Wheat flour, bread and biscuits enriched by linseed fibre - comparison of harvest year, linseed variety and addition level

Abstract

Wheat flour was fortified by 2.5, 5.0 or 10 wt. per cent of linseed fibre, gained from seeds of golden flax varieties Amon and Raciol and brown one Recital (granulation 500 - 700 m), prepared from 2015 and 2016 harvests. Using analytical tests, namely sedimentation according to Zeleny and Falling Number, basic technological quality of flour composites was mostly independent on all three observed factors (harvest year, linseed variety and addition). Rheological tests included the farinograph, the extensigraph and the amylograph proofs. Enhancement by brown and yellow flax fibre significantly contributed to rise of farinograph water absorption and to dough stability shortening, directed mainly by addition level. Extensigraph curves course depended on dough resting time, higher differences between wheat control and flour composites were observed after 60 min dough resting. Linseed fibre weakened dough extensibility, and energy as area under curve also partially decreased about 3, 8 and 25% in average as portion of alternative materials in dough has risen. Compared to control, suspension viscosities of tested flour composite generally increased; the strongest effect was recorded for composite samples from harvest year 2016. During dough leavening, tested samples were differentiated according to maturograph dough resistance, and interaction of all three factors was identified. Regardless to variantion in dough machinability, specific volumes of composite bread samples were similar through whole sample set - any unequivocal trend was found. Somewhat worse vaulting of bread was calculated for buns manufactured from raw materials of 2016 harvest. Reversely, linseed fibre produced in 2015 improved crumb softness, especially at 5% enhancement (about ca 50% in average). The lowest addition of linseed fibre resctricted biscuits spread during baking in the highest extent, but rising level of enhancement suppressed elevated dough elasticity. Both cereal products were considered as acceptable for common consumers. Multivariate PCA method verified changes mainly in protein visco-elastic properties, which were reflected in bread and biscuits quality in an opposite manner. Based on this statistics, quality of wheat controls was comparable in both harvest year if related to changes induced by linssed fibre. In opposite to this, technological and consumer's parameters of flour composites and manufactured cereal products were statistically dependent of harvest year of linseed. As presumed, the lowest addition level brough the smallest changes; multiplied fortification caused gradual variation in results of all conducted proofs. Owing to high dietary fibre content in linseed fibre (over 50%), the medium dosage of the alternative material (i.e. 5% addition) could be recommended for praxis.