MOREIRA Maria Del Rosario
capítulos de libros
Organic Fresh Vegetables: Green Technologies
MOREIRA MR; A PONCE; S ROURA
Food Science and Technologies: New Research
Nova Science Publishers
Año: 2008; p. 407 - 426
The exploration of green technologies for food preservation receives increasing attention due to consumer awareness of natural food products and a growing concern of microbial resistance towards conventional preservatives. Cut vegetable tissues trigger chemical reactions and release nutrients that support the growth of the microflora present on raw produce. Wounding lettuce leaves induce the synthesis of specific enzymes and the accumulation of specific phenolic compounds associated with tissue browning. Many spices and herbs exert antimicrobial activity due to their essential oil fractions, also some native microflora naturally present on fresh produce surfaces are capable of producing antimicrobial compounds playing an important role maintaining fresh vegetable quality and safety. Moreover, natural antimicrobials and antioxidants like oleoresins imbedded in edible films can be gradually released on the food surface, therefore, requiring smaller amounts of them to achieve the target shelf life. The use of edible films in food preservation has increased since they offer several advantages over synthetic materials. The innovative methods to control natural microflora and browning reactions on vegetables include mild heat shock treatments. They lack of an offensive chemical residue doing this technique an attractive alternative of preservation. The use of essential oils to preserve organic vegetables was investigated through in vitro and in vivo experiments. Some oils presented antimicrobial and antioxidant activities indicating their potential to become technological useful products as sanitizing agents. Clove and tea tree essential oils were highly inhibitory to E. coli; while olive and rosemary oleoresins presented antimicrobial effects against L. monocytogenes and against native microflora of squash. Chitosan film enriched with rosemary and olive improved the antioxidant protection of the minimally processed squash offering a great advantage in the prevention of browning reactions. The potential use of lactic acid bacteria occurring naturally in organic vegetables was investigated. E. faecium, L. lactis, E. hirae and E. canis showed novel antagonistic effects against Gram-negative bacteria with a potential role as food biopreservatives. Heat shock treatments prevented browning of minimally processed lettuce. The impact of wounding was reduced by the application of heat shock treatments at 50 °C, without changes in the sensory attributes. This work presented evidence for the potential application of mild heat shocks as a novel preservation technology for minimally processed vegetables compatible with organic and low input farming systems.