ENRICHMENT OF A BLUE CORN TORTILLA CHIP PARTIALLY SUBSTITUTED WITH GRAPE POMACE: EFFECT ON PHENOLIC BIOACCESSIBILITY AND APPEPARENT GLYCEMIC INDEX

The prevalence of non-communicable chronic diseases, such as obesity, overweight, and type II diabetes, is high among the Mexican population. Over 75% of the Mexican adult population presents overweight and obesity, representing a major public health concern. Corn is a staple food of the Mexican diet, mainly consumed as tortillas and tortilla chips. In recent years, the consumption of blue corn tortillas and chips has increased due to their sensory characteristics. Tortilla chips are characterized by high caloric and fat content. One alternative to reduce the side effects of their consumption is the use of agro-industrial by-products for partial flour substitution. Grape pomace, a winery by-product, is an interesting alternative due to its high content of phenolic compounds and dietary fiber; both bioactive compounds are effective in reducing the glycemic index of enriched foods. Therefore, the objective of this study was to formulate enriched blue corn tortilla chips with grape pomace and evaluate their sensory acceptability, phenolic profile, phenolic bioaccessibility, and apparent glycemic index after in vitro digestion. Cabernet Sauvignon grape pomace was used for the enrichment. Four enriched tortilla chips were formulated by replacing blue corn flour with 0% (control), 8%, 15%, and 25% grape pomace powder, and a sensory acceptance test (9-point hedonic scale, 120 participants) was performed. Proximal analysis, fiber content determination, total phenols (TF, Folin-Ciocalteu), flavonoids (AlCl₃), tannins (DMAC), anthocyanins (pH differential), and reducing sugars (DNS) were quantified. Once the best formulation was selected, an in vitro digestion model simulating gastrointestinal tract conditions was used to determine the bioaccessibility of TP and apparent glycemic index. The most accepted enriched totopo by consumers was the 8% enrichment, which was statistically similar to the control. 15% and 25% formulations were in the neutral and disliked zones, mainly due to the astringency given by tannins. The 8% substitution formulation was selected. Increases of 240%, 340%, and 38% in TP, flavonoids, and anthocyanins were observed. Tannins increased from non-detected to 40 mg EC/100 g FW. After the in vitro digestion, although TP were 14% higher for the enriched totopos than for the control (2.74 and 2.4 mg GAE/g FW), a large reduction in bioaccessibility was observed (74 and 35% for control and enriched totopos), mainly due to phenol-fiber interactions. A 30% reduction in reducing sugar content after in vitro digestion was observed (control: 11.94 and enriched: 8.27 mg GluE/g FW), probably due to the higher content of phenols and fiber in enriched totopos. In conclusion, enrichment of blue corn totopos with grape pomace increased phenolic content and reduced glucose release during digestion, indicating that the enriched formulation could be an alternative that contributes to reducing the glycemic response. MBOA thanks SECITHI for a postdoctoral fellowship.