The Impact Of Different Hop Compounds On The Growth Of Selected Beer Spoilage Bacteria In Beer

Beer spoiling lactic acid bacteria are a major reason for quality complaints in breweries around the world. Spoilage by a variety of these bacteria can result in haze, sediment, slime, off-flavours and acidity. As these bacteria occur frequently in the brewing environment, using certain hop products that inhibit the growth of these spoilers could be a solution to prevent problems. To investigate the impact of seven different hop compounds (alpha-acids,iso-alpha-acids, tetrahydro-iso-alpha-acids, rho-iso-alpha-acids, xanthohumol,iso-xanthohumol and humulinones) on the growth of six major beer spoilage bacteria (Lactobacillus brevis. L. backi, L. coryniformis, L. lindneri, L. buchneri, Pediococcus damnosous), two concentrations (10 and 25 mg/L) of each hop substance were added to unhopped beer. The potential growth of the spoilage bacteria was investigated over 56 consecutive days. A comparison of the results shows a strong inhibition of growth of all spoilage bacteria at 25 mg/L of tetrahydro-iso-alpha-acids closely followed by alpha-acids as the second most inhibitory substance. The results showed a high resistance ofL. brevisto all hop compounds as well as an inhibition ofL. coryniformisandL. buchneriat low concentrations of most hop components. In comparison with the control sample,L. lindnerishowed increased growth in the presence of some hop compounds (rho-iso-alpha-acids, xanthohumol,iso-xanthohumol, humulinones). (c) 2020 The Authors. Journal of the Institute of Brewing published by John Wiley & Sons Ltd on behalf of The Institute of Brewing & Distilling