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Wheat protein

Wheat protein. Nieqing Feiyan Yangjin Guiling. Key points. Amino acid in wheat protein Fractions of wheat protein Dough formation Tiny knowledge concerning wheat protein.

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Wheat protein

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  1. Wheat protein Nieqing Feiyan Yangjin Guiling

  2. Key points • Amino acid in wheat protein • Fractions of wheat protein • Dough formation • Tiny knowledge concerning wheat protein

  3. AA content of wheat protein • Glu 33.0% (the first major AA ) • Pro 10.5% (the second major AA) • Trp 1.3% ( the least AA) • EAAs 33.3%(inclusive of Cys and Tyr)

  4. Amino acid scores • Amino acid score= the mass of Amino acid in 1g of a test protein the mass in the recommended pattern • Amino acid scores of wheat protein

  5. In general, Lys is the first limiting AA

  6. Some uses of the Amino acid • Cysteine The –SH in Cys is replaced by the band –S-S quickly that increases the plasticity、viscosity and elasticity of the pastry. • Glutamic acid The high content of Glu makes pastry delicious

  7. Fractions of wheat protein • The original fraction procedure divided proteins into four major groups on basis of solubility: water-soluble albumins, salt-soluble globulins, alcohol-soluble gliadins, and acid- or alkali-soluble glutelins.

  8. The content of each fraction 5% 10% 69% 16%

  9. Some properties of the water-soluble albumins and salt-soluble globulins • Content free –SH • High content of alkaline and some other electriferous AA • Molecular weight of albumins is very low . About 12000～26000. • Most globulins’ molecular weight is lower than 40 000.

  10. The alcohol-soluble gliadins and acid- or alkali-soluble glutelins • high content of Gln and Pro, but very low content of lysine and ionized AA. • Some amine acids which have element “S” in the structure are important to the molecular texture and the functions of the dough though the content of these AA is very low .

  11. The –S-S- in gliadins is intramolecular, which is the reason of the tight structure of gliadins. It contributes to the plasticity and tractility of the dough • The -S-S- in glutelins is intermolecular, and this state makes the molecule large and losen. And it contributes to the viscosity and elasticity of the dough

  12. Dough formation When mixing and kneading a mixture of wheat flour and water (about 3:1 ratio), several transformations occur. The major reactions • 2-SH -S-S- interchange • Hydrophobic interaction • Other protein-protein interactions

  13. 2-SH —— -S-S- interchange • Oxidizing agents（add to improve the quality) —azoticarbonamide（偶氮甲酰胺） bromate（溴酸盐）、and iodate（碘酸盐） —These agents promotes the formation of disulfide linkages • Reducing agents —cysteine、bisulfite、and gluthathione(谷光甘肽） —These agents promotes the breakage of disulfide.

  14. Gluten protein Clabber小麦面筋凝乳 • processing technics Gluten protein mixed with Ascorbic acid some salad oil refrigerated under 2℃ for 3h dealed with warm water (90℃)for 2h gluten protein clabber • What’s the function of Ascorbic acid here? -- Ascorbic acid acts like an oxidizing agent Because it is rapidly converted to dehydroascorbic acid by ascorbic acid oxidase

  15. hydrophobic interaction Effect?? The shear and tensile forces. Result?? —Gluten proteins absorb water and partially unfold. —The unfolding molecules facilitates hydrophobic interaction

  16. Good function but lack of nutrition • Good function Gluten, especially the gltutenins, are rich in proline, they have very little folded structure. Therefore, no additional unfolding occurs during baking. • Lake of nutrition In milling process , the nutritional components of the endosperm, such as native lipids high in glycolipids(糖脂) and other nutritional proteins are separated from the gluten proteins. Especially , it’s low in Lys and Thr. The lack of the nutrition have become a limitation . This problem is requiring us to settle !

  17. Wheat proteins improve the quality of ice cream • Ice-modifying proteins • Extracted from winter wheat • Function • Stay smooth • Stay creamy Discussion ??? →fat molecules, air bubbles and ice crystals assemble within a highly concentrated mixture of sugar water

  18. Opioid Peptides鸦片样活性肽 • Plants use different tactics to scare off attackers. • Some plants contain poison • Some just anaesthetize their attackers(wheat) • Wheat • Wheat contains opioid peptides →Priests in ancient Egypt used wheat to hallucinate, and in bandages, to ease the pain of a wound. • All wheat-products, like bread, pasta, pizza, cookies, cake and pastries contain opioid peptides.

  19. Opioid Peptides鸦片样活性肽 • we, and other animals, are sensitive to such substances as morphine (吗啡）. • But why? • Morphine is an opioid substance. • Our body and brain contain receptors for opioid peptides.

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