High pressure-assisted thermal sterilization of low-acid fruit and vegetable purees: Microbial safety, nutrient, quality, and packaging evaluation

The objective of this study was to assess the influence of pressure-assisted thermal sterilization (PATS) on nutrients and quality of pumpkin, butternut squash, pea, beetroot, and purple potato purees. PATS processing parameters included preheating of purees at 98 degrees C for 5 min and pressurizing at 600 MPa in a vessel set at 90 degrees C for 5 min. Colorimetric temperature sensors, two types of Bacillus amyloliquefaciens spores, total aerobic and anaerobic plate count, HPLC, as well as spectrometer and spectrophotometer were utilized. The colorimetric temperature sensor based on its color value when extrapolated suggested the purees' temperature reached 122 degrees C. Thus, at least 9-log(10) reduction of B. amyloliquefaciens spores was achieved in a purple potato puree, and no detectable aerobic and anaerobic microorganisms were found after PATS in all purees. Vitamin C showed 3-14% reduction after PATS. Total chlorophyll and beta-carotene did not vary significantly (p > 0.05) after PATS, while betalains and anthocyanin were sensitive and decreased significantly. Interestingly, total color change (Delta E) of pumpkin, butternut squash, and beetroot purees ranged between 2.5 and 3.4 below the threshold (Delta E = 6) value that can be observed by the naked eyes. EVOH-based packages did not show any visual deformation, but their oxygen and water vapor transmission rates increased significantly (p < 0.05) after PATS. The present research suggests that PATS can be used to produce safe and high-quality shelf-stable fruit and vegetable products.