The effect of high hydrostatic pressure on the microbiological quality and physical–chemical characteristics of Pumpkin (Cucurbita maxima Duch.) during refrigerated storage

Pumpkins were processed at high hydrostatic pressure (HHP) ranging from 350 to 550MPa for 0.5min to 30min. Two different nonlinear mathematical models were compared to fit the inactivation kinetics. The second model consistently produced better fits to the inactivation data than the first model (Weibull model). According to the inactivation of microorganisms, pumpkin was subjected to 450MPa/15min and 550MPa/10min. The microbiological and physicochemical changes in pumpkin subjected to (HHP) and thermal-treated (854°C/5min) were compared during 4°C storage. The total plate counts (TPC) treated with thermal processing, 450MPa/15min and 550MPa/10min were 5.12, 4.02 and 1.71 log10 CFU/g, respectively on the 60th day. The growth of microorganisms caused the increase in ΔE, decrease in hardness in other treatments. Treatment of 550MPa for 10min had little effect on color during storage. There were no significant changes in the L⁎, a⁎ and b⁎ values (p>0.05). The hardness of pumpkin treated with 550MPa/10min decreased by 32.28% after 60days. A greater retention of the original color, Vc and antioxidant capacity and increased total phenols were observed in 550MPa/10min-treated samples immediately after processing. During storage, color changed, Vc content, total phenols and the antioxidant activity were decreased. While the soluble solids content (SSC), sugars and pH value of pumpkin with HHP or thermal treatment did not show significant change immediately during 60-day storage. Based on these results, working at 550MPa for 10min ensures physicochemical and high standard of sanitation parameters in pumpkin.