Abstract
Oats are rich in dietary fibre (DF) especially in β-glucan which has several health-promoting effects. Oats are not commonly used in extruded snacks because they often result in a poor expansion and hard structure. In the present study, defatted wholegrain oat flour (WF) and defatted endosperm oat flour (EF) were used as starch sources for extrudates. Five differently treated oat bran fractions (untreated, ultra-fine ground, enzymatically hydrolysed and hot water-extracted solubles and residue) were added to EF (10 or 20 %), and their influence on the chemical, textural and structural properties of extrudates was investigated. Extrudates made of WF had a poor expansion (151 %) and hard texture (399 N), whereas EF formed a better expanded (199 %) and less hard product (149 N). Addition of oat bran concentrate (OBC) decreased the expansion (171–176 %) and resulted in a harder texture (200–265 N) compared to that of EF 100 % extrudates. The lower expansion of WF and OBC-enriched extrudates was due to the higher content of insoluble fibre. However, no statistical differences were detected between the untreated, ultra-fine ground and enzyme-hydrolysed OBC. The water-insoluble (WIS-OBC) and water-soluble (WS-OBC) fractions had opposite effects on the EF-based extrudates: 10 % addition of WIS-OBC fraction significantly decreased the expansion (163 %) and increased the hardness (313 N), whereas the addition of WS-OBC (10 or 20 %) enhanced the expansion (218–226 %) and resulted in less hard textures (131–146 N). The soluble fibres and low protein content in WS-OBC fraction were hypothesised to cause the improved expansion and decreased hardness. The results demonstrated that extrudates with acceptable expansion and hardness can be produced with defatted oat endosperm flour and oat bran fractions. However, the water-insoluble bran components had a negative effect on the textural properties of extrudates.
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Abbreviations
- DF:
-
Dietary fibre
- EF:
-
Defatted oat endosperm flour
- EH:
-
Enzymatically hydrolysed
- IDF:
-
Insoluble dietary fibre
- Mw :
-
Molecular weight
- OBC:
-
Oat bran concentrate
- SDF:
-
Soluble dietary fibre
- TDF:
-
Total dietary fibre
- UF:
-
Ultra-fine ground
- WF:
-
Defatted wholegrain oat flour
- WIS:
-
Water-insoluble
- WS:
-
Water-soluble
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Acknowledgments
Funding from the Academy of Finland (Kaisa Poutanen), the Finnish Graduate School of Applied Bioscience: Bioengineering, Food & Nutrition, Environment (ABS) and the Doctoral Programme for Biomass Refining (BIOREGS) is gratefully acknowledged. Dr. Kaarina Viljanen, Dr. Atte Mikkelson, Arja Viljamaa, Marita Ikonen, Liisa Änäkäinen and Ritva Heinonen at VTT are acknowledged for their excellent assistance in chemical and microscopic analyses. Timo Holopainen at the University of Helsinki is acknowledged for his technical assistance during the extrusion trials. The authors thank Michael Bailey for revising the English language.
Role of the Funding Source
This research was jointly funded by the Academy of Finland (a state-owned funding agency promoting scientific research in Finland), the Finnish Graduate School of Applied Bioscience: Bioengineering, Food & Nutrition, Environment (ABS), the Doctoral Programme for Biomass Refining (BIOREGS) and the University of Helsinki and VTT Technical Research Centre of Finland. The research was carried out at the University of Helsinki, University of Eastern Finland and VTT. The Academy of Finland, ABS and BIOREGS had no role in the research work or in the publishing of the results.
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Juhani K. Sibakov and Satu J. Kirjoranta have equal authorship.
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Sibakov, J.K., Kirjoranta, S.J., Alam, S.A. et al. Effect of Oat Bran Fractions on Extrudates Made of Defatted Oats. Food Bioprocess Technol 8, 445–458 (2015). https://doi.org/10.1007/s11947-014-1425-4
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DOI: https://doi.org/10.1007/s11947-014-1425-4