Browsing by Author "Faia, Arlete Mendes"
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- Effect of nitrogen supplementation on yeast fermentation performance and mead qualityPublication . Pereira, Ana Paula; Ferreira, Alexandra Mendes; Oliveira, José M.; Estevinho, Leticia M.; Faia, Arlete MendesMead is a traditional drink, containing X-1 X% (v/v) of ethanol, which results from the alcoholic fermentation of diluted honey performed by yeasts. However, when it is produced in a homemade way mead producers find several problems, namely, the lack of uniformity in the final products low or premature fermentations arrest, and the production of "off-flavours" by the yeasts. These problems could be due to several factors, including lack of essential nutrients such as a deficiency in available nitrogen. Additionally , it has been reported that mead fermentation is a time-consuming process, often taking several months to complete. depending on the type of honey, yeast strain anti honey-must composition. Since mead production is a time-consuming process. to make its production viable it is necessary to reduce the fermentation time while producing an end product of quality. Thus. the aim of this study was to evaluate I he effect of nitrogen addition 10 honey-must on two active dry wine yeasts (ADWY) fermentation performance, as well as on the mead composition and volatile aroma compounds production.
- Effects of high cell density fermentations on the optimisation of mead fermentationPublication . Pereira, Ana Paula; Ferreira, Alexandra Mendes; Estevinho, Leticia M.; Faia, Arlete MendesMead is a traditional drink, containing 8-18% (v/v) of ethanol, which results from the alcoholic fermentation of diluted honey performed by yeasts. It has been reported that mead fermentation is a time-consuming process, often taking several months to complete, depending on the type of honey, yeast strain and honey-must’s composition. An important objective of mead makers is to reduce the fermentation time without decreasing the quality of the end product. It has been shown that significant time can be saved in the fermentation process by increasing the pitching rate, i.e., the amount of suspended yeast cells added to a batch fermenter. Therefore, the aim of this study was to determine the adequate inoculum size of two commercial winemaking strains of Saccharomyces cerevisiae (Lalvin QA23 and Lalvin ICV D47) for the optimisation of mead fermentation. Honey must was prepared according to the recipe developed by our team, supplemented with potassium tartrate, pH adjusted to 3.7 with malic acid and the nitrogen concentration adjusted to 267 mg/L with diammonium phosphate. The appropriate amounts of inoculum were pitched into the honey-must to obtain five different pitching rates. Several parameters were determined during the fermentation to evaluate the effect of the inoculum size on yeast growth, fermentation profile and mead composition. Minor differences between the two strains in respect to growth kinetics were detected. As expected the increasing of the inoculum size resulted in significant increases in cell biomass and CFUs’ numbers but also decreased the yeast net growth. The time required to reach the same stage of fermentation ranged from 24 to 96 hours depending on the inoculum size. In accordance to the results obtained the strain ICV D47 appears to be more suitable for the production of high quality meads, although the strain QA23 provided better fermentation profile. However, sugars were not fully consumed and about 25 mg/L of assimilable nitrogen remained at the end of all fermentations. This is the first study of the effect of inoculum size on the optimisation of mead fermentation, however further research is needed to improve its quality.
- Mead and Other Fermented BeveragesPublication . Pereira, Ana Paula; Oliveira, José M.; Ferreira, Alexandra Mendes; Estevinho, Leticia M.; Faia, Arlete MendesThis chapter introduces the production of mead, a traditional alcoholic fermented beverage. It starts with an introduction to mead that includes historical aspects of production and a description of some styles and derivative products. Then, the raw material in mead production, the honey, is characterized in terms of its physicochemical composition and microbiota. Next, we focus on some aspects of mead production, such as the steps involved, the problems associated with the fermentation (the yeast inoculation and the nutrient supplementation of must), and the application of immobilized yeasts to the production. At the end is presented a detailed description of honey and fermentation-derived volatiles, the main contributors to mead aroma. Finally, we present an approach to the sensory evaluation of mead, an indispensable method to assess the beverage quality.
- Optimização da produção de hidromel utilizando diferentes sistemas de imobilização de célulasPublication . Estevinho, Leticia M.; Pereira, Ana Paula; Faia, Arlete MendesO hidromel é uma bebida tradicional, com 8 a 18% (v/v) em etanol, obtida da fermentação alcoólica de mel diluído em água na presença de leveduras. A produção de mel é uma atividade económica importante em várias regiões de Portugal devendo o desenvolvimento de novos produtos à base de mel, como o hidromel, ser incentivado. Contudo, a produção de hidromel é demorada dependendo do tipo de mel, da estirpe de levedura e da composição do mosto. Assim, um dos principais objetivos dos produtores de hidromel é reduzir o tempo de fermentação, sem diminuir a qualidade do produto final. Numa perspetiva de valorização do mel a partir da produção de hidromel o objectivo principal deste trabalho foi desenvolver e optimizar o processo de produção desta bebida. Para tal, utilizou-‐se mel escuro e duas estirpes comerciais de levedura Saccharomyces cerevisiae, usadas em enologia. Para optimizar a produção de hidromel inicialmente selecionamos a melhor formulação de mosto-‐mel, em que foram efectuadas experiências com a adição de sais, vitaminas e vitaminas e sais à formulação base. De seguida, a formulação com melhores resultados foi utilizada para selecionar a melhor concentração de inóculo para a produção de hidromel. Das cinco concentrações testadas, foi escolhida uma concentração celular para comparar o desempenho fermentativo das leveduras sob a forma de células livres e imobilizadas (em camada simples e camada dupla), em sistema descontínuo. As fermentações foram monitorizadas diariamente para estudar o efeito dos parâmetros testados no crescimento das leveduras e no perfil fermentativo. No final das fermentações a qualidade do hidromel produzido foi avaliada por parâmetros enológicos e os compostos voláteis produzidos foram identificados e quantificados por GC. Com este trabalho foi possível obter resultados que permitem a optimização da produção de hidromel. No entanto, uma avaliação sensorial complementar da bebida forneceria informações úteis para os produtores.