Ethanol pretreatment and infrared drying of melon: Kinetics, quality parameters, and NIR spectra

Abstract

There is a growing interest in drying methods focusing on the reduction of drying time, and improvement of product quality. This work aimed to study the use of ethanol as a pretreatment to melon infrared drying (IRD), evaluating its effect on the drying kinetics and quality parameters. The pretreatment step included the melon immersion in different ethanol concentrations (50% and 100%) and immersion times (10, 20, and 30 min). IRD was performed at 60 C with control (untreated) and pretreated samples. Melon pretreated in 100% ethanol for 30 min had the shortest drying time and highest diffusivity value. The Page model obtained the best fit for the experimental data. All dried melons showed water activity below .60, and a reduction in the bioactive compounds. Samples immersed in 50% ethanol, in general, showed lower losses of total phenolics and carotenoids. Concerning color, there was a decrease in the luminosity (L*), while redness (a*) and yellowness (b*) were intensified. Principal component analysis applied to the near infrared (NIR) spectra of the dried samples showed a tendency of separation between samples pretreated with different concentrations of ethanol. In conclusion, IRD and ethanol pretreatment can be useful tools to reduce drying time, but some limitations on bioactive compounds were discussed. Practical applicationsThe concentration and the time of ethanol pretreatment application can result in different melon infrared drying rates and can influence important qualitative parameters. Therefore, it is important to evaluate these factors to optimize the dried melon production, resulting in lower drying time and better quality preservation.

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“…The Aghbashlo model is superior in predicting the drying behavior of pomegranate fruit. NIR drying is also used for olive leaves [42] and melons [43]. Onwude et al [44] used a mid-infrared unit (2.5-4 µm) for drying sweet potatoes to study the drying kinetics, mass and heat transfer.…”