Suitable Drying Temperature for Preserving Cucurbitacins in Fruit of Wild Cucumber and Wild Watermelon

摘要

The thermostable cucurbitacin A and B from mature fruit of wild cucumber (Cucumis myriocarpus) and wild watermelon (Cucumis africanus), respectively, are used in product development for various industries. Mature fruit from wild cucumber and wild watermelon suffer from high incidents of postharvest decays. Drying fruit at the recommended temperatures of 30 to 40 degrees C for medicinal plants resulted in molds developing on the material, with optimum temperature to prevent decays being at 52 degrees C. The influence of 52 degrees C and higher temperatures on active ingredients in the two fruit had not been documented. The objective of this study, therefore, was to determine the relative effects of increasing drying temperatures above the 52 degrees C standard on concentrations of cucurbitacin Aand B in fruit of wild cucumber and wild watermelon. Fruit pieces were oven-dried at 52, 60, 70, 80, 90, and 100 degrees C for 72 hours. Relative to 52 degrees C, higher temperatures resulted in 25% to 92% less cucurbitacin compared with the maximum produced at 60 degrees C. In contrast, relative to 52 degrees C, higher temperatures reduced concentrations of cucurbitacin B by 47% to 86%. In conclusion, the compromise temperature of 52 degrees C for preserving fruit pieces in wild cucumber and wild watermelon from decay should also be viewed as the optimum temperature for preserving cucurbitacin A and B.