Abstract
To enlarge the applications of whole wheat grain (WWG) and wheat bran (WB) as functional ingredients in foodstuffs that can promote human health, researchers have explored bioprocessing approaches to improve the bioaccessibility of phenolic compounds from these food matrices and, subsequently, their biological effects. The objective of this study was to compare the composition in nutrients, anti-nutrients, and bioactive compounds of WWG and WB, and their respective bioprocessed products: sprouted wheat (GERM) and WB hydrolysate (stabilized by spray-drying [SPD] and microencapsulated [MEC]). In addition, to evaluate the functional properties of these ingredients, the bioaccessibility of phenolic compounds and their potential antioxidant and anti-inflammatory activities were monitored in different digestion steps. GERM had increased amounts of insoluble dietary fiber, higher diversity of oligosaccharides, and higher concentration of monosaccharides, free phosphorous, and phenolic compounds than WWG. SPD had improved content of soluble dietary fiber, oligosaccharides, monosaccharides, free phosphorous, and phenolic compounds (vs. WB), whereas MEC was mainly composed of protein and had nearly 2-fold lower content of SPD components. All the ingredients showed lower amounts of phytic acid as compared with raw materials. In all samples, hydroxycinnamic acids were the most representative polyphenols followed by minor amounts of hydroxybenzoic acids and flavonoids. Gastrointestinal digestion of GERM, SPD, and MEC revealed high stability of total phenolic compounds in both gastric and intestinal phases. Hydroxycinnamic acids were the most bioaccessible compounds during digestion among the three bioprocessed wheat ingredients studied, although their bioaccessibility varied across ingredients. In this sense, the bioaccessibility of ferulic acid (FA) derivatives increased in GERM with progression of the digestion, while it was reduced in SPD and MEC up to the end of the intestinal phase. Microencapsulation of SPD with pea protein led to generally to lower bioaccessible amounts of phenolic acids. Comparison analysis of biological effects highlighted SPD for its most potent antioxidant effects in the gastrointestinal tract (3 out 4 antioxidant parameters with highest values), while no clear differences were observed with regard to in vitro anti-inflammatory activity. Overall, these results support the potential application of GERM, SPD, and MEC as functional and nutraceutical ingredients.
Highlights
Wheat (Triticum spp.), one of the important staple grains in many parts of the world, is a dietary source of starch, fiber, minerals, vitamins, and phytochemicals such as phenolic compounds, phytosterols, and sphingolipids, most of them concentrated in outer layers of the grain (Cheng et al, 2021)
Germination led to a significant increase in total dietary fiber (TDF) and insoluble dietary fiber (IDF) contents (1.24- and 1.54-fold increase, respectively), with no significant differences in soluble dietary fiber (SDF) and a significant reduction in β-glucan content (22.08%)
GERM showed similar SDF content compared to whole-wheat grain (WWG), higher diversity of oligosaccharides was detected in the former (Supplementary Material 1)
Summary
Wheat (Triticum spp.), one of the important staple grains in many parts of the world, is a dietary source of starch, fiber, minerals, vitamins, and phytochemicals such as phenolic compounds (phenolic acids, flavonoids, and alkylresorcinols), phytosterols, and sphingolipids, most of them concentrated in outer layers (bran) of the grain (Cheng et al, 2021). Wheat grain has been applied for white flour production used in the manufacture of a variety of foods, especially baked foods and breakfast cereals. The wheat flour milling industry produces large quantities (about 187 million tons/year) of bran, an inexpensive by-product mostly used for animal feed (Cheng et al, 2021). Based on strong scientific evidence demonstrating that consumption of dietary fiber (DF) is associated with gut health and reduction of cardiovascular diseases and colorectal cancer risk (Cãlinoiu and Vodnar, 2018), whole-wheat grain (WWG) and wheat bran (WB) are being increasingly applied in food production (Cheng et al, 2021). In the last years, strategies to increase the content of dietary bioactive compounds in WWG and WB while modifying the food structure toward improved delivery of bioactive compounds in the human gastrointestinal tract have attracted the interest of scientists (Mcclements et al, 2015)
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