A model food mimicking plant-based meat analogues for determination of matrix effects on growth of Listeria monocytogenes

Listeria monocytogenes is a pathogen of concern in plant-based meat analogues (PBMAs). Testing L. monocytogenes growth behavior in real products at various conditions requires screening of a large set of conditions and timepoints which is time-consuming, hence costly. A representative model PBMA has been developed that allows to test L. monocytogenes growth in the presence of different growth inhibitory parameters. To minimise handling and disposable use, L. monocytogenes was enumerated using a miniaturized most probable number (mMPN) method, which showed good correlation to CFU counting. The model PBMA was further demonstrated for a range temperatures (7-15 °C), a_w (down to 0.940, adjusted by NaCl) and lactic acid and acetic acid concentrations (up to 2.5 mM and 6 mM undissociated acid, respectively). The growth of L. monocytogenes strain FBR017 was quantified, and the kinetic growth parameters were determined. Besides soy, other plant protein sources including pea, wheat and wheat/soy combinations were tested. All matrices readily supported growth of L. monocytogenes FBR017 and the μ_max determined on the fitted data showed similar rates for all protein types showing that the type of plant protein did not significantly influence the growth rate of L. monocytogenes in PBMAs. The presented model PMBA allows to vary the concentration of undissociated organic acids (lactic acid and acetic acid) and other parameters (pH, a_w, NaCl). This allows determining effects of individual growth inhibiting parameters in a PBMA matrix at desired levels which would be impractical to test in industrially produced products.