Variability in the fermentation rate and colour of young lager beer as influenced by insecticide and herbicide residues

The influence of five pesticides, pendimethalin, trifluralin (dinitroaniline herbicides) fenitrothion, malathion, and methidathion (organophosphorus insecticides), on the fermentation of young lager beer was assessed. For this purpose, brewer wort was spiked with the pesticides to obtain a concentration of 1 μg/ml before the pitching with lager yeast (Saccharomyces carlsbergensis). The fermentation kinetic was sluggish for the samples treated with fenitrothion, malathion, and trifluralin but increased from the second to the sixth day in the methidathion and pendimethalin treatments in comparison with the blank sample. At the end of fermentation (12 days) statistically significant differences (p < 0.05) were found for the extract and attenuation values for the samples treated with fenitrothion and trifluralin. In these cases too, a higher amount of residual sugars (glucose, fructose, maltose and maltotriose) was found in the beer. Significant differences (p < 0.05) were also observed for pH and colour of the beer after fermentation among all treated samples. A good quadratic correlation (R > 0.94) was found for these parameters in all cases. The total polyphenol content was significantly lower in the fenitrothion and trifluralin treatments.