Listeria monocytogenes cross-contamination during apple waxing and subsequent survival under different storage conditions

Xiaoye Shen; Yuan Su; Zi Hua; Hongmei Zhu; Gülhan Ünlü; Carolyn Ross; Manoella Mendoza; Ines Hanrahan; Juming Tang; Mei-Jun Zhu

doi:10.1016/j.fm.2022.104166

Listeria monocytogenes cross-contamination during apple waxing and subsequent survival under different storage conditions

Food Microbiol. 2023 Apr:110:104166. doi: 10.1016/j.fm.2022.104166. Epub 2022 Oct 14.

Authors

Xiaoye Shen¹, Yuan Su², Zi Hua², Hongmei Zhu³, Gülhan Ünlü⁴, Carolyn Ross², Manoella Mendoza⁵, Ines Hanrahan⁵, Juming Tang⁶, Mei-Jun Zhu⁷

Affiliations

¹ School of Food Science, Washington State University, Pullman, WA, 99164, USA. Electronic address: xiaoye.shen@wsu.edu.
² School of Food Science, Washington State University, Pullman, WA, 99164, USA.
³ School of Food Science, Washington State University, Pullman, WA, 99164, USA; College of Food Science, Shanxi Normal University, Shanxi, 041004, China.
⁴ School of Food Science, Washington State University, Pullman, WA, 99164, USA; Animal, Veterinary & Food Sciences, University of Idaho, Moscow, ID, 83844, USA; Chemical and Biological Engineering, University of Idaho, Moscow, ID, 83844, USA.
⁵ Washington Tree Fruit Research Commission, Wenatchee, WA, 98801, USA.
⁶ Biological System Engineering, Washington State University, Pullman, WA, 99164, USA.
⁷ School of Food Science, Washington State University, Pullman, WA, 99164, USA. Electronic address: meijun.zhu@wsu.edu.

PMID: 36462821
DOI: 10.1016/j.fm.2022.104166

Abstract

This study evaluated Listeria monocytogenes cross-contamination between inoculated fruits, waxing brush, and uninoculated fruits during apple wax coating and investigated the fate of L. monocytogenes on wax-coated apples introduced via different wax coating schemes. There were 1.8-1.9 log₁₀ CFU/apple reductions of L. monocytogenes on PrimaFresh 360, PrimaFresh 606, or Shield-Brite AP-450 coated apples introduced before wax coating after 6 weeks of ambient storage (22 °C and ambient relative humidity). L. monocytogenes showed a similar trend (P > 0.05) on waxed apples under cold storage (1 °C and ∼ 90% relative humidity); there were 1.8-2.0 log₁₀ CFU/apple reductions of L. monocytogenes during the 12 weeks of cold storage regardless of wax coating type. For cross-contamination study, a waxing brush was used to wax one inoculated apple (6.2 log₁₀ CFU/apple); then, this brush was used to wax five uninoculated apples in a sequence. There were 3.7, 3.5, 3.3, 2.9, and 2.7 log₁₀ CFU/apple and 3.6 log₁₀ CFU/brush of L. monocytogenes transferred from the inoculated apple to uninoculated apple 1 to apple 5, and the waxing brush, respectively. The die-off rate of L. monocytogenes on wax-coated apples contaminated during wax coating was not significantly different from that contaminated on apples before wax coating, and 1.8-1.9 log₁₀ CFU/apple reductions were observed during the 12 weeks of cold storage. The application of wax coatings, regardless of wax coating type, did not impact the survival of endogenous yeasts and molds on apples during ambient or cold storage. L. monocytogenes transferred onto waxing brushes during wax coating remained relatively stable during the 2-week ambient holding. Fungicide application during wax coating reduced (P < 0.05) yeast and mold counts but had a minor impact (P > 0.05) on the survival of L. monocytogenes on apples after 12 weeks of cold storage. Collectively, this study indicated that a high cross-contamination risk of L. monocytogenes during apple waxing, and L. monocytogenes on wax-coated apples introduced via different scenarios is stable during subsequent cold storage, highlighting the need for potential intervention strategies to control L. monocytogenes on wax-coated apples.

Keywords: Apples; Cross-contamination; Listeria monocytogenes; Storage; Wax-coating; Waxing brush.

MeSH terms

Fruit
Fungicides, Industrial*
Listeria monocytogenes*
Malus*
Saccharomyces cerevisiae
Waxes / pharmacology

Substances

Waxes
Fungicides, Industrial