Extraction Of Anthocyanins From Aronia Melanocarpa And Development Of Edible Film

The anthocyanins,rich in Aronia melanocarpa,have antioxidant,antibacterial,and hypoglycemic effects.Therefore,Aronia melanocarpa has high research and development value.In recent years,natural deep eutectic solvents（NADES）,as green solvents,have replaced traditional organic solvents for the extraction of natural products due to their advantages of low volatility,high thermal stability,good solubility,non-toxicity,and low cost.In this study,NADES was used as an extractant to extract anthocyanins from Aronia melanocarpa by ultrasonic-assisted acidic NADES method,and the stability and biological activity of anthocyanins were investigated.Meanwhile,anthocyanin composite films were prepared using chitosan and zein as membrane substrates,NADES as plasticizers,and anthocyanins as bioactive substances.The performance and structural characterization of the composite films were performed to investigate the effects of NADES and anthocyanins on the composite films.The main research contents are as follows:（1）Study of the extraction process of anthocyanins from Aronia melanocarpa.Acidic NADES was designed as the extractant,and the ultrasonic-assisted acidic NADES method was established to extract anthocyanins.The physicochemical properties,structural characteristics and formation mechanism of NADES were investigated,and the extraction conditions were optimized by using artificial neural network and genetic algorithm on the basis of single-factor experiments.The results exhibited that NADES with a molar ratio of betaine to lactic acid of 1:3 prepared by hydrogen bonding had the advantages of low density,low viscosity and low p H value.The optimized best extraction conditions were:NADES with a water content of 32%,ultrasound power of 124 W,ultrasound time of 24minutes,and initial ultrasound temperature of 32℃.Under these conditions,the extraction yield of anthocyanins was 23.62 mg/g.（2）Study of the stability and biological activity of anthocyanins from Aronia melanocarpa.The stability,antioxidant activity and antibacterial effect of anthocyanins were investigated.The results indicate that light and heat have a promoting effect on the degradation of anthocyanins.When the temperature was greater than 50℃and the primary kinetic degradation constant k>0.0234,the higher the concentration of oxidant H₂O₂and reducing agent Na₂SO₃,the lower the retention of anthocyanins.Na⁺,K⁺,Cu²⁺,Mg²⁺,Zn²⁺and Ca²⁺had no significant effect on the stability of anthocyanins,but Fe²⁺could reduce the retention of anthocyanins.Potassium sorbate had no effect on the stability of anthocyanins.Compared with V_C,anthocyanins have stronger DPPH radical scavenging ability,ABTS radical scavenging ability and total antioxidant capacity.In addition,anthocyanins had antibacterial effects on Escherichia coli and Staphylococcus aureus.（3）Preparation and properties of anthocyanins composite film.The anthocyanins composite film was prepared using chitosan and zein as membrane substrates,NADES as plasticizers,and anthocyanins as bioactive substances.Firstly,the composite film ratios were optimized by single-factor experiments,and then compared with glycerol composite film and anthocyanins-free composite film to evaluate the effects of NADES and anthocyanins on the composite film in terms of rheological properties,mechanical properties,moisture content,water vapor permeability,water contact angle,surface morphology,thermal stability and antioxidant activity.The results showed that when the mass ratio of chitosan to zein was 2:1,the mass concentration of NADES was 2.0%,and the mass concentration of anthocyanins was 0.4%,the tensile strength and elongation at break of the composite film were 14.93 MPa and 52.81%,respectively,and the water vapor permeability was 1.072 g·mm·m^-2·h^-1·KPa^-1.The viscosity of the composite film solution was inversely proportional to the shear rate and temperature.Both NADES and anthocyanins could improve the performance of composite films,enhance their mechanical properties,moisture resistance,hydrophobicity,and antioxidant activity,as well as reduce the moisture content of the composite film.However,NADES could reduce the thermal stability of composite film,while anthocyanins could improve the thermal stability of composite film.In addition,the components of the composite film were bound by hydrogen bonding,and both NADES and anthocyanins had good compatibility with each component of the film,and their compatibility was better than that of the glycerol composite film.