Analysis of dehydration kinetics, status of water and oil distribution of microwave-assisted vacuum frying potato chips combined with NMR and confocal laser scanning microscopy

- The microwave used in VF markedly increased the moisture evaporation kinetics.
- NMR analysis showed the water status evaporate regular pattern in MVF process.
- The total oil content and different oil fractions were all lower in the MVF samples.
- CLSM images showed less oil adhere to the surface and trapped in the crust by MVF.
- The cells morphology in MVF samples resulted in the reduction of oil content.

In this study, the dehydration kinetics, status of water and oil distribution of microwave-assisted vacuum frying (MVF) potato chips were analyzed combining with NMR and confocal laser scanning microscopy (CLSM). Results showed that the MVF markedly increased the moisture evaporation kinetics and effective moisture diffusivity compared to vacuum frying (VF). The higher microwave power level (1000 W) used achieved higher moisture evaporation rate and higher effective moisture diffusivity, The Logarithmic model exhibited the best fit for the obtained data of MR versus frying time in the MVF. The NMR analysis showed the free water in the samples firstly evaporate and the linkage between water and structure of materials becomes tighter with the frying time. The total oil content, surface and structural oil content were all significantly lower in MVF samples than that in VF samples. The CLSM analysis confirmed that less oil adhere to the surface and less oil trapped in the structure in MVF slices. The surface morphology showed that there were less ruptured and damaged cells in MVF samples and helped to explain the reduction of oil content.

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