FORMULATION, PHENOLIC COMPOUNDS BIOACCESSIBILITY, AND APPARENT GLYCEMIC INDEX OF A POZOL-TYPE BEVERAGE ENRICHED WITH GRAPE POMACE POWDER

Pozol is a traditional maize-based fermented beverage from southeastern Mexico, normally consumed as part of breakfast. Although it is normally produced with white maize, it can also be prepared with blue maize. Grape pomace is a winery industry by-product rich in phenolic compounds and dietary fiber. The objective of this work was to formulate a pozol beverage enriched with grape pomace to increase its fiber and phenolic compounds (PC) content, to evaluate the bioaccessibility of PC and apparent glycemic index after in vitro digestion. Cabernet Sauvignon grape pomace was used for the enrichment. Five beverages were formulated by replacing blue maize flour with 0, 8, 10, 15, and 25% grape pomace powder (GPP). Pozol dough (20 g) was covered with banana leaves and fermented for 24 h at 32°C. Fermented dough (pozol) was mixed with 100 mL of water and 0.6 g of agave syrup, and a sensory acceptance test (9-point hedonic scale, 60 participants; protocol was accepted by the ethics committee CIEB-2019-1-051, and participants signed an informed consent form) was performed. PC were extracted (70% acetone and 80% methanol), and total phenols (Folin-Ciocalteu), flavonoids (AlCl₃), tannins (DMAC), anthocyanins (pH differential), and reducing sugars (DNS) were quantified. Using the best formulation, an in vitro digestion model was used to determine the bioaccessibility of PC, glucose content, and the apparent glycemic index. The most accepted beverage by consumers was the 15% enrichment, which was statistically similar to the control. Interestingly, lower substitution formulations were not as well accepted, mainly due to the acid flavor, while 25% substitution was rejected due to its high astringency conferred by its high tannin content. For this reason, the 15% substitution formulation was used. Enrichment had a large effect on phytochemical content, compared to the control. Increases of 222%, 742%, 4000%, and 33% for phenols, flavonoids, tannins, and anthocyanins were observed. In contrast, no differences were observed in reducing sugar content (approximately 20 mg GluE/mL). These results suggest that enrichment with grape pomace largely increases phytochemical content. This effect was more evident for tannins, which increased from 0.01 to 0.41 mg CE/mL for enriched pozol. After in vitro digestion, the observed content of PC was higher in enriched pozol. However, PC bioaccessibility was lower in enriched pozol (35.5% and 21.3% bioaccessibility for control and enriched pozol). After in vitro digestion, both pozol beverages showed a low apparent glycemic index, compared to white bread (13% for both formulations), indicating that both beverages represent low-glycemic-index beverages. In conclusion, enrichment of pozol with grape pomace powder increased phenolic content while maintaining a low apparent glycemic index. Therefore, enriched pozol could be an alternative that helps to reduce the glycemic response. MBOA thanks SECITHI for a postdoctoral fellowship.