Effect of various thermal processing on the structural and in vitro prebiotic characteristics of β-glucan from Hulless Barley

The favorable prebiotic effect of cereal β-glucans is associated with its structure characteristic, which may be influenced by thermal processing. This study aimed to evaluate the structure and in vitro fermentation characteristics of β-glucan isolated from hulless barley preprocessed with flaking-roasting (FR), stir-frying (SF), steam-flash explosion (SFE) and popping expansion (PE). The results showed that all thermal processing had no impact on the type of chemical groups. Compared with the native β-glucan, the molecular weight of PE-β-glucan increased from 147.36 × 103 Da to 5, 243.60 × 103 Da, whereas its crystallinity index decreasing from 52.9 ± 0.7% to 41.5 ± 1.1%. Furthermore, the PE-β-glucan exhibited a porous structure like that in native β-glucan, while the SFE-β-glucan displayed a compacted structure with the lowest molecular weight (89.90 × 103 Da). Expectedly, PE-β-glucan exerted the highest availability and increased the relative abundance of Bifidobacterium, while FR-, SF-, and SFE-β-glucan tended to promote the growth of Megasphaera and Lactobacillus. Additionally, the level of total SCFAs, acetate, propionate, and butyrate in PE-β-glucan were dramatically higher than those in other β-glucan. Overall, the chain conformation of β-glucan played a pivotal role in determining its bioavailability and probiotic characteristic, which could be improved evidently by PE processing.