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Previous issue date: 2010-09-10 === Among the main challenges in the beer industrial production is the market supply at the lowest cost and high quality, in order to ensure the expectations of customers and. consumers The beer fermentation stage represents approximately 70% of the whole time necessary to its production, having a obligatoriness of strict process controls to avoid becoming bottleneck in beer production. This stage is responsible for the formation of a series of subproducts, which are responsible for the composition of aroma/bouquet existing in beer and some of these subproducts, if produced in larger quantities, they will confer unpleasant taste and odor to the final product. Among the subproducts formed during the fermentation stage, total vicinal diketones is the main component, since it is limiting for product transfusion to the subsequent steps, besides having a low perception threshold by the consumer and giving undesirable taste and odor. Due to the instability of main raw materials quality and also process controls during fermentation, the development of alternative forms of beer production without impacting on total fermentation time and final product quality is a great challenge to breweries. In this work, a prior acidification of the pasty yeast was carried out, utilizing for that phosphoric acid, food grade, reducing yeast pH of about 5.30 to 2.20 and altering its characteristic from flocculent to pulverulent during beer fermentation. An increase of six times was observed in amount of yeast cells in suspension in the second fermentation stage regarding to fermentations by yeast with no prior acidification. With alteration on two input variables, temperature curve and cell multiplication, which goal was to minimize the maximum values for diketones detected in the fermenter tank, a reduction was obtained from peak of formed diacetyl and consequently contributed to reduction in fermentation time and total process time. Several experiments were performed with those process changes in order to verify the influence on the total fermentation time and total vicinal diketones concentration at the end of fermentation. This experiment reached as the best production result a total fermentation time of 151 hours and total vicinal diketone concentration of 0.08 ppm. The mass of yeast in suspension in the second phase of fermentation increased from 2.45 x 106 to 16.38 x 106 cells/mL of yeast, which fact is key to a greater efficiency in reducing total vicinal diketones existing in the medium, confirming that the prior yeast acidification, as well as the control of temperature and yeast cell multiplication in fermentative process enhances the performance of diketones reduction and consequently reduce the total fermentation time with diketones concentration below the expected value (Max: 0.10 ppm) === Dentre os principais desafios que se apresentam no mercado industrial de produ??o de cerveja nos dias atuais, podemos citar o abastecimento do mercado com o menor custo poss?vel e com qualidade, visando garantir as expectativas dos clientes e consumidores. A etapa de fermenta??o da cerveja representa aproximadamente 70% de todo o tempo necess?rio para sua produ??o, tendo uma obrigatoriedade de rigorosos controles de processo, para n?o se tornar gargalo da produ??o de cerveja. Essa etapa ? respons?vel pela forma??o de uma s?rie de subprodutos, os quais, ao mesmo tempo em que s?o determinantes da composi??o do buqu? de aromas existentes na cerveja, se produzidos em maior quantidade, podem passar para o produto final sabor e odor desagrad?veis. Dentre esses subprodutos, as dicetonas vicinais totais constituem o principal componente, uma vez que, al?m de serem limitantes quanto ? trasfega do produto para as etapas subsequentes, possuem um baixo limiar de percep??o pelo consumidor e passam sabor e odor desagrad?veis. Devido ? instabilidade da qualidade das mat?rias primas principais e dos controles de processo durante a fermenta??o, o desenvolvimento de formas alternativas de produ??o de cerveja com impactos positivos no tempo total de fermenta??o e na qualidade do produto final, ? um grande desafio dentro das cervejarias. Neste trabalho, foi realizada uma acidifica??o pr?via do fermento pastoso, utilizando-se, para isso, ?cido fosf?rico, grau aliment?cio e reduzindo-se o pH do fermento de aproximadamente 5,30 para 2,20. Al?m disso, com intuito de minimizar os valores m?ximos encontrados de dicetonas totais no tanque fermentador, foram alteradas duas vari?veis de entrada: a curva de temperatura e a multiplica??o celular. Obtiveram-se, como melhores resultados, o tempo total de fermenta??o de 151 horas e concentra??o de dicetonas totais de 0,08 ppm. Desta forma, foi confirmado que a acidifica??o pr?via do fermento, bem como o controle de temperatura e multiplica??o celular no processo fermentativo, aumentam a performance do processo atrav?s da redu??o das dicetonas totais e conseq?entemente, a redu??o do tempo total de fermenta??o com concentra??o de dicetonas abaixo do valor esperado (Max: 0,10 ppm)
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