Evaluation of fluorescence-marked gene probes and Fourier transform infrared spectroscopy as novel methods to detect beer spoilage bacteria
Abstract
A novel method using fluorescence-marked gene probes is introduced into beer analysis in the context of official food control. Two commercial test kits for the detection of Lactobacilli/Pediococci and Megasphaera/Pectinatus beer spoilage bacteria were used and compared to classical plating techniques. The new method was found to be very sensitive and convenient for the identification and assessment of hygienic risks in beer samples from all stages of production. Besides that, Fourier transform infrared spectroscopy (FTIR) in combination with multivariate data analysis was evaluated to detect beer spoilage directly from the sample without prior inoculation. However, the correlations of the FTIR calibrations showed only low sensitivity so that this approach is not yet usable in food control.
... However, FTIR has been shown to detect spoilage bacteria, Lactobacilli and Pediococci as well as Megasphaera and Pectinatu where specific kits were used for the first two organisms combined and the latter two organisms combined. While FTIR calibrations were not to the authors expectations, it could provide an early warning of possible losses from spoilage bacteria [79]. ...
Brewing is an ancient process which started in the middle east over 10,000 years ago. The style of beer varies across the globe but modern brewing is very much the same regardless of the style. While there are thousands of compounds in beer, current methods of analysis rely mostly on the content of only several important processing parameters such as gravity, bitterness, or alcohol. Near infrared and mid infrared spectroscopy offer opportunities to predict dozens to hundreds of compounds simultaneously at different stages of the brewing process. Importantly, this is an opportunity to move deeper into quality through measuring wort and beer composition, rather than just content. This includes measuring individual sugars and amino acids prior to fermentation, rather than total °Plato or free amino acids content. Portable devices and in-line probes, coupled with more complex algorithms can provide real time measurements, allowing brewers more control of the process, resulting in more consistent quality, reduced production costs and greater confidence for the future.
... Megasphaera mainly affects unpasteurised low-alcohol beers by producing C5 and C6 fatty acids, H 2 S and turbidity. Both genera (Pectinatus, Megasphaera) have comparable tolerances to hop bitter acids (Back, 2005;Noack, Kn€ odl, & Lachenmeier, 2008). ...
... Third, if oxygenation of alcohol would really have an effect, the application in industry would be very limited. For beer and wine, oxygenation seems hardly feasible as it would be considerably reducing the shelf-life of the products [e.g., beers are currently produced almost oxygen-free (Noack et al., 2008)]. In most spirits (besides very pure products such as vodka), the oxygenation would also lead to off-flavors by reaction with aroma compounds. ...
Understanding the activity and viability of bacterial populations provides an insight into their physiology, reactions to stress and response to environmental change. As the key goals in food safety involve the surveillance, control and risk reduction of foodborne pathogens, physiologically oriented studies are of great relevance, allowing for detection and prediction of growth and activity. This review examines the progress, utilization and pitfalls of innovative and emerging non-nucleic acid based methods that can be linked with data generated through genome sequencing projects to provide an enhanced understanding of foodborne pathogen physiology and activity.
A new European Directive requires food manufacturers to label the potential allergenic substances sulphur dioxide and sulphites if they are used as ingredients at concentrations of more than 10 mg/l in pre-packed foods. FTIR in combination with Partial Least Squares (PLS) regression is presented as a fast (30 samples/hour), simple and inexpensive procedure for the determination of sulphite concentrations in beer (simultaneously with standard parameters like ethanol and original gravity). FTIR/PLS offers considerable advantages when measured against the conventional enzymatic reference proce-dure and will acquire increasing importance as an effi cient high-throughput tool for screening alcoholic beverages. With information gained by FTIR screening, decisions can be made whether additional analyses (with more time-consuming and expensive but more accurate standard procedures) are required. The average concentrations expressed as SO 2 were 1.0 mg/l for spirits (n=101) and 4.2 mg/l for beer (n=195). The sulphite concentrations of spirits were found to be signifi cantly lower than those of beer (p<0.0001). The new requirement of allergen labelling presents in few cases a problem for manufacturer of beer and spirits as only 2 spirit (1.9%) and 9 beer samples (4.6%) exceeded the limit of 10 mg/l. However, a labelling of the sulphite concentration had not been carried out in any of these cases.
Controlling microbial spoilage of beer is best achieved by elimination of sources of contamination. However it must be realised that the brewing process is not aseptic and the occasional chance contaminant will often be encountered. The effects of such events can be minimised by reducing the susceptibility of beer to spoilage and by the use of techniques capable of rapidly determining low numbers of contaminant organisms before any harm is done. A number of rapid methods have been available to the brewing industry for some years but all are hampered by a lack of sensitivity. Consequently, a number of techniques for concentrating micro-organisms prior to testing have been investigated. The most effective was membrane filtration modified by the use of top-pressure and relatively high temperatures. On the spoilability front, studies of the role of beer components such as dissolved carbon dioxide and phenolic compounds have been carried out. These materials reduce the susceptibility of beers to spoilage.
Fourier Transform Infrared (FTIR) spectroscopy in combination with multivariate data analysis is introduced for the quality control and authenticity assessment of spirit drinks and beer in official food control. The spectra were measured using a FTIR interferometer, which is purpose-built for the analysis of alcoholic beverages and includes an injection unit for liquids with automatic thermostating of the sample. Only 2 min are required for FTIR measurement. For spirit drinks, no sample preparation is required at all. Carbon dioxide containing samples, such as beer were prepared by degassing.
A new procedure is presented for wavelength interval selection with a genetic algorithm in order to improve the predictive ability of partial least squares multivariate calibration. It involves separately labelling each of the selected sensor ranges with an appropriate inclusion ranking. The new approach intends to alleviate overfitting without the need of preparing an independent monitoring sample set. A theoretical example is worked out in order to compare the performance of the new approach with previous implementations of genetic algorithms. Two experimental data sets are also studied: target parameters are the concentration of glucuronic acid in complex mixtures studied by Fourier transform mid-infrared spectroscopy and the octane number in gasolines monitored by near-infrared spectroscopy. Copyright © 2003 John Wiley & Sons, Ltd.
Fourier transform-infrared spectroscopy (FT-IR) methods enable chemical discrimination of intact bacterial cells and produce complex whole-organism biochemical fingerprints (spectra), which are reproducible and distinct for different bacteria. Numerous researchers indicate that there is great potential for using FT-IR methods in combination with multivariate statistics (chemometrics) to detect and identify bacteria in water, culture media and foods. This article presents a review of the FT-IR techniques, sample preparation procedures and experimental conditions used in these studies, as well as advantages, disadvantages and challenges that remain for the development of FT-IR detection methods.
Fourier transform infrared (FT-IR) spectroscopy was used to classify various foodborne pathogens (Bacillus cereus, Salmonella enterica, Escherichia coli and Listeria spp.) at the genus and strain level by pattern recognition techniques. Spectra were obtained on bacterial suspensions in 0.9% NaCl on Anodisc (aluminum oxide) filters (105–106 cfu/mm2) (Whatman Inc., Clifton, NJ). Species and strain-specific FT-IR vibrational combination bands were present at wave numbers between 1700 and 700 cm−1. Clear segregations between different genera, species and strains of bacteria were observed by principal component analysis. Results of soft independent modeling of class analogy demonstrated that the tested foodborne bacterial strains could be correctly classified (>94%), confirming that FT-IR can detect biochemical differences between bacterial cells. FT-IR is a promising technique for the identification of foodborne pathogens and could provide rapid identification and classification of bacteria.