1,214
Views
1
CrossRef citations to date
0
Altmetric
Review Article

Folates - food sources, analyses, retention and bioavailability

(Dr) , (MSc) , (MSc) & (Prof)
Pages 138-146 | Published online: 13 Dec 2016

  • Engbersen AM, Franken DG, Boers GHJ, Stevens EMB,Trijbels FJM, Blom HJ: Thermo-labile 5,10-methylenetetrahydrofolate reducta-se as a cause of mild hypercysteinemia. Am J Hum Genet 1995; 56: 142–50.
  • Selhub J, Jacques PF, Bostom AG, D'Agostino RB, Wilson PWF, Belanger AJ, O'Leary DH, Wolf PA, Rush D, Schaefer EJ, Rosenberg IH: Relationship between plasma homocysteine, vitamin status and extracranial carotid-artery stenosis in the Framingham study population. J Nutr 1996; 126: 1258S-1265S.
  • Schorah CJ, Habibzadeh N, Wild J, Smithells RW, Seller MJ: Possible abnormalities of folate and vitamin Bwith, metabolism associated wi neural tube defects. Maternal Nutr and Pregnancy Outcome 1993; 678: 81–91.
  • van der Put NMJ, Steegers-Theunissen RPM, Frosst P, Trijbels FJM, Eskes TKAB, van den Heuvel LP, Mariman ECM, den Heyer M, Rozen R, Blom HJ: Mutated methylenetetra-hydrofolate reductase as a risk factor for spina bifida. Lancet 1995; 346: 1070–1.
  • Giovannucci E, Stampfer MJ, Colditz GA, Rimna EB, Trichopoulos D, Rosner BA, Speizer FE, Willett W: Folate, methionine, and alcohol intake and risk of colorectal adenoma. J Nat Cancer Inst 1993; 85: 875–84.
  • Kihlberg R: Om homocystein och folsyra. Scand J Nutr 1998; 42: 89–90.
  • Sandström B, Aro A, Becker,W, Lyhne N, Pedersen, J, Torsdottir, I: Nordiska Näringsre-kommendationer 1996. Nordiska Minister-râclet. Report. Nord 1996; 28: 129–33.
  • Yates AA, Schlicker SA, Suitor CW: Dietary reference intakes: the new basis for recom-mendations for calcium and related nutrients, B vitamins, and choline. J Am Diet Assoc 1998; 98: 699–702.
  • Gregory III JF: Bioavailability of folate. Eur I Clin Nutr 1997; 51: S54–S59.
  • Ball GFM: Folate. In: Bioavailability and ana-lysis of vitamins in foods. Chapman & Hall, London 1998; 439-96.
  • Eitenmiller RR, Landen WO: Folate. In: Eiten-miller RR, Landen WO, eds. Vitamin Analysis for the Health and Food Sciences, CRC Press, Bocca Raton, London, N. Y., Washington 1999; 411-66.
  • Gregory III JF: Chemical and nutritional as-pects of folate research: analytical procedures, methods of folate synthesis, stability, andbioavailability of dietary folates. Adv Food Nutr Res 1989; 33: 1–101.
  • Hawkes JG, Villota R: Folates in foods: reac-tivity, stability during processing, and nutritional implications. Food Sci Nutr 1989; 28: 439–538.
  • Blakley L: IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN): Nomen-clature and symbols for folic acid and related compounds, Recommendations 1986. J Biol Chem 1988; 263: 605-7.
  • Vahteristo L: Folates and their analysis: Deter-mination of folate derivatives and their stability by high-performance liquid chromatography. Dissertation, University of Helsinki 1998.
  • Parodi PW: Cow's milk folate binding protein: Its role in folate nutrition. The Australian J Dairy Technol 1997; 57: 109–18.
  • Wigertz K: Milk folates. Characterisation and availability. Dissertation, Univ of Lund 1997.
  • Department of Health, Scottish Office Home and Health Department, Welsh Office, Depart-ment of Health and Social Services, Northern Ireland: Folic acid and the prevention of neural tube defects. Health Publications Unit, Hey-wood Lancashire, Great Britain 1992.
  • Tamura T: Microbiological assay of folates. In: Picciano MF, Stockstad ELR, Gregory III, JF, eds. Folic Acid Metabolism in Health and Disease, Wiley-Liss, New York 1990; 121-37.
  • Gutcho S: Source of error in determination of erythrocyte folate by competitive binding radio-assay - comments. Clin Chem 1978; 24: 388–9.
  • Givas JK, Gutcho S: pH-dependence of the binding of folates to milk binder in radioassay of folates. Clin Chem 1975; 21: 427–8.
  • van den Berg H, Finglas PM, Bates C: FLAIR Intercomparisons on serum and red cell folate. Internat J Vit Nutr Res 1994; 64: 288–93.
  • Chen MF, Hill JW, McIntyre PA: The folacin contents of food as measured by a radiometric microbiologic method. J Nutr 1983; 113: 2192–6.
  • DeSouza S. Eitenmiller R: Effects of different enzyme treatments on extraction of total folate from various foods prior to microbiological assay and radioassay. J of Micronutrient Analy-sis 1990; 7: 37–57.
  • Finglas PM, Faure U, Southgate DAT: First BCR-intercomparison on the determination of folates in food. Food Chem 1993; 46: 199–213.
  • Gregory Ill JF, Day BPF, Ristow KA: Comparison of high performance liquid chro-matographic, radiometric and Lactobacillus casei methods for the determination of folacin in selected foods. J Food Sci 1982; 47 (5): 1568–71.
  • Klein BP, Kuo CHY: Comparison of micro-biological and radiometric assay for deter-mining total folacin in spinach. J Food Sci 1981; 46: 552–4.
  • Lumley I: A preliminary report on the second BCR intercomparison of methods for the determination of folates in food. Laboratory of the Government Chemist (internal report), Teddington, UK 1993.
  • Osterdahl BG, Johansson E: Comparison of radiometric and microbiological assay for the determination of folate in fortified gruel and porridge. Internat J Vit Nutr Res 1989; 59: 147–50.
  • Shane B, Tamura T, Stokstad ELR: Folate assay: a comparison of radioassay and micro-biological methods. Clin Chim Acta 1980; 100: 13–9.
  • Lawrance P: Individual folates in foodstuffs. MAFF Project 2B033, Report no. AS20/96/88. Laboratory of the Government Chemist, UK 1996.
  • Muller H: Neubestinunung und Bewertung der Folsäuregehalte von ausgewählten Lebens-mitteln pflanzlicher und tierischer Herkunft. Ern-Umschau 1995; 42: 170–4.
  • Pfeiffer CM, Rogers LM, Gregory III JF: Deter-mination of folate in cereal-grain food products using trienzyme extraction and combined affinity and reversed-phase liquid chromato-graphy. J Agric Food Chem 1997; 45: 407–13.
  • Vahteristo LT, Oilainen V, Varo P: HPLC determination of folate in liver and liver pro-ducts. J Food Sci 1996; 61: 524–6.
  • Vahteristo LT, Oilainen V, Varo P: Liquid chromatographic determination of folate mono-glutamates in fish, meat, egg, and dairyproducts consumed in Finland. J AOAC Internat 1997; 80: 373–8.
  • Vahteristo L, Lehikoinen K, Oilainen V, Varo P: Application of an HPLC assay for the deter-mination of folate derivatives in some vege-tables, fruits and berries consumed in Finland. Food Chem 1997; 59: 589–97.
  • Gregory III JF: Determination of folacin in foods and other biological materials. J AOAC 1984; 67: 1015–9.
  • Muffler H: Bestimmung der Folsäure-Gehalte von Gemiise und Obst mit Hilfe der Hoch-leistungsflüssigkeitschromatographie (HPLC). Z Lebensm Unters Forsch 1993; 196: 137–41.
  • White DR: Determination of 5-methyltetra-hydrofolate in citrus juice by reversed phase high-performance liquid chromatography with electrochemical detection. J Agric Food Chem 1990; 38: 1515–8.
  • Vahteristo L, Oilainen V, Koivistoinen PE, Varo P: Improvements in the analysis of reduced folate monoglutamates and folic acid in food by high-performance liquid chromato-graphy. J Agric Food Chem 1996; 44: 477–82.
  • Wigertz K, Jägerstad M: Comparison of a HPLC and radioprotein-binding assay for the determination of folates in milk and blood samples. Food Chem 1995; 54: 429–36.
  • Witthoft C, Bitsch I: HPLC methods to analyse folate pattern in food and in human plasma as a precondition to evaluate availability of food folates by biokinetic methods. In: Schlemmer U, ed. Proceedings of Bioavailability '93, Part 2, Bundesforschungsanstalt fiir Ernährung, Karlsruhe, Germany 1993; 431-5.
  • Uyeda K, Rabinowitz JC: Flourescence proper-ties of tetrahydrofolate and related compounds. Anal Biochem 1963; 6: 100–8.
  • Wilson SD, Horne DW: Evaluation of ascorbic acid in protecting labile folic acid derivatives. Proc Natl Acad Sci USA 1983; 80: 6500–4.
  • Bitsch I, Hammes B, Schulz A: Thermische Zersetzung der Tetrahydrofolsäure und ihre Sta-bilisierung durch SauerstoffausschluB. Lebens-mittelchem Gerichtl Chem 1988; 42: 56–7.
  • Chen T-S, Cooper RG: Thermal destruction of folacin: effects of ascorbic acid, oxygen and temperature. J Food Sci 1979; 44: 713–6.
  • Day BPF, Gregory III JF: Thermal stability of folic acid and 5-methyltetrahydrofolic acid in liquid model food systems. J Food Sci 1983; 48: 581-7,599.
  • O'Broin JD, Temperley Ii, Brown JP, Scott JM: Nutritional stability of various naturally occur-ring monoglutamate derivatives of folic acid. Am J Clin Nutr 1975; 28: 438–44.
  • Schulz A, Wiedemann K, Bitsch 1: Stabilisation of 5-methyltetrahydrofolic acid and subsequent analysis by reversed phase high-performance liquid chromatography. J Chromatogr 1985; 328: 417–21.
  • Lankelma J, van der Kleijn E, Jansen MJT: Determination of 5-methyltetrahydrofolic acid in plasma and spinal fluid by high-performance liquid chromatography, using on-column con-centration and electrochemical detection. J Chromatogr 1980; 182: 35–45.
  • GonneIle J-C, Ladjimi H, Prognon P: A rapid and specific extraction procedure for folate determination in rat liver and analysis by high-performance liquid chromatography with fluorimetric detection. Anal Biochem 1989; 176: 406–11.
  • Pedersen JC: Comparison of y-glutamyl hydro-lase (conjugase; EC 3.4.22.12) and amylase treatment procedures in the microbiological assay for food folates. Br J Nutr 1988; 59: 261-71.
  • Bell JG: Microbiological assay of vitamins of the B group in foodstuffs. Lab Pract 1974; 23: 235-42,252.
  • Lakshmaiah N, Ramasastri BV: Folic acid con-jugase from plasma, part II: studies on the source of enzyme in blood. Int J Vit Nutr Res 1975; 45: 194–200.
  • Lakshmaiah N, Ramasastri BV: Folic acid con-jugase from plasma, part III: use of the enzyme in the estimation of folate activity in foods. Int J Vit Nutr Res 1975; 45: 262–72.
  • Halsted CH: Jejunal brush-border folate hydro-lase - a novel enzyme. West J Med 1991: 155:605–9.
  • Horne DW, Krumdieck CL, Wagner C: Pro-perties of folic acid y-glutamyl hydrolase (con-jugase) in rat bile and plasma. J Nutr 1981; 111: 442–9.
  • Silink M, Reddel R, Bethel M, Rowe PB: y-glutamyl hydrolase (conjugase); purification and properties of the bovine hepatic enzyme. J Biol Chem 1975; 250: 5982–94.
  • Engelhardt R. Gregory III JF: Adequacy of enzymatic deconjugation in quantification of folates in foods. JAgr Food Chem 1990; 38: 154–8.
  • Cerna J, Kas J: Folacin in cereals and cereal products. In: Holas J, Kratochvril J, eds. Pro-gress in Cereal Chemistry and Technology. Proceedings of the VlIth World Cereal and Bread Congress 1882, Part A. Prague, Czecho-slovakia. Elsevier, New York 1983: 501-5.
  • Martin JI, Landen WO, Soliman A-GM, Eiten-miller RR: Application of a tri-enzyme extraction for total folate determination in foods. J Assoc Off Anal Chem 1990; 73: 805–8.
  • Tamura T, Mizuno Y, Johnston KE, Jacob RA: Food folate assay with protease, a-amylase, and folate conjugase treatments. J Agric. Food Chem 1997; 45: 135–9.
  • Rebello T: Trace enrichment of biological fola-tes on solid phase absorption cartridges and analysis by HPLC. Anal Biochem 1987; 166: 55–64.
  • Witthat, C: Entwicklung von HPLC-Methoden zur Folatbestimmung in biologischem Material. Validierung und Methodenvergleich im Rahm-en der Europäischen Gemeinschaftsforschung. Dissertation, University of Giessen 1998.
  • Selhub J, Ahrnad O, Rosenberg IH: Preparation and use of affinity columns with bovine milk folate-binding protein (FBP) covalently linked to sepharose 4B. In: McCormick DB, Wright LD, eds. Methods in Enzymology (Vol. 66), Academic Press, New York 1980; 686-90.
  • Seyoum E, Selhub J: Combined affinity and ion pair chromatographies for the analysis of food folate. J Nutr Biochem 1993; 4: 488–94.
  • Konings EJM: A validated liquid chromatogra-phic method for determining folates in vege-tables, milk powder, liver and flour. JAOAC 1999; 82: 119–27.
  • Finglas PM, van den Berg H, de Froidmont-Görtz I: Improvements in the determination of vitamins in foods: method intercomparison studies and preparation of certified reference materials (CRMs). Food Chem 1996; 57: 91–4.
  • Vahteristo L, Finglas PM, Witthöft C, Wigertz K, Seale R, de Froidmont-Görtz I. Third EU MAT intercomparison study on food folate analysis using HPLC procedures. Food Chem 1996; 57: 109–11.
  • Finglas PM, Wigertz K, Vahteristo L, Witthöft CM, Southon S, de Froidmont-Görtz I: Standar-disation of HPLC techniques for the determina-tion of naturally-occuring folates in food. Food Chem 1998; 64: 245–55.
  • Wigertz K, Hansen SI, Hiner-Madsen M, Holm J, Jägerstad M: Effect of milk processing on the concentration of folate-binding protein (FBP), the folate-binding capacity and the retention of 5-methyltetrahydrofolate. lot J Food Sci Nutr 1996; 47: 315–22.
  • Halcansson B, Jägerstad M, Oste R, Akesson B, Jonsson L: The effect of various thermal pro-cesses on protein quality, vitamins and selenium content in whole-grain wheat and white flour. J Cereal Sci 1987; 6: 269–82.
  • Lucock MD, Priestnall M, Daskalakis I, Schorah CJ, Wild J, Levene MI. Non-enzymatic degradation and salvage of dietary folate: phy-sicochemical factors likely to influence bioa-vailability. Biochem Mol Med 1995; 55: 43–53.
  • Malin JD: Total folate activity in Brussels sprouts: the effects of storage, processing, cooking and ascorbic acid content. J Food Technol 1977; 12: 623–32.
  • Ristow KA, Gregory III JF, Damron BL: Effects of dietary fiber on the bioavailability of folic acid monoglutamate. J Nutr 1982; 112: 750–8.
  • VLAG (Advanced Studies in Food Technology, Agrobiotechnology, Nutrition and Health Sciences): Bioavailability '97. Book of Abs-tracts, 25.-28. May 1997. Wageningen, TheNetherlands, 1997.
  • Schlemmer U ed: Proceedings of Bioa-vailability '93. Part 1, 2, 9.-12. May, Ettlingen, Schriftenreihe der Bundesforschungsanstalt fiir Ernährung, Karlsruhe, Germany, 1993.
  • Halsted CH: Intestinal absorption of dietary folates. In: Picciano MF, Stockstad REL, Gregory Ell JF, eds. Folic Acid Metabolism in Health and Disease, Wiley-Liss, N.Y. 1990: 23-45.
  • Reisenauer AM, Krumdieck CL, Halsted CH: Folate conjugase: two separate activities in human jejunum. Science 1977; 198: 196–7.
  • Selhub J, Powell GM, Rosenberg IH: Intestinal transport of 5-methyltetrahydrofolate. Am J Physiol 1984; 246: G515–20.
  • Abad AR, Gregory III JF: Determination of folate bioavailability with a rat bioassay. J Nutr 1987; 117: 866–73.
  • Keagy PM, Oace SM: Rat bioassay of wheat bran folate and effects of intestinal bacteria. J Nutr 1989; 119: 1932–9,
  • Anonymus: Interspecies differences in folate metabolism. Nutr Rev 1992; 50: 116–8.
  • Natsuhori M, Shimoda M, Kokue B-I, Hayama T, Takahashi Y: Tetrahydrofolic acid as the principal congener of plasma folates in pigs. Am J Physiol 1991; 261: R82–6.
  • Ristow KA, Gregory III JF, Damron BL: Thermal processing effects on folacin bio-availability in liquid model systems, liver and cabbage. J Agric Food Chem 1982; 30: 801–6.
  • Editorial: Long-term effects of ethanol consumption on folate status of monkeys. Nutr Rev 1983; 41: 227–8.
  • Keagy PM: Animal assays for folate bioavaila-bility: a critical evaluation. In: Picciano MF, Stockstad ELR, Gregory III JF, eds. Folic Acid Metabolism in Health and Disease, Wiley-Liss, New York 1990; 139-50.
  • Clifford AJ, Jones AD, Bills ND: Bioavai-lability of folates in selected foods incorporated into amino acid-based diets fed to rats. J Nutr 1990; 120: 1640–7.
  • Clifford, AJ, Heid MK, Peerson JM, Bills ND: Bioavailability of food folates and evaluation of matrix effect with bioassay. J Nutr 1991; 121: 445–53.
  • Jägerstad M, Lindstrand K, Westesson, A-K: Hydrolysis of conjugated folic acid by pancreatic conjugase. Scand J Gastroenterol 1972; 7: 593–7.
  • Bhandari SD, Gregory III JF: Inhibition by selected food components of human and porcine intestinal pteroylpolyglutamate hydro-lase activity. Am J Clin Nutr 1990; 51: 87–94.
  • Chandler CJ, Wang TIT, Halsted CH: Pteroyl-polyglutamate hydrolase from human jejunal brush borders. J Biol Chem 1986; 261: 928–33.
  • Cuskelly GJ, McNulty H, Scott JM: Effect of increasing dietary folate on red-cell folate: implications for prevention of neural tube defects. Lancet 1996; 347: 657–9.
  • Sauberlich HE, Kretsch MJ, Skala .111, Johnson HL, Taylor PC: Folate requirements and meta-bolism in nonpregnant women. Am J Clin Nutr 1987; 46: 1016-28.
  • von der Porten A, Gregory III JF, Toth JP, Cerda JJ, Curry SH, Bailey LB: In vivo folate kinetics during chronic supplementation of human sub-jects with deuterium-labeled folic acid. J Nutr 1992; 122: 1293–9.
  • Hages M, Pietrzik K: Untersuchung zur Bioverfiigbarkeit der Folsdure aus unterschied-lichen Dosierungen. Em-Umschau 1987; 34: 298–302.
  • Loew D, Eberhardt A, Heseker H, Kijbler W: Zur Plasmakinetik und Elimination der Fol-säure. Klin Wochenschr 1987; 65: 520–4.
  • Prinz-Langenohl R, Bronstnip A, Thorartd B, Hages M, Pietrzik K: Availability of food folates in humans. J Nutr 1999; 129: 913–6.
  • Bailey LB, Barton LE, Hiller SE, Cerda JJ: Bioavailability of mono- and polyglutamyl-folate in human subjects. Nutr Rep Internat 1988; 38: 509–18.
  • Brown JP, Scott JM, Foster FG, Weir DG: Inges-tion and absorption of naturally occurring pteroylmonoglutamates (folates) in man. Gastroenterol 1973; 64: 223–33.
  • Dencker H, Jägerstad M. Westesson A-K: Portal and peripheral plasma folates after ingestion of folic acid. Acta Hepato-Gastroenterol 1976; 23: 140–3.
  • Keagy PM, Shane B, Oace SM: Folate bio-availability in humans: effects of wheat bran and beans. Am J Clin Nutr 1988; 47: 80–8.
  • Kirwan JR, Narebor EM: Absorption of large oral doses of 5-formyltetrahydrofolic acid in man. Br J Cancer 1976; 34: 671–3.
  • Perry J, Chanarin I: Intestinal absorption of reduced folate compounds in man. Brit J Haematol 1970; 18: 329–39.
  • Etienne M-C, Speziale N, Milano G: HPLC of folinic acid diastereomers and 5-methyltetra-hydrofolate in plasma. Clin Chem 1993; 39: 82–6.
  • Kelly P, McPartlin J, Goggins M, Weir DG, Scott JM: Unmetabolized folic acid in serum: acute studies in subjects consuming fortified food and supplements. Am J Clin Nutr 1997; 65: 1790–5.
  • Schilsky RL, Choi KE, Vokes EE, Guaspari A, Guarnieri C, Whaling S, Liebner MA: Clinical pharmacology of stereoisomers of leucovorin during repeated oral dosing. Cancer 1989; 63: 1018–21.
  • Pfeiffer CM, Rogers LM, Bailey LB, Gregory III JF: Absorption of folate from fortified cereal-grain products and of supplemental folate consumed with or without food determi-ned by using a dual-label stable-isotope proto-col. Am J Clin Nutr 1997; 66: 1388–97.
  • Tamura T, Stockstad ELR: The availability of food folate in man. Br J Haematol 1973; 25: 513–32.
  • Gregory III JF, Toth JP: Stable-isotopic methods for in vivo investigation of folate absorption and metabolism. In: Picciano MF, Stockstad ELR, Gregory JF, eds. Folic Acid Metabolism in Health and Disease, Wiley-Liss, New York 1990; 151-69.
  • Stites TE, Bailey LB, Scott KC, Toth JP, Fisher WP, Gregory III JF: Kinetic modeling of folate metabolism through use of chronic admi-nistration of deuterium-labeled folic acid in men. Am J Clin Nutr 1997; 65: 53–60.
  • Bates CJ, Heseker H: Human bioavailability of vitamins. Nutr Res Rev 1994; 7: 93–127.
  • Said HM, Horne D, Wagner D: Absorption of dietary (milk) folate. Gastroenterology 1986; Abstract no. 1612.
  • Tani M, Iwai K: Some nutritional effects of folate-binding protein in bovine milk on the bioavailability of folates to rats. J Nutr 1984; 114: 778–85.
  • Tani M, Fushiki T, Iwai K: Influence of folate-binding protein from bovine milk on the absorp-tion of folate in the gastro-intestinal tract of rats. Biochim Biophys Acta 1983; 757: 274–81.
  • Swiatlo N, O'Connor DL, Andrews J, Picciano MF: Relative folate bioavailability from diets containing human, bovine and goat milk. J Nutr 1990; 120: 172–7.
  • Ek J, Magnus EM: Plasma and red blood cell folate in breast fed infants. Acta Paediatr Scand 1979; 68: 239–43.
  • Ek J, Magnus EM: Plasma and red blood cell folacin in cows' milk-fed infants and children during the first 2 years of life: The significance of boiling pasteurized cows' milk. Am J Clin Nutr 1980; 33: 1220–4.
  • Livsmedelsverket: Livsmedelstabell, Sverige 1996.
  • Holland B, Unwin ID, Buss DH: Vegetables, herbs and spices. The fifth supplement to McCane & Widdowson's The Composition of Foods (ISBN 0-85186-376-0) 1991.
  • Souci SW, Fachmann W, Kraut H: Die Zusam-mensetzung der Lebensmittel, Nährwert-Tabel-len. Food Composition and Nutrition Tables (1989/90). Edited by Deutsche Forschungsge-meinschaft fiir Lebensmittelchemie, compiled by Scherz H, Senser F, (5th edition), Medpharm Scientific Pub!., Stuttgart, 1994.
  • Levnedsmiddelstyrelsen: Levnedsmiddeltabel-ler, Danmark 1996.
  • Miiller H: Die Bestimmung der Folsdure-Ge-halte von Lebensmitteln tierischer Herkunft mit Hilfe der Hochleistungsflässigkeitschromato-graphie (HPLC). Z Lebensm Unters Forsch 1993; 196: 518–21.
  • Petersen MA: Influence of sous vide pro-cessing, steaming and boiling on vitamin retention and sensory quality in broccoli florets. Z Lebensm Unters Forsch 1993; 197: 375–80.
  • Williams PG, Ross H, Brand Miller JC: Ascorbic acid and 5-methyltetrahydrofolate losses in vegetables with cook/chill or cook/ hot-hold food service systems. J Food Science 1995; 60: 541–6.
  • Vahteristo L, Lehikoinen K, Oilainen V, Koi-vistoinen PE, Varo P: Ovenbaking and frozen storage affect folate vitamer retention. Le-bensm-Wiss u -Technol 1998; 31: 329–33.
  • Wigertz K, Svensson UK, Jägerstad M: Folate and folate-binding protein content in dairy products. J Dairy Res 1997; 64: 239–52.
  • Hoppner K, Lampi B: Folate retention in dried legumes after different methods of meal pre-paration. Food Science Internat 1993; 26: 45–8.
  • Lane HW, Nillen JL, Kloeris VL: Folic acid content in thermostabilized and freeze-dried space shuttle foods. J Food Science 1995; 30: 538–40.
  • Miiller H, Diehl JF: Effect of ionizing radiation on folates in food. LWT 1995; 29: 187–90.
  • Rosenberg IH, Godwin HA: Inhibition of inte-stinal y-glutamyl carboxypeptidase by yeast nucleic acid: an explanation of variability in utilisation of dietary polyglutamyl folate. J Clin Invest 1971; 50: 78a.
  • Tamura T, Shin YS, Buehring KU, Stokstad ELR: The availability of folates in man: effect of orange juice supplement on intestinal conjugase. Brit J Haematology 1976; 32: 123–33.
  • Bailey LB, Cerda JJ, Bloch BS, Busby MJ, Vargas L, Chandler CJ, Halsted CH: Effect of age on poly- and monoglutamyl folacin absorp-tion in human subjects. J Nutr 1984; 114: 1770-6. 134.Gregory III JF, Bhandari SD, Bailey LB, Toth JP, Baumgartner TG, Cerda JJ: Relative bio-availability of deuterium-labeled monogluta-myl and hexaglutamyl folates in human subjects. Am J Clin Nutr 1991; 53: 736–40.
  • Gregory III JF, Bhandari SD, Bailey LB, Toth JP, Baumgartner TG, Cerda JJ: Relative bio-availability of deuterium-labeled monogluta-myl and hexaglutamyl folates in human subjects. Am J Clin Nutr 1991; 53: 736–40.
  • Gregory III JF, Bhandari SD, Bailey LB, Toth JP, Baumgartner TG, Cerda JJ: Relative bio-availability of deuterium-labeled monogluta-myl tetrahydrofolates and folic acid in humansubjects. Am J Clin Nutr 1992; 55: 1147-53.0