Physical properties and functional characteristics of broccoli-soluble dietary fiber

Most broccoli stems and leaves aren't utilized, which has led to environment pollution. Dietary fiber (DF) is the primary functional component of green leafy vegetables and, as such, it has become a popular research topic. Compared with insoluble dietary fiber, soluble dietary fiber has multiple functional properties. Therefore, we evaluated the composition and physicochemical properties of broccoli-soluble dietary fiber (B-SDF) according to sugar composition, electron microscopy, spectroscopy, and thermal analysis. The results showed that the main monosaccharides of B-SDF included galactose and arabinose, and main molecular weight was lower than 6,000 Da (61.37%). B-SDF had a small particle size (average Z-particle size = 42.22 nm), which existed in an amorphous form. B-SDF presented a honeycomb network structure (dry state) and a complex network and loose structure (aqueous solution). These structural features exposed B-SDF to a significant number of polar groups and binding sites. B-SDF had significant water- and oil-holding capacity (12.86 ± 0.60 g/g and 2.42 ± 0.15 g/g, respectively), adsorption capacity of glucose (139 ± 10.19 mg/g), cholesterol (184.12 ± 4.37 mM/g (pH 2.0) and 191.05 ± 0.80 mM/g (pH 7.0)), and NO2− (22.75 ± 1.06 mg/g (pH 2.0) and 72.07 ± 1.25 mg/g (pH 7.0)). Its scavenging capacity of DPPH·, O2−·, and TAC was 95.95 ± 0.48 mg Trolox equivalent/100 g, 292.93 ± 29.42 mg VC equivalent/100 g and 2.49 ± 0.11 M FeSO4·7H2O equivalent/100 g, respectively. Notably, we found that B-SDF had unique angiotensin-converting enzyme (ACE) inhibitory activity with 83.40% ± 4.00% at 1 mg/mL concentration.