M. Dolores Selgas

Beef hamburgers enriched in lycopene using dry tomato peel as an ingredient.

The direct addition of dry tomato peel (DTP) to hamburgers may be useful both to obtain a new product enriched in lycopene and for providing a use for this by-product from the tomato industry. In this study, different amounts of DTP (0-6.0%w/w) were added to raw and cooked hamburgers, and the effects on the meats physico-chemical and sensorial characteristics were studied. The maximum DTP concentration compatible with good sensory acceptability and high lycopene content was determined. Addition of DTP increased the colour parameters a(∗) and b(∗) of raw and cooked hamburgers, and modified all textural properties probably because of the presence of fibre. The hardness values of cooked samples was significantly higher in the batch containing 6% DTP (67.6N) than in a control batch (50.9N, p<0.05). The addition of DTP to 4.5% results in hamburgers with good overall acceptability and a lycopene content of 4.9mg/100g of cooked hamburger.

Cell surface hydrophobicity and attachment of pathogenic and spoilage bacteria to meat surfaces.

Cell surface hydrophobicity of several pathogenic and spoilage bacteria was determined by hydrocarbon adherence, adhesion to nitrocellulose filter, salt aggregation and adherence to phenyl-sepharose beads. Hydrophobicity of each bacterium was dependent on the method of measurement. Hydrophobicity was compared with the strength of attachment (Sr) of the bacteria to beef muscle surfaces. Bacterial cell surface hydrophobicity, as determined by the bacterial adherence to xylene correlated well with attachment strength (r = 0.800, P < 0.05). Staphylococcus aureus, Clostridium perfringens and Yersinia enterocolitica showed the highest values of attachment strength.

Effect of E-Beam Treatment on the Chemistry and on the Antioxidant Activity of Lycopene from Dry Tomato Peel and Tomato Powder

Tomato powder (TP) and dry tomato peel (DTP) have been previously used in our laboratory as a source of lycopene to manufacture meat products ready-to-eat (RTE) submitted to E-beam irradiation with good technological and sensory results. Present work describes the studies performed in order to investigate the effect of radiation on chemical changes and antioxidant properties of lycopene. DTP and TP were irradiated (4 kGy). Changes on lycopene were analyzed by HPLC; inhibition of reactive oxygen species (ROS), possible modulation of mitogen-activated protein kinases (MAPK) cascade, nuclear factor κ-light-chain-enhancer of activated B cells (NP-κB) activation and expression of proteins involved in oxidation stress were analyzed in RAT-1 fibroblasts cell culture. Radiation reduced the content of all-E-lycopene and increased (Z)-lycopene, lycopene isomerization, and degradation being higher in DTP than in TP. E-Beam treatment increased the antioxidant ability of both DTP and TP in inhibiting spontaneous and H2O2-induced oxidative stress in cultured fibroblasts. Antioxidant activity was higher in DTP than in TP samples.