Extraction of Arabinoxylan from Animal Feed and Investigations into its Functionality as an Ingredient in Bread Dough.

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Abstract

Arabinoxylans (AX’s) are the predominant non-starch polysaccharides found in the structural matrix of cell walls in wheat grains, being present in large quantities in wheat bran, accounting for up to 25% of its composition. Their physicochemical properties define their functionality which can be beneficial in cereal-based products such as bread, where their addition could enhance the gluten matrix responsible for the aerated structure and quality of bread.Bioethanol production has grown rapidly, however, to be economically viable, cereal-derived first generation biorefineries need to adopt the process integration approaches employed in petrochemical refineries, and exploit the interaction opportunities arising from multiple product streams. A potential source of AX is its extraction from the wheat bran based low value animal feed produced as an end product of the bioethanol distillation process. The benefits of extraction are twofold, to enhance feed nutritional value by reducing fibre content and produce a high value product for use as a functional ingredient in the breadmaking industry. Extraction of AX involves precipitation with ethanol, giving opportunity for integration and economic extraction in the context of a bioethanol plant. Currently no commercial supply of AX is available in sufficient quantities to conduct functionality trials; therefore the objective of the current work was to study the feasibility of extracting AX from animal feed and, by developing a scaled-up extraction process based on that of Hollmann and Lindhauer (2005) and Du et al. (2009), to produce sufficient quantities to conduct functionality trials into its effects on the breadmaking process. Two animal feeds, representative of contrasting biorefinery operations, were used for AX extraction, Distillers’ Dried Grains with Solubles (DDGS) and C*Traffordgold®, with water and alkaline AX being extracted from each. Monosaccharide analysis of the feedstocks confirmed the presence of arabinoxylans, with DDGS containing 12.5% AX and TG 13% AX, with A/X ratios of 0.55 and 0.61, respectively. The purity of AX extracted at both lab scale and on scale up was consistent, with 29.5% and 23% extracted at lab scale and 30% and 25% extracted in the scaled up process for WEAX from DDGS and TG, respectively. The purity of AEAX was lower, with 18% and 14% at lab scale and 15% and 14% for scale up for DDGS and TG, respectively. The results indicate that the same purity of crude extract can be achieved at both lab and larger scale extraction, however lower yields and absolute yields were observed at scale up and anticipated to be due to the crude nature of the process, which needs further optimisation.Addition of crude AX extracts to bread dough gave insights into its effects and potential benefits and issues. The type and origin of AX was found to affect bread dough characteristics in different ways. WEAX from both DDGS and TG exhibited effects on all stages of the breadmaking process, by improving stability and reducing softening at mixing, and slowing proving allowing the dough to retain a better aerated structure, leading to an open aerated finished loaf structure. AEAX from both types of animal feed generally caused destabilization of gas cells and coalescence, resulting in loaves with a tighter crumb structure. The AX dosage appeared to have a non-linear effect, with some positive changes at 1% addition turning to negative changes when added at 2%. This work has provided insights into the functionality of AX in bread dough, and a process has been developed to allow greater than lab scale production of arabinoxylan. The effects of AX need to be understood more clearly to retain beneficial effects, whilst supressing detrimental ones, preferably while avoiding the need for extensive purification. The work supports the possibility for AX extracts to be produced commercially as bread ingredients that could enhance bread structure and nutritional quality, and provides an elegant solution for synergy between two wheat-based industries serving both the food and non-food needs of society.

Keyword(s)

Arabinoxylan, AX, WEAX, AEAX,, Water Extractable Arabinoxylan, Alkaline Extractable Arabinoxylan, DDGS, Distillers Dried Grains with Solubles, Arabinoxylan Extraction ; Arabinoxylans in breadmaking, Arabinoxylans in bread dough,

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