| Muskmelon is a kind of fruit with outstanding advantage in the aspects of plant condition in the northwest of China and is widely planted both with huge area and yield. In order to increase its additional value of product, the studies were performed to optimize the extraction of pectin from waste muskmelon peels and determine its characteristics.In this study, microwave-assisted extraction (MAE) was applied to extraction of pectin from muskmelon peels. A response surface method (RSM) was adopted to optimize the parameters based on single factor experimental results. The quadratic regression model with pectin yield and the microwave holding time, power and feed liquid ratio was established. In addition, AN OVA showed the regression model was significantly and had high predictability.The order of coded factors on the effect of the yield of pectin from muskmelon peel (YPM) is as following, power>feed liquid ratio> holding time. The optimum parameters of MAE were as following:microwave power 380w, holding time 6.2 min and feed liquid ratio 1:21. The YPM with the optimum parameters was 1.85%.A RSM was used to study on main effects and interactive effects of the extraction of muskmelon pectin based on single factor experiments by using ultrasonic-assisted extraction (UAE). The quadratic regression model with pectin yield and the ultrasonic holding time, power and feed liquid ratio was established. The results showed the model was significant and can be used to predict the yield of pectin extraction. The order of factors on the effect of YMP is as following, feed liquid ratio>holding time> power. The optimum UAE for muskmelon pectin was obtained at holding time 41 min, power 300W and feed liquid ratio 1:21 with the max yield of 1.76%.The muskmelon pectin obtained under two process conditions were determined on physical-chemical properties-and compared. Measured the pectin by MAE galacturonic acid content was 74.96%, ash content was 2.83%,esterification degree was 67.71%, pH was 2.89, loss on drying 7.04%, YMP was 1.85%. Measured the pectin by UAE galacturonic acid content was 76.24%, ash content was 2.52%,esterification degree was 67.71%, pH was 2.80, loss on drying 7.96%, YMP was 1.76%. Fourier transform infrared spectroscopy(FTIR) was used to identify the extracted pectin. The pectin from two extraction methods were all in line with the national standard and the difference is not significant, so choose the MAE method to extract muskmelon pectin by a higher YMP.Besides, the gelling characteristics of the pectin was investigated. The results showed that the texture characteristics of the product have been significantly improved and sensory quality was enhanced by adding pectin from muskmelon; the gel strength was also enhanced due to muskmelon pectin, and the enhanced rate of gel strength reached to the level of 140%. The test also showed that the physical characteristics of muskmelon pectin was fine.Rheological properties of pectin was an important property in the food industry, and many factor could influence it. In this paper, the relationship between rheological properties of muskmelon pectin and the shear rate,concentration,temperature,heating time,pH,sugar and calcium ion were researched. The viscosity of pectin solution enhanced with the increased the concentration of pectin,sugar and calcium. The viscosity was decreased with pH=2 and alkaline conditions.At other lower pH conditions, muskmelon pectin viscosity was increased. The increasing of heating time and temperature could reduce the viscosity of muskmelon pectin. According to the simulated power law equations,the solution of muskmelon pectin was a typical pseudoplastic fluid(n<1) in different situations and its viscosity decreased with the increasing of shear rate.Aiming to provide the theoretical basis for application in the food industry of muskmelon pectin through the research of its gel and rheological properties. |
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