title: Aqueous ethanol extraction of dietary soy protein isolate improves 59Fe absorption by the rat from a casein-based test meal.
abstract: A commercial soy protein isolate (SPI) was further processed in an attempt to understand how a diet based on SPI can cause decreased iron retention by the rat from a separately administered casein-based test meal. Groups of eight rats were fed either a casein-based diet or a diet based on SPI. The acid-precipitated SPI was incorporated into diets as such, after neutralization, after 60% (v/v) ethanol extraction and neutralization, or after 60% ethanol exposure and neutralization. All dietary SPI was heat-treated by exposure to steam at 108 degrees C for 30 min. Rats were fed their respective diets, each containing 25 mg Fe/kg, for 13 d, and then all rats were fed a 59Fe-radiolabeled 2.5-g casein test meal containing 64 micrograms of iron. Ingested radioactivity was determined following the meal, and retained radioactivity over the subsequent 10-d period. Absorption was not distinguishable for groups fed the casein-based (78.3 +/- 3.6%) and the ethanol-extracted, SPI-based diet (80.2 +/- 5.4%). Absorption was lower (P less than 0.01) for groups fed each of the other SPI-based diets: SPI as such (68.3 +/- 8.9%), neutralized SPI (69.8 +/- 5.0%) and ethanol-exposed SPI (67.6 +/- 4.8%). An ethanol-extractable component of SPI may be responsible for decreased iron absorption by animals fed SPI prior to a radiolabeled test meal.
authors.affiliation: Department of Food Science, Penn State University, University Park 16802.
authors.forename: D B
authors.initials: DB
authors.lastname: Thompson
mesh_terms: D000042:Absorption; D000818:Animals; D001835:Body Weight; D002364:Caseins / Q000008:administration & dosage; D000431:Ethanol; D005511:Food Handling; D006454:Hemoglobins / Q000378:metabolism; D007501:Iron / Q000493:pharmacokinetics*; D007504:Iron Radioisotopes; D008297:Male; D014674:Plant Proteins, Dietary / Q000302:isolation & purification / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D030262:Soybean Proteins
chemical_list: D002364:Caseins; D006454:Hemoglobins; D007504:Iron Radioisotopes; D014674:Plant Proteins, Dietary; D030262:Soybean Proteins; D000431:Ethanol; D007501:Iron