RESUMO
Fresh-cut mangoes are nutritious and offer consumers freshness, flavour and convenience. They however have a shorter shelf life compared to whole fruits due to their high susceptibility to microbial contamination. The effects of gamma irradiation and chemical preservatives on the microbiological quality of refrigerated fresh-cut mangoes were evaluated. Well matured fruits of Kent and Keitt varieties sliced into cubes were microbiologically analysed initially to determine counts of total viable cells (TVC), coliforms, Salmonella sp., Staphylococcus aureus and Escherichia coli. The samples were subjected to various irradiation doses (0, 1.0, 1.5, 2.0 and 2.5 kGy) and chemical preservatives (sucrose, citric acid, sodium benzoate and a combination of these chemicals in equal proportions) and stored at 6°C and 10ºC for 15 days. TVC was subsequently estimated at 3-day intervals for the treated samples. TVC was estimated as 3.53 ± 0.25 and 4.86 ± 0.38 log10cfu/g for the Kent and Keitt varieties respectively. No coliforms Salmonella sp., E. coli or S. aureus were detected in both varieties. Irradiation at doses of 1.5 kGy to 2.5 kGy in combination with storage at 6ºC was able to eliminate all viable cells after 9 days compared to 12 days of storage at 6ºC in the case of chemical preservatives. Irradiation is more effective and ideal compared to chemical preservatives in improving the microbiological quality and therefore extending the shelf life of refrigerated fresh-cut mangoes.
RESUMO
The standard MRS components were optimized using response surface methodology for increasing yield of Streptococcus phocae PI80 viable cells and its bacteriocin. The highest amounts of bacteriocin activity and viable cells were recorded from prediction point of optimized MRS medium and achieved two fold higher (33049.8 AU.mL-1 and 14.05 LogCFU.mL-1) than un-optimized counterpart.