Modifying wheat bran for food applications: Effect of wet milling and enzymatic treatment: Bachelor's thesis

Olli-Pekka Lehtinen

Research output: ThesisBachelor's thesisTheses

Abstract

The aim of this study was to develop sustainable methods to modify the structure of wheat bran used in food applications. The methods of interest were wet milling and enzymatic treatment. The effect of these methods on a product quality was tested in a pilot scale baking process.

Wheat bran is composed of many nutritionally valuable components, such as dietary fibre, antioxidants and proteins. Due to its relatively low price, wheat bran holds a great potential as an ingredient to be added into food products. However, most of the previous studies have shown that the addition of wheat bran usually decreases the quality of food products. The focus of this study was on modifying the properties of wheat bran, so that it could be used as a filler ingredient. Besides the particle size reduction and enzymatic treatment, the stability of wheat bran-water suspensions was studied by following the phase separation. The aim of the modifications was to release valuable components from the wheat bran matrix, to concentrate the dietary fibre and to alter the physico-chemical properties of wheat bran.

Wet milling and subsequent centrifugation increased the fibre content of the wheat bran fractions and increased the proportion of insoluble fibre. The enzymatic treatment increased the amount of reducing sugars in the soluble fraction after centrifugation. The highest solubilisation was obtained by using enzymes Depol 740L and Ecopulp TX200A. In addition, the phase stability of the wheat bran water mixtures increased in proportion to the level of milling. The effect of modified wheat bran on the quality of the breads was not as good as wanted due to the decreased volume and hardness of the test breads. Similar results were obtained both with dry and wet milled wheat bran fractions. The negative effect of wheat bran on the bread’s structure was most clearly seen with 20 % addition level.

As a conclusion, wheat bran could be used as a bakery ingredient and a source of dietary fibre, when the addition level is lower than 20 % (of the dry mass in dough). However, the protocol for particle size reduction and the chosen enzymes are of utmost importance. As the desired properties of bread seemed to decrease in proportion to added wheat bran, the effect of particle size, enzymatic hydrolysis and addition level would need further studies.
Original languageEnglish
QualificationBachelor Degree
Awarding Institution
  • Metropolia University of Applied Sciences
Supervisors/Advisors
  • Sibakov, Juhani, Supervisor, External person
  • Halsas, Mikko, Supervisor, External person
Award date20 May 2012
Place of PublicationHelsinki
Publisher
Publication statusPublished - 2012
MoE publication typeG1 Polytechnic thesis, Bachelor's thesis

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Keywords

  • wheat bran
  • particle size
  • wet milling
  • enzymatic treatment
  • baking
  • bread

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