Study On Alcohol-Free Beer Fermentation With Special Yeasts

With greater interest in considering the warnings about alcohol abuse and health,consumer preference for “alcohol-free” beer and wine is increasing, especially alcohol-freebeer. In our country, the ethanol content of alcohol-free beer is restricted in0.5%(v/v) and aspecific gravity is and higher than3.0°P. If the wort gravity is adjusted to3.0°P, and aSaccharomyces cerevisiae strain is used to alcoholic fermenting, it will produce about1.2%(v/v) alcohol with a real attenuation65%, therefore non-alcoholic beer can’t be got with theyeast Saccharomyces cerevisiae and normal fermentation technology.There are two methods to produce alcohol-free beer, one is based on gentle removal ofalcohol from regular beer, it can be achieved by reverse osmosis, dialysis and evaporation,however considerable investments are required into the special equipments for alcoholremoval. The other method is biological approaches that are based on limited ethanolformation during wort fermentation. In this experiment, special yeasts were used infermentation to devising a new approach that producing alcohol-free beer. The main researchresults were as follows:1Saccharomycodes ludwigii was chose to ferment wort, and it was safe for peoplehealth.2Saccharomycodes ludwigii growed8h beginning logarithmic growth when28℃cultivated, its coacervation was feebleness, fermentation rate was best at12℃and ultimatefermentation degree was13.8%using10°P wort.3For approaching industrial production scale,2000mL graduated flask and400L kettlefermentation were carried out, the results showed fermentation capability of largerfermentation scale consisted with triangular flask.4Diluting the original gravity to5°P using the water that pH was the same as originalfermented worts, comparing with marketable alcohol-free beer, some differences in werefound physical and chemical indexes, flavor substances and residual sugar, especially a massof maltose were residual in fermented worts, pH was higher, esters were lower and withoutacetate isobutyl, higher alcohols were similar, therefore beers taste were different.Saccharomycodes ludwigii fermentation beer had chrysanthemum aroma, gentler and weaker,but it had sweet taste and worty flavor when original gravity was higher.5Many methods were adopted to wipe off sweet: reducing original gravity to5°P andusing L3strain which real attenuation was15%through EMS mutagenesis.63-methylthiopropionaldehyde was proposed to contribute to the worty off-flavor, distinction threshold in beer was5.0μg/L and established GC/MS quantification method, thendifferent beers were analyzed with this method, the result was that the content of3-methylthiopropionaldehyde was below50μg/L, therefore, its control standard was not morethan55μg/L.7The best fermentation technology was got that using L3strain,5°P and pH4.7wort,and3%inoculation,24h activation wort dealing，then the laboratorial experiments and100Lkettle fermentation were carried out by the certain fermentation technology, the resultsshowed that3-methylthiopropionaldehyde in fermented beer could be controlled belowstandard（55μg/L）, and pH was about4.2, what’s more, physical and chemical indexes, flavorsubstances were normal, and taste was gentle, weak, especially sweet and worty flavordisappeared.