Seedless grape pomace to increase fiber content in extruded corn snacks

Introduction. Extruded snack nutritional value can be enhanced by incorporating functional ingredients like seedless grape pomace-a winery's valuable by-product that is usually discarded. Materials and methods. This work aimed to evaluate the impact of seedless grape pomace from two varieties (red and white) on extruded corn snack quality: expansion characteristics, starch digestibility, color, texture, and functional properties. The best formulation was evaluated by the nutritional profile, antioxidant activity, and polyphenol content. Results and discussion. Grape variety affected the content of total starch, snacks porosity, starch digestion index, lightness, browning index, cutting, compression and puncture forces, chewiness, and functional properties of extruded snacks added with grape pomace. Increasing the amount of grape pomace in snacks resulted in a decrease in expansion index, water absorption and solubility indices, total starch content, lightness, friability, cutting, compression and piercing forces, and crispness, while chewiness, browning index, and starch digestibility index increased when as the addition level of the plant additive was higher. The recommended addition levels were 30% for white seedless grape pomace and 20% for the red one. The characterization of these two samples in comparison with the control demonstrated that if even the porosity, texture parameters, lightness, and functional properties were lower, the general quality of the final product was acceptable. The fortified samples had a higher content of protein, ash, lipids, and fiber, and they demonstrated significantly higher antioxidant activity compared to the control. The fiber content was more than 23 fold higher in the the white seedless pomace-containing sample and more than 37 fold in the red one compared to the control corn snack. Furthermore, some individual polyphenols like quercetin, luteolin, and myricetin were identified only in the fortified snacks, depending on grape variety. The FT-IR spectra registered higher absorbances for the fortified snacks than those of control. Conclusion. The results confirmed the opportunity to valorize seedless grape pomace in the extrusion process to obtain functional snacks with potential health benefits.