Fermentation as a Sustainable Tool to Decrease Zeen Oak Acorns (Quercus canariensis Willd.) Tannin Content for Potential Agri-food Use: A Preliminary Study

The Zeen oak (Quercus canariensis Willd.) belongs to the group of deciduous species distributed around the Mediterranean. The use of the oak acorn has a long world history in human food, popular medicine, animal feed and tanneries. However, this remains challenging because of its high content of tannins, responsible for bitterness and astringency. Fermentation could be applied as food detoxification process. This research investigated the use of fermentation, using Saccharomyces cerevisiae, as a green tool to decrease Zeen oak tannin content. A factorial design approach was used to investigate the impact of fermentation by Saccharomyces cerevisiae on Zeen oak tannins. It was based on 2 factors: Saccharomyces cerevisiae concentration and fermentation duration at 30 °C, and 2 levels (−1, +1). For determination of optimum points, four responses were selected: levels of tannins and in vitro antioxidant activity, assessed by DPPH RSA determination. This approach allowed defining optimal in vitro fermentation conditions for detoxification: a concentration of 3.5 g/L for Saccharomyces cerevisiae and 4 days of fermentation. These conditions led to a significant decrease in Zeen oak tannins by—72%. Interestingly, they did not impair Zeen oak antioxidant activity. These findings suggest that fermentation could be suggested as a green effective tool for detoxification.