Rapid Assessment of the Microbiological Quality of Pasteurized Vanilla Cream by Means of Fourier Transform Infrared Spec
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Rapid Assessment of the Microbiological Quality of Pasteurized Vanilla Cream by Means of Fourier Transform Infrared Spectroscopy in Tandem with Support Vector Machine Analysis Alexandra Lianou 1 & Christos Malavazos 2 & Ioannis Triantafyllou 2 & George-John E. Nychas 1 & Efstathios Z. Panagou 1
Received: 9 August 2017 / Accepted: 6 October 2017 # Springer Science+Business Media, LLC 2017
Abstract The objective of this study was to assess the performance of Fourier transform infrared (FTIR) spectroscopy as a rapid and non-invasive technique for the automated microbiological quality evaluation of pasteurized vanilla cream, a ready-to-eat milk-based product. Vanilla cream samples were subjected to (i) microbiological analyses for the determination of aerobic plate count (APC), (ii) sensory evaluation, and (iii) FTIR spectroscopy measurements. The analyses were undertaken in cream samples obtained directly from the manufacturer and stored at different isothermal conditions (4, 8, 12, and 15 °C), as well as from retail outlets. Spectral data collected from cream samples were correlated with microbiological and sensory data to discriminate the samples in two quality classes, namely class 1 (accept, APC < 4.5 log CFU/g) and class 2 (reject, APC ≥ 4.5 log CFU/g). Support vector machine classification (SVM-C) models were developed to provide qualitative estimations of the cream samples’ microbiological status based on FTIR spectral fingerprints. The developed SVM models were further validated against independent samples obtained from the market and exhibited a satisfactory performance. Specifically, overall classification accuracies above 90% were obtained for various SVM kernels assayed (linear, polynomial, radial basis function) for the test datasets analyzed, indicating that FTIR spectroscopy could be a
* Efstathios Z. Panagou [email protected] 1
Laboratory of Microbiology & Biotechnology of Foods, Department of Food Science & Human Nutrition, School of Food, Biotechnology & Development, Agricultural University of Athens, Iera Odos 75, 118 55 Athens, Greece
2
Hypertech SA, IT & Organization Unit, Perikleous 32, 152 32 Athens, Greece
promising method for the real-time assessment of vanilla cream’s microbiological quality. Keywords FTIR . Microbiological quality . Vanilla cream . Support vector machines
Introduction Vanilla cream is a traditional ready-to-eat, non-fermented, sweet milk-based product, which is typically subjected to heat treatment (pasteurization) prior to packaging to ensure its microbiological quality and safety. Nonetheless, under certain circumstances, the microbiological stability of this product may be compromised as a result of germination of surviving bacterial spores, or in the case of a post-process contamination event (Panagou and Nychas 2008). Indeed, given its composition (ample nutrient availability) and intrinsic properties (neutral pH and high water activity), vanilla cream is expected to provide a favorable environment for microbial proliferation in the absence of efficient temp
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