Open AccessSurvival kinetics of Listeria monocytogenes on chickpeas, sesame seeds, pine nuts, and black pepper as affected by relative humidity storage conditions
Author(s) -
Joelle K. Salazar,
Vidya Natarajan,
Diana Stewart,
Quincy Suehr,
Tanvi Mhetras,
Lauren J Gonsalves,
Mary Lou Tortorello
Publication year - 2019
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0226362
Subject(s) - listeria monocytogenes , pepper , inoculation , relative humidity , population , biology , horticulture , food science , zoology , bacteria , medicine , genetics , physics , environmental health , thermodynamics
Nuts and seeds have been increasingly associated with recalls due to contamination with Listeria monocytogenes . Storage of these food commodities occurs at various relative humidity (RH) conditions for months or years. The objective of this study was to assess L . monocytogenes survival on four commodities representing dried legumes, seeds, and spices categories: chickpeas, sesame seeds, pine nuts, and black pepper kernels. Inoculated products at 10 log CFU/g were stored for 180 days (6 months) at 25°C and different relative humidity (RH) levels: 25% (low), 45% (ambient), and 75% (high). After 180 days at 25% RH, L . monocytogenes populations decreased to 2.67–6.59 log CFU/g; the highest survival of the pathogen was observed on pine nuts and sesame seeds with decay rates of -0.014± 0.001 log CFU/g per d. Significantly greater population reductions on all products were observed during storage at 45 and 75% RH. At 45% RH, L . monocytogenes levels decreased to 1.90–6.36 log CFU/g. On chickpeas and black pepper stored at 75% RH, the pathogen population decreased to below the limit of enumeration (1 log CFU/g) yet were still detected via enrichments. The lowest survival of L . monocytogenes occurred at 75% RH on black pepper with a decay rate of -0.058±0.003 log CFU/g per d. Overall, regardless of RH level, the ability of the products to support survival of the pathogen may be expressed in the following order: pine nuts > sesame seeds > chickpeas > black pepper. The results of this study can aid in understanding how L . monocytogenes survives on dried legumes, seeds, and spices, and the data can contribute to the risk assessment of this pathogen.