Feasibility of Determination of Foodborne Microbe Contamination of Fresh-Cut Shredded Cabbage Using SW-NIR

Abstract

Shredded cabbage is widely used in much ready-to-eat food. Therefore, rapid methods for detecting and monitoring the contamination of foodborne microbes is essential. Short wavelength near infrared (SW-NIR) spectroscopy was applied on two types of solutions, a drained solution from the outer surface of the shredded cabbage (SC) and a ground solution of shredded cabbage (GC) which were inoculated with a mixture of two bacterial suspensions, Escherichia coli and Salmonella typhimurium. NIR spectra of around 700 to 1100 nm were collected from the samples after 0, 4, and 8 h at 37 °C incubation, along with the growth of total bacteria, E. coli and S. typhimurium. The raw spectra were obtained from both sample types, clearly separated with the increase of incubation time. The first derivative, a Savitzky–Golay pretreatment, was applied on the GC spectra, while the second derivative was applied on the SC spectra before developing the calibration equation, using partial least squares regression (PLS). The obtained correlation (r) of the SC spectra was higher than the GC spectra, while the standard error of cross-validation (SECV) was lower. The ratio of prediction of deviation (RPD) of the SC spectra was higher than the GC spectra, especially in total bacteria, quite normal for the E. coli but relatively low for the S. typhimurium. The prediction results of microbial spoilage were more reliable on the SC than on the GC spectra. Total bacterial detection was best for quantitative measurement, as E. coli contamination could only be distinguished between high and low values. Conversely, S. typhimurium predictions were not optimal for either sample type. The SW-NIR shows the feasibility for detecting the existence of microbes in the solution obtained from SC, but for a more specific application for discrimination or quantitation is needed, proving further research in still required.

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“…Early non-destructive detection within 24 h, in the case of Botrytiscinerea and Colletotrichum acutatum , can stop cross-contamination and economic loss ( 81 ). Studies conducted by Matulaprungsan et al ( 82 ) on cabbage contamination by E. coli and S. typhimurium created artificial conditions and inoculated samples of shredded cabbage for various time periods to explore the potential of NIR analysis ( Table 6 ). During spectral analysis, this method showed a spectral shift due to the leaking from cabbage cells and the growth of bacteria ( 82 ).…”

“…Studies conducted by Matulaprungsan et al ( 82 ) on cabbage contamination by E. coli and S. typhimurium created artificial conditions and inoculated samples of shredded cabbage for various time periods to explore the potential of NIR analysis ( Table 6 ). During spectral analysis, this method showed a spectral shift due to the leaking from cabbage cells and the growth of bacteria ( 82 ). This shifting behavior was treated using the SG-derivative method ( 82 ), followed by tomato pathogen analysis ( 83 ).…”

“…During spectral analysis, this method showed a spectral shift due to the leaking from cabbage cells and the growth of bacteria ( 82 ). This shifting behavior was treated using the SG-derivative method ( 82 ), followed by tomato pathogen analysis ( 83 ). Spectral analysis revealed that the shredded samples had better separation between inoculation times than the ground samples ( 82 ), which makes the former the method of choice for analysis.…”

“…This shifting behavior was treated using the SG-derivative method ( 82 ), followed by tomato pathogen analysis ( 83 ). Spectral analysis revealed that the shredded samples had better separation between inoculation times than the ground samples ( 82 ), which makes the former the method of choice for analysis. Shredded cabbage, therefore, resulted in a higher r-value ( r = 0.91–0.95), indicating reliable prediction ( 82 ).…”

“…Spectral analysis revealed that the shredded samples had better separation between inoculation times than the ground samples ( 82 ), which makes the former the method of choice for analysis. Shredded cabbage, therefore, resulted in a higher r-value ( r = 0.91–0.95), indicating reliable prediction ( 82 ). E. coli detection in lettuce also resulted in an accuracy rate of 100% in the validation set using NIR spectroscopy and partial least-squares discriminant analysis (PLS-DA) ( 36 ).…”