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Unformatted text preview: Pass the sugar….. Understand the following methods of CHO analysis
Extraction of oligosaccharide & polysaccharides Chemical methods: total CHO & reducing sugars Enzymatic methods: glucose & total starch Gravimetric method: total dietary fibers Chromatographic methods: HPLC & GC Carbohydrates account for 70% energy in human diet. About 52%come from starch and 18% from sugars. Carbohydrates that cannot be digested or absorbed are dietary fibers. Dietary fibers promote better health Bowl movement and gut health Provide satiety Sweeteners During in foods – sucrose, honey, and high fructose corn syrup cooking, react with protein to generate color, flavor, aroma (Millard reaction) Give soft gel, viscosity, and other properties to foods CHO Content of Some Foods CHO
Milk, 4.8% Egg, 0.7% Honey, 82% French fry, 24.8% Wheat bread, 47.5% Beef, 0% The “Saccharides” Monosaccharide
◦ Smallest form, non-hydrolysable.
Oligosaccharide ◦ Made of several monosaccharides, hydrolysable.
Polysaccharide ◦ Very large polymers of monosaccharides Simple Sugars: glucose, fructose, galactose Soluble in water, not in chloroform or hexane Can bend light (refractive index) Glucose has two Geometric isomers “α – D – Glucose” “β – D – Glucose” Often made of 2-4 simple sugars, but can be as large as 20 units long. They are still considered relatively low MW compounds, and will yield monosaccharides upon hydrolysis. Examples: sucrose, lactose, maltose, maltotriose, stachyose, raffinose REDUCING sugars Glucose Fructose Galactose NON-REDUCING Sucrose Raffinose Trehalose Act as Reducing Agents (electron donators) Reduces Cu2+ to Cu+ in alkali media. Large molecular weight molecules food polysaccharides Important ◦ Starch (amylose, amylopectin) ◦ Fiber (cellulose, hemicellulose, lignin) ◦ Pectin (galacturonic acid polymers) ◦ Gums (natural and synthetic hydrocolloids) ◦ Alginate (marine algae) ◦ Chitin (crabs, lobsters and shrimps) CFR 101.12(a) - Nutritional labeling
TOTAL CARBOHYDRATES is a difference calculated as: Total carbohydrate =
Total weight of food – crude protein – total fat – moisture – ash If you want to make a nutritional claim about sugars, starch, or fiber, they have to be analyzed Mono, oligo, polysaccharides Hot 80% ethanol (CaCO3)
Optional CaCO3 to control neutral pH In solution In sediment Polysaccharides Mono, oligosaccharides Weak anion exchange resin
Remove impurities with negative charges Purified Mono, oligosaccharides Extract CHO based on solubility. Most Most monos and oligos are highly soluble in Hot EtOH. polysaccharides are not soluble in hot EtOH. Hot EtOH will extract monos and oligos. Polysaccharides will be in the sediment Therefore, Pigment removal - variety of ways to remove e.g., charcoal, lead salts, organic solvent extraction. Protein removal - proteins interfere sugar determination. Sugars are neutral molecule. What is the best way to remove proteins? Use Ion exchange resins to remove proteins or other compounds with different charge An Anion Exchange Resin will absorb and remove proteins with negative charges A Cation Exchange Resin will absorb and remove proteins with positive charges Acids Don’t result in hydrolysis of some sugars want any changes to the sugar during analysis ie. glucose and fructose suddenly appearing in your sample neutralizes acid and maintain a pH
3 + 2+ 2 2 CaCO3 5.5-6.5 CaCO + 2H = Ca + H O + CO ↑ Sugars+pectins+cellulose Hot Water (80oC, pH 2-3)*
In solution In sediment cellulose Sugars+pectins Hot ethanol 80%
In solution In sediment Pectins Sugars * Acidified hot water causes partial hydrolysis of pectins and facility extraction Your job is to extract carbohydrates from freeze-dried oranges (a dry powder). The orange juice powder contains glucose, fructose, sucrose, pectins, and cellulose. (the rest glucose fructose sucrose pectins and cellulose (the of the powder is composed of small amounts of protein, fat, and minerals) and List ALL of the carbohydrates that may be extracted in: Water (80° C, pH 2.5). 80% Ethanol (60° C). 100% Chloroform (70° C). ...
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- Fall '09