Packaging methods for minimally processed foods

Consumers demand for minimally processed foods have significantly increased, primarily due to their interest in fresh and convenience foods, modern social trends, single person households, and willingness to spend money for quality products (Yang et al. 1994; Singh et al. 2010). They constitute a full meal or a significant portion of it (fresh cut fruits, salads etc.), receive minimal processing treatments, often followed by refrigeration and freezing. A number of processing treatments applied to minimally processed foods do not ensure the 'sterility'. The operations of washing, sorting, peeling and cutting necessary to produce ready-to-eat products result in the reduction of the shelf life of the fresh-cut produce, with respect to the intact product, due to the accelerated enzymatic activity, moisture loss and microbial proliferation (Lucera et al. 2010). A large number studies have been conducted to prevent the detrimental phenomena occurring after cutting; most of them are based on treatments with reducing agents, acidifying agents, chelating substances and antimicrobial compounds (Lanciotti et al. 2004; Tripathi and Dubey 2004; Rico et al. 2007). In particular control of the enzymatic browning in fresh-cut commodities, ascorbic acid and citric acid are widely used alone or in combination as substitutes for sulphite (Gimenez et al. 2003; Lee et al. 2003; Rocculi et al. 2004; Cocci et al. 2006; Albanese et al. 2007). Different calcium salts have also been studied for decay prevention, sanitation and nutritional enrichment of fresh fruits and vegetables (Martin-Diana et al. 2007). Fresh cut fruits and vegetables have a limited shelf life, due to mechanical stress, cell and membrane damage, water loss, enzyme activity, and microbial proliferation (Conte et al. 2009). The use of innovative non-thermal processing methods such as ultra-high pressure processing, pulsed electric fields, microwave sterilisation, ionizing radiations and active packaging have extended the shelf life and increased the safety of minimally processed foods. Many factors influence the shelf life of fresh and convenience foods, and packaging is one of the key factors to keep the product fresh.