Effect of Hot-Water Blanching Pretreatment on Drying Characteristics and Product Qualities for the Novel Integrated Freeze-Drying of Apple Slices

Abstract

The effect of hot-water blanching (HWB) on drying characteristics and product qualities of dried apple slices with the novel integrated freeze-drying (NIFD) process was investigated by comparing with 3 different FD methods. Compared with the NIFD process without HWB pretreatment (VF-FD), the NIFD process with HWB pretreatment (HWB-VF-FD) resulted in a significantly higher mass loss and more sufficient freezing in vacuum-frozen samples, significantly higher rehydration ratio (RR), higher shrinkage ratio (SR), smaller Vitamin C (V C ) content and lower hardness and better apparent shape in freeze-dried samples, and fewer change to the color of the dried or rehydrated samples ( < 0.05). Compared with the conventional FD process with HWB pretreatment (HWB-PF-FD), HWB-VF-FD cost significantly less processing time and FD time and obtained significantly higher RR ( < 0.05), almost the equivalent SR, V C content, and hardness, and similar appearance in dried samples. The microstructure of apple cell tissues was analyzed by transmission electron microscopy and scanning electron microscopy to interpret the above differences in drying characteristics and product qualities. The results suggested that the NIFD process of apple slices with HWB pretreatment was a promising alternative method to decrease drying time, achieve similar product quality, and simplify the process steps of the conventional FD technology.

Effect of Blanching, Varietal Difference of Irish Potato Flour and Sprouted Maize Flour on Energy Density of Gruels of Three Irish Potatoes Varieties (Cipira, Pamela and Dosa) in Dschang, West-Cameroon: Optimization Using Response Surface Methodology (RSM)

“…The lowering of the fiber content by the treatment would be the consequence of a destruction of these compounds by heat treatment and elimination in the blanching water. Similar observations have also been reported by Wang et al [24], who observed a loss of watersoluble compounds such as fibres following blanching. The interactive effect would be due to the fact that the different varieties of Irish potato studied are very rich in soluble fiber, which would therefore be easily extracted and eliminated by blanching water.…”

“…This change leads to an increase in membrane permeability and thus increased water removal through evaporation [23]. Wang et al [24], also demonstrated that water blanching reduces the water content of apples. It should be noted that the water levels obtained (<14%) are favourable for good conservation in tropical areas over a long period of time [25].…”

Influence of Pretreatments on Microwave Vacuum Drying Kinetics, Physicochemical Properties and Sensory Quality of Apple Slices

“…The ascorbic acid content in the OD and ST samples was signifi cantly higher than in the non-pretreated sample and the opposite tendency was observed in the SB, SB+OD, and UT samples. The loss in V C was attributed to the thermal disruption and leakage of water-soluble V C during pretreatment [Wang et al, 2018;Horuz et al, 2017]. However, it was reported that the presence of sugar would stabilize vitamin C in fruits [Pasławska et al, 2017].…”

“…Pretreatments prior to drying are often used to reduce the initial moisture content, accelerate the drying process, improve quality of dried products, modify the physicochemical properties of dried material, and infl uence the heat and mass transfer during drying [Doymaz et al, 2010]. Some common pretreatments include blanching, osmotic dehydration, sulfi te treatment or a combination of the above treatments [Camel et al, 2019;Wang et al, 2018;Doymaz et al, 2010]. The sulfi ting at low concentration is the most commonly used pretreatment method for apples and other fruits for its features of simple operation and well preserved color of products.…”

High pressure‐assisted vacuum‐freeze drying: A novel, efficient way to accelerate moisture migration in shrimp processing

“…Its principle is to freeze the solvent contained inside the products to a solid state and then induce sublimation of the frozen material as vapor under vacuum conditions to achieve the goal of drying (Antal, Tarek‐Tilistyák, Cziáky, & Sinka, ; Gao et al., ). It can better preserve most of the initial material properties, such as taste, aroma, color, flavor, nutrients, biological activity, and rehydration ability (Georgiev, Kosturski, Margenov, & Stary, ; Wang, Fu, Chen, Hu, & Xie, ). Furthermore, it also retains its original shape, appearance, and texture with minimal shrinkage and high porosity (Ma et al., ; Ma, Qu, & Sun, ).…”