Impact of water content on enzymatic modification of wheat bran: Dissertation

Enzymatic conversions have a fundamental role in several industrial food manufacturing processes and in the upgrading of agro-industrial residues. Enzymatic reactions are typically conducted in excess water because reduction of water content usually decreases enzymatic conversion. Processing at high solids content could, however, offer several economical advantages. Wheat bran is one of the most important by-products of the cereal industry. Bran is a good source of dietary fibre, protein and health-beneficial compounds, but its use in food applications is limited because unprocessed bran is usually detrimental to product quality. The present work aimed to examine and develop techniques to utilize hydrolytic enzymes, especially xylanase, at reduced water content in order to increase the technological functionality of wheat bran in food applications. The applicability of the modified bran was demonstrated in extruded cereal-based snacks. The results showed that improved technological functionality of bran can be achieved by enzymatic modification at a low water content of 40-50%. Consistency of the reaction mixture, mixing method and bran particle size were important factors affecting the intensity of the modification process at reduced water content. It was possible to increase the enzyme action by changing the granular structure of the material to a continuous paste using an extruder, without increasing the water content. Modification of bran by hydrolytic enzymes by a low-moisture process increased the crispiness and reduced the hardness and piece density of bran-enriched puffed snacks. The results can be utilized for improving the technological functionality of bran in food applications and for developing new processes for the enzymatic modification of plant raw materials at reduced water content.