning characteristic.FA and GA significantly decreased the storage modulus and loss modulus of starch gels,and had a destructive effect on the starch gel structure,while QC could enhance the gel network structure of rice starch.These results indicated that the effects of different polyphenols on physicochemical properties of rice starch were significantly different.（2）Structural characterization of rice starch-polyphenol complexes:starch and polyphenols co-gelatinized to form complexes and characterize its structure.The results showed that polyphenols inhibited the polymerization of starch during gelatinization and made the microstructure of rice starch loose and porous.Compared to the mixture of rice starch and GA,new signals appeared at 1685 and 1447 cm^-1 in the Fourier transform infrared spectroscopy of starch-GA complexes,while the partial absorption peaks of FA,QC and starch complexes shifted or disappeared;The absorption peak intensity of FA and starch complexes near 3384 cm^-1 decreased,and the number of hydroxyl groups decreased,indicating that FA and starch interacted mainly through hydrogen bonding.The peak intensity ratio of rice starch-polyphenol complexes at（1045/1022）cm^-1 decreased with the increasing concentration of polyphenols,suggesting the ordered structure of starch were significantly decreased.X-ray diffraction results demonstrated that GA inhibited the retrogradation of rice starch and formed a new minor crystalline region at 2θ=12.7°in the complexes.There was no new crystallization peak appeared in FA,QC and rice starch complexes,indicating that polyphenol and rice starch did not form an orderly long-range crystal structure.GA and QC significantly reduced the decomposition temperature of rice starch,indicating that the density of starch in the complexes was reduced,making it easier to decompose when heated.（3）Digestive and release properties of rice starch-polyphenol complexes:investigated the enzymatic hydrolysis of the complexes and the release rule of FA and GA in different environments.The results showed that the enzymatic hydrolysis rates of FA,GA and starch complexes were significantly lower and higher than that of control starch,respectively;with the increase concentrations of FA and GA,the content of rapidly digestible starch（RDS）significantly decreased,while the content of resistant starch（RS）increased,and FA had a significant inhibitory effect on starch digestion.The release amount of GA and FA in the complexes increased with increased p H and temperature.In the intestinal fluid environment,the release amount of FA from the complexes had an increasing tendency,while that of GA was significantly decreased,indicating that the intestinal fluid environment had a destructive effect on the structure of GA.