High hydrostatic pressure inactivation of total aerobic bacteria, lactic acid bacteria, yeasts in sour Chinese cabbage

This study investigated the inactivation of total aerobic bacteria (TAB), lactic acid bacteria (LAB), yeasts in sour Chinese cabbage (SCC) treated by high hydrostatic pressure (HHP). The pressure level ranged from 200 to 600 MPa and the treatment time were 10–30 min. All samples were stored at 4, 27 and 37 °C for 90 days. The pressure level of 200 MPa had no significant impact on these microorganisms. The counts of TAB were significantly reduced by 2.7–4.0 log10 CFU/g at 400 MPa and 4.2–4.5 log10 CFU/g at 600 MPa from 6.2 log10 CFU/g; the counts of LAB were also reduced by 2.4–4.3 log10 CFU/g at 400 MPa from 7.0 log10 CFU/g and LAB was completely inactivated at 600 MPa; the counts of yeasts were reduced by 1.5–2.0 log10 CFU/g at 400 and 600 MPa from 4.2 log10 CFU/g. Storage temperatures significantly influenced the microbial proliferation in HHP-treated SCC depending on the pressure levels. The surviving TAB and LAB at 400 MPa equaled initial counts after 15-day storage at 27 and 37 °C, whereas they were inhibited at 4 °C up to 60 days. The surviving TAB at 600 MPa did not grow. Yeasts at 400 and 600 MPa decreased below detectable level after 2 days at all the three storage temperatures. From the microbial safety point of view, the result indicated that HHP at 600 MPa could be used as an alternative preservation method for SCC.