Durum wheat semolina characterization by means of a rapid shear-based method

Glutopeak test (GPT) is a rapid shear-based method, recently introduced by Brabender GmbH & Co. (Duisburg, Germany), for discriminating gluten quality. The instrument records the time to reach peak torque during the formation of gluten network. It has been successfully proposed for flour characterization, while no information is available for durum wheat products. Twenty-height durum wheat semolina samples were considered and characterized in terms of protein content, gluten index, and alveographic indices. Semolina (9 g) and distilled water (10 ml) were weighted into the sample cup of the GPT. Temperature was maintained at 35°C and the paddle was set to rotate at 2,750 rpm. Each test ran for 5 min and maximum torque, peak maximum time and the area under the peak were recorded. A significant correlation between the protein content and the peak (r = 0.70, p <0.01) was observed, indicating strong aggregation properties. As for the quality of gluten, the statistical analysis showed a significant correlation between the area under the peak and the gluten index (r = 0.76, p <0.01) and W alveographic index (r = 0.70, p <0.01). In other words, the greater the energy required to form the gluten, the higher the gluten and W indices. On the basis of the conventional alveographic test, semolina samples were divided into three classes of quality: poor (W<180 *10-4 J), medium (180<W<250 *10-4 J) and good (W>250 *10-4 J) quality. The test was able to distinguish the samples of high quality (area> 2400 AU) from those of low quality (area <2400 UA). As expected, medium quality semolina exhibited an intermediate behavior. For this class, the time of maximum peak was the parameter significantly correlated to the quality of gluten (r = 0.73, p <0.05). These preliminary results are encouraging to propose GPT as a rapid and reliable approach for semolina characterisation.