Rex Ellis

Quantitative determination of phytate in the presence of high inorganic phosphate

Abstract The review on the determination of phytate and inositol phosphates by Oberleas (1) indicates that most methods for the determination of phytate are derived from the method of Heubner and Stadler (2). This method is based on the principle that ferric ion forms a stable complex with phytate in dilute acid solution and is the only phosphate compound, at least in significant concentration in nature, with this property. However, the phytate values were high when we applied the procedure of Oberleas (3) to samples with high inorganic phosphate content such as rat feces or semipurified rat diets. This appeared to be a result of inorganic phosphate coprecipitating with ferric phytate. As a preliminary step to study phytate balance in rats, a modified procedure of the Oberleas (3) method was developed that appears to free the ferric phytate precipitate of inorganic phosphate. The procedure and its efficiency are reported in this communication.

Carbonyls in oxidizing fat. V. The composition of neutral volatile monocarbonyl compounds from autoxidized oleate, linoleate, linolenate esters, and fats

The steam volatile monocarbonyl compounds in mildly autoxidized esters of oleic, linoleic, linolenic acids, and animal and vegetable fats were quantitatively estimated. The major aldehydes in oleate and linoleate were those that might be expected from the scission of reported monomeric hydroperoxide isomers. The predominance of hept-2,4-dienal and propanal in linolenate suggested that the major monomeric hydroperoxides were 12-and 16-hydroperoxy conjugated dienoic isomers. The number of minor aldehydes increased with degree of unsaturation of the fatty acid. The amounts of monocarbonyl compounds in the fats examined generally agreed with their average fatty acid composition. Appreciable amounts of heptanal in lamb and beef fat and heptanal and decanal in butterfat, under the conditions of oxidation, could not have come from the three unsaturated acids. Heating at 165°C. in all samples increased the proportions of the most unsaturated major aldehydes.

Mineral balance of adult men consuming whole or dephytinized wheat bran

Abstract Ten men consumed for 15 days each, 36 g daily of either whole or dephytinized wheat bran. Mineral intakes were the same for each dietary regimen. Phytic acid intake was 2 or 0.2 g and the phytate/zinc molar ratio was 12 or 1.2 when eating whole or dephytinized bran, respectively. Apparent absorption (intake-fecal excretion) of iron, zinc, copper, managenese, magnesium, and calcium tended to be lower when whole bran was consumed. However, balances (intake-[fecal+urinary excretion]) for the last 10 days were for the most part positive regardless of which type of bran and more positive when whole bran was eaten. The whole wheat bran did not have a deleterious effect on mineral nutriture of adult men under the conditions of this study.

Carbonyls in oxidizing fat: XII. The isolation of free aldehydes from autoxidized triolein, trilinolein and trilinolenin

Methods of aldehyde isolation have been com-pared in the separation of free aldehydes from autoxidizing triglycerides of pure unsaturated fatty acids. Vacuum distillation was the mildest method of aldehyde isolation. Amounts of decomposed monocarbonyl precursors were directly related to acidity of extraction conditions. Analysis of autoxidizing trilinolenin showed, after attainment of an early maximum, a decrease in monocarbonyl values from vacuum distillation and Girard T reagent methods. Known aldehydes isolated by the acid celite methods increased progressively. These results were considered to be due to a decline in monomeric hydroperoxides as related to free aldehydes, and decomposition of not only monomeric peroxides but also polymers by the acid celite methods. Amounts of decomposed monocarbonyl precursors (broken down) were directly related to acidity of extraction conditions. Analysis of autoxidizing trilinolenin showed a decrease in monocarbonyl values from vacuum distillation and Girard T reagent values and an increase in these values with (those of) the acid celite reaction methods. This was considered to be due to a decline in monomeric hydroperoxides and decomposition of polymers by the acid celite methods. Studies with autoxidizing lard demonstrated several factors having a strong influence on the amount of aldehydes isolated by the phosphoric acid celite reaction method. Passage through the column decreased hydroperoxide values 10−15%. Amount of monocarbonyl compounds was directly related to the time of exposure on the column. The yield of aldehydes decreased with increase in the amount of oxidized material applied to the 2,4-dinitrophenylhydrazine reaction column.

Bioavailability to rats of iron and zinc in calcium-iron-phytate and calcium-zinc-phytate complexes

Abstract The bioavailability of iron in Fephytate and Ca 3 Fephytate and of zinc in Zn 2 phytate and Ca 4 Zn 2 phytate was assayed in rats. Hemoglobin response was the same to the iron of Fephytate as the reference iron compound, Fe(NH 4 ) 2 (SO 4 ) 2 .6H 2 ) but the response to iron of Ca 3 Fephytate was significantly less than to both Fephytate and the reference. The zinc of Zn 2 phytate and Ca 4 Zn 2 phytate promoted growth as effectively as did ZnSO 4 . The femur bone zinc response to Ca 3 Zn 2 phytate and Zn 2 phytate did not differ significantly but the femur zinc responses to both complexes were significantly less than to ZnSO 4 . In contrast to iron, calcium in a preformed calcium-zinc-phytate complex appears to have no significant effect on the bioavailability to rats of the zinc in the complex.

Carbonyls in oxidizing fat. VII. A comparison of methods of isolating monocarbonyl compounds

Comparison of quantitative methods for the isolation of aldehydes from lard oxidized at 23C showed an extreme sensitivity of precursors to isolation conditions. Differences existed in the quantity and class compositions of the monocarbonyl compounds isolated. Acid conditions caused considerable breakdown of alkanal and alk-2-enal precursors. Steam distillation (100C) released alkanals, alk-2-enals, and alk-2,4-dienals. The mild Girard T method apparently produced a small amt of alk-2-enals from precursors, but except in the initial stages isolated the lowest amounts of aldehydes. Complete evaluation of the method for isolation of free aldehydes was not possible because alkanals were released from precursors during the vacuum distillation procedure (50C). The Schwartz (dilute phosphoric acid), Girard T, and vacuum distillation methods isolated similar amounts of alk-2,4-dienals. Curious changes in relationships, possibly indicative of oxidation stages, were observed as autoxidation progressed.

Carbonyls in oxidizing fat. X. Quantitative differences in individual aldehydes isolated from autoxidized lard by mild methods of extraction

Major aldehydes characteristic of the oxidation of the unsaturated fatty acids present in lard differed somewhat in proportions isolated by the mild methods of separation. This indicated an extra sensitivity of specific fatty acid primary oxidation products to conditions, and some deviation from the normal in the breakdown caused by the methods. Linolenate primary oxidation products showed the greatest sensitivity to separation conditions and the stage of oxidation. The mild methods differed in the amounts of individual aldehydes separated to a degree dependent on the stage of oxidation. These results favor the Girard T method for the isolation of free aldehydes from autoxidized lard.

Metal ion catalysis of autoxidation in a lard gel

The prooxidant effects of transition metal compounds upon lard triglycerides in an aqueous heterogeneous model system were examined. Catalytic activity of a metal salt depended on its identity, the phase in which it is dissolved, the buffering salts and pH of the system. The iron and copper inorganic salts dissolved in the aqueous phase were powerful catalysts. Other transition metal salts had little positive effect on autoxidation at acid and neutral pH values. Manganous chloride had an inhibiting action. Freeze-drying reversed catalysis patterns, and Mn++ and Co++ became the strongest prooxidants. Cobaltous and manganese stearates were the most active of such compounds. Reversals in catalytic activity were due to the formation or disappearance of aquo ions.

Autoxidative stability of rendered fat from growing and mature steers fed protected safflower oil

Growing and mature steers with increased linoleic acid (18∶2) in their adipose tissues were reared by the Nutrition Institute, U.S. Department of Agriculture. The 18∶2 content of rendered fats from these animals fed protected safflower oil varied from 6.5–20.6% and from 3.4–5.8% for the growing and mature steers, respectively. Increasing the 18∶2 levels resulted in decreased stability to autoxidation of the rendered subcutaneous fats.

Carbonyls in oxidizing fat. VIII. Effect of the Pool and Klose method on monocarbonyl precursors in autoxidized lard

Monocarbonyl compounds isolated by the Pool and Klose method greatly exceeded those obtained by a mild quantitative vacuum distillation method. As indicated by amounts of individual aldehydes, the Pool and Klose method of reaction with 2,4-dinitrophenylhydrazine on hydrated alumina partially decomposed hydroperoxides of unsaturated fatty acid glycerides and appeared to shift the normal balance of isomeric hydroperoxides. High proportions of unsaturated aldehydes were separated, and a new, highly unsaturated class in substantial amounts was present. Evidence, based on yield and type of aldehyde, suggests that in polyunsaturated fatty acids the hydroperoxide may preferentially form at the appropriate carbon furthest removed from the carboxyl group in the pentadiene system. This might partially explain the low proportions of alk-2,4-dienals in the free aldehydes of lard oxidized under mild conditions.