Microwave-Vacuum Drying of High Moisture Food Products

摘要

Dehydration is the most widely used and oldest method of food preservation and it represents a very important aspect of food processing. The high temperature and long drying time associated with conventional hot-air drying of high/moisture foods like fruits and vegetables often causes heat damage and adversely affects texture, color, flavor and nutritional value of the products. Although freeze-drying can be applied to avoid heat damage and produces products with excellent structural retention, it is a costly process and is only suitable for high-value products. Microwave-vacuum drying has been investigated as a potential method for obtaining good quality dehydrated products. The low temperature and accelerated mass transfer conferred by vacuum, combined with rapid energy transfer by microwave heating, generates very rapid, low temperature drying. Microwave-vacuum drying process can also be utilized to expand the structure of some products to yield a puffy texture which is similar to that created by frying. This article gives an overview of basic principles and technologies of microwave-vacuum drying and highlights some recent investigations carried out in this field where microwave-vacuum drying is compared with conventional hot air drying and freeze-drying in terms of drying kinetics and product quality.