b'ON THE EDGEBrewing Beer that Tastes Fresh LongerUnlike wine, which generally improves with time, beer does not age well. Usually, within a year of bottling, the beverage starts to develop an unpleasant papery or cardboard-like flavour that drinkers describe as stale. Now, researchers reporting in ACS Publications Journal of Agricultural and Food Chemistry have engineered lager yeast to make more molecules that protect beer against staling, resulting in improved flavour stability.Scientists have linked stale beer flavours to aldehyde compounds, such as (E)-2-nonenal and acetaldehyde. Many of these compounds are produced by yeast during fermentation, First Lab in a Field Experiment Reveals a Sunnierand chemical reactions Side of Climate Change during beer storage can Pioneering experiments using heated field plots to test theincrease their levels. responses of crops to temperature have revealed an unexpectedBrewers have tried plus side of climate change for farmers. The field trialdifferent approaches experimentthe first of its kindwas set up to investigateto reduce levels of the link between warmer Octobers in the United Kingdom andthese compounds, higher yields of oilseed rape. such as controlling the The crop, planted in autumn and harvested early thefermentation conditions following summer, is particularly sensitive to temperature ator adding antioxidants, but certain times of the year, with annual yields varying by up tostaling remains a problem 30 per cent as a result. It is known that warmer temperatures infor the beer industry. Thats October are correlated with higher oilseed rape yields, but thewhy Qi Li and colleagues reason for this trend was unclear. wanted to genetically modify The results of this study by the John Innes Centre reveal thatlager yeast to produce the temperature in October is surprisingly important for themore of a molecule called timing of flowering, and warmer Octobers result in a delay toNADH. Extra NADH could flowering the following spring. boost the activities of natural Temperature is critical for oilseed rape lifecycle because ityeast enzymes that change determines at what point the plant goes through the transitionaldehydes into other types from vegetative state to flowering, with delays in floweringof compounds that dont being associated with higher yields. contribute to a stale flavour, This process, called vernalization, is well understood inthe researchers reasoned.the lab as a requirement of a prolonged exposure to coldThe researchers used temperature. However, an increasing body of research suggestsa genetic technique called vernalization might work differently under more variableoverexpression, in which they artificially increased the levels conditions experienced by a plant in the field. of various genes related to NADH production. With this method, In this study, the team used soil surface warming cables tothey identified four genes that, when overexpressed, increased raise the temperature of field plots by between four and eightNADH levels. The team found that beer from the overexpressing degrees Celsius, simulating warmer October temperatures. Twoyeast contained 26.3 to 47.3 per cent less acetaldehyde than varieties of oilseed rape with differing vernalization requirementscontrol beer, as well as decreased levels of other aldehydes. were trialled. Lab tests on dissected plants showed that warmingIn addition, the modified strains produced more sulfur in October conditions delayed floral transition by between threedioxide, a natural antioxidant that also helps reduce staling. and four weeks for both varieties. Genetic tests showed genesOther flavour components were marginally changed. This associated with vernalization in cold conditions were also highlyapproach could be useful for improving the flavour stability expressed in the warm conditions. and prolonging the shelf life of beer, the researchers say. The study shows that vernalization in oilseed rape takesSource: American Chemical Societyplace predominantly in October, during which time the mean temperature is between 10 to 12 C. The technology used in the study has been used before in natural grasslands to simulate winter warming, but the trials conducted by the John Innes Centre research team are the first time its been used on a crop in the field. Source: John Innes Centre128seed.ab.ca'