The influence of infrared assisted hot air drying on quality of coconut chips

Abstract

The development of snack foods while maintaining their nutritional integrity presents a significant challenge within the food industry. This study aims to identify the most suitable drying technique for producing high-quality coconut chips. The conventional drying method (hot air convective drying) was compared with the emerging drying techniques such as infrared drying (IRD) and infrared-assisted hot air drying (IRHAD) for the production of coconut chips. The coconut kernel was sliced at two different thicknesses (0.5 and 1.4 mm) and then subjected to osmotic dehydration in a sugar solution. Drying was done at 65 °C for the production of a premium quality final product. It was observed that IRHAD at 65 °C resulted in a better quality final product. The physicochemical properties of the coconut chips samples showed minimal variation between the two thickness levels. The physical properties observed for coconut chips samples of 0.5 mm and 1.4 mm thickness, dried using IRHAD for 90 min and 120 min respectively, were as follows: rehydration ratio of 2.01% and 1.69%, and hygroscopicity of 5.43% and 2.02%, respectively. The biochemical properties for the same thicknesses included a moisture content of 2.4% and 1.30%, ash content of 1.29% and 1.25%, total carbohydrate levels of 43 g glucose/100 g and 45.33 g glucose/100 g, protein content of 4.87% and 5.32%, and fat content of 36.20% and 46.35%, respectively. The total phenolic content was measured at 3.89 g gallic acid eq/100 g and 3.42 g gallic acid eq/100 g, while the DPPH radical scavenging activity was 34.51% and 39.38%. Additionally, the FRAP values were 0.97 trolox eq/100 g and 0.96 trolox eq/100 g, respectively. The moisture ratio was fitted to the seven drying models, and the performance of the models was assessed by statistical parameters. The diffusion approximation model exhibited a high coefficient of determination (R²) for all the drying methods. For the diffusion approximation model of infrared-assisted hot air drying (IRHAD), the values of R², RMSE, and χ² were 0.9998, 0.0054, and 0.0002, respectively, for the 0.5 mm thick coconut chips sample, and 0.9997, 0.0058, and 0.0003, respectively, for the 1.4 mm thick sample. As a result, the IRHAD method is the optimal choice for producing coconut chips, as it offers enhanced biochemical properties, improved drying kinetics, and favorable physical characteristics. This method is particularly suitable for applications in the development of high-quality, nutritious dried snack food.