Phenolic Release during In Vitro Digestion of Cold and Hot Extruded Noodles Supplemented with Starch and Phenolic Extracts

Abstract

Dietary phenolic compounds must be released from the food matrix in the gastrointestinal tract to play a bioactive role, the release of which is interfered with by food structure. The release of phenolics (unbound and bound) of cold and hot extruded noodles enriched with phenolics (2.0%) during simulated in vitro gastrointestinal digestion was investigated. Bound phenolic content and X-ray diffraction (XRD) analysis were utilized to characterize the intensity and manner of starch-phenolic complexation during the preparation of extruded noodles. Hot extrusion induced the formation of more complexes, especially the V-type inclusion complexes, with a higher proportion of bound phenolics than cold extrusion, contributing to a more controlled release of phenolics along with slower starch digestion. For instance, during simulated small intestinal digestion, less unbound phenolics (59.4%) were released from hot extruded phenolic-enhanced noodles than from the corresponding cold extruded noodles (68.2%). This is similar to the release behavior of bound phenolics, that cold extruded noodles released more bound phenolics (56.5%) than hot extruded noodles (41.9%). For noodles extruded with rutin, the release of unbound rutin from hot extruded noodles and cold extruded noodles was 63.6% and 79.0%, respectively, in the small intestine phase, and bound rutin was released at a much lower amount from the hot extruded noodles (55.8%) than from the cold extruded noodles (89.7%). Hot extrusion may allow more potential bioaccessible phenolics (such as rutin), further improving the development of starchy foods enriched with controlled phenolics.

Complexation of starch and phenolic compounds during food processing and impacts on the release of phenolic compounds

“…In the food industry, (hydro)thermal treatments are essential to produce starchy foods, during which interactions among food components may occur with the destruction of starch granules. For example, phenolics and macromolecules such as gluten and starch may interact during the baking procedure of bread (bakery products) (Kan et al., 2020; Sui et al., 2016), or through the extrusion of pasta (Wang, Li, Brennan, et al., 2022).…”

“…The bioavailability of some simple phenolic compounds, such as p ‐coumaric, gallic, caffeic, and rosmarinic acids (Konishi et al., 2004, 2005; Zhao et al., 2004), have been defined. However, in vivo data on some complex phenolic compounds are still scarce, as the release and absorption of phenolic compounds can be dependent on the food matrix (Kan et al., 2020; Wang, Li, Brennan, et al., 2022). The remaining phenolic compounds embedded inside complexes (resistant starch), and these released but not absorbed in the gastro–small intestine phase can reach the colon where gut microbiota further increase their bioaccessibility, that is, when the complex phenolic compounds are degraded into smaller phenolic acids, they can be absorbed across the intestinal mucosa (Tuohy et al., 2012).…”

“…The inhibitory effect of phenolic substances on digestive enzymes in the small intestine is mainly considered, which is the main site for starch digestion. In the starch–phenolic model system or phenolic compounds fortified foods (i.e., noodles (Wang, Li, Brennan, et al., 2022), such as biscuits (Tu et al., 2021), cooked rice with adzuki bean (Morina et al., 2020)), starch is progressively hydrolyzed meanwhile bound phenolics are released in a controlled manner from the food matrix in the small intestine, thus becoming available to exert their potential binding with digestive enzymes (Wang, Li, Wu, et al., 2022). Compared to biscuits and crispy bread, whole milk can hardly delay the release of phenolic compounds (Mandalari et al., 2016).…”

“…The compactness of food structure interferes with the phenolic release and then increases or decreases their binding with enzymes. Extruded noodles with complexes between starch and phenolic compounds show a higher bioaccessibility of phenolics in the simulated small intestinal phase (27.56%–66.50%) than that in the simulated gastric phase (7.80%–13.70%) (Wang, Li, Brennan, et al., 2022), whereas extruded noodles with starch–phenolic mixture release phenolics mainly in gastric phase (over 85%) (Wang, Li, Wu, et al., 2022), indicating lower bioaccessibility in the small intestine.…”

“…Bound phenolic compounds usually bind with the cell wall polysaccharides (Vitaglione et al., 2008), which are less bioaccessible in the human upper gastrointestinal tract compared to free phenolic compounds (Quiros‐Sauceda et al., 2014). However, the amount of free or bound phenolic compounds in isolated starch is negligible, with insignificant complexation between those phenolic compounds and starch (Wang, Li, Brennan, et al., 2022). Thus, plant‐based phenolic compounds are often added into isolated starch to enhance functional and nutritional properties.…”