Optimization on Extraction Technology and Component Analysis of Wax from Munage Grapes Pericarp

Cuticular wax is one of the important factors affecting the storability of fruits and vegetables. Thus, Munage grape was used as material in this study, and response surface methodology was used to optimize the process parameters of extracting cuticular wax from grapes by soaking in organic solvent. At the same time, the components and content of the cuticular wax were identified and analyzed by gas chromatography-mass spectrometry (GC-MS). The results showed that on the basis of single factor, the optimum conditions of wax extraction optimized by response surface methodology were as follows: The mixing ratio of dichloromethane and hexane was 3:1 mL/mL, the liquid-solid ratio was 2:1 mL/g, and the extraction time was 7.5 min. Under the optimal extraction conditions, the wax extraction amount was 43.60±1.04 mg/100 g, which was 0.98% difference from the predicted value of response surface. A total of 61 compounds were identified in epidermal wax, including 13 kinds of fatty acids, 13 kinds of hydrocarbon compounds, 10 kinds of alcohols, 9 kinds of esters, 5 kinds of aldehydes, 4 kinds of terpenoids, and 7 kinds of unclassified compounds. The relative content of fatty acids was the highest, accounting for 58.06% of the total wax content. This provided a theoretical reference for the further study of the relationship between the composition of cuticular wax in grapes and postharvest qualities of fruits.