Microbial and Sensory Effects of Combined High Hydrostatic Pressure and Dense Phase Carbon Dioxide Process on Feijoa Puree

摘要

High hydrostatic pressure (HHP) is used for microbial inactivation in foods. Addition of carbon dioxide (CO_2) to HHP can improve microbial and enzyme inactivation. This study investigated microbial effects of combined HHP and CO_2 on Escherichia coli, Bacillus subtilis, and Saccharomyces cerevisiae, and evaluated sensory attributes of treated feijoa fruit puree (pH 3.2; Microorganisms in their growth media and feijoa puree were treated with HHP alone (HHP), or saturated with CO_2 at 1 atm (HHPcarb), or 0.4%w/w of CO_2 was injected into the package (HHPcarb+CO_2; Microbial samples were processed at 200 to 400 Mpa, 25 ℃, 2 to 6 min. Feijoa samples were processed at 600 Mpa, 20 ℃, 5 min, then served with and without added sucrose (10%w/w; Treated samples were analyzed for microbial viability and sensory evaluation. Addition of CO_2 enhanced microbial inactivation of HHP from 1.7-log to 4.3-log reduction in E. coli at 400 Mpa, 4 min, and reduction of ＞6.5 logs in B. subtilis (vegetative cells) starting at 200 Mpa, 2 min. For yeast, HHPcarb+CO_2 increased the inactivation of HHP from 4.7-log to 6.2-log reduction at 250 Mpa, 4 min. The synergistic effect of CO_2 with HHP increased with increasing time and pressure. HHPcarb+CO_2 treatment did not alter the appearance and color, while affecting the texture and flavor of unsweetened feijoa samples. There were no differences in sensory attributes and preferences between HHPcarb+CO_2 and fresh sweetened products. Addition of CO_2 in HHP treatment can reduce process pressure and time, and better preserve product quality.