Content area
Abstract
Oenological tannins are extracted from plants and agro-industrial byproducts for application in the wine industry; they are used for their ability to improve the protein stability of wine and also to protect it against negative physicochemical changes and unpleasant sensory attributes. The potential applications of tannin extract are determined by the phytochemical composition and the production cost, which mainly depends on the complexity of the raw material used and the manufacturing process of the tannin extract. In general, tannins are extracted from the lignocellulosic barrier, which limits their release during the diffusion process. Many treatments are used to reduce the recalcitrance of lignocellulosic material and to intensify the tannins extraction yield. This review gives a general description of different classes and properties of oenological tannins, and it elucidates in detail conventional methods for the industrial production of tannins, as well as the emerging extraction techniques and characterization methods developed from previous studies. Indeed, clear interest has been noticed in the extraction of tannin using emerging techniques, and this is linked to their many advantages such as the use of non-toxic solvents, and short extraction time. However, their implementation at the industrial level for oenological tannin content remains a challenge, particularly in terms of installation and equipment costs. Additionally, conventional methods are non-complex processes with higher yields/outcomes than these techniques. Several characterization techniques have revealed the molecular diversity of oenological tannins that influence their proprieties. The botanical origin of the tannins can be identified by spectroscopy, GC-FID/MS, and RP-HPLC. Electrochemical methods (CV and LSV) can be a rapid alternative for classifying tannins.