Freeze Dryers
Freeze-drying (FD), known as lyophilization, is a standard method for making high-quality food powders and solids (Karam et al., 2016). This approach is suitable for drying thermally fragile and oxidation-prone foods since it stops most microbiological processes (Falade & Igbeka, 2007). The approach protects sensitive, non-evaporable material. Material is in a high-vacuum container on racks or belts. Food is mainly frozen before filling the dryer. Vacuum pumps condense vapor and heats the food. Rapid freeze-drying employs extended metal sheets between items and heated plates to increase heat transfer to rough regions and moisture removal. The expanding metal and plates are constructed for maximum heat transmission. Refrigerated condensers compress water. Apples, asparagus, blackberries, cocoa, garlic, guava, ginger, maple syrup, pumpkins, strawberries, tea, tomatoes, and others have been FD-treated. Vitamins and other bio-compounds may be lost during freeze-drying. This makes soup, quick drinks, desserts, and other meals with consistency requirements like freeze-dried food rehydration and porosity. FD intensification using new technologies or pretreatments has addressed various processing challenges (Bhatia et al., 2020). Freeze-drying initially dehydrates fruits by 90%. Salt absorption, water desorption, membrane pectin cell degeneration, and water crystal pore size impact freezing dried fruits' rehydration. Frozen-dried food rehydrates fast and tastes fresh. Freezing dry products reduces volume, has little chemical transition, reduces volatile component loss, lasts long, and has antioxidant qualities (Abbasi & Azari, 2009). Freeze drying is costly and energy-intensive. Due to extended freezing drying time, the product may dissolve, lose smell, and become stiff and low-rehydratable (Harnkarnsujarit & Charoenrein, 2011).