Several researchers have described the physical, mechanical, physiological and acoustic properties characterizing the maturity of other types of fruit. For example, Kato (1997) described the relationship between the density and maturity of Japanese watermelon. Pleasantly sweet watermelon that does not include cavities has a density that is equal to or greater than 0.934. Specific gravity is a physical and physiological property that is recognized by horticulturists and postharvest technologists. Researchers have used the specific gravity to determine the maturity of mango (Jarimopas and Kittawee, 2007), mangosteen (Sornsrivichai et al., 1999), and dragon fruit (Wanichang and Jarimopas, 2008). However, in practice, specific gravity is rarely applied to sorting in the modern packing line, although it can serve as an alternative monitoring indicator.