Environmental Stress and Aroma Production During Wine Fermentation

The sensory description of wine uses the widest range of descriptive terminology of all food products, reflecting the complex nature of a product whose character depends on the balance of hundreds of individual flavour-active compounds. There are many tools that can influence flavour profiles or wine styles, one of which is the choice of a specific yeast strain. Yeasts contribute to wine flavour by producing volatile metabolites with different flavour profiles. The impact of changing environmental conditions on the production of flavour compounds by yeast strains remains largely unexplored. This is the first study investigating the impact of two mild fermentation stresses, hyperosmotic and temperature stress, on aroma production in synthetic must by commercial Saccharomyces cerevisiae wine strains. Hyperosmotic stress was imposed by cultivation of the yeast for 21 days in the must containing either 0.3 or 0.5 M sorbitol. The transient temperature stresses were applied for 16 h at 8° or 37°C for either two or eight days after commencement of the fermentation. Greater glycerol and acetic acid levels were produced by most yeasts when only hyperosmotic stress was applied. Hyperosmotic and temperature stress conditions produced a limited number of significant changes to the profile of the esters, higher alcohols and volatile fatty acids. These changes differed significantly for each strain and stress treatment, suggesting that the fermentation conditions can significantly alter the aromatic profile of a wine, although these stress impacts cannot be predicted in general. The changes to the aromatic profile are specific to each individual wine yeast strain

Mineral nutrition of peas (Pisum sativum L.3, varieties asgrow 40 and okaw

Deficiencies of the macronutrients and boron. The presente work was carried out in order to study: a - The effect of the omission and presence of the macronutrients and boron on the growth of the plants - variety Asgrow 40; b - deficiency symptoms of macronutrients and boron in the same variety; c - the effects of the deficiencies of each macronutrient and boron on the dry matter production and on the chemical composition of the plant-variety Asgrow 40. I - Deficiencies of the macronutrients Young peas plants (Pisum sativum, L.), variety Asgrow 40 were grown in pots containing pure quartz. Several times a day they were irrigated by percolation with nutrient solution. The treatments were: complete solution and deficient solution, in which each one of the macronutrient was omitted as well boron. Soon as the malnutrition symptoms apperared, the plants were harvested and divided into: roots, stalks, inferior and superior leaves, flowers, husk containing the seeds. The dry matter was analysed chemically. Conclusions: 1 - Symptoms of malnutrition were observed for N, P, K, Ca and B; 2 - The omission of the macronutrients and boron affected the dry matter production, excepted for magnesium and or sulphur; 3 - The nutrient content in the dry matter, expressed in porcentages (%) and or parts per million (ppm) in deficient leaves and healthy leaves were:O presente trabalho teve o objetivo de estudar alguns aspectos da nutrição da ervilha (Pisum sativum, L.), variedade Okaw ("Torta-de-Flor-Roxa") e Asgrow 40 no que concerne: 1 - Efeitos das omissões dos macronutrientes e do boro, na obtenção de um quadro sintomatológico das carências, na variedade Asgrow 40. 2 - Efeitos das carências dos macronutrientes e do boro na produção de matéria seca e composição química na variedade Asgrow 40. Sementes de ervilha (Pisum sativum, L.) da variedade Asgrow 40, foram postas a germinar em silica, mantendo-se um teor de umidade adequado. Passou-se a regar as plântulas com soluções nutritivas com omissões dos nutrientes, entre 20 e 25 dias após a germinação. Tão logo se delineou o quadro sintomatológico das carências, as plantas foram coletadas, mensuradas em altura (cm) e peso da matéria seca (g). Divididas em raízes, caules, folhas inferiores e superiores, flores, vagens e analisadas. Os dados mostram que: 1 - As omissões dos macronutrientes com excessão do magnésio e do enxofre, apresentaram sintomas visuais de deficiência características. 2 - A produção da matéria seca foi afetada em todos os tratamentos com omissão de nutrientes, com excessão daqueles nos quais foram omitidos o magnésio e/ou enxofre. 3 - Os teores dos nutrientes expressos em porcentagem e/ou partes por milhão em folhas apresentando ou não sintomas de carências foram