Alternative Woods in Enology: Characterization of Tannin and Low Molecular Weight Phenol Compounds with Respect to Traditional Oak Woods. A Review

Abstract

Wood is one of the most highly valued materials in enology since the chemical composition and sensorial properties of wine change significantly when in contact with it. The need for wood in cooperage and the concern of enologists in their search for new materials to endow their wines with a special personality has generated interest in the use of other Quercus genus materials different from the traditional ones (Q. petraea, Q. robur and Q. alba) and even other wood genera. Thereby, species from same genera such as Q. pyrenaica Willd., Q. faginea Lam., Q. humboldtti Bonpl., Q. oocarpa Liebm., Q. stellata Wangenh, Q. frainetto Ten., Q. lyrata Walt., Q. bicolor Willd. and other genera such as Castanea sativa Mill. (chestnut), Robinia pseudoacacia L. (false acacia), Prunus avium L. and P. cereaus L. (cherry), Fraxinus excelsior L. (European ash) and F. americana L. (American ash) have been studied with the aim of discovering whether they could be a new reservoir of wood for cooperage. This review aims to summarize the characterization of tannin and low molecular weight phenol compositions of these alternative woods for enology in their different cooperage stages and compare them to traditional oak woods, as both are essential to proposing their use in cooperage for aging wine.

Behaviour of Low Molecular Weight Compounds, Iron and Copper of Wine Spirit Aged with Chestnut Staves under Different Levels of Micro-Oxygenation

“…Phenolic acids are non-flavonoid compounds found in the aged WS as a result of the wood contact. The toasted wood (oak and chestnut) commonly used in enology comprises hydroxybenzoic acids (C 6 -C 1 ), such as gallic acid and syringic acid, as well as ellagic acid, a dilactone that has origin on the hydrolytic release of 6,6’-dicarbonyl-2,2′,3,3′,4,4′-hexahydroxybiphenyl units (HHDP) from ellagitannins [ 42 ]. They exist in the wood in the free form or conjugated, and also derive from the thermal degradation of gallotannins, lignin and ellagitannins, respectively, during the heat treatment in cooperage [ 43 ].…”

“…Phenolic aldehydes are non-flavonoid compounds usually classified into two groups: (i) the benzoic aldehydes (C 6 -C 1 ), which can be monomethoxylated (guaiacyl-type; vanillin) or dimethoxylated (syringyl-type; syringaldehyde); (ii) the cinnamic aldehydes (C 6 -C 3 ) , monomethoxylated (guaiacyl-type; coniferaldehyde) and dimethoxylated (syringyl-type; sinapaldehyde). These compounds are found in the toasted wood [ 33 ], from the wood itself [ 42 ], in which they exist either in the free form or linked to the cell wall constituents, and may also arise from lignin breakdown during the heat treatment in cooperage [ 56 ], being released into the WS during ageing.…”

Chemistry and Technology of Wine Aging with Oak Chips

“…The "extractable fraction" of wood represents up to 10-15% of dry heartwood. Certainly, ellagitannins are the most abundant components in this fraction and, together with other compounds, are the source of many of the interesting sensory characteristics found in aged wines [53]. Eight ellagitannins have been identified in traditional oak species: castalagin, vescalagin, granidin, and roburins (A, B, C, D, and E), with the two most abundant compounds being the stereoisomers, vescalagin and castalagin [53][54][55].…”

“…Certainly, ellagitannins are the most abundant components in this fraction and, together with other compounds, are the source of many of the interesting sensory characteristics found in aged wines [53]. Eight ellagitannins have been identified in traditional oak species: castalagin, vescalagin, granidin, and roburins (A, B, C, D, and E), with the two most abundant compounds being the stereoisomers, vescalagin and castalagin [53][54][55]. Ellagitannins are transferred to the wine during aging, contributing to sensations of bitterness and astringency and behaving as antioxidants due to their capacity to consume oxygen [15,[53][54][55].…”

“…Eight ellagitannins have been identified in traditional oak species: castalagin, vescalagin, granidin, and roburins (A, B, C, D, and E), with the two most abundant compounds being the stereoisomers, vescalagin and castalagin [53][54][55]. Ellagitannins are transferred to the wine during aging, contributing to sensations of bitterness and astringency and behaving as antioxidants due to their capacity to consume oxygen [15,[53][54][55]. Moreover, ellagitannins directly affect wine color via reactions with anthocyanins forming red orange anthocyanin-ellagitannin complexes that are much more stable over time than free anthocyanins [55].…”