Lastly, not only microwaves speed up the cooking of pasta, but they provide for a faster breakdown of starch and the preservation of a stronger gluten network in the outer pasta layer. Microwaves can be usefully applied even to pasteurization and sterilization, notably for all liquid foodstuffs such as milk and fruit juice, as well as, although less easily, for semi-solid and solid foods. Adoption of microwave pasteurization and sterilization technology for pre-packaged meals is possible (accepted from the U.S. Food and Drug Administration): in these cases, the packaging material must be specifically selected for this use. Micro-organisms are killed at lower temperatures than those required for conventional pasteurization, thanks to magnification of the thermal effects of these waves, and to several other lethal and sublethal effects of these waves on micro-organisms, as electroporation and breakage of the cell membranes. Microwaves have been adopted also in several industrial drying processes (including the drying of pasta), in support of both conventional pasta drying processes with hot air or vacuum methods, or using frozen liquid products: “microwave assisted hot air drying”, “microwave vacuum drying” and “microwave freeze drying”. These combined technologies provide faster drying, which better respect the organoleptic properties of the foodstuff. There are now applications for a large variety of food products, especially of plant origin. Finally, interesting results have been obtained with microwave blanching, especially for the treatment of certain dried herbs: After sprinkling the herbs with a minimum amount of water, they are processed in the microwave for a very short time, to inactivate enzymes while preserving pigments (especially chlorophyll), obtaining better results compared to conventional blanching methods in hot water or steam.
Sous vide cooking
Under vacuum cooking (sous vide) is a method in use since the 1970s in certain prestigious and innovative restaurants, but only from the beginning of the new Millennium it is used for industrial production. In sous vide cooking, foodstuff is rolled in an air-tight plastic wrap, and then it is processed maintaining precise temperature control. The intention is to cook the item evenly, in a stable environment at precisely controlled temperatures, and to extend the shelf-life of minimally processed foods in airtight plastic pouches that prevent any risk of recontamination during storage. This method offers several benefits: it can enhance taste and nutrition, because sous vide cooking prevents evaporative losses of flavour volatiles and moisture, and inhibits off-flavours from oxidation. Compared to conventional cooking, temperatures are generally lower and heating times longer; but in return, precise temperature control gives superior reproducibility, better control of doneness, and reduces the loss of weight due to the evaporation of internal moisture. In almost all cases, the vacuum-sealed pouch containing the food is immersed either in a water bath or a convection steam oven; thanks to the high thermal conductivity of water and steam, the desired temperatures come up quickly. After cooking, the food can be refrigerated or frozen in its vacuum sealed pouch and sent to the distribution centres. For these reasons, sous vide cooking is ideal for minimally processed foods in order to preserve their texture, flavor and nutritional properties. Other benefits are perfect reproducibility of the end result under the same conditions (cooking time and temperature), and the possibility of making food safe (especially meat) at lower temperatures than those of traditional cooking methods. In general, compared to conventional cooking, the sous vide method contributes to increase the tenderness of meat, making it juicier and rich of flavor. This applies also to less expensive cuts of meat, which are usually tougher: these cuts are frequently marinated, tenderized or brined before vacuum packaging to produce better results. Sous vide cooking is excellent also for cooking vegetables, fruits and legumes, with the result of making them tender and intensifying their flavor and nutritional value.
Literature
Baldwin D.E., Sous vide cooking: A review. 2012. International Journal of Gastronomy and Food Science. 1:15:30
Chandrasekaran S., Ramanathan S., Basak T., 2013. Microwave food processing – a review. Food Research International. 52:243-261
Thostenson E.T., Chou TW., 1999. Microwave processing: fundamentals and applications. Composites: 30:1055-1071
