| The research of Chinese Bayberry(Myrica rubra Sieb.Et Zucc.),a characteristic plant in Zhejiang,is currently focusing on its fruits.There has been a serious waste of its leaves resources for a long time.Chinese bayberry leaves proanthocyanidins(BLPs)exhibits its good antioxidant properties due to its unique structure of the original delphinidin and shows great potential for development as a natural antioxidant.At the same time,BLPs contain a large number of phenolic hydroxyl groups,so that they are hydrophilic but not lipophilic,thus it is difficult to directly apply them in oil systems which are prone to oxidation reactions.In this study,the gelatin-proanthocyanidins(GLT-BLPs)colloidal complexes were prepared through self-assembly mode,then the colloidal complexes were used in the preparation of food-grade Pickering emulsions,after that,the edible oleogels were prepared by using the Pickering emulsion as a template,also with stabilized by xanthan gum.Finally,the use of edible oleogels for the replacement of artificial butter in baked products was carried out.The main contents and results are as follows:(1)The preparation and characterization of the GLT-BLPs colloidal complexes were studied.The morphology,particle size distribution,the ?-potential and the interfacial tension at oil-water interfacial of GLT-BLPs colloidal complexes were investigated.The results showed that the shape of GLT-BLPs colloidal complexes were smooth spherical;with the increase of BLPs,the combination of BLPs and GLT became tight,and the particle size and ?-potential decreased.Through Fourier transform infrared spectroscopy(FTIR),circular dichroism(CD)and isothermal titration calorimetry(ITC),the interaction between GLT and BLPs was further confirmed as a spontaneous exothermic reaction and mainly driven by hydrogen bonds.What's more,the combination of BLPs could enhance the interfacial adsorption capacity of GLT when the ratio is appropriate,the combination of excessive proanthocyanidins would cause protein aggregation,thus we choose the ratio weight of BLPs-GLT were 1:8 and1:4 for further preparation of Pickering emulsions.(2)The food-grade Pickering emulsions were prepared by using GLT-BLPs colloidal complexes instead of emulsifier.Then the physicochemical property such as physical stability,particle size distribution,?-potential and the morphology of droplet of the emulsion were investigated.The storage stability of the emulsions was studied by accelerating the oxidation,thereby judging the antioxidant properties of the BLPs.As the results shown,the GLT-BLPs colloidal complexes stabilized emulsions showed more physically stable than the emulsions prepared by GLT only,such as the average particle size of the emulsion droplets prepared by the complexes was smaller,its size distribution was narrower,and the ?-potential value was also lower than that of emulsion droplets prepared by GLT alone.From the observation of microstructure,GLT-BLPs colloidal complexes layer well enfolded the oil droplets to stabilize the emulsions.From storage stability experiments,we could tell that the presence of BLPs can effectively delay its oxidation process and improve the stability of the emulsions,reducing the primary oxidation products by 30.3% and 42.6% and the secondary oxidation products by 41.8% and 45.9%.(3)Using GLT-BLPs colloidal complexes stabilized Pickering emulsion as a template,a dried product obtained by freeze-vacuum drying and then sheared to form edible oleogels.In order to improve the stability of the oleogels,polysaccharides(arabic gum,pectin,xanthan gum)as stabilizers was added to stabilize the template emulsion,the choose of polysaccharide type and the added ratio in the formed oleogels was optimized based on the oil leakage rate of <1%,the results showed that adding 0.6 wt%of xanthan gum can significantly improve the physical stability of the oleogels.Observation of the emulsion and oleogels by cryo-electron microscopy showed that the oil droplets were effectively encapsulated in the network structure.After measuring the rheological properties of the oleogels,it was found that the elastic modulus G'of oleogels was higher than the viscosity modulus G'',which exhibited their solid-like rheological properties.Besides,the presence of BLPs could effectively delay the oxidation process of the oleogels with a high content of oil,and its antioxidant effect is comparable to commercially available antioxidants BHT.(4)The previously prepared oleogels were used for replacement of artificial butter in the actual baked food system(sponge cakes and cookies).The rheological properties of the cake batter before baking were measured.The results showed that the cake batter prepared with the oleogels were better than the one prepared with liquid vegetable oil in stress scans,frequency scans,yield stress,and creep recovery measurement,which were also closer to the batter prepared with artificial butter.Texture analysis and sensory evaluation of sponge cakes and matcha-flavor biscuits were investigated.In cake products,the cakes prepared with oleogels showed relatively comparable results in hardness and chewiness of butter cakes,and had significant advantages over cakes prepared with pure vegetable oils.In addition,cakes prepared with oleogels had good overall consumer acceptance in sensory evaluation.About the cookie products,as the substitution ratio of butter increases,the hardness of the cookies was affected to some extent,but the fracturability was basically unchanged,and the results of sensory evaluation also showed the oleogels could be a suitable candidate to replace artificial butter.However,the presence of the BLPs may affect the color of the final product,which could be solved by adding colorful flavored materials to prepare a flavored product.Using the food-grade Pickering emulsion stabilized by GLT-BLPs colloidal complex as a template to prepare oleogels can effectively replace artificial butter in the application of food systems,meanwhile to reduce the intake of trans-fatty acids and saturated fatty acids. |
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