| The anthocyanin is an important natural functional pigment in berries,such as blueberries,whose stability will be influenced significantly by sucrose during blueberry product processing.Although traditional methods including encapsulation and acylation can help to maintain the stability of anthocyanins,the methods themselves will cause issues on color and safety features of products.In this experiment,the p H differential method,Peroxide free radical scavenging method,fluorescence spectroscopy,synchronous fluorescence spectroscopy,circular dichroism spectroscopy were used to analyze the effects of soybean protein isolate and casein on the stability and antioxidant activity of blueberry anthocyanins and the interaction mechanism between the two proteins and blueberry anthocyanins.Finally,the blueberry anthocyanins and blueberry anthocyanin-protein complexes were sequentially subjected to in vitro saliva,stomach,and small intestine digestion simulations to determine the digestibility of casein and soy protein isolate on blueberry anthocyanins and blueberry anthocyanins.The conclusion is as follows:(1)Stability of casein and soy protein isolate on blueberry anthocyaninsThe effects of soy protein isolate and casein on the stability of blueberry anthocyanins were evaluated by light,heat at 80℃,and the addition of ascorbic acid.The following conclusions were drawn: the addition of light,heat and ascorbic acid reduced the color stability and The content of total anthocyanins,the presence of soy protein isolate and casein significantly slowed the degradation of anthocyanins,but the protective effect on the thermal stability of anthocyanins was not obvious,which may be due to the complexation with anthocyanins due to protein structural degeneration at high temperatures Decreased,the higher the content of soy protein isolate,the better the protection of anthocyanins,and the casein has the best protection at 0.10 mg/m L,which may be caused by the high concentration of casein self-assembly and sedimentation.(2)Antioxidant activity of casein and soy protein isolate on blueberry anthocyaninsThe effects of soybean protein isolate and casein on the stability of blueberry anthocyanins were evaluated by light,heat at 80 ℃,and ascorbic acid.It showed that after illumination,the antioxidant value of blueberry anthocyanin was significantly reduced,and the addition of soy protein isolate and casein significantly slowed down the reduction of antioxidant value;After heat treatment,the antioxidant value of anthocyanins decreased,and the addition of two proteins eased the decrease of the antioxidant value of anthocyanins;Similarly,the addition of VC led to the degradation of anthocyanins,and the total antioxidant value decreased,while the addition of soy protein isolate and casein significantly increased the total antioxidant value,even higher than the components without VC added.The change trend of antioxidant value is consistent with the total anthocyanin content trend,indicating that soy protein isolate and casein protect the stability of blueberry anthocyanins.(3)Study on the interaction mechanism between casein,soy protein isolate and anthocyaninsThe mechanism of interaction between casein and soy protein isolate and blueberry malvidin-3-O-galactoside was analyzed by fluorescence spectrum,synchronous fluorescence spectrum and circular dichroism chromatography.The addition of M3 G caused fluorescence quenching of the two proteins,their quenching forms were both static quenching,and the main driving force were electrostatic interaction;The hydrophobicity of tyrosine residues and tryptophan residues of SPI were reduced,the polarity were enhanced,α-helix,β-turn,random coil increased,β-sheet decreased;For casein,the hydrophobicity of tyrosine residues increased,the polarity decreased,the polarity of tryptophan increased,and the hydrophobicity decreased;the α-helix and β-sheet decreased,β-turn,and random coil increased.(4)Study on in vitro digestibility of two proteins with blueberry anthocyanin complexThe in vitro saliva,stomach and small intestine digestion of blueberry anthocyanin and blueberry anthocyanin-protein complex were simulated.The results showed that anthocyanins did not degrade significantly during saliva digestion.In the stomach digestion stage,anthocyanins were gradually digested.Casein had a slight protective effect on anthocyanins after 1 hour of stomach digestion;After 2 hours of gastric digestion,the residual rate of anthocyanins continued to decrease.The presence of casein and SPI both increased the residual rate of anthocyanins.The total antioxidant value of the complex was also higher than that of anthocyanins alone.During the digestion stage of the intestine,the anthocyanin residue rate decreased sharply,and the anthocyanin was rapidly digested,indicating that the main digestion site of anthocyanin was in the small intestine.The anthocyanin residue rate in the anthocyanin-protein complex was significantly increased,and the total antioxidant value of the two complexes was also significantly higher than the components of anthocyanin alone.These conclusions provides a certain basis for the mutual research of blueberry anthocyanins and proteins in the future,and provides a theoretical basis for future blueberry-protein product development. |
