Alcoholic Fermentation

RESUMO: A conservação da cana-de-açúcar na forma de silagem vem se destacando nos últimos anos em razão dos benefícios na operacionalidade. No entanto, quando ensilada sem aditivos a cana apresenta fermentação alcoólica com perda no valor nutritivo, resultante da atividade de leveduras. Considerando a hipótese que o uso da cal na ensilagem da cana pode inibir o desenvol- vimento das

This article examines the ways in which amateur home winemakers interact online, on specialist internet forums and social media platforms. It explores peoples’ motivations for making wine as a serious leisure pursuit, using concepts of techne, technoscience and tradition to analyse the different ways in which knowledge is generated and transferred in this field. Online winemaking communities develop their own internalised cultures, providing a realm within which certain types of knowledge are generated and shared.

Malolactic fermentation (MLF) is a secondary wine fermentation conducted by lactic acid bacteria (LAB). This fermentation is important in winemaking as it deacidifies the wine, it contributes to microbial stability and lastly it contributes to wine aroma through the production of metabolites. Oenococcus oeni is the main species used in commercially available starter culture currently, but research has indicated that different Lactobacillus species also partake in MLF and this has shifted the focus in the MLF field to evaluate the potential of lactobacilli as starter cultures for the future. There are 17 different species of Lactobacillus associated with winemaking either being associated with the grapes/beginning of alcoholic fermentation or the MLF and wine. Lactobacillus associated with wine is mainly facultative or obligatory heterofermentative and can withstand the harsh wine conditions such as high ethanol levels, low pH and temperatures and sulphur dioxide. Wine lactobacilli contain the malolactic enzyme encoding gene, but sequence homology shows that it clusters separate from O. oeni. Lactobacillus also possesses more enzyme encoding genes compared to O. oeni, important for the production of wine aroma compounds such as glycosidase, protease, esterase, phenolic acid decarboxylase and citrate lyase. Another characteristic associated with wine lactobacilli is the production of bacteriocins, especially plantaricins which would enable them to combat spoilage LAB. All these characteristics, together with their ability to conduct MLF just as efficiently as O. oeni, make them suitable for a new generation of MLF starter cultures.

Mead (honey-wine) results from the alcoholic fermentation of diluted honey using a wine yeast strain. However, mead elaboration can be hampered by several problems, including delayed or arrested fermentation, production of an unpleasant aroma, poor quality and inconsistency of the final product. These difficulties are due to honey’s low nutrient content, its natural antifungal components, and the inability of the yeast strain to adapt to these unfavourable growth conditions. In this study, we evaluated the results of adding pollen at concentrations ranging from 10 to 50 g/l as a fermentation activator to improve the fermentation kinetic and the quality of meads. The effect of pollen addition on the honey must, fermentation kinetics, physicochemical characteristics, aroma profiles and sensorial aspects of the obtained meads were evaluated. The results showed that pollen addition improved fermentation rates, alcohol yields, and the final characteristics of meads. An increase in the volatile contents of the meads and an improved sensory profile was observed with pollen addition; however, this improvement was not correlated with the concentration of pollen. The adequate dose of pollen was determined by the final characteristics and sensory profile of the meads.► Pollen could be a good and appropriate activator of alcoholic fermentation in the production of mead. ► Pollen addition improved fermentation rates, alcohol yields and the final characteristics of meads. ► An increase in the volatile contents of the meads and an improved sensory profile was observed with pollen addition; however, this improvement was not correlated with the concentration of pollen. ► The adequate dose of pollen was determined by the final characteristics and sensory profile of the meads. ► The addition of 30 g/hl of pollen is the dose most appropriate because, besides giving mead better accepted, would mean less use of pollen at industrial level.

The population dynamics of mixed-culture and sequential-cultures in fruit-must fermentation is a very interesting problem from both the theoretical and technological stand point. By mixed-culture we refer to those fermentations in which more that one strain/species are present from the beginning of the process; and by sequential to those in which different microorganisms are added along the process. These kinds of fermentations play a key role in industry of fermented beverages. The mathematical models of such processes should represent the dynamics of multiple species growing in a mixture of substrates as the fruit must composition includes an important proportion of hexoses and pentoses. Since the flavor is a basic aspect of beverages, and in general of all fermented foods, it is fundamental to study the population dynamics and its impact in the organoleptic properties, through the influence in the volatile compound profile. The goal of this paper is to present a panorama of the investigations of these fermentative ecosystems from a biological, mathematical, and technological stand point.