Susane Trevisan1, Ali Salimi Khorshidi2, John H Page3, Anatoliy Strybulevych3, Nancy P Ames1,4, James D House1, and Martin G Scanlon1
1Department of Food and Human Nutritional Sciences, University of Manitoba, Canada, 2Red River College Polytechnic, Canada, 3Department of Physics and Astronomy, University of Manitoba, Canada, 4Agriculture and Agri-Food Canada, Richardson Centre for Functional Foods and Nutraceuticals, Canada
A current food safety issue is the presence of acrylamide, a probable carcinogen, in bakery products, such as bread1. One strategy to tackle this issue is to reduce the concentration of the free amino acid asparagine in wheat1,2. However, factors affecting free asparagine in wheat (environment3, genotype4, and fertilization treatments5) also affect wheat gluten protein content and composition, changing dough rheological properties and the final bread quality. Therefore, it is crucial to evaluate if strategies to reduce free asparagine concentration in wheat cause detrimental effects on dough rheology. Low-intensity ultrasound (LIU) is a non-destructive and a low-cost technique that has been shown to be a promising alternative for studying dough properties6,7. Therefore, this novel research aimed to study the relationship of free asparagine concentration in wheat against dough rheological properties obtained from LIU and compare with data from linear shear oscillatory time sweep tests. A set of 10 samples, varying widely in wheat free asparagine concentration, was used for this study. LIU and shear tests were conducted on non-yeasted dough samples. Linear fitting was carried out to investigate the time-dependent changes in the loss tangent, which has been shown to be inversely related to dough elastic-like characteristics. This is shown in Fig.1 for the two extreme values for asparagine concentration. Analysis was performed to investigate the relationship between the absolute normalized slopes of the time-dependent changes in the loss tangent against free asparagine concentration. In Fig. 2, a significant (p<0.10) negative correlation was found for the slopes of loss tangent from both tests against free asparagine concentration, indicating that samples with higher free asparagine concentration had less changes over time in their rheological properties. The mechanisms for changes in both loss tangents relate to the nature of interactions between proteins, and these will be discussed.
Fig. 1. Longitudinal loss tangent () (left) and shear loss tangent () (right) as a function of time (seconds) for non-yeasted wheat flour dough samples with the highest (A, ▼) and lowest (J, ◯) free asparagine concentration. Red lines are the linear fits. Data points represent means and SE (n ≥ 2).
Fig. 2. Absolute normalized slopes of the curves for (left) and (right) over time against free asparagine concentration (mg g-1) and Pearson’s r correlation analysis for non-yeasted dough samples. Data points represent means ± SE (n ≥ 2).
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