Measurement and prediction of the susceptibility of lager beer to spoilage by lactic acid bacteria

J.L. FERNANDEZ AND W.J SIMPSON. 1995. The ability of 14 strains of hop-resistant lactic acid bacteria ( Lactobacillus spp., Pediococcus spp.) to grow in 17 different lager beers was assessed using a biological challenge test. All beers were spoiled by at least one strain: all strains could grow in at least one beer. The sensitivity of different beers to spoilage by lactic acid bacteria varied. Spoilage potential could be described in the form of a 'Resistance to Spoilage Value' (RSV) based on the ability of the organisms to grow in each beer. Parameters which correlated to RSV included pH, beer colour and the content of free amino nitrogen, total soluble nitrogen, a range of individual amino acids, maltotriose and the undissociated forms of SO₂ and hop bitter acids. Predictive models based on the technique of partial least squares regression and constructed using values for undissociated SO₂ content, undissociated hop bitter acids content, polyphenol content, maltotriose content, free amino nitrogen content and a colour intensity component allowed RSV to be predicted.