Original Article

European Journal of Clinical Nutrition (2008) 62, 594–599; doi:10.1038/sj.ejcn.1602746; published online 4 April 2007

The impact of freezing and toasting on the glycaemic response of white bread

Contributors: PB planned and designed the study and was responsible for the collection of data and writing the manuscript. HJL advised on the study design and contributed to the preparation of the manuscript.

P Burton1 and H J Lightowler1

1Nutrition and Food Science Group, School of Life Sciences, Oxford Brookes University, Oxford, UK

Correspondence: Dr H Lightowler, Nutrition and Food Science Group, School of Biological and Molecular Sciences, Oxford Brookes University, Gipsy Lane Campus, Headington, Oxford OX3 0BP, UK. E-mail: hlightowler@brookes.ac.uk

Received 3 July 2006; Revised 14 February 2007; Accepted 19 February 2007; Published online 4 April 2007.

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Abstract

Objective:

 

To investigate the impact of freezing and toasting on the glycaemic response of white bread.

Subjects/methods:

 

Ten healthy subjects (three male, seven female), aged 22–59 years, recruited from Oxford Brookes University and the local community. A homemade white bread and a commercial white bread were administered following four different storage and preparation conditions: (1) fresh; (2) frozen and defrosted; (3) toasted; (4) toasted following freezing and defrosting. They were administered randomized repeated measures design. Incremental blood glucose, peak glucose response, 2 h incremental area under the glucose response curve (IAUC).

Results:

 

The different storage and preparation conditions resulted in lower blood glucose IAUC values compared to both types of fresh white bread. In particular, compared to the fresh homemade bread (IAUC 259 mmol min/l), IAUC was significantly lower when the bread was frozen and defrosted (179 mmol min/l, P<0.05), toasted (193 mmol min/l, P<0.01) and toasted following freezing and defrosting (157 mmol min/l, P<0.01). Similarly, compared to the fresh commercial white bread (253 mmol min/l), IAUC was significantly lower when the bread was toasted (183 mmol min/l, P<0.01) and frozen, defrosted and toasted (187 mmol min/l, P<0.01).

Conclusions:

 

All three procedures investigated, freezing and defrosting, toasting from fresh and toasting following freezing and defrosting, favourably altered the glucose response of the breads. This is the first study known to the authors to show reductions in glycaemic response as a result of changes in storage conditions and the preparation of white bread before consumption. In addition, the study highlights a need to define and maintain storage conditions of white bread if used as a reference food in the determination of the glycaemic index of foods.

Keywords:

glycaemic response, bread, food storage, food preparation, blood glucose

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