Soluble dietary fibre from oat and barley grains, method for producing a fraction rich in B-glucan and use of the fraction in foods, pharmaceuticals and cosmetics
The present invention relates to a process for the extraction of soluble dietary fiber from oat and barley grains using enzymatic hydrolysis treatment, wherein the grain is milled and any endosperm depleted fractions thereof being rich in B-glucans are recombined, without further heat treatment, dispersed in water and then subjected to sequential enzymatic treatment with starch degrading enzymes, followed by an optional step of enzyme inactivation by wet heat treatment, and a subsequent step wherein the hydrolysate mixture is spontaneously or centrifugally separated into at least 3 distinct fractions: a first fraction, which comprises the soluble dietary fiber complex, containing more than 20% B-glucan on a dry matter basis, a second aqueous fraction, and a third fraction comprising most of the protein and oil together with the insoluble fibrous material from the milled grain.
1. A process for extraction of soluble dietary fibre complex from oat and barley grains using an enzymatic hydrolysis treatment,
wherein
non-heat treated grain is milled and endosperm depleted fractions thereof being rich in β-glucans are recombined, without any further heat treatment; and
dispersed in water; and
subjected to enzymatic treatment with starch degrading enzymes in a sequence utilizing first α-amylase and then amyloglucosidase enzyme, said starch degrading enzymes being substantially cleaned of β-glucanase side activity, said endosperm depleted fractions, water and starch degrading enzymes forming a hydrolysate mixture,
said enzymatic treatment is followed by an optional step of enzyme inactivation by wet heat treatment,
whereby the hydrolysate mixture forming spontaneously at least one viscous, aqueous top layer upon a second aqueous layer, is subjected to a separation process to isolate said at least one viscous, aqueous top layer comprising soluble dietary fibre complex, containing more than 20% β-glucan on a dry matter basis.
2. A process according to claim 1 , wherein a second aqueous fraction layer substantially free of β-glucans, and at least a third fraction layer comprising protein and oil together with insoluble fibrous material from the milled grain are isolated.
3. A process according to claim 1 , wherein the β-glucan has a molecular weight of at least 400,000 Daltons.
4. A process according to claim 1 , wherein the β-glucan has a molecular weight of at least 800,000 Daltons.
5. A process according to claim 1 , wherein the β-glucan has a molecular weight of at least 1,300,000 Daltons.
6. A process according to claim 1
wherein the milled cereal grain is treated with starch degrading enzymes in a sequence utilizing first α-amylase and then amyloglucosidase enzyme being free of β-glucanase side activity.
7. A process according to claim 1 ,
wherein the milled cereal grain is treated with starch degrading enzymes in a sequence utilizing first α-amylase and then amyloglucosidase enzyme being free of β-glucanase side activity, in which the amyloglucosidase enzyme is used for 40 minutes or less, at a temperature exceeding 55° C.
8. A process according to claim 1 ,
wherein amyloglucosidase enzyme is substantially cleaned of β-glucanase side activities prior to use, in a two step procedure using anion exchange followed by hydrophobic interaction chromatography, a major protein band eluting from the hydrophobic interaction chromatography column being utilized as the cleaned enzyme.
9. A process according to claim 1 ,
wherein the separated top-layer rich in soluble dietary fibre is further treated in a wet state, after optionally further diluting with water, with one or a combination of more than one of the following enzymes of the type: xylanases, amyloglucosidases, pullulanases, cellulases.
10. A process according to claim 1 ,
wherein the top-layer rich in soluble dietary fibre is further treated in a wet state, after optionally further diluting with water, with amyloglucosidase enzyme, in which the amyloglucosidase enzyme is substantially cleaned of β-glucanase side activities prior to use, in a two step procedure using anion exchange followed by hydrophobic interaction chromatography, a major protein band eluting from the hydrophobic interaction chromatography column being utilized as the cleaned enzyme.
11. A process according to claim 1 , wherein the β-glucan is dried.