Study on Stability and Degradation Kinetics of Anthocyanins from Mulberry
Mulberry anthocyanins are unstable and can be easily degraded due to the change of external factors.In this study,with anthocyanin retention rate and color change as the evaluation indexes,the effects of light,pH value,temperature,additives,metal ions and other factors on the stability of mulberry anthocyanins are investigated and the degradation kinetics is explored.The results show that outdoor light accelerates the degradation of anthocyanins,k value increases from 1.80×10-2 under dark conditions to 14.12×10-2,and t1/2 decreases from 38.5 h to 5.2 h.The stability of anthocyanins is high in acidic environment(pH value of 1.00,3.00).Anthocyanins are prone to degradation in neutral(pH value of 7.00)and alkaline environments(pH value of 9.00),after 96 h,the anthocyanin retention rates decrease to 83.25％,72.44％respectively,and the color changes from red in acidic encironment to grayish green and dark green respectively.After being stored at 80,100 ℃ for 10 h,the ΔE*of anthocyanins changes to 3.409 7,6.192 8 respectively,and the red color fades.The retention rates of anthocyanins are only 65.39％and 38.83％.Acidity agent(citric acid)has a significant stabilizing and coloring effects on anthocyanins,while preservatives(potassium sorbate,sodium benzoate)and antioxidant(ascorbic acid)accelerate the degradation of anthocyanins.The addition of Al3+,Fe3+,Fe2+and other metal ions destroy the structure of anthocyanins to a certain extend,and the color changes to blue purple,yellow brown,blue black respectively.Mulberry anthocyanins have poor storage stability,and are suitable for low-temperature,dark and acidic environments,and should avoid contact with preservatives,antioxidants and other additives,as well as iron and aluminum products.The research results have provided basic data and theoretical basis for the storage,processing and application of anthocyanins.
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