Whole Flour of Purple Maize as a Functional Ingredient of Gluten-Free Bread: Effect of In Vitro Digestion on Starch and Bioaccessibility of Bioactive Compounds

Abstract

The growing demand for gluten-free products requires the study of alternatives to produce nutritionally and technologically favorable foods. The aim was to evaluate the content and antioxidant capacity of gluten-free bread enriched with whole flour of purple maize (PM) and how starch and bioaccessibility of antioxidant compounds were modified during in vitro digestion. Gluten-free bread was prepared with the addition of 34%, 50%, and 70% PM, and white maize bread served as control. The content of total polyphenols, anthocyanins, and antioxidant capacity through FRAP and TEAC was measured. Specific volume, crumb texture, and starch digestibility were determined in the breads. Simultaneously, in vitro digestion and dialysis by membrane were performed to evaluate the bioaccessible and potentially bioavailable fraction. Bread with 34% PM had a similar specific volume and crumb texture to the control, but higher content of polyphenols (52.91 mg AG/100 g), anthocyanins (23.13 mg c3-GE/100 g), and antioxidant capacity (3.55 and 5.12 µmol tr/g for FRAP and TEAC, respectively). The PM breads had a higher antioxidant content and capacity and higher slowly digestible and resistant starch than the control. These parameters increased as the PM proportion rose. After digestion, anthocyanins were degraded, polyphenols and antioxidant capacity decreased, but they remained potentially bioavailable, although to a lesser extent. Bread with 34% shows acceptable technological parameters, lower starch digestibility, and contribution of bioactive compounds with antioxidant capacity. This indicates that purple maize flour represents a potential ingredient to produce gluten-free bread with an improved nutritional profile.

Phenolic Characterization of a Purple Maize (Zea mays cv. “Moragro”) by HPLC–QTOF-MS and Study of Its Bioaccessibility Using a Simulated In Vitro Digestion/Caco-2 Culture Model

“…These findings suggest that "Moragro" maize has the potential to be a valuable crop for both human health and sustainable agriculture. 6 Purple maize is a rich source of phenolic compounds, mainly anthocyanins, that give a dark purple-red color to the grains. The anthocyanin composition of some purple maize has been well studied.…”

“…The flour also has a higher content of slowly digestible and resistant starch in comparison to traditional white maize flour. These findings suggest that “Moragro” maize has the potential to be a valuable crop for both human health and sustainable agriculture …”

Preparation of Resistant Starch Types III + V with Moderate Amylopullulanase and Its Effects on Bread Properties

“…RS type I, RS type II, RS type III, and RS type IV) are used in the baking of bread [7,9]. However, it was found that the sensory and textural properties of bread are negatively affected by increasing the RS content, such as through crumb stiffening and darker colors [10]. Also, some research has found that several RSs at certain levels do not significantly affect the sensory quality of bread [9].…”