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

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. 1.Vegetable oil 2.Exudate Gum 3.Extractive Gum 4.Starch 5.Pectin Due: Tuesday 4/19

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

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: 1.Gums Figures 10.1, 10.2, p. 245

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: 1.Gums 2.Pectins Figures 10.1, 10.2, p. 245

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: 1.Gums 2.Pectins 3.Starches All are polymers of sugars (= polysaccharides) Figures 10.1, 10.2, p. 245

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

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

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

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

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

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

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

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

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

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)

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

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

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

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

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

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

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 , 10.15, p. 254

Rubber – Hevea brasiliensis Euphorbiaceae – known for milky latex (“milky sap”) – in laticifers Figs , 10.18, 10.19, p

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

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

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

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

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

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

Student Presentations – Gums, Latex, Resin