Dietary fiber-rich powder from dragon fruit peel and its effects on nutrient digestion, intestinal function and food application

Abstract

The Western diet, which is rich in refined carbohydrates and unhealthy fats but low in dietary fiber, has been linked to an increased risk of metabolic disorders and gut barrier dysfunction. In the present study, the dietary fiber-rich powder from dragon fruit (Hylocereus undatus) peel (DFP) was developed as a functional food ingredient. DFP contains high dietary fiber (65.2%), primarily cellulose and pectin, along with bioactive phytochemicals such as phenolic compounds and betacyanins. This study aimed to investigate the effect of DFP on in vitro starch digestibility, its application in bakery products, and its impact on intestinal permeability and gut microbiota in rats fed a high-fat, high-fructose (HFHFr) diet. The incorporation of DFP in flours significantly altered the gelatinization enthalpy, peak viscosity, and pasting temperature, which correlated with a reduction in starch digestibility. Adding DFP (1-5% w/w) to wheat cookies resulted in remarkably lower hydrolysis index and predicted glycemic index, indicating reduced digestibility of starch and a lower impact on blood sugar levels. Moreover, DFP markedly increased the amount of bioactive compounds, which correlated with improved antioxidant capacity in the cookies. It also led to reductions in heat-induced toxicants, including, malondialdehyde (a lipid peroxidation product) and dietary advanced glycation end products. In addition to its effects on starch digestibility, DFP showed promising results in mitigating gut barrier dysfunction in rats. Supplementation of the diet with DFP (5% w/w) suppressed HFHFr diet-induced intestinal barrier dysfunction by decreasing serum lipopolysaccharide-binding protein levels and mRNA expression of Toll like receptor 4 in colonic tissue, along with an up-regulation of colonic tight junction protein expression after 12 weeks of the study (p < 0.05). For cecal microbiota, DFP significantly promoted the proliferation of SCFA-producing bacteria, consistent with the increased concentration of total SCFA in cecal contents. Taken together, dietary-rich powder from dragon fruit peel can be considered a valuable ingredient in flour-based food applications for regulating blood glucose, and a modulating compound for alleviating intestinal barrier dysfunction.