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carbs - Questions you may have pondered Food Carbohydrates...

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1 Food Carbohydrates FDST 4040/6040 2008 Questions you may have pondered…. z Why does bread stale? …. faster in the frig? z Why is bread crust brown? Why is juice brown? z How do you thicken gravy? z How do you make your own banana pudding? z How do you add flavor oils to beverages? z What are the common low cal sweeteners and why/how used? Aspartame, safety, seminar z “Beautiful Bowels” and fiber? Questions for next time z Why & how does orange juice brown? z What is honey considered to be a pre biotic? z What is difference between cane sugar and high fructose corn syrups as sweeteners? z What is difference between metabolism of cane sugar and high fructose corn syrups? Modified starches z What is the effect of acid on starch? What are the applications? z What is effect of alkali on starch? What are the applications? z Describe the formation of octenyl succinic anhydride. What are the applications? Overview z Terms and definitions z Structures z Reactions F ti lit z Functionality z Case studies, class exercises z Maillard Browning Reaction (Ana, Olamide) Some Terms z Aldoses – have an aldehyde group z Ketoses – have a ketone group z Pentoses – have five (pentane) carbons z Hexoses – have six (hexane) carbons z A polyhydroxy-aldehyde or polyhydroxy- ketone and derivatives (there are many).
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2 Properties in water z CHO are very soluble in water z Form many hydrogen bonds with water z Polar, interact as dipole-dipoles z E.g. sucrose: 179 g/ 100 mL water, 0 C 487g/ 100 mL water, 100 C Functional groups z Hydroxyls (alcohols) z Aldehydes/ ketones (carbonyls) z Amines (addition of amines to hydroxyls with loss of water) z Acids (oxidation of primary hydroxyls or aldehydes) z Phosphates (addition of phosphate to hydroxyls with loss of water – phosphoester) More functional group additions z Hydroxyls can be methylated – addition of methanol to a hydroxyl, loss of water, ether link Hydroxyls can be acetylated addition of z Hydroxyls can be acetylated – addition of acetic acid to a hydroxyl, loss of water, ester link z (decrease in water solubility) SIMPLE SUGARS Christen & Smith 2000 Christen & Smith 2000
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3 Christen & Smith 2000 Reducing sugars z Sugars that contain a free aldehyde or ketone group are reducing sugars Oxidation & Reduction z Aldehydes are easily oxidized to carboxylic acids z Which reduce something else z Thus, these sugars are called reducing sugars z Oxidation of Cu2+ or Ag+ is basis of many sugar assays and some enzyme assays Reactions of sugars - oxidation z Complete oxidation of sugars to CO2 and H2O z Aldehyde oxidized to carboxyl (with Br2 + H2O); D glucose to D gluconic acid an H2O); D-glucose to D-gluconic acid, an aldonic acid, calcium source z Oxidize primary alcohol to carboxyl group to form uronic acid Oxidation of CHO γ -Gluconolactone D-Gluconic acid δ -Gluconolactone Food chem Christen & Smith 2000
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4 Reduction of sugars - z Reduction of carbonyl to polyol to make sugar alcohols z Polyols are sweet, used as humectant (control Aw) diuretic sugar substitute (control Aw), diuretic, sugar substitute Reduction
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