Thiamin 6 pp - Thiamin: History Thiamin Spring 2011...

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Thiamin Spring 2011 Thiamin: History • Japanese naval surgeon first observed association of diet and beriberi – officers who consumed protein-rich diets healthy compared to lower ranked men with beriberi who consumed rice – Changed diet of lower ranked men to include more protein, switched rice to wheat flour or barley • Beriberi no longer a problem Thiamin: History • Dr. Eijkman Dutch medical researcher working in Indonesia during late 1800’s • Fed chickens the same white rice consumed by humans who developed beriberi – rapid development of a polyneuritis • Chickens fed “brown rice” healthy Thiamin: History • Grijns, Funk, and Williams worked to purify compound in rice “polishings” that was curative factor for beriberi • Funk first used term “vitamine” • Thiamin referred to as vitamine B1 • 1930s chemical structure identified Thiamin: Chemical Structure Essential features are linked pyrimidine and thiazole rings, hydroxyethyl side chain position 5 of thiazole ring which becomes phosphorylated in the cell and unsubstituted carbon at position 2 of thiazole ring Thiamin: Food Sources Pork muscle (0.78 mg/100 g) Beef muscle (0.13 mg/100 g) Baker’s Yeast (2 33 mg/100 g Baker’s Yeast (2.33 mg/100 g) Peanuts Uncooked (1.14 mg/100 g Peanuts Cooked (0.18 mg/100 g) Fortified cornflakes (1.2 mg/100g) Enriched rice (0.41 mg/100 g)
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Form of Thiamin in Food •Majority of thiamin in food in phosphorylated form except fortified foods •Mandatory fortification of “enriched” cereal grain products in US Stability of Thiamin in Food •Alkaline pH such as use of bicarbonate during cooking to preserve the green color increases thiamin destruction •Unstable to heat and oxygen •Cooking in large volumes of liquid – leaches into liquid –often discarded •Use of sulfite to preserve food can result in major chemical breakdown –splits methylene bridge Antithiamine Compounds in Food •Thiaminases are thiamine-splitting enzymes in raw fish and ferns –Can destroy thiamine during food storage, during its preparation, and in the G.I. tract –Inactivated by cooking •Polyphenolic compounds such as tannic acid, cholorogenic acid, and caffeic acid in –Coffee, tea, betel nuts, ferns –Heat stable Antithiamin Factors Cleave Thiamin Molecule Thiamin: Absorption • Thiamin phosphate in food converted to free thiamin by phosphatases • Both free thiamin and thiamin monophosphatecan be actively absorbed • Low intake: saturable active transport – Competitively inhibited by thiamin analogs • Large dose: passive diffusion Thiamin Transport • Once inside intestinal cell thiamine is largely phosphorylated
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This note was uploaded on 12/09/2011 for the course HUN 4445 taught by Professor Sitren during the Spring '08 term at University of Florida.

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Thiamin 6 pp - Thiamin: History Thiamin Spring 2011...

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