Free iron in pale, dark and alcohol-free commercial lager beers

Predicting and improving complex beer flavor through machine learning

The perception and appreciation of food flavor depends on many interacting chemical compounds and external factors, and therefore proves challenging to understand and predict. Here, we combine extensive chemical and sensory analyses of 250 different beers to train machine learning models that allow predicting flavor and consumer appreciation. For each beer, we measure over 200 chemical properties, perform quantitative descriptive sensory analysis with a trained tasting panel and map data from over 180,000 consumer reviews to train 10 different machine learning models. The best-performing algorithm, Gradient Boosting, yields models that significantly outperform predictions based on conventional statistics and accurately predict complex food features and consumer appreciation from chemical profiles. Model dissection allows identifying specific and unexpected compounds as drivers of beer flavor and appreciation. Adding these compounds results in variants of commercial alcoholic and non-alcoholic beers with improved consumer appreciation. Together, our study reveals how big data and machine learning uncover complex links between food chemistry, flavor and consumer perception, and lays the foundation to develop novel, tailored foods with superior flavors.

Electrochemical Evaluation of Cd, Cu, and Fe in Different Brands of Craft Beers from Quito, Ecuador

The presence of heavy metals in craft beers can endanger human health if the total metal content exceeds the exposure limits recommended by sanitary standards; in addition, they can cause damage to the quality of the beer. In this work, the concentration of Cd(II), Cu(II), and Fe(III) was determined in 13 brands of craft beer with the highest consumption in Quito, Ecuador, by differential pulse anodic stripping voltammetry (DPASV), using as boron-doped diamond (BDD) working electrode. The BDD electrode used has favorable morphological and electrochemical properties for the detection of metals such as Cd(II), Cu(II), and Fe(III). A granular morphology with microcrystals with an average size between 300 and 2000 nm could be verified for the BDD electrode using a scanning electron microscope. Double layer capacitance of the BDD electrode was 0.01412 μF cm^-2, a relatively low value; Ip_ox/Ip_red ratios were 0.99 for the potassium ferro-ferricyanide system in BDD, demonstrating that the redox process is quasi-reversible. The figures of merit for Cd(II), Cu(II), and Fe(III) were; DL of 6.31, 1.76, and 1.72 μg L^-1; QL of 21.04, 5.87, and 5.72 μg L^-1, repeatability of 1.06, 2.43, and 1.34%, reproducibility of 1.61, 2.94, and 1.83% and percentage of recovery of 98.18, 91.68, and 91.68%, respectively. It is concluded that the DPASV method on BDD has acceptable precision and accuracy for the quantification of Cd(II), Cu(II), and Fe(III), and it was verified that some beers did not comply with the permissible limits of food standards.

Iron migration from undamaged and dented juice tinplate cans

BACKGROUND

Iron migration from tinplate cans to pineapple drink was studied over time using flame atomic absorption spectroscopy, taking into consideration storage temperature, sell-by date and can condition (dented/undamaged). An organoleptic test, at the sell-by date, was also performed.

RESULT

Analysis of iron in drinks from tinplate cans, glass and polyethylene terephthalate (PET) bottles was performed up until the sell-by date. For undamaged canned drinks stored at room temperature, iron was found to remain constant at 0.23 ± 0.01 mg L(-1) , from the 24th day until 1 year after production. Iron found in glass and PET bottles also remained constant until the sell-by date, at 0.15 ± 0.04 and 0.12 ± 0.04 mg L(-1) , respectively. However, migration of iron from dented cans was found to be significant. Twelve months after production, iron content in dented cans, stored at room temperature (22 °C) and in a refrigerator chamber (4 °C) was 14.4 ± 1.0 and 5.5 ± 0.4 mg L(-1) , respectively.

CONCLUSION

Results showed that for a 35 kg child the intake of three damaged canned drinks may contribute to more than 50% of the iron provisional maximum tolerance daily intake. © 2015 Society of Chemical Industry.

Transcriptome analysis of beer-spoiling Lactobacillus brevis BSO 464 during growth in degassed and gassed beer

Lactobacillus brevis BSO 464 (Lb464) is a beer-spoilage-related (BSR) isolate of interest given its unique physiological attributes; specifically, it is highly hop-tolerant and exhibits very rapid growth in pressurized/gassed beer. RNA sequencing was performed on Lb464 grown in pressurized and non-pressurized beer to determine important genetic mechanisms for growth in these environments. The data generated were compared against data in a previous transcriptional study of another lactic acid bacterium (LAB) during growth in beer, namely, Pediococcus claussenii ATCC BAA-344(T) (Pc344). Results revealed that the most important genetic elements for Lb464 growth in beer are related to biogenic amine metabolism, membrane transport and fortification, nutrient scavenging, and efficient transcriptional regulation. Comparison with the previous transcriptional study of Pc344 indicated that the total coding capacity (plasmid profile and genome size) of a LAB isolate allows for beer-spoilage virulence and adaptation to different beer environments, i.e., the ability to grow in degassed beer (during production) or gassed beer (packaged product). Further, differences in gene expression of Lb464 and Pc344 during mid-exponential growth in beer may dictate how rapidly each isolate exhausts particular carbon sources during. The presence of headspace pressure/dissolved CO2 was found to drive Lb464 transcription during mid-exponential growth in beer towards increasing cell wall and membrane modification, transport, osmoregulation, and DNA metabolism and transposition events. This transcriptional activity resembles transcriptional patterns or signatures observed in a viable, but non-culturable state established by non-related organisms, suggesting that Lb464 overall uses complex cellular regulation to maintain cell division and growth in the stressful beer environment. Additionally, increased expression of several hypothetical proteins, the hop-tolerance gene horC, and DNA repair and recombination genes from plasmids pLb464-2, -4, and -8 were observed in the gassed beer environment. Thus, plasmids can harbor genes with specific (gassed) beer growth advantages, and confirm that plasmid transfer and acquisition as important activities for adaptation to the beer environment.

Prediction of the ageing of commercial lager beer during storage based on the degradation of iso-α-acids

BACKGROUND

Iso-α-acids and their chemically modified variants are responsible for the bitterness of beer and play a disproportionately large role in the final quality of beer. The current study was undertaken to predict the degradation of commercial lager beers related to changes in the concentration of trans-iso-α-acids during storage by using high-pressure liquid chromatography.

RESULTS

In the analysed beers the concentration of isohumulone (average concentration 28 mg L(-1)) was greater than that of isocohumulone (20 mg L(-1)) and isoadhumulone (10 mg L(-1)). The kinetic parameters, activation energy and rate constant, of the trans-iso-α-acids were calculated. In the case of dark beers, the activation energy for the degradation of trans-isocohumulones was found to be higher than for trans-isohumulones and trans-isoadhumulones, whereas in pale and alcohol-free beers activation energies for the degradation of the three trans isomers were similar.

CONCLUSION

The loss of iso-α-acids can be calculated using the activation energy of the degradation of trans-iso-α-acids and the temperature profile of the accelerated ageing. The results obtained in the investigation can be used in the beer industry to predict the alteration of the bitterness of beer during storage.