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Publication
Lager beer stability during storage at room temperature
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Advisor(s)
Abstract(s)
O trabalho apresentado nesta dissertação pretendeu avaliar a estabilidade de uma cerveja do tipo
lager quando armazenada à temperatura ambiente, através da aplicação de diferentes estratégias.
Este estudo foi desenvolvido em cinco vertentes que englobaram a análise sensorial, o estudo dos
parâmetros de qualidade típicos utilizados pela indústria cervejeira, o estudo da cor, a evolução do 5
hidroximetilfurfural (HMF) e a determinação do perfil volátil da cerveja.
Primeiramente, foram separadas as garrafas de cervejas representativas de um lote de produção
colocando uma parte do lote a 4 °C e outra parte à temperatura ambiente (condições normais de
armazenagem). As amostras foram analisadas durante 1 ano em condições normais de envelhecimento e
para alguns parâmetros, tais como cor e HMF, foi também realizado o envelhecimento forçado de modo a
avaliar o seu efeito.
Os dados sensoriais mostram que há um momento de viragem, no qual os provadores profissionais
conseguem detetar características de envelhecimento ainda que não percetíveis ao consumidor corrente.
Relativamente aos parâmeros do controlo de qualidade da cerveja, os resultados mostram que apenas os
parâmetros cor, turvação e o teor de dicetonas vicinais (VDK) sofrem alterações significativas durante este
período. Através da aplicação dos métodos EBC e CIELab, para a determinação da cor da cerveja, observou
se uma evolução crescente dos parâmetros de cor à medida que a cerveja envelhece. Segundo a técnica
HPLC-DAD demonstrou-se que o HMF apresenta uma tendência linear crescente ao longo do tempo,
confirmando-se a sua forte relação com o processo de envelhecimento. Finalmente, os dados obtidos por
SPME-CG-MS mostram que a fração volátil sofre alterações devido ao processo de envelhecimento,
principalmente a partir do sétimo mês.
De um modo geral a cerveja evidenciou uma evolução química que não foi detetada pelos
consumidores ao fim dos 12 messes em que este estudo foi desenvolvido.
The work reported in this thesis evaluates the stability of a lager beer when stored at room temperature, through the application of different strategies. This study was conducted in five areas that included the sensory analysis, the study of typical quality parameters used by the brewing industry, the study of colour, development of 5-hydroxymethylfurfural (HMF) and the determination of the volatile profile of the beer. Firstly, bottles of beers representing a production batch were separated, by placing a part of the batch at 4 ° C and another part at room temperature (under normal storage conditions). The samples were analysed for 1 year of normal ageing. For some parameters, such as colour and HMF, forced ageing was also performed in order to evaluate its effect. Sensory data show that there is a turning point in which the professional tasters are able to detect some ageing characteristics, even if not perceptible by the regular consumers. For the beers quality parameters, the results show that only the colour, turbidity and the content of vicinal diketones (VDK) undergo significant changes during this period. Through the application of CIELab and EBC methods for determining the colour of beer, there was a growing evolution of the colour parameters with the storage time. According to HPLC-DAD technique it was demonstrated that the HMF concentration has a linear tendency to increase over time, confirming its strong relationship with the ageing process. Finally, the data obtained by SPME-GC-MS showed that the volatile fraction undergoes changes due to the ageing process, especially from the seventh month on. Generally, beer has showed a chemical evolution that was not detected by regulars consumers in the twelve months that this study was carried out.
The work reported in this thesis evaluates the stability of a lager beer when stored at room temperature, through the application of different strategies. This study was conducted in five areas that included the sensory analysis, the study of typical quality parameters used by the brewing industry, the study of colour, development of 5-hydroxymethylfurfural (HMF) and the determination of the volatile profile of the beer. Firstly, bottles of beers representing a production batch were separated, by placing a part of the batch at 4 ° C and another part at room temperature (under normal storage conditions). The samples were analysed for 1 year of normal ageing. For some parameters, such as colour and HMF, forced ageing was also performed in order to evaluate its effect. Sensory data show that there is a turning point in which the professional tasters are able to detect some ageing characteristics, even if not perceptible by the regular consumers. For the beers quality parameters, the results show that only the colour, turbidity and the content of vicinal diketones (VDK) undergo significant changes during this period. Through the application of CIELab and EBC methods for determining the colour of beer, there was a growing evolution of the colour parameters with the storage time. According to HPLC-DAD technique it was demonstrated that the HMF concentration has a linear tendency to increase over time, confirming its strong relationship with the ageing process. Finally, the data obtained by SPME-GC-MS showed that the volatile fraction undergoes changes due to the ageing process, especially from the seventh month on. Generally, beer has showed a chemical evolution that was not detected by regulars consumers in the twelve months that this study was carried out.
Description
Keywords
Cerveja Envelhecimento Análise sensorial Cor HMF Voláteis Beer Ageing Sensory analysis Colour Volatile Applied Biochemistry . Faculdade de Ciências Exatas e da Engenharia