Drying characteristics of Thompson seedless grapes using infra-red dryer.

Abstract

The drying characteristics of Thompson seedless grape (vitis vinifera L.) were investigated using laboratory scale infra-red dryer at four levels of intensity of infra-red radiation (0.861, 0.973, 1.039 and 1.161 kW/m 2 ). The drier was also equipped with three axial flow fans to supply air with at three different temperatures (40, 50 and 60 o C) and constant velocity of 2 m/s over the samples to carry the evaporated moisture. The results showed that the moisture content of dried grapes was decreased from (287.15 ±1, %d.b.) to (19.83 -12.37, % db). It has been found that, both air temperature and infra-red radiation intensity affects rate of drying. Two drying models: Lewis model and Henderson and Pabis's model were examined. The models were compared using the statistical coefficients such as (R), (SE), (χ 2 ), (MBE) and (RMSE). Lewis's model was the best model for describing the drying curves of Thompson seedless grapes. A diffusion model was used to describe the moisture transfer and the effective diffusivity at each drying temperature and radiation intensity. The effective diffusivity ranged from (2.2393x10 -9 ) to (2.3033x10 −10 m 2 /s) and was significantly affected by radiation intensity. The average value of activation energy was (3.2051 kW/kg). The seedless Thompson grape dried at radiation intensity of (0.973 kW/m 2 ) and air temperature of (60 °C) recorded the highest quality of the dried samples in terms of, total soluble solid, total sugar, reducing sugars and remained Residual sulphur (SO2).

Thin‐layer mathematical modeling for drying of turmeric slices in infrared dryer

“…The reduced thickness and thin layer of the turmeric slices attribute to the absence of constant rate period for the IR drying of the turmeric slices (Jeevarathinam et al, 2021). Matouk et al (2019), Tarawade et al (2022), Osae et al (2020), and Pei et al (2022) also reported similar results on the IR drying of grapes, mulberry, and ginger.…”

“…The incidence of falling rate period indicates that the drying rate depends on the diffusion of the moisture from inside of the food product to its surface(Akpinar & Toraman, 2016;Manikantan et al, 2022). The reduced thickness and thin layer of the turmeric slices attribute to the absence of constant rate period for the IR drying of the turmeric slices(Jeevarathinam et al, 2021) Matouk et al (2019),Tarawade et al (2022),Osae et al (2020), andPei et al (2022). also reported similar results on the IR drying of grapes, mulberry, and ginger.…”