Investigation and Rapid Discrimination of Food-Related Bacteria under Stress Treatments Using IR Microspectroscopy.

Daniel Klein,Carsten Engelhard,Jessica Reinmüller,Peter Kaul,René Breuch

doi:10.3390/foods10081850

Daniel Klein, Carsten Engelhard + Show 3 more

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https://doi.org/10.3390/foods10081850

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Abstract

Because the robust and rapid determination of spoilage microorganisms is becoming increasingly important in industry, the use of IR microspectroscopy, and the establishment of robust and versatile chemometric models for data processing and classification, is gaining importance. To further improve the chemometric models, bacterial stress responses were induced, to study the effect on the IR spectra and to improve the chemometric model. Thus, in this work, nine important food-relevant microorganisms were subjected to eight stress conditions, besides the regular culturing as a reference. Spectral changes compared to normal growth conditions without stressors were found in the spectral regions of 900–1500 cm−1 and 1500–1700 cm−1. These differences might stem from changes in the protein secondary structure, exopolymer production, and concentration of nucleic acids, lipids, and polysaccharides. As a result, a model for the discrimination of the studied microorganisms at the genus, species and strain level was established, with an accuracy of 96.6%. This was achieved despite the inclusion of various stress conditions and times after incubation of the bacteria. In addition, a model was developed for each individual microorganism, to separate each stress condition or regular treatment with 100% accuracy.

Highlights

Because meat and meat products are highly appreciated by consumers, for their nutritional value and taste, the global supply of meat is expected to continue to increase in the coming years [1]
As bacteria are subject to constant fluctuations in their growth conditions, both in nature and along the supply chain, they have developed capabilities to constantly adapt to conditions, or even change to a state of viability, but are non-cultivable [3,4,5]
The following nine microorganisms were cultivated on nutrient agar (10 g/L meat peptone, 10 g/L meat extract, 5 g/L sodium chloride and 18 g/L agar-agar (Merck KGaA, Germany)) and prepared according to our previously published method [12,37,38]: Bacillus subtilis DSM 10, Bacillus coagulans DSM 1, Escherichia coli K12 DSM 498, Escherichia coli

Summary

Introduction

Because meat and meat products are highly appreciated by consumers, for their nutritional value and taste, the global supply of meat is expected to continue to increase in the coming years [1]. Meat is highly prone to microbial spoilage and, rapid and easy identification of contamination is a major concern in food safety [1,2] This will help to ensure measures to minimize health hazards, and prevent foodborne illness and unnecessary food waste along the supply chain [2]. As bacteria are subject to constant fluctuations in their growth conditions, both in nature and along the supply chain, they have developed capabilities to constantly adapt to conditions, or even change to a state of viability, but are non-cultivable [3,4,5] This makes sub-lethally damaged cells difficult to detect with classical laboratory culture techniques [2]. These viable, but non-culturable, microorganisms can be revived within the supply chain, and affect the product’s usability, but may be a health hazard [2,9,10,11]

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