Lactic Fermentation of Non-Tannin and High-Tannin Cereals: Effects on In Vitro Estimation of Iron Availability and Phytate Hydrolysis

The effect on iron availability estimated in vitro and phytate hydrolysis was investigated in non-tannin and high-tannin cereals, lactic fermented as flour/water slurries or gruels. A natural starter culture initiated fermentation and addition of germinated flour and phytase in the fermentation process was tested. Lactic fermentation of nontannin cereals with added flour germinated sorghum seeds or wheat phytase increased iron solubility from about 4% up to 9 and 50%, respectively. Soaking flour in water before adding starter culture had a similar effect. The increase in soluble iron was strongly related to enzymatic deeradation of phytate (p<0.001). The reduction of inositol hexa- and pentaphosphates was about 50% with added germinated flour. Reduction was > 90% after soaking the flour prior to fermentation and almost complete with 50 mg phytase added. High-tannin cereals showed a minor increase in soluble iron after fermentation, ascribed to the inhibitory effect of tannins (both on iron solubility and on enzymatic hydrolysis of phytate). Lactic-fermented cereal foods have a potential in developing countries to improve iron nutrition.     

Emulsifying Properties of Ethanol Soaked Soybean Flour

Soy flours prepared from soybeans soaked at 60°C for 6 hr in distilled water, 15% ethanol, or 0.1M NaHCO₃ in 15% ethanol were tested for their emulsifying capacity (EC) at pH 4.5, 6.5, and 9.0. At pH 4.5 and 6.5, there were no significant differences in EC among treatments; at pH 9.0, the EC was highest for soy flour from beans soaked in water, intermediate for flour from beans soaked in 15% ethanol, and lowest for flour from beans soaked in 0.1 M NaHCO₃ in 15% ethanol. The relationship between the amount of soluble protein and EC was inverse with EC decreasing sharply up to about 60 mg soluble protein/50 mL of flour dispersion. Photomicrographs of air incorporation during emulsion formation are presented.     

Influence of Milling Method and Peanut Extract on in vitro Iron Availability from Maize and Sorghum Flour Gruels

Maize and sorghum flours were milled by four different methods (a traditional, semi-traditional, mechanical and industrial method). Iron availability was estimated by an in vitro technique. The total, soluble and ionizable (available) iron as well as the phytate and neutral detergent fiber content of the gruels varied with type of flour and also with amount of peanut used in the preparation. The ionizability of iron decreased with increases in phytate and neutral detergent fiber. Iron in the gruels from flours milled by the traditional method was more available than that in other gruels.     

Nitrogen extractability of sesame (Sesamum indicum L.) seed and the preparation of two protein isolates

Nitrogen extractability from sesame flour in water is greatest using a flour: solvent ratio of 1:40 and an extraction time of 15 min. At pH 4.0-6.5, <10% nitrogen is extracted, whilst >90% is extracted at pH 11.0. In the presence of NaCl (0.5-1.0M) nitrogen extractability is greatest at pH values > pH 4.0. The two sesame protein isolates produced were bland-tasting, light-coloured and contained approximately 95% protein. The alkali isolate (extracted in water at pH 10.0 and precipitated at pH 4.0) was readily solubilised and showed a good protein recovery (60%). The salt isolate (extracted in 1M NaCl at pH 6.0 and precipitated at pH 4.0) was less soluble and showed a lower protein recovery (50%). The sesame products were extracted sequentially using various solvents. Sesame flour proteins were mainly salt-soluble (67%), alkali isolate proteins mainly water-soluble (41%) and alkali-soluble (41%), and salt isolate proteins mainly alkali-soluble (35%). The amino acid composition of the sesame products is described. Oil-expelled cake showed poor nitrogen extractability (53% at pH 11.0 in water) and was, therefore, a poor source for protein isolate production.     

Seed treatments affect functional and antinutritional properties of amaranth flours

The effects of seed treatments, including cooking, popping germination and flour air classification, on the functional properties and antinutritional factors of Amaranthus caudatus and Amaranthus cruentus seeds were studied. Thermal treatments increased the water absorption with a maximum value of 5.1 and 6.3 g g⁻¹ in flour of popped seeds of both species. Generally, fat absorption increased after the treatments. Air classification and germination followed by drying at low temperature increased the foam stability of the flours, while thermal treatment and germination followed by drying at higher temperatures reduced the foam stability. All treatments except air classification decreased the emulsion stability. Also, all treatments except germination followed by drying at 30 °C increased the flour dispersibility, whereas the soluble nitrogen index was increased in the germinated seed flours and decreased in thermal treated seeds and air‐classified flours. Air classification increased the contents of phenolic compounds and phytate and decreased the contents of enzyme inhibitors, whereas the thermal treatments reduced the contents of phenolic compounds, phytate and enzyme inhibitors to a greater extent for cooking than for popping. Germination followed by drying reduced the level of phenolic compounds, phytate and enzyme inhibitors. Copyright © 2006 Society of Chemical Industry     

Phytate content and phytate degradation by endogenous phytase in pea (Pisum sativum)

In order to rapidly reduce the content of inositol tri–hexaphosphates in pea flour by action of the endogenous phytase, raw materials as well as incubation conditions have been evaluated. The phytate (inositol hexaphosphate) content was analysed in 27 pea varieties; the influence of storage time and the difference in phytate content between the germ and the cotyledon were determined. Furthermore, degradation of inositol phosphates by the endogenous phytase enzyme was studied in pea flour, germ and cotyledon. To find the maximum phytate degradation, the effects of temperature and pH during pea flour incubation were investigated. The most efficient phytate degradation in pea flour incubation was achieved at pH 7.5 and 45 °C. At this condition an almost complete degradation of phytate and a 66% reduction in the sum of inositol hexa‐, penta‐, tetra‐ and triphosphates were reached in 10 h. The storage time of pea seeds or removal of the germ did not have a major effect on the phytate content. Since several inositol pentaphosphate isomers were produced during phytate degradation, it can be concluded that peas contain several phytate‐degrading enzymes, or one phytate‐degrading enzyme with unspecific initial hydrolysation pattern. © 2001 Society of Chemical Industry.     

The interaction of zinc(II) and phytic acid with soya bean glycinin

Binding of phytic acid to Zn(II) free glycinin was not observed in 0.5 M KCl at pH 6.2. The addition of varying quantities of phytic acid to a Zn(II)- glycinin system at pH 6.2 ([KCl]=0.5 M ) initially resulted in binding of phytate and increased binding of Zn(II) to glycinin probably as a phytate-Zn(II)-glycinin complex. Further addition of phytate resulted in precipitation of zinc and protein. Bovine serum albumin also showed increased affinity for Zn(II) owing to the presence of phytic acid. Phytic acid-Zn(II) precipitates have a capacity of removing glycinin from solution, presumably by surface adsorption. The presence of soluble Zn(II) inhibits this adsorption. Bovine serum albumin is removed from solution by phytic acid-Zn(II) precipitates only when soluble zinc is present.     

PROTEIN-PHYTATE INTERACTION IN SOYBEANS. III. THE EFFECT OF PROTEIN-PHYTATE COMPLEXES ON ZINC BIOAVAILABILITY

A study was conducted to determine the influence of pH on the chemical form of phytate in a commercial soy isolate and its effect on zinc bioavailability by monitoring weight gain in weanling rats. Ultrafiltration studies demonstrated that the free phytate content of soy isolate solutions was greatest at pH 5.0; above this the neutralization of soy isolates resulted in the formation of a soluble proteinphytate complex. The bioavailability of zinc from diets providing protein from egg, acid and neutral soy isolates and containing various levels of added zinc was measured. The growth of rats receiving zinc from the neutral soy isolate was significantly lower than that of rats deriving zinc from either the acidic soy isolate or egg white diets. It is proposed that the reduction in bioavailability of zinc caused by the neutralization of soy protein isolate is related to the formation of a protein-zinc-phytic acid complex resistant to hydrolysis in vivo.     

Functional Properties of Winged Bean [Psophocarpus tetragonolobus (L.) DC] Proteins

A protein concentrate (71.45% protein on a dry weight basis) was prepared from winged bean [Psophocarpus tetragonolobus (L.) DC] seeds. Solubility of the protein concentrate was minimal at a pH of 4.0. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of the bean flour proteins and protein concentrate indicated 9 subunits each, with apparent molecular weight ranges of 27,000–380,000 and 14,200–143,000 daltons, respectively. Least gelation concentrations and water and oil absorption capacities of the seed flour and the protein concentrate were determined. Emulsion and foaming properties of the protein concentrate were investigated. Effect of moist heat on seed protein digestibility was assessed in vitro. Protein concentrate had lower tannins and trypsin, chymotrypsin, and α-amylase inhibitory activities compared to bean flour.     

Effect of Phytate and Other Myo-inositol Phosphate Esters on α-Amylase Digestion of Starch

The effects of phytate and other myo-inositol phosphate esters (containing one or more phosphate groups) on α-amylase digestion of soluble potato starch were evaluated by an in vitro procedure. Human salivary or Bacillus subtilisα-amylase was treated with either 2 mM or 5 mM phytate, myo-inositol-2-monophosphate (l–2-MP), or phytate hydrolyzed to various degrees, and then incubated at 37°C with the starch at pH 4.15 or 6.90. Starch digestion varied with degree of phosphorylation of inositol, inositol phosphate ester concentration, pH and enzyme source. At pH 4.15, phytate (2 mM) and I-2-MP (2 mM) reduced starch digestion by salivary α-amylase to 8.5 and 78.3%, respectively, of the control.     

Interactions Among Calcium, Zinc and Phytate with Three Protein Sources

Various combinations of calcium (4.94 mmol), zinc (0.0071 mmol) and phytate (0.284 mmol) were added either to soy concentrate, casein or torula yeast to determine effects of their interaction on in vitro solubility of protein, calcium, zinc, and phytate (PA). Two Ca sources, calcium carbonate (CaCO₃) and calcium-citrate-malate complex (CCM) were used. Two pH levels, 2.0 and 5.5, were used to simulate gastrointestinal pH conditions. An increase in pH significantly reduced (P<0.01) Zn solubility in all treatments with all protein sources. The solubility of Ca and PA were significantly decreased (P< 0.01) when both components were present probably due to formation of insoluble Ca-PA complexes. At pH 5.5, with casein and yeast proteins, Zn was significantly more (P< 0.01) soluble in samples with CCM, in the absence of PA, than in those with CaCO₃.     

Sweetpotato α- and β-Amylases: Characterization and Kinetic Studies with Endogenous Inhibitors

Sweetpotato α- and β-amylases were characterized to assist optimization of direct hydrolysis of starch by endogenous amylases. In kinetic studies purified starch was substrate, and ascorbate, oxalate, phenolics, phytate and sweetpotato extracts were assayed for inhibitory activity. α-Amylase had optimum pH between 5.8 and 6.4 and was stable from pH 5.0 to 9.0. Optimum activity occurred at 71.5°, but it was inactivated by heat in the absence of Ca²⁺ at > 63°. The Km for soluble starch was 2.08 mg/mL. The molecular weight was 45000 daltons. α-Amylase activity was reduced up to 70% by 0.2 mM K-ascorbate and moderately by Na-oxalate and Na-phytate. β-Amylase had optimum pH between 5.3 and 5.8, and was stable from pH 4.0 to 8.0. Its maximum activity was at 53° and it was inactivated at 60°. Km for soluble starch was 3.71 mg/mL. At 0.08 mM, K-ascorbate strongly inhibited β-amylase activity.     

In Vitro Digestibility of Phytate-Reduced and Phenolics-Reduced Soy Protein Isolates

The effect of removal of phytate and phenolic compounds upon the in vitro digestibility of soy protein isolates by trypsin and pronase enzymes at pH 8.0 and by pepsin at pH 2.0 was studied by pH stat and dialysis equilibrium methods, respectively. Phenolics-reduced (PRSPI) and phytate and phenolics-reduced (PPRSPI) soy protein isolates were both slightly more digestible than control (CSPI). 11S soy-protein with 0.07% phytate was slightly more digestible than 7S soy protein with 1.41% phytate. Kinetic studies indicated that differences in in vitro digestibility of soy protein isolates was probably due to accumulation of end products rather than stearic hindrance at enzyme-substrate reaction sites.     

Hard Red Spring wheat/C-TRIM 20 bread: Formulation,processing and texture analysis

C-TRIM, a β-glucan-rich fraction, was added to Hard Red Spring wheat (HRSW) flour to increase soluble fiber content of bread, and to obtain a minimum of 0.75 g/bread serving (0.75 g/30 g or 2.5%) required by FDA for health claim. Three treatments or blends FGT0 (100% wheat flour – control), FGT1 (58% flour, 25% gluten and 17% C-TRIM) and FGT2 (60% flour, 22.5% gluten, and 17% C-TRIM) were used in the study. The total amount of soluble fiber from C-TRIM in FGT1 and FGT2 was 4.07–4.17% which was more than the amount required by FDA. The presence of C-TRIM increased both, the Farinograph water absorption and the arrival time. The dough mixing tolerance index (MTI) was also increased by C-TRIM. The FGT1 had higher stability than FGT2, whereas, the loaf volume of FGT1-B was also significantly higher than FGT0-B control and FGT2-B bread. The DSC results indicated that the amount of freezable-water in C-TRIM treated bread (FGT1-B and FGT2-B) was significantly higher than the control wheat flour bread (FGT0-B). This may be attributed to the higher amount of water absorbed by C-TRIM during bread dough (FGT1-D and FGT2-D) preparation and trapped or bound within the bread matrix after baking as compared to the control. After storage of FGT0-B, FGT1-B, and FGT2-B breads 2, 5, and 7 days storage at 25 °C, 4 °C, and −20 °C, the texture of bread were measured with a Texture Analyzer and the data analyzed statistically. The FTG0-B control bread firmness was significantly higher than FGT1-B and FGT2-B C-TRIM treated breads after 7 days storage at 25 °C. The amount of 0.1 M acetic acid-extractable protein was lower in FGT1-B than the control wheat flour (FGT0-B) sample. In addition, more protein was extracted at pH 7.0 than pH 4.5 because of less charges at neutral pH than pH 4.5. The free zone capillary electrophoresis analysis showed obvious differences in the protein charge and size between the dough and bread.     

Supplementation of alkaline phytase (Ds11) in whole-wheat bread reduces phytate content and improves mineral solubility

Abstract: In this study, alkaline phytase was added to whole‐wheat bread and the phytate content and mineral profiles were compared to commercially available acidic phytase. At neutral pH, some phytate (approximately 20%) was degraded by endogenous phytase in wheat flour, while 40% of phytate was hydrolyzed by alkaline phytase DS11 and a 35% reduction was observed with acidic phytase. Most of the enzymatic activity occurred during the proofing stage, and the rate of reaction depended on pH. DS11 phytase effectively degraded the phytate level within a 30 min treatment at pH 7; however, at least 60 min was needed with acidic phytase to achieve the same hydrolysis level. Mineral profiles were also dramatically affected by the phytate reduction. The biggest increase was observed in Fe²⁺ by the phytase treatment. The Fe²⁺ content increased 10‐fold at pH 7 and 8‐fold at pH 5 with alkaline phytase DS11. Alkaline phytase DS11 was shown to be effective at phytate reduction in whole‐wheat bread preparation. Additionally, phytate degradation enhanced the mineral availability of bread.     

Interactions Between Phytate, Protein, and Minerals in Whey Fractions of Black Gram

Whey fractions cor taining proteins (albumins), phytate, and minerals were prepared from black gram (Phaseolus mungo L.) cotyledons and were employee to study the interactions between protein, phytate, and minerals at pH 2.80, 6.40, and 8.40. Black gram cotyledons contained 1.7% phytate, of which 88.7% existed in watersoluble form. Phytate phosphorus represented for about 89% of total phosphorus in black gram cotyledons. Recovery of phytate in fraction I (pH 2.80), fraction II (pH 8.40), and fraction III (pH 6.40) was 45%, 69%, and 4%, respectively, after 48 hr dialysis. At pH 2.80, complexation occurred between phytate and proteins. Complexation between phytate and proteins at pH 8.40 was mediated by divalent cations such as calcium, magnesium, and zinc. Fraction II had higher concentrations of divalent cations (calcium, magnesium, and zir c) than the other two fractions I and III.     

Effect of malt pretreatment on phytate and tannin level of two sorghum (Sorghum bicolor) cultivars

The seeds of two cultivars of Sudanese sorghum (Sorghum bicolor), namely Wad Ahmed and Tabat, were germinated for 4 days to obtain 1‐, 2‐ and 4‐day‐old malts. Sorghum malt (5% and 10%) was added to sorghum flour. The mixtures were incubated at 30 °C with shaking for 30, 60, 90 and 120 min. Malting loss was very slight for both cultivars and for all incubation periods. Phytic acid and tannin contents were assayed for all treatments. The results revealed that phytate and tannin contents were significantly (P ≤ 0.05) reduced when sorghum flour was pretreated with malt. When a mixture containing 10%, 4‐day‐old malt and sorghum flour was incubated for 120 min, it significantly (P ≤ 0.05) reduced phytate and tannin contents by 92% and 98%, respectively, for Wad Ahmed cultivar, while for Tabat they were reduced by 93% and 96%, respectively. The rate of reduction of phytate and tannin content increased with incubation time and malt age and concentration.     

Peniophora lycii phytase is stabile and degrades phytate and solubilises minerals in vitro during simulation of gastrointestinal digestion in the pig

BACKGROUND: Microbial phytases (EC 3.1.3) are widely used in diets for monogastric animals to hydrolyse phytate present in the feed and thereby increase phosphorus and mineral availability. Previous work has shown that phytate solubility is strongly affected by calcium in the feed and by pH in the gastrointestinal (GI) tract, which may have an effect on phytase efficacy. An in vitro model simulating the GI tract of pigs was used to study the survival of Peniophora lycii phytase and the effect of the phytase on phytate degradation, inositol phosphate formation and mineral solubilisation during in vitro digestion of a 30:70 soybean meal/maize meal blend with different calcium levels. RESULTS: The phytase retained 76 and 80% of its initial activity throughout the gastric in vitro digestion. Total phytate hydrolysis by P. lycii phytase was in the same range at total calcium levels of 1.2 and 6.2 mg g^?1 dry matter (DM), despite very large differences in phytate solubility at these calcium levels. However, at 11.2 and 21.2 mg Ca g^?1 DM, phytate hydrolysis was significantly lower. The amount of soluble mineral was generally increased by P. lycii phytase. CONCLUSION: Stability of P. lycii phytase during gastric digestion was not found to be critical for phytate hydrolysis. Furthermore, original phytate solubility was not an absolute requirement for phytate degradation; phytate solubility seemed to be in a steady state, allowing insoluble phytate to solubilise as soluble phytate was degraded. This is new and interesting knowledge that adds to the current understanding of phytate–phytase interaction. Copyright © 2007 Society of Chemical Industry     

Hydrolysis and Ultrafiltration Treatment to Improve the Nutritive Value of Rapeseed Proteins

In order to improve their nutritive value, rapeseed proteins were hydrolyzed with pepsin (60 min) and trypsin (120 min). The hydrolysate was centrifuged at 10,000 ×g for 10 mln and the soluble fraction was ultrafiltered with a Romicon cartridge having a molecular weight cut-off of 10,000 daltons. Nutritional experiments with rats demonstrated that the net protein ratios obtained with rapeseed hydrolysate and ultrafdtrate (4.68 and 4.55 respectively) were higher (P < 0.05) than that of casein (4.40). The protein digestibility of the ultrafiltrate (90.3) was not different from that of casein (91.1) but higher than that of raw rapeseed flour (81.9). These hydrolysis and ultrafiltration treatments improved the nutritive value of rapeseed proteins by permitting the isolation of by-products of a molecular weight lower than 5000 daltons.     

Rapid Measurement of Phytate in Soy Products by Mid-infrared Spectroscopy

ABSTRACT: The rapid measurement of phytate from soybean and its products, such as soy flour, defatted meal, soymilk, and tofu, was investigated using Fourier transfer infrared spectroscopy (FT-IR) with an attenuated total refraction accessory. The phytate, separated from protein by trichloroacetic acid (TCA), was precipitated completely by the addition of calcium, pH > 7.0, even in the presence of TCA. The precipitate was dissolved in citrate buffer (pH 6.0) and then used for infrared measurement. The absorbance at 1070 cm⁻¹ correlated well the phytate content of the each sample. The measurement of phytate can be done rapidly by FT-IR with an ATR accessory and gives reproducible values.