Combined effect of antimicrobial coating and gamma irradiation on shelf life extension of pre-cooked shrimp (Penaeus spp.).

The present study was conducted to evaluate the combined effect of low-dose gamma irradiation and antimicrobial coating on the shelf life of pre-cooked shrimp (Penaeus spp.). Antimicrobial coatings were obtained by incorporating various concentrations of thyme oil and trans-cinnamaldehyde in coating formulations prepared from soy or whey protein isolates. Coated shrimps were stored at 4 +/- 1 degrees C under aerobic conditions and were periodically evaluated for aerobic plate counts (APCs) and Pseudomonas putida. Sensory evaluations were performed for appearance, odor, and taste using a hedonic test. Results showed that gamma irradiation and coating treatments had synergistic effects (p < or = 0.05) in reducing the APCs and P. putida with at least a 12-day extension of shelf life. Without irradiation, the inhibitory effects of the coating solutions were closely related to the concentration of thyme oil and trans-cinnamaldehyde. No detrimental effects of gamma irradiation on organoleptic parameters (appearance, odor, and taste) were observed. However, incorporation of thyme oil and trans-cinnamaldehyde reduced the acceptability scores for taste and odor.

Mechanical and barrier properties of cross-linked soy and whey protein based films.

Sterilized biofilms based on soy protein isolate (SPI, S system) and a 1:1 mixture of SPI and whey protein isolate (WPI, SW system) were achieved through the formation of cross-links by means of gamma-irradiation combined with thermal treatments. The effect of the incorporation of carboxymethylcellulose (CMC) and poly(vinyl alcohol) was also examined. gamma-Irradiation combined with thermal treatment improved significantly the mechanical properties, namely, puncture strength and puncture deformation, for all types of films. Irradiated formulations that contain CMC behave more similarly as elastomers. CMC showed also significant improvements of the barrier properties, namely, water vapor permeability, for irradiated films of the S system and for non-irradiated films of the SW system.