engleski

Fermentation and enzymatic treatment for degradation of fructans in amaranth and wheat bran

Wheat and amaranth bran can be used to enrich foods with dietary fibre ; however, they also contain fructans. Fructans and other fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) can trigger symptoms in individuals with irritable bowel syndrome and non-celiac wheat sensitivity. Fructose, when is present in excess to glucose, is also classified as FODMAP. Therefore, this study aimed to investigate the success of degrading fructans in amaranth bran (by-product of oil cold pressing) and wheat bran (by-product of milling) by fermentation with yeast, lactic acid bacteria or enzymatic treatment. Aqueous bran suspensions (15%) were incubated with Saccharomyces cerevisiae alone or in co-culture with the following: Kluyveromyces marxianus, Lactobacillus fermentum, Lactobacillus casei and Lactobacillus brevis (Lessafre LIVENDO LV1 starter) or inulinase at 37°C for 1h or 24h (2000 U/g, BIO-CAT). In addition, separate enzymatic treatment was carried out with inulinase at 0.1 % and invertase (1000 U/g, BIO-CAT) at 1 % of the weight of the bran. The content of fructans, fructose and glucose before and after treatments was analysed enzymatically using AOAC method 999.03 (with Fructan Assay Kit, Megazyme, Ireland) and AOAC method 985.09 (with D-Fructose/D-Glucose Assay Kit, Megazyme, Ireland). Untreated amaranth bran contained 0.96 ± 0.00 g/100 g d.w. of fructans and 0.13 ± 0.02 g/100 g d.w. of fructose, while wheat bran contained 2.64 ± 0.04 g/100 g d.w. of fructans and 0.14 ± 0.05 g/100 g d.w. of fructose. All treatments resulted in significantly (p<0.05) lower fructan content depending on the bran type, treating agents and time, but not fructose content. After 1 h-incubation with yeast alone or with both enzymes, the fructan content of amaranth bran was reduced by 77 and 85%, respectively, while the reduction for wheat bran was 62 and 66%, respectively. Nevertheless, the amount of fructose after treating amaranth bran with enzymes exceeded its cut-off value (0.5 g/100 g). The 24h-fermentation of amaranth bran with S. cerevisiae degraded 94% of the fructans, but also increased the fructose content to 0.30 g/100 g d.w., while other microbial fermentations yielded no fructose and the fructans content was ≤0.19 g/100 g d.w. For wheat bran, the most successful were 24h-treatments with S. cerevisiae and inulinase or LV1 starter, which resulted in 93% fructan degradation with no fructose increase. All treated samples, regardless of bran type, always showed higher glucose content than fructose one, ranging from 0.02 to 6.41 g/100 g d.w. depending on the interaction of the bran type with agents and the treatment time. Overall, the fructans of amaranth and wheat bran can be successfully degraded by combining yeast with inulinase or lactic acid bacteria, but a longer period of time might be needed for samples high in fructans to ensure a safe level below the cut-off value (0.3 g per serving). Future studies should investigate the potential applications of treated bran in food production.

FODMAP ; fructose ; lactic acid bacteria ; yeast ; inulinase

nije evidentirano