High-speed durum semolina quality tests on doughLAB

doughLAB enables manufacturers to select the correct processing conditions for producing the best pasta. Testing at higher energy input produces more rapid, accurate and relevant results.

Physical dough tests are important because they determine the behavior of dough during mechanical handling, which affects the quality of the finished pasta. Physical dough tests provide an indication of the resilience of the gluten matrix that develops and is important in giving cooked pasta its firmness and cohesive texture. The test also indicates the amount of water required for the dough to reach a defined consistency. Semolina makes strong doughs that resist the stress of mixing, producing flat curves with indistinct peaks that are difficult to analyze and don’t adequately differentiate between semolina flours of different quality.

The doughLAB is a laboratory scale (300 g bowl and 50 g bowl) z-arm dough mixer to determine flour processing quality. It can perform conventional tests (63 rpm, 30°C) and high-energy mixing tests to emulate commercial dough mixers.

Materials and Methods

Twenty semolina samples (Tamworth, Australia) were mixed on doughLAB using the 50 g bowl, standard speed (63 rpm) and accelerated speeds (120 and 180 rpm). Repeatability was evaluated by one-way ANOVA.

Results

1. Dough Development

Figure 1. Dough mixing curve of semolina at 63, 120, and 180 rpm.

Increasing mixing speed resulted in better peak resolution and earlier dough development time on the doughLAB. (Figure 1) At higher speeds, a second peak was evident in several samples which suggests that testing semolina, or any difficult-to-develop samples, at standard speed would bias results to detect only the first peak. The second peak was taken to be the true mixing peak. Dough development time and stability values were more repeatable at 120 rpm (smaller root mean squares (RMS) and lower coefficients of variation (CV)) than at 63 rpm. Dough development time at 120 rpm is approximately half that at 63 rpm.

2. Water Absorption

Figure 2. Water absorption of semolina at 63, 120, and 180 rpm.

Relative water absorption values appear to be independent of the rate energy is applied when mixing dough. This would allow the conventional water absorption values to be estimated using high-speed tests without any loss of discrimination between samples. Parallel lines of water absorption calculation show that water absorption for the conventional test can be estimated from high-speed tests simply by applying a suitable offset to the test value. (Figure 2)

Conclusion

Testing at higher speeds could be used to reduce test time, increase laboratory efficiency and produce more accurate results to give the miller and pasta producer a better indication of dough stability.

Acknowledgements

Mark Bason, Jennifer Dang and Alison Curtis, Perten Instruments of Australia, Sydney, Australia; and for the semolina samples, Mike Sissons, Department of Primary Industries, Tamworth Agricultural Institute, Tamworth, Australia.