Sanitization of Oak Barrels for Wine-A Review

Wine Barrel Biofilm as a Source of Yeasts with Non-Conventional Properties

This study investigated the main microbial groups characterizing the interior surface of oak barrels from different years (1890, 1895, 1920, 1975, 2008) used in the production of vino cotto. The yeasts were characterized for the following properties: γ-aminobutyric acid (GABA) production, antioxidant activity, air-liquid interfacial biofilm formation, and anthocyanin adsorption capacity. Community-level physiological profile analysis revealed that the microbial communities inside the barrels used the tested carbon sources in different manners. The following yeast species were identified: Millerozyma farinosa, Zygosaccharomyces bisporus, Wickerhamiella versatilis, Zygosaccharomyces bailii, Starmerella lactis-condensi, and Zygosaccharomyces rouxii. All the strains were able to produce GABA, and S. lactis-condensi, Z. bisporus and Z. rouxii were the highest producers (more than 600 mg/L). The Z. rouxii and Z. bailii strains showed the highest antioxidant activity. Only seven strains out of ten M. farinosa formed air-liquid interfacial biofilm. None of the M. farinosa strains adsorbed anthocyanins on their cell wall. The other strains adsorbed anthocyanins in a strain-dependent way, and the highest adsorption was observed for the W. versatilis strains. The yeasts isolated in this study could be used to increase the functional properties and the quality of fermented foods and beverages.

Study on discharge characteristics of fermentor and oak barrel washing wastewater from typical wineries in Ningxia, China

Wine wastewater management is critical to the sustainable development of the wine industry. In this study, three wineries were selected with growing wine production scales of Ningxia. The number of fermentors and oak barrels washing wastewater were counted during the production period of 2019. The water quality was analyzed and finally the pollutant production was estimated. The results showed that fermentor (barrel) cleaning method greatly influences wastewater amount. The five-step method during fermentor washing stage produced more wastewater than direct high-pressure washing. However, high-temperature fumigation in the oak barrels washing stage can effectively reduce wastewater. The residue of grape juice in fermentors and oak barrels made the main pollutant of washing fermentor (barrel) wastewater COD, and the unit product of washing oak barrels' wastewater produced more COD than washing fermentor wastewater. COD production of washing fermentor wastewater per unit product was ranked as Winery C (412.5 g·kL^-1) > Winery B (331.5 g·kL^-1) > Winery A (33.6 g·kL^-1), in oak barrels washing stage, Winery C (679.2 g·kL^-1) > Winery A (507.2 g·kL^-1) > Winery B (350 g·kL^-1). The results showed that a good linear relationship between annual wastewater production and COD production of the winery (R² is 0.9777 and 0.9934, respectively). Compared with the first-level standard of cleaner wine production, the production of fermentors and oak barrels washing wastewater in winery accounts for 11-18% of total wine production wastewater, while COD production accounts for 17-43% of total COD.

Application of natural and synthetic zeolites in the oenological field

Zeolites are crystalline hydrated aluminosilicates, of natural or synthetic origin, characterized by a microporous structure and high adsorption properties. They are employed as soil amendments and fertilizer carriers in agriculture, as catalysts, detergents, adsorbents and molecular sieves in many chemical processes, as well as in water and soil decontamination, and in food processing. They have been also tested in the oenological field for several potential applications; yet an overview on such topic is not still available. The present review summarizes the recent and innovative applications of zeolites in winemaking and supplies a critical discussion about their potential to prevent protein haze, tartrate instability or the appearance of certain defects, like light-struck off-flavour and earthy off-flavours. Further applications of these minerals in the management of winery wastes and in the analytical field are also reviewed. The outcomes of this work evidenced the need of further research on the use of zeolites in oenology for better exploiting their peculiar sorption and exchange properties, selecting the most efficient natural types and improving the performances of the synthetic ones, without disregarding the potential secondary effects of these treatments on wine quality.

Quality differentiation of cocoa beans: implications for geographical indications

Geographical indications may stimulate collective actions of governance for quality control, trade and marketing as well as innovation based on the use of local resources and regional biodiversity. Cocoa production, however, dominated by small family agriculture in tropical regions, has rarely made use of such strategies. This review is aimed at understanding major research interests and emerging technologies helpful for the origin differentiation of cocoa quality. Results from literature search and cited references of publications on cocoa research were imported into VOSviewer for data analysis, which aided in visualizing major research hotpots. Co-occurrence analysis yielded major research clusters which guided the discussion of this review. Observed was a consensus recognizing cocoa quality resulting from the interaction of genotype, fermentation variables and geographical origin. A classic view of cocoa genetics based on the dichotomy of 'fine versus bulk' has been reexamined by a broader perspective of human selection and cocoa genotype evolution. This new approach to cocoa genetic diversity, together with the understanding of complex microbiome interactions through fermentation, as well as quality reproducibility challenged by geographical conditions, have demonstrated the importance of terroir in the production of special attributes. Cocoa growing communities around the tropics have been clearly enabled by new omics and chemometrics to systematize producing conditions and practices in the designation of specifications for the differentiation of origin quality. © 2021 Society of Chemical Industry.

Impact of High-Power Ultrasound for Barrel Regeneration on the Extraction of Wood Volatile and Non-Volatile Compounds

High-power ultrasound (HPU) is an innovative cleaning method used in wineries for oak barrel sanitation and regeneration. The process is associated with hot water (HPUhw) to ensure microbial stabilization and has been proved to be highly effective in recent years. This study thus examines the impact of different cleaning treatments on the subsequent extraction of wood compounds in wine and their impact on organoleptic properties. Red wines aging in barrels treated (HPUhw and steam) in different years (1, 2, and 3 years) were examined during the first 12 months for chemical exchange from wood to wine. Specific analyses were realized on ellagitannins, the physicochemical composition, and oak wood volatile compounds. Only a small increase in some wood volatile compounds occurred in the case of HPUhw, including furfural, 5-methylfurfural, trans-whisky lactone, vanillin, and syringaldehyde. The sensory analysis carried out by a panel of experts showed that the impact on the organoleptic properties of wines is similar with both processes (HPUhw and steam). However, since HPUhw treatment requires lower energy for the same efficiency, it could be an interesting alternative to steam treatment, given the promising prior microbial results.

Wine Aging Technology: Fundamental Role of Wood Barrels

The aging of wines is a process used to preserve wine but also to enhance its properties. It is a process of great interest, mainly because of the additional properties it adds to wines and because of its economic implications. Historically, barrels have been employed for centuries for preserving and aging wine due to their resistance and relative impermeability. In general terms, the wine aging process can be divided into two phases: oxidative and reductive aging. Oxidative aging traditionally takes place in barrels while reductive phase occurs in the bottle. During both processes, oxygen plays a fundamental role as well as other factors, for instance: temperature, light, bottle position, microbial growth or storage time. Likewise, during the aging process, a series of chemical reactions take place influencing the composition and organoleptic profile of wine. At this point, oxidative aging in barrels is a fundamental step. Barrels are directly involved in the produced changes on wine's composition due to the transference of oxygen and phenolic and aromatic compounds from wood to wine. This way, barrels act as an active vessel capable of releasing compounds that affect and improve wine's characteristics. Regarding, the importance of barrels during aging process, some attention must be given to the species most used in cooperage. These species are conventionally oak species, either French or American. However, other non-conventional species are currently being studied as possible wood sources for the production of wines, such as chestnut robinia or other oak species. In the last decades, new approaches have been developed for barrel aging to find new alternatives more suitable, affordable and feasible to sanitize the process, such as other materials different from wood or the use of wood chips, which is regulated since 2006 by the EU. However, even though some of them have shown promising data, barrels are currently the most used technology for the oxidative stage of table wines aging.