Introduction
Cooking is a heat treatment whose purpose is to transform a food product in an appetizing and nutritious food but also free of pathogènes. Like any heat treatment it induces a number of biological transformations (inactivation of enzymes and of micro-organisms), chemical transformations (caramelization, reactions of hydrolysis and oxidation, Maillard reaction, ..) that have themselves physical consequences (texture, color, ..)
Some of these changes may have a beneficial effect: increasing the digestibility of protein and of the starch; destruction of anti-nutritional factors, production of flavorings. But the heat treatment can also lead to side effects like denaturation or destruction of nutrients (vitamins, proteins, ..) and the production of some neoformed compounds (NFC) whose some are suspected to be carcinogens (Tessier et al, 2007).These phenomena depend on the level of the temperature and the processing time.
Microwaves have the ability to heat the material. This heating is related to the absorption of electromagnetic waves by molecules constituting the matter and in particular the water molecule. The particularity of microwaves compared to conventional processes is the mode of intake of energy. While in a conventional heating energy is provided from the surface of the body to be heated, in the case of microwave energy, it is provided inside the product mass (Schiffmann, 1995). The main impact is a rapid increase in product temperature and greater homogeneity in the distribution of heat inside the product. Therefore, the duration of treatment is generally shorter than in conventional heating.
Many studies highlight the interest of microwave heating in terms of nutritional quality (Villamiel et al, 1996; Habiba, 2001, Zia-ur-Rehman et al, 2002) microbiological quality (Abhayawick 2000, Hanna et al , 2006) and energy saving (Laguerre, 1999; Abhayawick, 1999).Thus, in the area of food industry, micro-waves are used for operations as diverse as drying, cooking, pasteurization, tempering, etc..
In contrast, at the catering level, the microwave ovens are used almost exclusively for reheating already cooked dishes. This practice is largely due to the lack of knowledge on the potential of this technology for cooking and to the absence of procedures for carrying out traditional recipes in microwave oven. There is indeed, to our knowledge, no systematic study whose aim is to adapt various types of traditional recipes to microwave with a view to preserving the nutritional quality.
Moreover, in recent years the concept of “functional food” made its appearance in the food industry. The concept of “functional meal”, from other side, has been proposed by Rodgers (2004a). It is a meal that is made from functional ingredients (fiber, antioxidants, micronutrients, ..) but also with the addition of probiotics (lactic bacteria) that increase the lifespan of the dish. Many authors have indeed demonstrated the inhibitory effect of some bacteriocins produced by Pediococcus pentosaceus, Lactococcus lactis, Lactobacillus acidophilus and Lactobacillus plantarum, on spores of Clostridium botulinum (Okereke and Montville, 1991). These dishes containing both, functional ingredients and some protective cultures, and chilled very quickly, present improved sensory and nutritional characteristics and a longer shelflife (Rodgers, 2004b).
