Research On Phenolics Oxidation Loss Process Of Honeysuckle During Modified Atmosphere Heat Pump Drying

Honeysuckle is a kind of important Chinese medicinal materials and widely used. It should be appropriately dried after harvest, otherwise quality deterioration will appear such as the color deterioration and functional components damage, which directly affects its commercial value. Preliminary research results confirm that the quality deterioration is mainly caused by polyphenol oxidase catalyzed phenolics. Honeysuckle was the experimental material. Firstly, this study confirmed the detection and extracting condition meanwhile of functional components. Secondly, investigated degradation law of functional components during the modified atmosphere heat pump drying was investigated. Lastly, the phenolics oxidation loss mechanism in the process of enzymatic and non-enzymatic browning by simulation tests was revealed. This paper is aimed at providing theoretical basis for browning inhibition and acquiring high quality honeysuckle.Experiments obtained the detection condition meanwhile of chlorogenic acid and cynaroside by HPLC: the flow rate was 1m L/min; the detection wavelength was set at 327 nm and 350nm; the column temperature was 25℃; the injection volume was 10μL; the mobile phase was 1% phosphoric acid(A) and 1% phosphoric acid-methyl alcohol(B)(V:V=10:90); gradient elution:0~25~30min, 30%~59%~100%B. In order to determine the optimum extracting condition of chlorogenic acid and cynaroside from honeysuckle, response surface methodology was employed to optimize primary parameters and establish a regression mode was established based on the single factor experiment using their yields as indicators. Results showed that the regression mode properly reflected relationships among indicators and parameters; the optimum extraction condition was time 1.25 h, temperature 71℃, alcohol concentration 60%(V/V) and liquid-to-material 1:25(g/m L). Under the optimum extraction condition, the yield of chlorogenic acid and cynaroside were 3.741% and 0.067% respectively, which were close to the predicted values.The modified atmosphere heat pump drying experiment was conducted to discuss the change law of moisture ratio during the drying process, investigate the influence of temperature, load and oxygen volume fraction on chlorogenic acid, cynaroside content and L value, and establish dynamic model and the degradation kinetics model of chlorogenic acid and cynaroside. Results showed that by logarithmic transformation and linear fitting, the Page equation for describing the dynamic modeling is obtained. Using stepwise regression analysis, the expressions of equation coefficients are confirmed. Degradation kinetics of chlorogenic acid and cynaroside did not follow zero order and first order reaction kinetics. The degradation kinetics models of chlorogenic acid and cynaroside during modified atmosphere heat pump drying were established through introducing a exponent r related to time t in the first order reaction kinetics equation.HPLC was used to analyze the chlorogenic acid and cynaroside browning simulated oxidation product, it was concluded that the enzymatic and non-enzymatic oxidation product of chlorogenic acid was not the same completely, and there are mainly two kinds of oxidation products. 0~3min, enzymatic browning reaction was violent, chlorogenic acid was consumed abundantly, and the intermediate product could be detected immediately; after 10 min, reaction rate slowed down, and mainly happened non-enzymatic browning. Enzymatic and non-enzymatic oxidation of cynaroside was roughly same, there were two kinds of oxidation product, which had greater polarity than cynaroside, and browning reaction rate was slower.