Fumonisin B(1)-nonproducing strains of Fusarium verticillioides cause maize (Zea mays) ear infection and ear rot

Fumonisins are polyketide mycotoxins produced by Fusarium verticillioides (synonym F. moniliforme), a major pathogen of maize (Zea mays) worldwide. Most field strains produce high levels of fumonisin B(1) (FB(1)) and low levels of the less-oxygenated homologues FB(2) and FB(3), but fumonisin B(1)-nonproducing field strains have been obtained by natural variation. To test the role of various fumonisins in pathogenesis on maize under field conditions, one strain producing FB(1), FB(2), and FB(3), one strain producing only FB(2), one strain producing only FB(3), and one fumonisin-nonproducing strain were applied to ears via the silk channel and on seeds at planting. Disease severity on the harvested ears was evaluated by visible symptoms and by weight percent symptomatic kernels. Fumonisin levels in kernels were determined by high-performance liquid chromatography. The presence of the applied FB(1)-nonproducing strains in kernels was determined by analysis of recovered strains for fumonisin production and other traits. All three FB(1)-nonproducing strains were able to infect ears following either silk-channel application or seed application at planting and were as effective as the FB(1)-producing strain in causing ear rot following silk-channel application. These results indicate that production of FB(1), FB(2), or FB(3) is not required for F. verticillioides to cause maize ear infection and ear rot.     

Determination of N-(carboxymethyl)fumonisin B(1) in corn products by liquid chromatography/electrospray ionization--mass spectrometry

It is well-known that fumonisin B(1) (FB(1)) in corn meal decreases during baking, frying, and cooking, but it is still not exactly clear how heating affects the formation of N-(carboxymethyl)fumonisin B(1) (NCM-FB(1)), the reaction product of FB(1) and reducing sugars. In model experiments corn grits were spiked with FB(1) (2 mg/kg) and D-glucose (50 g/kg) or sucrose (50 g/kg) and manufactured into extrusion products at various temperatures (160--180 degrees C) and moisture levels (16--20%). A liquid chromatography/electrospray ionization-mass spectrometry method using isotopically labeled fumonisin FB(1)-d(6) as an internal standard was developed for the determination of NCM-FB(1). For sample cleanup solid-phase C18 cartridges were used. The detection limit achieved with this method was 10 ng/g (signal-noise ratio = 3:1) using the protonated molecule [M + H](+) signal of NCM-FB(1) (m/z 780) in the selected ion monitoring mode. Low concentrations of NCM-FB(1) (29-97 ng/g) were detected in all samples spiked with D-glucose and FB(1), whereas those spiked with FB(1) and sucrose showed only NCM-FB(1) in samples produced at 180 degrees C (NCM-FB(1) = 27 ng/g). Various corn-containing food samples from the German market were analyzed for the presence of NCM-FB(1), FB(1), and hydrolyzed fumonisin B(1) (HFB(1)). All samples were contaminated with FB(1) (22--194 ng/g) and HFB(1) (5--247 ng/g). Six of nine samples contained NCM-FB(1) in low concentrations ranging from 10 to 76 ng/g. From these data and the low toxicity of NCM-FB(1) it can be concluded that the significance of NCM-FB(1) in food seems to be a minor one.     

N-(1-deoxy-D-fructos-1-yl) fumonisin B(1), the initial reaction product of fumonisin B(1) and D-glucose

Incubation of fumonisin B(1) and D-glucose in aqueous solutions resulted in the formation of N-(1-deoxy-D-fructos-1-yl) fumonisin B(1) in addition to the previously reported N-(carboxymethyl) fumonisin B(1). N-(1-Deoxy-D-fructos-1-yl) fumonisin B(1) is the first stable product formed after the Amadori rearrangement of the Schiff base formed by the reaction of the primary amine of fumonisin B(1) and the aldehyde group of D-glucose. N-(1-Deoxy-D-fructos-1-yl) fumonisin B(1) was synthesized by reacting fumonisin B(1) with an excess of D-glucose in methanol and heating for 6 h at 64 degrees C. It was purified using C(18) and strong cation exchange solid-phase extraction cartridges and characterized by nuclear magnetic resonance and liquid chromatography-mass spectrometry. Subsequently, N,N-dimethylformamide was found to be a better reaction solvent, requiring reaction for only 2-3 h at 64 degrees C and eliminating the formation of methyl esters. Alkaline hydrolysis of N-(1-deoxy-D-fructos-1-yl) fumonisin B(1) gave a mixture of hydrolyzed fumonisin B(1) and hydrolyzed N-(carboxymethyl) fumonisin B(1).     

Purification, identification, and characterization of peanut isocitrate lyase

Isocitrate lyase (ICL, EC 4.1.3.1) is commonly present in oil-rich seeds in catalyzing the cleavage of isocitrate to glyoxylate and succinate and plays an essential role in lipid metabolism and gluconeogenesis. When peanut kernels (Tainan 14) were germinated at 30 degrees C, the cotyledon ICL activities increased substantially in the initial 4 days, and the 4-day-germinated cotyledons were subjected to ICL purification by Tris-HCl buffer extraction, heat treatment at 55 degrees C for 1 h, (NH4)2SO4 fractionation at 25-35% saturation, DEAE-cellulose chromatography, and Sephacryl S-300 gel filtration. A single 64 kDa SDS-PAGE protein band was obtained with 7.7% recovery and 37.5-fold purity. It was identified as ICL by LC-MS/MS analyses and Mascot Search with 494 as the highest Probability Based Mowse Score (PBMS). On the basis of the sequence of the homologous ICL of Glycine max, 26% of the peptide sequences of the peanut ICL were identified. During gel filtration, separation of peanut catalase (identified by LC-MS/MS and Mascot Search with 405 as the highest PBMS) from peanut ICL was achieved. The highest measured peanut ICL enzymatic activities were obtained at 45 degrees C and pH 7.0-7.8, respectively. The enzyme activities were stable (>80%) as stored for 8 h at 30 degrees C, 15 days at 4 degrees C, or 60 days at -25 degrees C. As affected by the supplements in the reactants for activity determinations, ICL activity was not affected by glucose up to 4%, sucrose up to 5%, or ethanol up to 8.33%.     

Characterization of fumonisin B(1)-glucose reaction kinetics and products

The reaction of fumonisin B(1) with the reducing sugar D-glucose can block the primary amine group of fumonisin B(1) and may detoxify this mycotoxin. A method to separate hundred milligram quantities of fumonisin B(1)-glucose reaction products from the excess D-glucose with a reversed-phase C(18) cartridge was developed. Mass spectrometry revealed that there were four primary products in this chain reaction when fumonisin B(1) was heated with D-glucose at 65 degrees C for 48 h: N-methyl-fumonisin B(1), N-carboxymethyl-fumonisin B(1), N-(3-hydroxyacetonyl)-fumonisin B(1), and N-(2-hydroxy, 2-carboxyethyl)-fumonisin B(1). The N-(1-deoxy-D-fructos-1-yl) fumonisin B(1) (fumonisin B(1)-glucose Schiff's base) was detected by mass spectrometry when fumonisin B(1) was heated with D-glucose at 60 degrees C. The nonenzymatic browning reaction of fumonisin B(1) with excess D-glucose followed apparent first-order kinetics. The activation energy, E(a), was 105.7 kJ/mol. Fumonisin B(1) in contaminated corn could precipitate the nonenzymatic browning reaction with 0.1 M D-glucose at 60 and 80 degrees C.     

Mycoflora and fumonisin contamination in Brazilian corn from sowing to harvest

The present study aimed to analyze the mycoflora and potential mycotoxin contamination of soil and corn samples collected at different plant maturity stages in Cap?o Bonito and Ribeir?o Preto, two regions of the State of S?o Paulo, Brazil. In addition, the data obtained were correlated with the occurrence of wind-dispersed fungi and the predominant climatic conditions of the two regions studied. Corn mycoflora profiles showed that Fusarium verticillioides prevailed in 35% of the samples from Cap?o Bonito and in 49% of the samples from Ribeir?o Preto. Examination of wind-dispersed fungi also revealed a high incidence of F. verticillioides. Soil mycoflora analyses showed that Penicilliumwas the most prevalent genus, although F. verticillioides was present in 55.5% of Cap?o Bonito's samples and in 26.7% of Ribeir?o Preto's samples. With respect to water activity, the corn kernels most contaminated with F. verticillioides had water activity levels of 0.70-0.80. HPLC analysis of fumonisins revealed that 88.5% of Cap?o Bonito's kernels were contaminated with fumonisin B(1) (FB(1)) (0.09-10.87 microg/g) and 53.8% with fumonisin B(2) (FB(2)) (0.05-0.52 microg/g); Ribeir?o Preto's kernels presented contamination levels of 93.5% for FB(1) (0.11-17.69 microg/g) and 61.3% for FB(2) (0.05-5.24 microg/g). No aflatoxins were detected by thin-layer chromatography in corn grains of either region. The concomitant occurrence of F. verticillioides and fumonisins in most of the field corn assayed demonstrates the importance of an effective control of cultivation throughout the plant maturity stages.     

Degradation of malathion, in aqueous extracts of asparagus (Asparagus officinalis)

Malathion was incubated in water extracts of vegetables at various temperatures and pH, and the amount of malathion present over time was analyzed by a gas chromatograph with a flame photometric detector. Malathion was degraded to a nondetectable level in a 1% asparagus extract incubated at pH 7.4 and 37 degrees C for 4 h. Carrot extract showed the second highest rate of malathion degradation (76%), followed by kale extract (23.7%), spinach extract (9.7%), and broccoli extract (1.5%) under the same conditions. The highest degradation rates of malathion were observed at 37 degrees C, when three different temperatures were tested (5, 25, and 37 degrees C) at pH 7.4. Rate constants were 0.134 min(-)(1) from a 1% asparagus solution and 0.095 min(-)(1) from a 0.5% asparagus solution. The highest degradation rate of malathion was achieved at pH 9 among the pHs tested (pH 4, 7.4, and 9) in a 0.5% asparagus solution. The 0.5% asparagus solution degraded dicarboxylic acid esters by almost 100% for dimethyl succinate and diethyl adipate, by 64% for diethyl acetyl succinate, and 30% for diethyl benzyl malonate when incubated at pH 9 for 20 min. The results support the hypothesis that the enzyme that degrades malathion in the asparagus solutions is a carboxylesterase.     

Preparation of phytate-removed deamidated soybean globulins by ion exchangers and characterization of their calcium-binding ability.

Phytate-removed deamidated soybean globulins were prepared using ion-exchange resins to provide them with a functional property to enhance calcium absorption in the body. The phosphorus level was reduced from 45 to 20 micromol/g using 0.05 g/mL of AE-4, an anion-exchange resin with a (2-hydroxyethyl)dimethylammonium group, in 0.2% soybean globulin solution for 1 h at 4 degrees C, and 90-92% of the phosphorus in defatted soybeans could be removed. As for deamidation, CE-4, a cation-exchange resin of the carboxylate type, showed a much higher deamidation activity than CE-1 and CE-2, cation-exchange resins of the sulfonate type. No peptide bond hydrolysis was observed for any cation-exchange resin treated at 4 degrees C. There was no significant difference in the amount of acid amide deamidated at temperatures between 4 and 50 degrees C. The deamidation level was able to increase to 73% using 0.10 g/mL of CE-4 in a 0.2% soybean globulin solution for 6 h at 4 degrees C. The amount of calcium bound to the soybean globulins decreased with removal of the phytate but increased with deamidation.     

Natural occurrence of fumonisins B(1) and B(2) in domestic maize of Taiwan.

Samples of maize grown in various districts of Taiwan were collected and analyzed for the presence of fumonisin B(1) (FB(1)) and fumonisin B(2) (FB(2)) using high-performance liquid chromatography. Forty-nine (44.5%) and 2 (1.8%) of 110 samples were found to contain FB(1) (109-1148 ng/g) and FB(2) (222-255 ng/g), respectively. The frequency of detection and also the maximum FB(1) concentration were found in samples from Penton (2/2, 262 ng/g), followed by Chiayi (18/26, 264 ng/g), Tainan (8/16, 160 ng/g), Hualinen (5/14, 1148 ng/g), Taitung (7/20, 109 ng/g), and Yunlin (9/26, 361 ng/g). Of the 110 samples examined, only 2 samples from Hualinen had been detected containing FB(2). During an analysis of the distribution pattern of FB(1), it became apparent that >79% of tested samples had FB(1) concentrations <100 ng/g, whereas 2.7% (or 3 samples) contained FB(1) >300 ng/g. These results clearly illustrated that domestically produced maize for human consumption is frequently contaminated with FB(1).     

Methylation methods for the quantitative analysis of conjugated linoleic acid (CLA) isomers in various lipid samples

Precise methylation methods for various chemical forms of conjugated linoleic acid (CLA), which minimize the formation of t,t isomers and allylmethoxy derivatives (AMD) with the completion of methylation, were developed using a 50 mg lipid sample, 3 mL of 1.0 N H(2)SO(4)/methanol, and/or 3 mL of 20% tetramethylguanidine (TMG)/methanol solution(s). Free CLA (FCLA) was methylated with 1.0 N H(2)SO(4)/methanol (55 degrees C, 5 min). CLA esterified in safflower oil (CLA-SO) was methylated with 20% TMG/methanol (100 degrees C, 5 min), whereas CLA esterified in phospholipid (CLA-PL) was methylated with 20% TMG/methanol (100 degrees C, 10 min), followed by an additional reaction with 1.0 N H(2)SO(4)/methanol (55 degrees C, 5 min). Similarly, CLA esterified in egg yolk lipid (CLA-EYL) was methylated by base hydrolysis, followed by reaction with 1.0 N H(2)SO(4)/methanol (55 degrees C, 5 min). These results suggest that for the quantitative analysis of CLA in lipid samples by GC, proper methylation methods should be chosen on the basis of the chemical forms of CLA in samples.     

Effects of caseins on thermal stability of bovine beta-lactoglobulin

Casein fractions have been shown to act as molecular chaperones and inhibit aggregation of whey proteins in dilute solutions (< or =1% w/v). We evaluated if this approach would stabilize protein solutions at higher concentration and thermal processing temperatures desired for beverage applications. Mixtures of beta-lactoglobulin (BLG) (6% w/v) with either beta-casein (BCN) (0.01-2% w/v) or alpha s-casein (ACN) (2% w/v) were adjusted to pH 6.0 and heated (70-90 degrees C) for 20 min, cooled, and then analyzed to determine the degree of aggregation. Aggregation was determined by solution turbidity as optical density (OD) at 400 or 600 nm. The addition of 0.05% (w/v) BCN or greater caused a drop in turbidity for solutions heated at 70-90 degrees C. In contrast, inhibition was observed in BLG-ACN mixtures at 70 degrees C but not at > or =75 degrees C. Moreover, prolonged heating (90 min) of BLG with 2% (w/v) BCN (pH 6.0) at 90 degrees C produced a clear solution while BLG-ACN solutions formed translucent gels after heating for 15 min. The weight-averaged molar mass and root-mean-square (rms) radius of soluble aggregates were determined by size exclusion chromatography in conjunction with multiangle laser light scattering (SEC-MALS). SEC-MALS confirmed the turbidity results by showing that the BLG-BCN mixture (8% w/v protein) produced aggregates with lower molar mass and smaller rms radius (majority 20-40 nm). These results showed that BCN is a feasible component to stabilize higher concentrations of whey proteins in beverages.     

Excretion of (14)C-fumonisin B(1), (14)C-hydrolyzed fumonisin B(1), and (14)C-fumonisin B(1)-fructose in rats.

14C-Fumonisin B(1) (FB(1)) was produced by Fusarium proliferatum M-5991 in modified Myro liquid medium and purified to >95% purity with a specific activity of 1.7 mCi/mmol. Nine male and nine female F344/N rats were each dosed by gavage with 0.69 micromol of (14)C-FB(1), (14)C-hydrolyzed FB(1), or (14)C-FB(1)-fructose/kg body weight. Urinary excretion of (14)C-FB(1) and (14)C-FB(1)-fructose was 0.5% and 4.4% of the total dose, respectively, and was similar between male and female rats. Urinary excretion of (14)C-hydrolyzed HFB(1) was significantly greater (P > 0.05) in female rats as compared with male rats (17.3% vs 12.8% of the total dose, respectively). There were no significant (P > 0.05) differences in biliary excretion of the three fumonisin compounds with a mean of 1. 4% of the dose excreted at 4 h after dosing. Lesser amounts continued to be excreted up to 9.25 h after dosing. Although biliary excretion of the (14)C-FB(1), (14)C-hydrolyzed FB(1), and (14)C-FB(1)-fructose was similar, increased urinary excretion of the (14)C-hydrolyzed FB(1) as compared to (14)C-FB(1) and (14)C-FB(1)-fructose indicated a greater absorption of the hydrolyzed form.     

Comparative studies on the delignification of pine kraft-anthraquinone pulp with hydrogen peroxide by binucleus Mn(IV) complex catalysis

Pine kraft-anthraquinone (kraft-AQ) pulp was bleached in alkaline solution with hydrogen peroxide catalyzed by either [L(1)Mn(IV)(micro-O)(3)Mn(IV)L(1)](PF(6))(2)] (C1) or [LMn(IV)(2)(micro-O)(3)] (ClO(4))(2) (C2) at 60 and 80 degrees C for 120 min with a catalyst charge of 10 ppm on pulp. The resulting bleached pulp was hydrolyzed with cellulase to obtain insoluble and soluble residual lignins. The alkaline bleaching effluents were acidified to precipitate alkaline-soluble lignins. These lignin preparations were then characterized by 2D heteronuclear multiple-quantum coherence (HMQC) NMR spectroscopic techniques. The results showed that biphenyl (5-5) and stilbene structures of the residual lignin in the pulp are preferentially degraded in both the C1- and C2-catalyzed bleachings, whereas beta-O-4, beta-5, and beta-beta structures undergo degradation to a lesser extent. In both cases, the degradation of the residual lignin increased with the increase in reaction temperature from 60 to 80 degrees C. Thus, the result of C1-catalyzed delignification is not in agreement with the observed decrease in the disappearance rate for substrates in the C1-catalyzed oxidation of lignin model compounds with hydrogen peroxide when the reaction temperature is increased from 60 to 80 degrees C. In addition, the resulting residual lignins in the C2-catalyzed bleaching at 80 degrees C are less degraded than the corresponding lignins in the C1-catalyzed bleaching at both 60 and 80 degrees C. Thus, C1 is more effective than C2 as catalyst in the binucleus Mn(IV) complex-catalyzed bleaching of pine kraft-AQ pulp with hydrogen peroxide.     

Formation of whey protein isolate (WPI)-dextran conjugates in aqueous solutions

The conjugation reaction between whey protein isolate (WPI) and dextran in aqueous solutions via the initial stage of the Maillard reaction was studied. The covalent attachment of dextran to WPI was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with both protein and carbohydrate staining. The formation of WPI-dextran conjugates was monitored by a maximum absorbance peak at approximately 304 nm using difference UV spectroscopy. The impact of various processing conditions on the formation of WPI-dextran conjugates was investigated. The conjugation reaction was promoted by raising the temperature from 40 to 60 degrees C, the WPI concentration from 2.5 to 10%, and the dextran concentration from 10 to 30% and lowering the pH from 8.5 to 6.5. The optimal conjugation conditions chosen from the experiments were 10% WPI-30% dextran and pH 6.5 at 60 degrees C for 24 h. WPI-dextran conjugates were stable under the conditions studied.     

Impact of Soaking Temperature and Duration on Fissure Incidence of Rough Rice Kernels

Internal stresses owing to moisture and temperature gradients often result in the development of rice kernel fissures. Fissured rough rice kernels tend to break upon milling and potentially reduce the market value of rice. This work was conducted on the premise that fissures may be healed by soaking in water at a specific temperature and duration. Fissured rough rice kernels of a long‐grain cultivar, Wells, were selected by X‐ray imaging. Fissured kernels were soaked in a water bath at six soaking temperatures (22, 60, 65, 70, 75, and 80°C) and three soaking durations (1, 2, and 3 h) and then gently dried for characterization. X‐ray images revealed that soaking at 75°C for 3 h healed up to 70.0% of the fissured kernels. Soaking at 22, 60, or 65°C did not result in healing. For normal kernels, soaking at different temperatures for 3 h created fissures. Bending tests using a texture analyzer showed that brown rice breaking force increased from 18.5 N (fissured kernels) to 43.7 N (healed kernels). Soaking rough rice in water at a temperature slightly above its onset gelatinization temperature may potentially heal fissures.     

Extraction of fumonisins B1 and B2 from white rice flour and their stability in white rice flour,cornstarch, cornmeal,and glucose

To extract fumonisin B1 (FB1) and fumonisin B2 (FB2) from Thai white rice flour, different solvent mixtures, temperatures, pH values, and addition of enzymes or ethylenediaminetetraacetic acid disodium salt (Na2EDTA) were examined. Three extractions with 0.1 M Na2EDTA achieved the highest recoveries. Initial recoveries of fumonisins added to white rice flour, cornstarch, cornmeal, and glucose varied with commodity. Fumonisins disappeared in Thai white rice flour after 12 h, but 55% remained in another white rice flour. With cornstarch 20-30% fumonisins remained after 24 h; only 43% of 14C-labeled FB1 materials extracted from cornstarch was eluted with methanol from an immunoaffinity column. Fumonisins were stable in cornmeal for 24 h but only approximately 50% remained after 30 days. With glucose, 25% of FB1 and FB2 remained 24 h after addition; N-(1-deoxy-D-fructos-1-yl)FB(1) andN-(carboxymethyl)FB(1) were detected in lower amounts than residual FB(1) after 3 months.     

Comparison of extraction buffers for the detection of fumonisin B(1) in corn by immunoassay and high-performance liquid chromatography

The Associatian of Official Analytical Chemists approved method for quantification of fumonisin B(1) (FB(1)) in corn meal or corn-based food products includes extraction into methanol (MeOH)/water (3:1, v/v). Disposal of the extraction medium can pose safety and environmental problems. To secure a rapid and inexpensive screen for FB(1) contamination, a sensitive competitive ELISA using a rabbit polyclonal antibody was developed. This assay was used in a comparative study measuring the extraction efficiency of FB(1) in aqueous or organic solvent buffers using 16 field corn samples. An aqueous phosphate buffer was found to be suitable for extracting FB(1), thus eliminating the need for organic solvents. HPLC and ELISA determinations compared well in fortified samples at known concentrations between 1 and 50 microg/mL of extract. Overestimation at levels >50 microg/mL were common. The characteristics and application of the ELISA for screening purposes are discussed.     

Liquid chromatographic determination and stability of the Fusarium mycotoxin moniliformin in cereal grains

Moniliformin is a mycotoxin produced by Fusarium subglutinans and other Fusarium species. A rapid, liquid chromatographic method for its determination in corn and wheat is described. Samples are extracted in acetonitrile-water (95 + 5); following defatting with n-hexane, an aliquot of the extract is evaporated and cleaned up on small C18 and neutral alumina columns successively. Reverse-phase liquid chromatography (LC) is conducted on a C18 column with 10 or 15% methanol or acetonitrile in aqueous ion-pair reagent as mobile phase, with detection by ultraviolet absorption at 229 and 254 nm. Average recoveries of moniliformin (potassium salt) added to ground corn and wheat at levels of 0.05-1.0 micrograms/g were 80% (n = 20) and 85% (n = 12), respectively, and the limit of detection was ca 0.01-0.18 micrograms/g, depending on LC conditions. Analysis of 24 samples of wheat, 4 samples of rye, and 12 samples of corn showed moniliformin in only 2 corn samples (0.06 and 0.2 micrograms/g). Moniliformin was also detected in a sample of artificially damaged (slashed) corn (0.2 micrograms/g) and selected kernels of corn that were field-inoculated with F. subglutinans and F. moniliforme (50 micrograms/g and 0.5 micrograms/g, respectively). In stability studies, moniliformin (potassium salt, 1 microgram/g) in ground corn and ground wheat heated at 50, 100, and 150 degrees C for 0.5-2 h decomposed moderately, e.g., 55% remained in corn after 0.5 h at 100 degrees C.     

Solubility, tensile, and color properties of modified soy protein isolate films

Protein solubility (PS) values of different soy protein isolate (SPI) films were determined in water, 0.01 N HCl, 0.01 N NaOH, 4 M urea, and 0.2 M 2-mercaptoethanol. Tensile and color (L, a, and b values) properties of films also were determined. Control films were cast from heated (70 degrees C for 20 min), alkaline (pH 10) aqueous solutions of SPI (5 g/100 mL of water) and glycerin (50% w/w of SPI). Additional films were cast after incorporation of dialdehyde starch (DAS) at 10% w/w of SPI or small amounts of formaldehyde in the film-forming solutions. Also, control film samples were subjected to heat curing (90 degrees C for 24 h), UV radiation (51.8 J/m(2)), or adsorption of formaldehyde vapors. PS of control films was highest (P < 0.05) in 2-mercaptoethanol, confirming the importance of disulfide bonds in SPI film formation. All treatments were effective in reducing (P < 0.05) film PS in all solvents. Both DAS and adsorbed formaldehyde rendered the protein in films practically insoluble in all solvents. Adsorption of formaldehyde vapors and heat curing also substantially increased (P < 0.05) film tensile strength from 8.2 to 15.8 or 14.7 MPa, respectively. However, heat curing decreased (P < 0.05) film elongation at break from 30 to 6%. Most treatments had small but significant (P < 0.05) effects on b color values, with DAS-containing films having the greatest (P < 0. 05) mean b value (most yellowish). Also, DAS-containing, heat-cured, and UV-irradiated films were darker, as evidenced by their lower (P < 0.05) L values, than control films. It was demonstrated that PS of SPI films can be notably modified through chemical or physical treatments prior to or after casting.     

Inhibition against heat coagulation of ovotransferrin by ovalbumin dry-heated at 120 degrees C

Ovalbumin (OVA) was aggregated stepwise by dry heating at 120 degrees C with a gradual increase in its heating times (10 min-6 h). The inhibiting effects of DHOVAs (OVAs dry-heated for various times up to 6 h) on the heat coagulation of ovotransferrin (OT) were studied. DHOVAs and OT were solubilized at 5% (w/w) concentration with 10 mM sodium phosphate buffer, pH 7.4. Their solutions were mixed at the volume ratio of 1:1 and reheated at 60 degrees C for 3. 5 min. Some remarkable differences according to dry-heating time were observed: coagulum formations were greatly inhibited in the solutions mixed with DHOVAs treated for more than around 2.0 h, with decreasing turbidity as dry-heating time increased. In addition, the effects of reheating time and temperature, as well as those of pH and ionic strength, were also examined on coagulum formation and turbidity development in connection with dry-heating time. Thus, the inhibiting effects of dry-heated egg white on the heat coagulation of fresh egg white previously described were confirmed on the molecular level of OVA and OT.