1. 1) INTRODUCTION  Wheat ( Triticum aestivum L.) is used in a wide range of applications including bread, pasta, noodles, cakes and cookies  It is broadly grouped into two - hard or soft – based on the kernel texture  Flours from hard and soft wheat also have different characteristics that affect their functionalities and end-use properties  Hard wheat is preferred for bread where an elastic and extensible gluten network is desired  Soft wheat is preferred for cookies and cakes, where an elastic gluten network is undesirable  The technological behavior of flour is not only linked to the protein and gluten content, but it is also the result of complex interactions between macromolecules that are responsible for dough performances Changes in protein conformation and sulphydryl content in soft and hard wheat flour during mixing* Enoch T. Quayson 1,a, Alessandra Marti 1,2 and Koushik Seetharaman 1 1 Department of Food Science and Nutrition, University of Minnesota, Saint Paul, MN, US 2 Department of Food, Environmental and Nutritional Sciences (DeFENS), University of Milan, Italy a quays001@umn.edu 3) MATERIALS  Branson : soft kernel, 9.5% protein  TW301020 : hard kernel, 13.1% protein kindly provided by Ontario Cereal Crops, Canada 2) OBJECTIVE Investigating protein secondary structure and thiol content changes in hard and soft wheat flours during mixing 4) EXPERIMENTAL Dough preparation  Farinograph-AT (C.W. Brabender Inc., South Hackensack, NJ, US)  AACC method (54-21) for the identification of optimal water absorption to reach the 500 Farinograph Units (FU) Dough sampling  Dough Development Time (min): time from first addition of water to the point of maximum consistency range  Time to Breakdown (min): time from start of mixing until there has been decrease of 30 FU from peak points  Stability Departure (min): time point where top of curve leaves 500 FU line Attenuated Total Reflectance (ATR) – Fourier transform infrared (FTIR) spectroscopy  Bruker Tensor 37 (Bruker Optics, Inc., Billerica, MA, USA)  Spectra aquisition: spectral range: 4000-600 cm -1 ; 32 scans at 4 cm -1 resolution  Specta elaboration: spectra normalisation; H 2 O/D 2 O spectra subtraction; second derivative; integration (1) Estimation of protein secondary structure (1) Beta-sheet: 1620 -1644 cm -1 ; Random: 1644 -1652 cm -1 ; Alpha-helix: 1652 -1660 cm -1 ; Beta-turn: 1660 -1685 cm -1 Dough lyophilization  Accessible Thiols (2) 0.5mM 5,5’-dithiobis(2-nitrobenzoate) (DTNB) assay  Total Thiols (2) DTNB assay in presence of 1% sodium dodecyl sulfate (SDS) 7) RESULTS: ACCESSIBLE AND TOTAL THIOLS  Branson and TW301020 have comparable accessible thiols, but different amount of total thiols  Branson shows higher amount of total thiols compared to TW301020, suggesting that thiols are less involved in disulfide linkages Figure 3. Thiols content of Branson (a) and TW301020 (b) (a) BRANSON (soft wheat) (b) TW301020 (hard wheat) * In memory of Dr. Koushik Seetharaman 8) CONCLUSIONS 5) RESULTS: MIXING PROPERTIES BRANSON (soft wheat) TW301020 (hard wheat) Figure 1. Mixing profiles Table 1. Farinograph indices  Branson starts breaking down – loosing 30 FU from the peak – before the curve leaves 500 FU line, suggesting dough weakening Branson (soft wheat) TW301020 (hard wheat) Dough Development Time (min:ss)01:0206:21 Time to Breakdown (min:ss)02:1815:30 Stability Departure (min:ss)03:0914:21 Stability (min:ss)02:3513:04 6) RESULTS: PROTEIN CONFORMATION  At the Dough Development Time, the amount of the secondary structures follows the order beta-sheet = beta-turn > random>alpha-helix in both flours  No significant differences (p>0.05) between Branson and TW301020 are observed at the Dough Development Time Figure 2. Estimation of protein secondary structure of Branson (a) and TW301020 (b) BRANSON (soft wheat) TW301020 (hard wheat) (a) (b)  At the Stability Departure, TW301020 is characterized by higher beta-sheet, random and alpha-helix structures, and lower beta-turns than Branson  During mixing of Branson, beta-turn structures increase at the expenses of beta-sheet structures  During mixing of TW301020, random structures increase at the expenses of beta-turns  No changes are observed in TW301020 dough between Stability Departure and Time to Breakdown, in agreement with torque stability during mixing (Fig. 1)  Total thiols increase during the mixing period  No changes are observed in TW301020 dough between Stability Departure and Time to Breakdown, in agreement with torque stability during mixing (Fig. 1)  Branson (soft wheat) and TW301020 (hard wheat) exhibit different protein secondary structural changes during mixing  High dough stability of TW301020 could be related to the stable beta-sheets structures in comparison with Branson  Branson and TW301020 show differences in total thiols  TW301020 has lower total thiols than Branson, suggesting differences in protein interactions between the flours  Total thiols of TW301020 was stable during mixing accounting for high dough stability REFERENCES (1) Bock and Damodaran (2013). Bran-induced changes in water structure and gluten conformation in model gluten dough studied by Fourier transform infrared spectroscopy. Food Hydrocolloids, 31, 146-155 (2) Iametti et al. (2006). Properties of the protein and carbohydrate fractions in immature wheat kernels. Journal of Agricultural and Food Chemistry, 54, 10239-10244