Reduction of oil uptake with osmotic dehydration and coating pre-treatment in microwave-assisted vacuum fried potato chips

Abstract Microwave-assisted vacuum frying (MVF) was reported to improve the processing efficiency with the microwave heating method, while the oil uptake of products also needs to be reduced to enhance the overall quality. In this research, the effectiveness of osmotic dehydration and coating pre-treatment on reducing the oil absorption of MVF potato chips were evaluated with the verification of empirical models. Meanwhile, the effects of different pre-treatment on dielectric properties, moisture loss kinetics, texture, and color of MVF samples were analyzed. Results suggested that the oil uptake of MVF products was reduced by 16.6%∼31.4% and 27.8% with osmotic dehydration pre-treatment in 1%∼5% NaCl and 2.5% MSG solution, which is related to the enhanced moisture removal induced by the dielectric property improvement. The coating pre-treatment with 25% maltodextrin, 1.0% CMC-Na, and 1.5% chitosan had no negative effect on the dielectric properties and the moisture loss rate of samples during frying. While the oil absorption of MVF products was reduced by 53.5%, 36.8%, and 15.2% respectively due to the colloidal layer barrier formed by the coating pre-treatment. The empirical model provided better fits for the oil absorption process of MVF samples with osmotic dehydration pre-treatment, while it is not applicable to the coating pre-treatment. The hardness and color of MVF products was generally improved by the osmotic dehydration and coating pre-treatment. The osmotic dehydration and coating pre-treatment can be utilized as an alternative de-oiling method for MVF potato chips, but the law and mechanism of reducing the oil uptake are differs.