Thursday Lecture – Hydrogels, Latexes, Resins

1. Thursday Lecture – Hydrogels, Latexes, Resins Reading: Textbook, Chapter 10

2. ASSIGNMENT • Find labels on food products that show each of the following types of ingredients. Tape or fasten them to a piece of paper, and highlight the ingredient from each category. • Vegetable oil • Exudate Gum • Extractive Gum • Starch • Pectin • Due: Tuesday 4/19

3. Hydrogels Water-modifying Substances  alter behavior of water Example = gravy, thickening by starch so water molecules can no longer move freely Figures 10.1, 10.2, p. 245

4. Hydrogels • Water-modifying Substances  alter behavior of water • Example = gravy, thickening by starch so water molecules can no longer move freely • Classes of Plant-Derived Hydrogels: • Gums Figures 10.1, 10.2, p. 245

5. Hydrogels • Water-modifying Substances  alter behavior of water • Example = gravy, thickening by starch so water molecules can no longer move freely • Classes of Plant-Derived Hydrogels: • Gums • Pectins Figures 10.1, 10.2, p. 245

6. Hydrogels • Water-modifying Substances  alter behavior of water • Example = gravy, thickening by starch so water molecules can no longer move freely • Classes of Plant-Derived Hydrogels: • Gums • Pectins • Starches • All are polymers of sugars (= polysaccharides) Figures 10.1, 10.2, p. 245

7. Gums Polysaccharides composed of sugars other than glucose: Arabinose, galactose, mannose, xylose Figure 10.2, p. 245

8. Gums • Polysaccharides composed of sugars other than glucose: • Arabinose, galactose, mannose, xylose • water-soluble, or can absorb water Figure 10.2, p. 245

9. Gums • Polysaccharides composed of sugars other than glucose: • Arabinose, galactose, mannose, xylose • water-soluble, or can absorb water • gum + water  gel Figure 10.2, p. 245

10. Gums • Polysaccharides composed of sugars other than glucose: • Arabinose, galactose, mannose, xylose • water-soluble, or can absorb water • gum + water  gel • - only partially digested by people, mostly no adverse effects Figure 10.2, p. 245

11. Uses of Gums • As foods: • “texturize” foods • emulsifiers – disperse fat and protein molecules evenly in water

12. Uses of Gums • As foods: • “texturize” foods • emulsifiers – disperse fat and protein molecules evenly in water • prevent formation of ice crystals • increase shelf life of products

13. Uses of Gums • As foods: • “texturize” foods • emulsifiers – disperse fat and protein molecules evenly in water • prevent formation of ice crystals • increase shelf life of products • In medicines: • used as a binder

14. Uses of Gums • As foods: • “texturize” foods • emulsifiers – disperse fat and protein molecules evenly in water • prevent formation of ice crystals • increase shelf life of products • In medicines: • used as a binder • laxatives

15. Uses of Gums • As foods: • “texturize” foods • emulsifiers – disperse fat and protein molecules evenly in water • prevent formation of ice crystals • increase shelf life of products • In medicines: • used as a binder • laxatives • Industrial: • sizing material – fills in pores in paper, textiles

16. Uses of Gums • As foods: • “texturize” foods • emulsifiers – disperse fat and protein molecules evenly in water • prevent formation of ice crystals • increase shelf life of products • In medicines: • used as a binder • laxatives • Industrial: • sizing material – fills in pores in paper, textiles • lubricants (especially in oil drilling operations)

17. Sources of Plant Gums - Exudates • Exudate Gums: plant is injured to initiate gum production • gum arabic, Acacia senegal * gum tragacanth, Astragalus Figs. 10.4, 10.5, 10.6, 10.7, p. 247-248

18. Sources of Plant Gums - Extractives Extractive gums – from endosperm or wood of Fabaceae species Figure 10.8, p. 249 Locust bean gum – Ceratonia siliqua, Carob; St. John’s Bread * Guar gum - Cyamopsis *

19. Xanthan Gum – Made by Bacterium, Xanthomonas campestris Fermentation Product – uses various starting materials, both plant and animal origin Polysaccharide – somewhat complex structure, useful physical properties Note – can be derived from wheat, so it can contain gluten  Should be avoided by those who are allergic to glutens

20. Figure 10.10, p. 251 Pectins Pectins – polysaccharide composed of units of pectic acid and its derivatives Different types of pectins – vary in # molecules + methylation Pectin-rich mesocarp

21. Figure 10.10, p. 251 Pectins Pectins – polysaccharide composed of units of pectic acid and its derivatives Different types of pectins – vary in # molecules + methylation Pectins – found in middle lamella of cell wall, epidermis Pectin-rich mesocarp

22. Figure 10.10, p. 251 Pectins Pectins – polysaccharide composed of units of pectic acid and its derivatives Different types of pectins – vary in # molecules + methylation Pectins – found in middle lamella of cell wall, epidermis Pectin-rich mesocarp Use of pectins – mostly in jellies and jams

23. Figure 10.10, p. 251 Pectins Pectins – polysaccharide composed of units of pectic acid and its derivatives Different types of pectins – vary in # molecules + methylation Pectins – found in middle lamella of cell wall, epidermis Pectin-rich mesocarp Use of pectins – mostly in jellies and jams Sources of pectins: Apple pomace (residue after pressing for juice) Citrus peels

24. Starches Figure 10.11, p. 252 Polymers of glucose Starch: alpha bonds between glucose molecules Cellulose: beta bonds between molecules of glucose

25. Starches Figure 10.11, p. 252 Polymers of glucose Starch: alpha bonds between glucose molecules Cellulose: beta bonds between molecules of glucose Uses: food products, sizing

26. Latex Latex = mixture of organic compounds produced in laticifers Laticifer = cells or groups of cells that form tubes, canals, or networks Latex may be inelastic or elastic Rubber – elastic latex composed of polymers Figs. 10.14, 10.15, p. 254

27. Rubber – Hevea brasiliensis Euphorbiaceae – known for milky latex (“milky sap”) – in laticifers Figs. 10.17, 10.18, 10.19, p. 255-256

28. Guayule – Parthenium argentatum * Asteraceae – southwestern U.S./Mexico developed as alternative source of natural rubber Figure 10.20, p. 257

29. Chicle – Manilkara zapota Figure 10.23, p. 259; Box 10.2, p. 258 New World - Sapotaceae

30. Plant Resins • Resins – compounds that are synthesized and secreted into specialized canals or ducts within the plant, in xylem, phloem, or bark • Chemically: resins are polymerized terpenes, usually + volatile oils • Uses of resins: • incense (frankincense and myrrh) Figure 10.24, p. 259

31. Plant Resins • Resins – compounds that are synthesized and secreted into specialized canals or ducts within the plant, in xylem, phloem, or bark • Chemically: resins are polymerized terpenes, usually + volatile oils • Uses of resins: • incense (frankincense and myrrh) • embalming Figure 10.25, p. 260

32. Plant Resins • Resins – compounds that are synthesized and secreted into specialized canals or ducts within the plant, in xylem, phloem, or bark • Chemically: resins are polymerized terpenes, usually + volatile oils • Uses of resins: • incense (frankincense and myrrh) • embalming • mastic * • lacquer • artist’s paints • naval stores (pines) Figure 10.26, p. 261

33. Plant Resins • Resins – compounds that are synthesized and secreted into specialized canals or ducts within the plant, in xylem, phloem, or bark • Chemically: resins are polymerized terpenes, usually + volatile oils • Uses of resins: • incense (frankincense and myrrh) • embalming • mastic * • lacquer • artist’s paints • naval stores (pines) • amber – jewel of plant origin Figure 10.27, p. 261

34. Student Presentations – Gums, Latex, Resin