Inactivation of naturally occurring microbiota in cucumber juice by pressure treatment

•Homogenization played an unfavorable role in the inactivation of TPC by HHP.•Nisin had a synergistic effect on the inactivation of TPC with HHP.•A decreased decompression time with HHP enhanced the inactivation effect of TPC.•The biphasic model provided the best fit with the data to describe the effects of HHP on TPC.

The inactivation effects of high hydrostatic pressure (HHP) (350 MPa/10 min, 400 MPa/4 min and 500 MPa/2 min) with homogenization (20 MPa/2 min), nisin (100 IU/mL) and decompression time (< 3 s and 7–8 s) on naturally occurring microbiota in cucumber juice were investigated. Initial concentration of yeasts and molds (Y&M) was 5.6 × 103–2.4 × 104 CFU/mL, and total plate count (TPC) was 1.0 × 105–3.5 × 105 CFU/mL. Y&M were inactivated below the detection level (≤ 10 CFU/mL) in all cases. The reduction of TPC in non-homogenized cucumber juice (NHCJ) was 2.5–3.0 log cycles, which was significantly higher than 1.0 log cycle in homogenized cucumber juice. The combination of nisin with HHP had a synergistic effect on the inactivation of TPC. The reduction of TPC in NHCJ with a decompression time of < 3 s was approximately 4.5 log cycles, which was significantly higher than a decompression time of 7–8 s. Five non-linear models including the biphasic, Weibull, modified Gompertz, log-logistic and Baranyi models were fitted to TPC inactivation curves for the NHCJ at 300, 350 and 400 MPa for 2–15 min and 500 MPa for 2–8 min at a decompression time of < 3 s. The biphasic model provided the best fit for the data.