Microwave Osmotic Drying

MW drying has lately been identified as a major new technology for reducing processing time without compromising the fresh product’s nutritional and organoleptic qualities [39]. This is owing to microwaves’ ability to permeate dielectric materials and generate internal heat [38]. The heat generated within the dried particle creates a vapor pressure within the product, causing moisture to be driven to the surface and preventing case hardening [80]. Other prevalent issues in microwave-processed foods include nonuniform heating, a lack of color and flavor development, a soggy surface, significant moisture loss, and a firm texture [61]. To improve mass transfer phenomena while reducing long processing times without compromising nutritional and sensory final quality, two general strategies have been considered: the use of pre-treatments prior to drying processing [40, 72] and the use of emerging technologies during drying of vegetable matrixes [30, 85]. Among the several pre-treatment processes, osmotic dehydration (OD) is distinguished by the simultaneous diffusion of moisture and solids between the meal and the hypertonic solution in which it is immersed. Osmotic dehydration is the technique of removing water from fruits and vegetables by immersing them in a hypertonic solution (a high salt or sugar solution) under temperature and time control. Water migrates from within the fruit or vegetable to the hypertonic solution across a semipermeable membrane during this process, and the fruit or vegetable gets partially dehydrated ([75] and Markowski, 2017). It has been reported that MW combined with other drying methods, such as OD, provided better drying characteristics than their respective drying methods or MW drying alone, while using a non-thermal processing and environmentally friendly technology [13, 22, 63].