The effect of electron-beam irradiation on microbial counts, color, texture, and enzyme activity of mushroom slices was evaluated at dose levels of 0.5, 1, 3.1, and 5.2-kGy. Irradiation levels above 0.5 kGy reduced total plate counts, yeast and mold, and psychrotrophic counts to below detectable levels and prevented microbial-induced browning. Firmness of all samples was similar during storage except for the 5.2-kGy sample. Color was preserved by irradiation as evidenced by the higher L* values. Electron-beam irradiation at these levels did not affect the polyphenol oxidase activity. Irradiation at 1 kGy was most effective in extending shelf-life of mushroom slices.

No abstract

The purpose of this study was to determine the effect of a combination of a 1% calcium chloride dip with low dose irradiation on microbial populations, and biochemical and physical properties, of fresh diced tomatoes during a two-week storage period. Vine tomatoes at the light-red stage (trial 1) and Celebrity tomatoes at the table ripe stage (trial 2) were diced, dipped in 1% CaCl(2), and irradiated at 1 kGy from a Co(60) source. Tomatoes were also contaminated with cocktail of nalidixic-acid resistant Salmonella strains (S. Poona, S. Hartford, S. Gaminara, S. Michigan, and S. Montevideo) and subjected to gamma irradiation. Calcium treatment alone stimulated ethylene production in the diced tomatoes, whereas irradiation treatment alone suppressed ethylene production. The combination of calcium and irradiation treatments resulted in no change in ethylene production compared to the nontreated control, but respiration rate was suppressed by both irradiation and calcium treatment. The calcium dip was found to limit irradiation-induced loss of firmness. Irradiation, by itself and in combination with calcium treatment, resulted in a >3 log CFU/g decrease in total aerobic counts and psychrotrophs. Additionally, irradiation at 1.5 kGy eliminated > 3 log CFU/g of Salmonella organisms from tomatoes contaminated with Salmonella. Counts continued to decrease to an undetectable level over the 11 day storage period. The results indicate that the combination of calcium treatment and irradiation can reduce the risk of disease due to pathogenic organisms such as Salmonella and can eliminate the problem of softening induced by irradiation.