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Métodos de Controlo de Qualidade na Produção de Cerveja Artesanal
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A cerveja é uma bebida mundialmente conhecida e que faz parte dos hábitos alimenta-res de muitas sociedades. Recentemente, o crescimento na procura de produtos de qualidade e diferenciadores levou ao crescimento dos negócios de cerveja artesanal, como é o caso da cervejeira lisboeta 8ª Colina.
Este trabalho pretendeu consolidar alguns parâmetros físico-químicos, tanto durante a fermentação como durante a maturação, de duas das cervejas da 8ª Colina que têm vindo a apresentar grandes variações entre lotes. Assim, foram analisados durante a fermentação a evolução da densidade aparente, da atenuação e teor alcoólico, a evolução da temperatura e a evolução do pH. Durante a maturação, foram analisados os parâmetros de carbonatação, temperatura e pressão. Adicionalmente, foi testado um método de controlo microbiológico para deteção da presença de microrganismos contaminantes nestas cervejas, baseado na ino-culação de placas de meio de cultura de mosto cervejeiro.
Foram construídos intervalos de valores aceitáveis para os parâmetros densidade final, atenuação e teor alcoólico por forma a servirem de elemento de validação para futuras pro-duções destas cervejas. Foram também encontradas diferenças na evolução da densidade apa-rente e do pH entre os lotes fermentados por levedura reutilizada e lotes produzidos com levedura nova, recomendando-se por isso a adoção de práticas que permitam averiguar o es-tado da levedura reutilizada antes da sua inoculação.
Verificou-se que a evolução da carbonatação ao longo dos dias de maturação foi forte-mente influenciada pelas variações da temperatura durante esta fase, que foram mais eleva-das que o esperado, devendo por isso ser feita uma revisão do sistema de controlo da tempe-ratura dos fermentadores e também do procedimento de correção da carbonatação.
Por fim, verificou-se que o método de controlo microbiológico não foi o mais adequado para o objetivo proposto uma vez que a maioria dos ensaios foram inválidos e não ter sido possível identificar colónias diferenciadas das colónias da levedura cervejeira. Desta forma, recomenda-se a melhoria dos procedimentos de recolha de amostras e de inoculação das pla-cas, bem como a testagem de meios de cultura seletivos para microrganismos contaminantes comuns da cerveja como é o caso das bactérias do género Lactobacillus e Pediococcus, e das leveduras selvagens.
Beer is a world-renowned drink that is part of the eating habits of many societies. Re-cently, the growth in demand for quality and differentiated products has led to the rise of the craft beer business, as is the case of the Lisbon brewery 8ª Colina. This work aimed to consolidate some physical-chemical parameters, both during fer-mentation and during maturation, of two of the beers from 8ª Colina that have been showing great variations between batches. The evolution of apparent density, attenuation and alcohol content, temperature and pH were analyzed during fermentation. During maturation, the pa-rameters of carbonation, temperature and pressure were analyzed. Additionally, a microbio-logical control method was tested to detect the presence of contaminating microorganisms in these beers, based on the inoculation of plates of culture medium composed of brewer's wort. Ranges of acceptable values were made for the parameters final density, attenuation and alcohol content in order to serve as a validation element for future productions of these beers. Differences were also found in the evolution of apparent density and pH between batches fermented with reused yeast and batches produced with new yeast, therefore recom-mending the adoption of practices that allow checking the status of reused yeast before inoc-ulation. The evolution of the carbonation along the days of maturation was strongly influenced by temperature variations during this phase, which were higher than expected, and therefore a review of the temperature control system of the fermenters and the carbonation correction procedure is advised. Finally, it was shown that the microbiological control method was not the most suitable for the proposed objective, since most of the tests were not valid nor was possible to identify colonies differentiated from brewer's yeast. Therefore, it is recommended to improve the pro-cedures for the collection of the samples and for plate inoculation, as well as testing selective culture media for common contaminating micro-organisms in beer, such as bacteria of the genus Lactobacillus and Pediococcus, and wild yeasts.
Beer is a world-renowned drink that is part of the eating habits of many societies. Re-cently, the growth in demand for quality and differentiated products has led to the rise of the craft beer business, as is the case of the Lisbon brewery 8ª Colina. This work aimed to consolidate some physical-chemical parameters, both during fer-mentation and during maturation, of two of the beers from 8ª Colina that have been showing great variations between batches. The evolution of apparent density, attenuation and alcohol content, temperature and pH were analyzed during fermentation. During maturation, the pa-rameters of carbonation, temperature and pressure were analyzed. Additionally, a microbio-logical control method was tested to detect the presence of contaminating microorganisms in these beers, based on the inoculation of plates of culture medium composed of brewer's wort. Ranges of acceptable values were made for the parameters final density, attenuation and alcohol content in order to serve as a validation element for future productions of these beers. Differences were also found in the evolution of apparent density and pH between batches fermented with reused yeast and batches produced with new yeast, therefore recom-mending the adoption of practices that allow checking the status of reused yeast before inoc-ulation. The evolution of the carbonation along the days of maturation was strongly influenced by temperature variations during this phase, which were higher than expected, and therefore a review of the temperature control system of the fermenters and the carbonation correction procedure is advised. Finally, it was shown that the microbiological control method was not the most suitable for the proposed objective, since most of the tests were not valid nor was possible to identify colonies differentiated from brewer's yeast. Therefore, it is recommended to improve the pro-cedures for the collection of the samples and for plate inoculation, as well as testing selective culture media for common contaminating micro-organisms in beer, such as bacteria of the genus Lactobacillus and Pediococcus, and wild yeasts.
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Palavras-chave
8ª Colina densidade aparente carbonatação temperatura levedura