Desarrollo y caracterización de recubrimientos comestibles antimicrobianos para la conservación de productos derivados de la pesca

Abstract

In order to improve the microbial quality increase the shelf-life of fresh fish products, antimicrobial edible films and coatings are proposed as an emerging technology with a high potential to complement the present conservation procedures used by the food industry. Two distinct strategies were combined to preserve fresh fish (Merluccius merluccius) under refrigeration: i) the application of an antimicrobial edible coating enriched with oregano essential oil or carvacrol and ii) the reduction of initial microbial load by good handling practices and a superficial treatment with sodium hypochlorite. The use of both combined strategies resulted in a reduction of the counts of all bacterial groups after 12 days of storage, which ranged from 1.5 log and 8 log in Pseudomonas and H2S producing bacteria, respectively. On the other hand, new antimicrobial agents were studied in vitro, incorporated in different coating matrices: whey protein isolated (WPI) and fish gelatin (FG). Lauric arginate (LAE) was incorporated into FG films in several concentrations. The LAE affected pH and surface tension of the film-forming solution. The films were not affected in their optical properties by the incorporation of this antimicrobial agent was not affected moisture of the films. The increase in LAE concentration, but the solubility in water was. It mechanical properties of the films were affected, but the water vapor permeability. These active films were more effective against Gram-positive bacteria compared to Gram-negative bacteria. Another agent studied were the extracts of marine fennel. Antioxidant capacity (AC) and total content of polyphenols present in the extracts were evaluated, and their effect on the incorporation into edible films based on WPI and FG. To obtain the extracts two drying methods were evaluated: conventional hot air drying and by freeze drying. The dehydrated plants were treated with two concentrations of ethanol. The extracts obtained by freeze drying and high level of ethanol presented higher concentration of polyphenols and higher AC. Active films were prepared with different level of extracts and the physical, antioxidant and antimicrobial properties were evaluated. The added extract affected the physical and mechanical properties of the active films. AC of the films was quantified by ABTS but no antimicrobial activity was observed.