Modelling the survival of Listeria monocytogenes in oat plant-based milk alternatives: The synergistic potential of HHP and nisin

Abstract

The growing popularity of plant-based milk alternatives (PBMAs), particularly oat-based beverages, is driven by consumer demand for sustainable, vegan, and lactose-free options. High Hydrostatic Pressure (HHP) is a non-thermal technology capable of extending shelf life and enhancing microbial safety, especially when combined with natural antimicrobials such as nisin. This study aimed to quantitatively assess the inactivation of L. monocytogenes strains LO28 and 10403S in oat-based PBMA treated with HHP alone or in combination with nisin (500 IU/mL). Inoculated oat PBMA samples with or without nisin were subjected to 300, 350, and 400 MPa (20 °C) for different holding times, up to 40 min. Inactivation followed a log-linear behavior at 300 MPa and biphasic kinetics at 350 and 400 MPa. The addition of nisin significantly (p < 0.05) reduced the time to 3-log reduction (3DP) compared to HHP alone at all pressures for LO28 and at 400 MPa for 10403S. For LO28 at 350 MPa, 3DP values decreased from 7.65 ± 0.42 min (HHP alone) to 3.11 ± 0.28 min (HHP + nisin), indicating a synergistic effect as nisin alone had no impact. Secondary modeling confirmed that HHP efficacy was both strain- and nisin-dependent. Pressure resistance (zP) was significantly lower for LO28 (102.7 ± 2.7 MPa) than 10403S (193.8 ± 10.6 MPa). Nisin notably reduced zP in 10403S (193.8 ± 10.6 to 107.4 ± 4.6 MPa) enhancing its pressure sensitivity. These findings demonstrate that HHP combined with nisin represents an effective hurdle strategy for producing safe, refrigerated, clean-label oat-based PBMAs. Optimized processing conditions may allow lower pressures or shorter treatment times, reducing costs while preserving product quality. Further work should assess microbial stability during refrigerated storage and consumer acceptance.