The use of lyophilization for fruit and vegetable preservation. A review

The lyophilization or freeze-drying (FD) is one of the most important technologies for obtaining dried food products and is mainly used to produce high-quality fruit and vegetable products. FD has two major drawbacks: low productivity (slow process, batch operation) and relatively high specific energy consumption, which has increased the need for improvements using innovative technologies. The main aspects of the physical basics and the three steps (freezing, primary drying, and secondary drying) are briefly presented. A new variant of FD, atmospheric freeze-drying, is also mentioned. A short overview is provided of the latest developments in FD techniques, highlighting their most characteristic and important features: how well they preserve the original texture, colour, nutritional value, and rehydration capacity. The review also discusses different coupled methods, including the integration of FD systems with other techniques such as ultrasound, microwave, infrared radiation, pulsed electric fields, and carbon dioxide laser perforation. The review evaluates the advantages and disadvantages of freeze-drying, discusses the expected quality of freeze-dried products, and identifies parameters that should be measured to assess the product’s shelf life.