Kinetic modeling of anthocyanin degradation and microorganism growth during postharvest storage of açai fruits (Euterpe oleracea).

The unavoidable damage of acai (Euterpe oleracea) fruits (AF) during picking leads to microbial contamination and anthocyanin degradation, which prejudice the consumed fruit drink. Thirteen lots of AF (24 kg) from different municipal districts of the Para State (Brazil) were monitored during a 75-h-long storage in the dark at 30 degrees C for microbial growth, and 7 lots for anthocyanin degradation. On arrival at the laboratory, anthocyanins presented a mean concentration of 828 mg kg(-1) fruits with a standard deviation of 323 mg kg(-1) fruits whereas mean microbial contamination was 2.64 10(6) CFU g(-1) of dry matter for total mesophilic bacteria, 1.98 10(3) MPN g(-1) DM for fecal coliforms, and 1.11 10(5) CFU g(-1) DM for moulds and yeasts. Kinetic growth of the microbes could be fitted to a quadratic equation with an unusual rapid growth during the 1st 24 h. The kinetics of anthocyanin degradation fitted a 1st-order equation. The mean velocity constant of the reaction (k(1)) was of 0.0137 h(-1) and the mean half-life (t(1/2)) of the anthocyanins was 50 h. These results indicate that the AF simultaneously suffer extensive anthocyanin degradation and explosive microbial growth during the postharvest period needing a special care.