Removal of ochratoxin A from contaminated red wines by repassage over grape pomaces

Ochratoxin A contamination of red wines might be quite severe in certain high-risk regions and vintages, thus requiring corrective measures to fulfill acceptable standards for human consumption. This work proposes an innovative and environmentally friendly corrective measure to reduce ochratoxin A levels by repassage of contaminated musts or wines over grape pomaces having no or little ochratoxin A contamination. Grape pomaces have a high affinity for ochratoxin A and have been shown to remove ochratoxin A from must and wine during vinification. Time course experiments showed that ochratoxin A adsorption by pomaces is a rapid process, reaching equilibrium in less than 10 h, and is not affected by the tested toxin concentrations. Repassage of wine from Primitivo grapes spiked with 2-10 microg/kg ochratoxin A over pomaces obtained from the same grapes removed up to 65% ochratoxin A within 24 h. Similar results (50-65% ochratoxin A reduction) were obtained with Primitivo or Negroamaro wines repassed over pomaces from different grape varieties including white grapes (Malvasia, Greco di Tufo) and red grapes (Sangiovese, Aglianico). Grape pomaces maintained a good efficacy in removing ochratoxin A after being reused four times. Unlike other enological fining agents, the use of grape pomaces to adsorb ochratoxin A from red wines of the same grape variety (Primitivo) did not affect relevant wine quality parameters, including color intensity and health-promoting phenolic content (trans-resveratrol, quercetin, total polyphenols). These quality parameters were instead positively or negatively affected when contaminated wines were repassed over grape pomaces from other grape varieties, the effect being related to the intrinsic characteristics of the pomace variety. The proposed decontamination procedure can be applied in a modern winery provided that contaminated grapes are identified early and processed separately from uncontaminated grapes.