Parameters optimization and quality evaluation of mechanical properties of infrared radiation thin layer drying of pumpkin samples

Abstract

AbstractThis work aims to estimate quality characteristics of dried pumpkin samples in an infrared dryer under natural and forced drying air convection systems. Drying time, rehydration ratio, and shrinkage as a function of infrared intensity, sample thickness, sample distance from the infrared lamps, and air velocity were optimized using response surface methodology. Maximum rehydration ratio and minimum drying time and shrinkage were assumed as criteria for optimizing drying conditions of the samples. The optimum values of process variables were 1 m/s air velocity, a sample thickness of 2 mm, 2,000 W of infrared intensity, and sample to infrared lamps distance of 550 mm. Based on the significant effect, sample thickness was the most prominent factor. The optimal values of drying times, rehydration ratios, and shrinkages of the dried samples under natural and forced convection were 1.068 hr and 1.017 hr, 10.375 and 9.141 (g rehydrated sample/g dried sample), and 69.38 and 73.17 (%), respectively.Practical ApplicationsPumpkin as one of the tasty, valuable and healthy nutrition vegetables containing a lot of biologically active substances is rich in phenolics, polysaccharides, flavonoids, vitamins, mineral salts, and a good source of carotene and water‐soluble vitamins. Because of the high initial moisture content, it is very sensitive to microbial spoilage. Thus, the drying can be greatly minimized microbial activities and deterioration chemical reaction by the removal of moisture up to a certain level. In addition, choosing the right type of dryer, design, simulation, and optimization of the drying process are largely dependent on the knowledge of the drying characteristics. It is worth mentioning, the developed statistical multivariate model equations accompanied by the optimal process conditions can be very useful for the design and operation of IR dryer when there is no certain multidimensional infrared drying model for high‐value foodstuffs such pumpkin.