Studies On Biological Acidification Of Wort In Brewing Process

The technology of biological acidification means that the first unhopped wort after mashing filtration is the culture medium and it is pitched with Lactobacillus which is is not spoilage bacterium. In the normal mashing process, the wort pH value is adjusted by the acidic wort that is added in the mashing or wort boiling or both, without adding other acids to meet the need of beer production. In this paper, the fermentation conditions of the strains for biological acidification were optimized, the technology of fermentation conditions were improved and compared, and the beer was brewed with biological acidic wort in the lab scale.Strain TL-5 was used in the trial. Its optimal growth temperature was between 30℃to 50℃and the initial pH suitable for growth and acid production was 6.0. The fermentation conditions were optimized as follows: lactic acid production velocity of L. fermentum was fastest when the fermentation temperature was 46℃, wort extraction concentration was 10%(w/w), ratio of carbon to nitrogen was 48, invironmental pressure was 0.05 MPa without agitation. The lactic acid content was influenced greatly by pitching time, and the limit of lactic acid production by this strain was 1.3%. Lactic acid production with different division proportion was studied. It was found that the initial concentration of lactic acid was achieved after 6 hours with 50 % division proportion and after 2.5 hours with 10 % division proportion. Improvement the fermentation technology, compared batch, seim-continued and continued fermentation. The wort was mashed with diluted phosphorus acid and lactic acid by Strain TL-5 respectively and the beer was fermented. After analysis of wort and beer, it was found that the color of wort with biological acid was lower, amino acid constitution was better, and the amino acid content and beer fermentation degree was higher. The beer was smooth and nice bitterness after tasting.