Influences of microwave pre-drying and explosion puffing drying induced cell wall polysaccharide modification on physicochemical properties, texture, microstructure and rehydration of pitaya fruit chips

The effects of microwave (1.0, 2.0, and 4.0 W/g) and explosion puffing combination drying (MDx-EPD) on cell wall polysaccharides modification was investigated, and the influences of these modification on the physical and physicochemical properties of pitaya fruit chips were analyzed. Compared with conventional hot air-explosion puffing drying, MDx-EPD significantly increased volume expansion, and yielded products with superior porous microstructure and crispier texture. The MDx-EPD dried chips showed faster rehydration rates, as well as decreasing Tg (14.01–15.33 °C). The anhydrouronic acid contents of the water extractable polysaccharide fractions of the MDx-EPD dried chips were increased by 8–16%, and this, together with the increase in the amount of pectic neutral sugars for the same fractions, were indicative of cell wall polysaccharides solubilization, which could contribute to the improvement of rehydration properties. Data from molar mass distribution suggested the occurrence of cell wall polysaccharide degradation, which could be partially responsible for the decreasing Tg. In conclusion, the relationship between the modification in composition, structure and extractability of cell wall polysaccharides and the alteration in volume expansion, microstructure, Tg and rehydration behaviors confirmed that cell wall polysaccharide played a significant role in the physicochemical and physical properties of pitaya fruit chips.