Haze Formation and the Challenges for Peptidases in Wine Protein Fining

Abstract

To meet consumer expectations, white wines must be clear and stable against haze formation. Temperature variations during transport and storage may induce protein aggregation, mainly caused by thaumatin like-proteins (TLPs) and chitinases (CHIs), which thus need to be fined before bottling of the wine. Currently, bentonite clay is employed to inhibit or minimize haze formation in wines. Alternatively, peptidases have emerged as an option for the removal of these thermolabile proteins, although their efficacy under winemaking conditions has not yet been fully demonstrated. The simultaneous understanding of the chemistry behind the cleavage of haze proteins and the haze formation may orchestrate alternative methods of technological and economic importance in winemaking. Therefore, we provide an overview of wine fining by peptidases, and new perspectives are developed to reopen discussions on the aforementioned challenges.

Recombinant Thaumatin-Like Protein (rTLP) and Chitinase (rCHI) from Vitis vinifera as Models for Wine Haze Formation

“…According to Eilers et al [ 29 ], Cys residues mediate helix interactions (they are often located at helix-helix interaction sites) and they can work as sensors for protein denaturation [ 30 ]. Cys residues of wine haze proteins are exposed during protein denaturation and can cross-link proteins under S -sulfonation [ 9 , 31 ]. The increase in the CPM fluorescence signal under gradual denaturation of rTLP and rCHI evidences the exposure of Cys residues, which can participate in protein S-S exchanges from temperatures above 55 °C, rearranging disulfide bridges along the polypeptide chains and consequently promoting aggregation [ 9 ].…”

“…Cys residues of wine haze proteins are exposed during protein denaturation and can cross-link proteins under S -sulfonation [ 9 , 31 ]. The increase in the CPM fluorescence signal under gradual denaturation of rTLP and rCHI evidences the exposure of Cys residues, which can participate in protein S-S exchanges from temperatures above 55 °C, rearranging disulfide bridges along the polypeptide chains and consequently promoting aggregation [ 9 ]. In the thermal shift assays, rCHI showed a lower T m (59 °C) than rTLP (63 °C).…”

“…Moreover, these protein-protein interactions are influenced by numerous wine matrix components such as polyphenols [ 1 ], metal and sulfite ions [ 2 ], organic acids [ 3 ] as well as specific physicochemical conditions such as moderate temperature [ 4 , 5 ], high ionic strength [ 6 ] and acidic pH [ 7 ]. Although TLPs are reported to have hydrophobic spots that bind polyphenolic compounds [ 8 ] and irregular structures that interact via intermolecular disulfide bridges [ 9 , 10 ], CHIs are reported to be less stable and to denature irreversibly [ 11 ]. In addition, minor variations in pH conditions and ionic strength can affect the interaction of polyphenols with hydrophobic residues of HUPs, since their conformational states depend on their isoelectric points (pI) and the net charges that are present on the protein surfaces [ 12 ].…”

“…In addition, minor variations in pH conditions and ionic strength can affect the interaction of polyphenols with hydrophobic residues of HUPs, since their conformational states depend on their isoelectric points (pI) and the net charges that are present on the protein surfaces [ 12 ]. Therefore, the understanding of the interaction between thermolabile wine proteins and other wine matrix components is a fundamental step in the search for novel clarification methods [ 9 ].…”

Influence of Must Clarification Technique on the Volatile Composition of Albariño and Treixadura Wines

“…Another common enological operation performed to clarify musts or wines is the use of fining agents, which, alone or in combination with the techniques cited above, increase the settling efficiency, make the precipitation of suspended solids easier, minimize the browning, ensure stability, and improve the organoleptic characteristics, such as the modulation of mouthfeel perception or the reduction of off-flavors. These clarifying agents can have different origins: organic, inorganic, animal, or plant [ 11 , 16 , 17 , 18 ].…”