CAN SORGHUM MEET THE BREAD NEEDS OF 21ST CENTURY CONSUMERS? John RN Taylor and Janet Taylor University of Pretoria, South Africa O NOT COPY

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1 CAN SORGHUM MEET THE BREAD NEEDS OF 21ST CENTURY CONSUMERS? John RN Taylor and Janet Taylor University of Pretoria, South Africa

2 Traditional Africa Rural Burkina Faso Making Porridge

3 Modern Africa Adomi Bridge, Ghana Making Money

4 Wheat imports (tons x 1000) Wheat imports Urban population Year GHANA Wheat imports and Urban population (FAOStat Data) Urban population (millions)

5 Wheat production and imports (tons x 1000) Year Wheat imports Urban population Wheat production NIGERIA Wheat imports/production and Urban population (FAOStat Data) Urban population (millions)

6 Wheat production and imports (tons x 1000) Urban population Wheat production Wheat imports Year SOUTH AFRICA Wheat imports/production and Urban population (FAOStat Data) Urban popluation (millions)

7 MAKING DOUGH WITH SORGHUM FLOUR DOUGHS Wheat Sorghum Sorghum (same water as wheat) (50% more water)

8 Wheat FERMENTED DOUGHS Sorghum

9 Artisan Wheat Bread

10 Commercial Sorghum Bread

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12 Commercial Gluten-free Bread

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14 Roles in breadmaking of the major polymers in wheat, sorghum and maize flours Endosperm component Non-starch polysaccharides Proteins Starch Wheat Arabinoxylans Gliadin and Glutenin Essentially linear Relatively large molecules S-S Cross-link end to end Relative hydrophilic Gelatinization temp. range o C Significance in breadmaking ++Ve Dough waterholding -Ve Disrupt gluten continuity ++++Ve Responsible for the cohesive, visco-elastic properties and gasholding properties of wheat bread dough ++Ve Contribute to flexibility and springiness of wheat bread +++ve Responsible for maintaining dough and bread cellular structure when gluten is denatured during baking Sorghum and Maize Glucurono-arabinoxylans More complex, substituted and cross-linked Sorghum- kafirin Maize- zein Tightly folded Relatively small molecules S-S Cross-link but not really known how Relatively hydrophobic Very inert Sorghum o C Maize o C Significance in breadmaking -Ve Presumably contribute to poor dough cohesiveness ----Ve Primarily responsible for poor dough cohesiveness, lack of dough visco-elasticity and poor gas-holding +++Ve Responsible for holding gas during dough/batter fermentation and maintaining dough/batter and bread cellular structure during baking --Ve During baking, yeast is killed before starch gelatinizes

15 IMPROVEMENT OF ARABINOXYLAN FUNCTIONALITY Endosperm cell walls in sorghum malt ICC Symposium 1976 Commercial pentosanase J. Cassier et al. Bread production from pure millet and sorghum flours by using cereal endosperm-cell wall-pentosan as a universal baking factor R. Bressani et al. Processing of sorghum by lime-cooking for the preparation of tortillas

16 IMPROVEMENT OF PROTEIN FUNCTIONALITY SEM of commercial zein-starch doughs made with dibutyl tartrate 1992 Wheat Dough Fibres

17 We have focussed on two ways to improve the dough functionality of maize zein and sorghum kafirin prolamin proteins 1. Chemical modification of the proteins 2. Genetic modification of the proteins

18 TRYING TO IMPROVE ZEIN DOUGH FUNCTIONALITY Effects of Hydrogen Peroxide and Peroxidase Oxidising Agents on Doughs Made from Commercial Zein Also form Disulphide Bonds between cysteine residues

19 Zein alone Zein +Starch Effects of Hydrogen Peroxide and Peroxidase on Extensibility of Doughs from Commercial Zein and Commercial Zein+starch Taylor J.R.N. et al J Cereal Sci 70:108

20 CLSM (Z Stack) of Commercial Zein Doughs - Effect of Preparation with Hydrogen Peroxide a. Water, b. Water dough stretched, c. Hydrogen peroxide, d. Hydrogen peroxide dough stretched

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22 Dough from Commercial Zein-Starch With Hydrogen Peroxide Treatment

23 Oxidation of proteins with hydrogen peroxide ---> Hydroxyl and Carbonyl groups added to hydrophobic amino acid residues: leucine, isoleucine, valine and alanine Proline oxidised to hydroxyproline and pyroglutamic acid Xu G. and Chance M.R Chem. Rev. 107, 3514

24 Commercial Zein-starch Doughs Prepared with Dilute Lactic Acid A = Zein + Starch flour in water after mixing B = Zein + Starch flour in 1.3% Lactic acid after mixing; C = Dough properties D = Alveograph dough bubble of Zein + Starch dough prepared in 1.3% Lactic acid Sly et al J Cereal Sci 60:157.

25 Maize flour+commercial Zein Dough Alveograph bubble Kuzwayo T et al. (unpublished)

26 Top Crumb Effect of Zein and Sourdough Fermentation on Maize Bread Quality Maize Maize + Maize Sourdough + Zein

27 Crumb Structure of Maize flour+commercial Zein Breads Zein fibre A. Maize Alone, B. Maize + Zein G. Maize + Maize Sourdough + Zein Maize flour particle Sourdough crumb Kuzwayo T et al. (unpublished)

28 ph3 kda IEF Commercial (α-zein) ph10 SDS-PAGE ph3 kda a) b) α-zein ) γ-zein ) α-zein ) β-zein) 2-D PAGE of Commercial Zein and Total Zein IEF Total zein TOTAL ZEIN IS A FAR MORE COMPLEX FORM OF ZEIN AND IS ACTUALLY THE TYPE OF ZEIN PRESENT IN MAIZE FLOUR ph10 SDS- PAGE

29 Making Doughs with Total Zein Commercial zein, dough made with 1.3% acetic acid Total zein and 1.3% acetic acid (No dough formed) Cast commercial zein bioplastic film using glacial acetic acid, Then dough made with water Cast Total zein bioplastic film using glacial acid, then dough made with water Cast Total zein bioplastic film using glacial acetic acid, rinsed, then dough made with water King B.L. et al J Cereal Sci 71

30 A C B D FORMATION OF DOUGHS ISOLATED KAFIRIN As with Total zein Kafirin will not form a dough when mixed with dilute acetic acid at elevated temperature Effects of mixing acetic acid (5.4%) with kafirin or zein preparations at 50 C. A= Commercial zein, B = Total Zein, C = Kafirin minus γ-, D= Kafirin

31 2D-PAGE of Transgenic HD γ-kafirin suppressed sorghum line and its Null (normal digestibility) control ph3 NC2 ph3 TG-HD-2 IEF IEF ph10 ph10 SDS-PAGE SDS-PAGE

32 PY O T C O WHAT WE WANTED WITH KAFIRIN O N SEM of Wheat Glutenin Fibres and Fibrils Orth, RA et al Cereal Chem. 50:688

33 KAFIRIN Viscoelastic Dough Fibres Produced by Patented Process of Coacervation with Water from a solution in Glacial Acetic Acid Elhassan MSM et al Food Chem.

34 NND NND WND WND 0.5 mm NHD WHD WHD WHD NC1 NC2 TGHD1 TGHD2 Stereomicroscopy of Kafirin Doughs From normal and high digestibility sorghum (expressing different combinations of the Kafirin subclasses) N = Normal endosperm, W = Waxy, ND = Normal digestibility, HD = High Digestibility, TG = Transgenic, NC = Its Null non-transgenic control

35 Force (N) Gluten WHD1 TG-HD Time (s) Stress-relaxation curves for kafirin visco-elastic doughs compared to wheat gluten

36 % Stress Recovery over Storage time of Coacervated Kafirin and Zein preparations compared to Gluten Taylor J. et al Food Chem Storage at 10 o C Day 0 Day 2 Day 16 Wheat gluten Kafirin High α-kafirin Kafirin minus-γ High α-kafirin minus -γ Total zein High α-zein Commercial zein (essentially α-zein)

37 PY C O O T D N C B O A WHY THE KAFIRIN AND ZEIN PREPARATIONS HAVE DIFFERING STRESS RECOVERIES? CLSM illustrating fibril formation of zein and kafirin preparations A= Commercial zein, B= Total zein C= Kafirin minus γ-, D= Kafirin Arrow shows laterally associated fibrils

38 High Protein Digestibiity (HD) line HD Coacervated a c pb pb TRYING TO FUNCTIONALISE THE KAFIRIN IN SORGHUM PROTEIN BODIES pb pb cw b d Effect of glacial acetic Coacervation treatment on isolated kafirin sorghum protein bodies cw pb (Magabane et al. unpublished) pb pb pb Normal Protein Digestibility (ND) Line ND Coacervated

39 CLSM of crumb of sorghum + potato starch bread Made with b) Chemical acidification c) Sourdough IMPROVEMENT OF STARCH FUNCTIONALITY SOURDOUGH FERMENTED SORGHUM BREAD SEC of Sorghum Sourdough Dough Liquid and Protein and Extracted with SDS a) Before fermentation, b) After fermentation Results suggest that a strong starch gel, without interference of aggregated protein, is desirable for this type of bread. From: Schober, T J et al J Agric Food Chem

40 Effects of Acidification and Sourdough Fermentation on Maize dough and Bread Falade AT et al. J Cereal Sci. 2014

41 Are most Cereal Scientists Ignoring the Obvious? Popular Breads don t have to be pan-type breads

42 The Custard (Batter) Breadmaking Process

43 SORGHUM DOUGH SHEETING AND INCLUSION OF PRE-GELATINIZED FLOUR a b c d a) No pre-gelatinized flour, (b) 10% pre-gelatinized flour, c) 20% pre-gelatinized flour, (d) 30% pre-gelatinized flour Magabane et al. (unpublished) Dough Development by Sheeting and its Application to Bread Production from Composite Flours W Bushuk and JH Hulse 1974 Cereal Science Today

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45 PCA of Descriptive Sensory Evaluation of Injera made from different sorghum types compared with Teff injera

46 CONCLUSIONS 1. Kafirin and Zein Prolamins do exhibit visco-elastic properties, But they may be too hydrophobic for them to be functional in sorghum and maize flour doughs 2. Sorghum/maize Arabinoxylan functionality can probably be substantially improved by Xylanases, but not to the extent the that they alone will enable the production of high quality pan-type breads 3. Sorghum/maize Starch dough/batter functionality can be substantially by: Pre-gelatinization, using High amylopectin lines and by Sourdough fermentation 4. By applying 2. and 3. sorghum flour should make high quality leavened flatbreads WE NEED TO RE-EDUCATE OURSELVES AND CONSUMERS AS TO WHAT IS BREAD

47 A HUGE THANK YOU TO AFRICA S NEXT GENERATION FOOD SCIENCE AND TECHNOLOGY LEADERS Abadi Mezgebe - Ethiopia Alex Sly South Africa Amir AwadElkareem - Sudan Bianca King South Africa Isaac Oguntoyinbo - Nigeria Itumeleng Magabane South Africa Joseph Anyango - Kenya Mohammed Elhassan - Sudan Senayit Yetneberk - Ethiopia Sharon Njila - Zimbabwe Thandiwe Khuzwayo South Africa Wura Falade - Nigeria