6 Microwave Processing of Meat

In recent years, the rapid growth of chilled and frozen food market is due to rapid reheating instruments such as domestic or commercial microwave oven as well as conventional ovens. The goal of these products manufacturers is to cook the products to a temperature that would ensure the reduction of pathogenic bacteria to a safe level. It is a common way to heat the chilled foods in a microwave oven to a minimum temperature of 70°C for at least 2 minutes or an equivalent temperature/time condition, e.g. 75 °C for 30 seconds, 65 °C for 10 minutes, etc. A small change in heating time in a microwave oven has a large effect on the survival of Salmonella spp. In inoculated meat loaves, Salmonella survived after 3.5 minutes heating but it was not found when the heating time was increased to 4 minutes (European Chilled Food Federation, 1996; Farber et al., 1998; Levre & Valentini, 1998). The ever-increasing range of processed foods is produced with microwave reheating instructions surround the world as well as increased microwave applications. In industrial applications, the microwave systems have been developed for drying, pre-cooking of bacon/meat, pasteurization of ready meals and the tempering of meat and fish. There is, however, a growing new application such as blanching, baking and microwave phytoextraction. Microwave heating was primly applied in agriculture, in grain drying and insect control. In addition, it was used for food drying, blanching, pasteurization and cooking (Chen et al., 1971; Lin & Li, 1971; Maurer et al., 1971; Bhartia et al., 1973; Nelson, 1973; Jaynes, 1975; Avisse & Varaquaux, 1977; Nykvist & Decareau, 1976; Sobiech, 1980; Shivhare et al., 1994; Tulasidas et al., 1995; Begum & Brewer, 2001; Hong et al., 2001; Sumnu, 2001; Ramesh et al., 2002; Beaudry et al., 2003; Severini et al., 2004; Williams et al., 2004; Zhang et al., 2004). Frozen materials are usually thawed or tempered before further processing in food industry. Thawing is usually regarded as complete when all the material has reached 0 °C and no free ice is present. This is the minimum temperature at which the meat can be boned or other products cut or separated by hand. Lower temperatures (e.g. -5 to -2 °C) are acceptable for mechanical chopping of product, but such material is `tempered' rather than thawed. The two mentioned processes are not same with together because tempering only constitutes the initial phase of a complete thawing process while thawing is often considered as simply the reversal of the freezing process. However, inherent in thawing is a major problem that it does not occur in freezing operation. Thawing operation has some steps, at first the surface