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Effect of cooking on polyphenol bioaccessibility and digestibility of porridge oats

Published online by Cambridge University Press:  19 October 2012

L. Ryan
Affiliation:
Functional Food Centre, Oxford Brookes University, Gipsy Lane, Oxford, OX3 0BP, UK
P. S. Thondre
Affiliation:
Functional Food Centre, Oxford Brookes University, Gipsy Lane, Oxford, OX3 0BP, UK
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Abstract

Type
Abstract
Copyright
Copyright © The Authors 2012

Oat-based products have gained considerable attention in recent years as they are a rich source of the soluble fibre, α-glucan. In addition oats contain large amounts of antioxidants such as vitamin E and bioactive phytochemicals including various phenolic compounds and avenanthramides( Reference Peterson, Hahn and Emmons 1 ). Certain polyphenols are known to reduce the glycaemic response to carbohydrate containing foods. We have previously shown a significant negative correlation between the polyphenol content and the amount of rapidly digested starch (RDS) of raw oats( Reference Thondre, Ryan and Henry 2 ). The objective of the present study was to investigate the polyphenol content and bioaccessibility of cooked oat samples and to determine the digestibility of porridge oats after cooking.

Ten commercially available porridge oats (S1–S10) were cooked according to the manufacturers' instructions and subjected to in vitro digestion( Reference Thondre, Monro and Mishra 3 ). The amount of rapidly digested starch (RDS) was measured in the samples after 20 minutes during the intestinal phase( Reference Mishra and Monro 4 ). Polyphenol contents of cooked oat porridges were measured by the Folin-Ciocalteau method( Reference Sharma and Gujral 5 ) both before and after an in vitro digestion procedure( Reference Ryan, OConnell and OSullivan 6 ) and expressed as Gallic Acid Equivalents (GAE).

Values are means of three independent experiments. PP=polyphenol; RDS=rapidly digested starch.

Cooking increased the polyphenol release from porridge oats. There was an increase in the polyphenol release of all the porridge oats samples following in vitro digestion. There was a significant difference between uncooked and cooked porridge oats in their in vitro digestibility (P<0.01). Previously we have seen a significant (P<0.01) negative correlation between the polyphenol content and RDS (r=−0.743) of pure raw oats samples2, which does not seem to exist when we compare cooked porridge oats with added ingredients such as sugar and fruits. In conclusion, cooking has an important role to play in the bioaccessibility of polyphenols from porridge oats. Furthermore, cooked oats rather than raw oats (as commonly consumed in yoghurt products) may have reduced digestibility of starch. Future work will seek to investigate the glycaemic response to raw and cooked oat samples in vivo.

References

1. Peterson, DM, Hahn, MJ & Emmons, CL (2002) Food Chem 79, 473478.CrossRefGoogle Scholar
2. Thondre, PS, Ryan, L & Henry, CJK (2011) Proc Nut Soc 70, E138.Google Scholar
3. Thondre, PS, Monro, JA, Mishra, S et al. (2010) Food Res Intl 43, 14761481.Google Scholar
4. Mishra, S & Monro, JA (2009) J Cereal Sci 50, 6166.Google Scholar
5. Sharma, P & Gujral, HS (2010) Food Chem 120, 673678.CrossRefGoogle Scholar
6. Ryan, L, OConnell, O, OSullivan, L et al. (2008) Plant Foods Hum Nutr 63, 127133.Google Scholar