Effect of multi-flash drying and microwave vacuum drying on the microstructure and texture of pumpkin slices

The influence of different drying methods on the microstructure, porosity, and texture of pumpkins slices was assessed, aiming to find the best process conditions. Pumpkins (Cucurbita moschata) were selected, peeled, sliced, blanched and dehydrated by different methods: i) microwave multi-flash drying (MWMFD), ii) microwave vacuum drying (MWVD), iii) conductive multi-flash drying (KMFD), iv) freeze-drying (PD), and v) air-drying (AD). Micrographs of dried samples showed the compacted structure of AD samples and the spongy structure of FD samples. Otherwise, large pores and a highly porous structure were observed in samples dried by KMFD, MWVD, and MWMV. Porosity MWMFD samples were 2.6 times higher than those observed in AD pumpkins and slightly higher than the observed in FD samples. Puncture test results from KMFD, MWVD and MWMFD samples showed force oscillation that is typical of crispy products, which was not observed from AD and FD samples. Moreover, KMFD, MWVD, and MWMFD samples showed low color changes. Thus, microwave under vacuum and both multi-flash drying processes result in dried-and-crisp pumpkins, with high porosity and big pores. Therefore, these drying processes are suitable for the production of dried-and-crisp pumpkins.