Phytate Reduction in Oats during Malting

To reduce phytate in oat products and thereby increase mineral bioavailability, optimal conditions for phytate degradation in oats were investigated. The effects of malting and incubation on phytate reduction in oats were determined and compared with phytate degradation in wheat, rye and barley. Studies of incubation temperatures showed an optimum for phytate reduction in oats between 37–40°C which differed from that in wheat (55°C). Malting of oats for 5 days at 11°C and subsequent incubation for 17 hr at 37–40°C reduced phytate by 98%. Addition of malted rye also reduced the phytate content of oats to low levels.     

The effect of thermal treatment on β‐glucosidase inactivation in vanilla bean (Vanilla planifolia Andrews)

The conditions for enzyme activity (pH and temperature) and kinetic parameters for the thermal inactivation of β‐glucosidase enzyme in vanilla beans have been investigated. The maximum enzyme activity was detected at pH 6.5 and 38 °C. The values obtained for V_max and K_m were 62.05 units and 2.07 mm, respectively. When hot water treatment (the most practical method of vanilla bean killing) was applied, β‐glucosidase treated at pH 6.0 and 60 °C for 3 min lost 51% of activity, while at 70 °C for 90 s the enzyme lost 60% of activity and at 80 °C for 30 s the enzyme lost 48% of its activity. When vanilla beans were cured in an oven at 60 °C for 36 to 48 h all β‐glucosidase activity was lost.     

Zinc and Phytate Distribution in Peas. Influence of Heat Treatment, Germination, pH, Substrate, and Phosphorus on Pea Phytate and Phytase

The largest proportions of zinc and phytate, 88.7 and 97.1%, respectively, were in the Garfield pea cotyledon; the greatest concentrations were in the germ. Cooking peas by two different methods resulted in 13% phytate reduction. Peas incubated 6.5 hr from 25 to 80°C yielded maximum phytate loss (25%) at 60°C due to phytase activated hydrolysis. Germination (10 d) decreased pea phytate 75% and increased phytase activity 12-fold. Semi-purified germinated pea phytase showed temperature optimum at 45°C, pH optimum of 5.2, 30% inhibition by 1 mM inorganic P, and substrate preference for pyrophosphate. Incubation of early germinated peas at optima pH and temperature is suggested for maximum phytate reduction.     

Purification and characterization of a phytate-degrading enzyme from germinated oat (Avena sativa)

A phytate-degrading enzyme (myo-inositol hexakisphosphate phosphohydrolase) has been purified about 5,400-fold from germinated oat seedlings to apparent homogeneity. The molecular mass of the native monomeric enzyme was estimated to be about 67 kDa. Optimal pH for degradation of phytate was 5.0 and the optimal temperature 38 °C. Kinetic parameters for the hydrolysis of Na-phytate are K_M 30 µM and k_cat 356 s⁻¹ at 35 °C and pH 5.0. The oat phytase exhibits a broad affinity for various phosphorylated compounds and hydrolyses phytate in a stepwise manner. The first hydrolysis product was identified as D /L -l(1,2,3,4,5) P₅. © 1999 Society of Chemical Industry     

Effect of phytate and storage conditions on the development of the ‘hard‐to‐cook’ phenomenon in common beans

Postharvest storage of beans (Phaseolus vulgaris L.) can alter the color, texture, flavor and time required for cooking. These alterations have been associated with the ‘hard‐to‐cook’ phenomenon (HTC) and a reduction in the quality of the grains. HTC has been linked to the genotype, environment and/or storage conditions of the grains, but very few studies have shown the interrelationship between these factors. Therefore, the objective of this study was to analyze the effect of two genotypes, Paraiso and Peruano, grown under the same phosphorus levels, on the development of HTC. These genotypes were evaluated for phytate, protein, tannin and phosphorus contents, hydration time and cooking time when stored for 45, 90 and 135 days, at 29 °C and 5 °C at a relative humidity of 75%. HTC was observed in Peruano after 135 days, which correlated with a reduction in the phytate content. Paraiso did not show HTC even though there was a reduction of tannins during the storage period. The lower storage temperature appeared to control HTC for both genotypes. Overall, the content of phytate can be an indicative factor for the cookability of fresh beans when the relationship between genotype and storage conditions has been determined. Copyright © 2007 Society of Chemical Industry     

Reduction of Metmyoglobin by Extracts of Bovine Liver and Cardiac Muscle

Enzymatic reduction of metmyoglobin (in vivo) was investigated using a partially purified metmyoglobin reductase from bovine cardiac muscle. Greater substrate reduction (P<0.05) occurred at pH 6.3 versus 7.0 or 7.3 and at 375°C compared to 22°C using either partially purified cytochrome as or potassium ferrocyanide as reaction mediators. Differences in effectiveness between potassium ferrocyanide and the cytochrome b, preparation were dependent on specific pH/temperature conditions. The cytochrome preparation alone (i.e. without metmyoglobin reductase) reduced metmyoglobin at a rate comparable to that of the reductase. At 22°C the cytochrome b=, preparation assay displayed much slower re-oxidation than the cardiac reductase/ferro-cyanide assay (48 vs 2 hr, respectively).     

Tannase from Aspergillus melleus improves the antioxidant activity of green tea: purification and biochemical characterisation

Tannase is an inducible enzyme used extensively in food, feed, pharmaceutical and chemical industries. In this study, tannase production and its biochemical properties were evaluated. From 42 Aspergillus strains analysed for potential tannase selection, Aspergillus melleus yielded the best results. Production was analysed using a complete factorial planning of 2³. Maximum activity (452.55 U mL^?1) was obtained in the optimal conditions of substrate (5.0 g), initial moisture (60%), tannic acid (2%) and 48 h of fermentation. The molecular weight of the purified enzyme was estimated as 69.52 kDa; its optimum temperature and pH were 40 °C and 5.5, respectively. Regarding the chemical effectors used, tannase was inhibited by ZnCl₂, ZnSO₄, Triton X‐100 and SDS. The addition of tannase to green tea improved its antioxidant potential by approximately 85% when compared to the control. The present results suggest that tannase may be used as an adjuvant to increase the antioxidant potential of green tea.     

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.     

Thermal Degradation of Flavor Enhancers, Inosine 5'-monophosphate, and Guanosine 5'-monophosphate in Aqueous Solution

The mechanism of thermal degradation of inosine 5′-monophosphate (IMP) and guanosine (GMP) was investigated kinetically in aqueous solution as a function of pH and temperature. The degradation of IMP and GMP followed first order kinetics. The rate constants were considerably affected by pH and temperature. The half-life times at 100°C were: IMP, 8.7 hr (pH 4.0), 13.1 hr (pH 7.0), 46.2 hr (pH 9.0); GMP, 6.4 hr (pH 4.0), 8.2 hr (pH 7.0), 38.5 hr (pH 9.0). These times were shortened to about one-third by raising the temperature 10°C. The predominant degradation products were nucleosides and phosphoric acid, indicating that the main reaction of the thermal degradation was the hydrolysis of the phosphoric ester bond in the nucleotides.     

Characterisation and application of Halomonas shantousis SWA25, a halotolerant bacterium with multiple biogenic amine degradation activity

Biogenic amines are identified as toxicological substances in foods and may have detrimental effects on consumers’ health. In recent years, the application of microorganisms that can degrade biogenic amines has become an emerging method for their reduction. The degradation characteristics and application potential of a salt-tolerant bacterium Halomonas shantousis SWA25 were investigated in this study. H. shantousis SWA25 exhibited degradation activity against eight biogenic amines at 10–40°C (optimum, 30–40°C) and pH 3.0–9.0 (optimum, 6.0–7.0) in the presence of 0–20% (w/v) NaCl (optimum, 0%). Specifically, H. shantousis SWA25 degraded all tryptamine (TRY) and tyramine (TYR) in 6 h, all phenethylamine (PHE) in 9 h, 66.7% of histamine (HIM), 52.4% of cadaverine (CAD), 48.0% of spermidine (SPD), 42.9% of putrescine (PUT) and 42.0% of spermine (SPM) in 20 h at 30°C and pH 7.0 with shaking at 120 r min^?1. The enzymes from H. shantousis SWA25 responsible for degradation of biogenic amines were mainly amine oxidases located on the cell membrane. Further studies showed that H. shantousis SWA25 effectively degraded TRY, PHE, PUT, CAD, HIM and TYR in commercial fish sauce and soy sauce samples. Nevertheless, significant SPD and SPM degradation were not observed due to low initial concentrations. Therefore, H. shantousis SWA25 can be applied as a potential biogenic amines degradation bacterium in foods.     

Stability of Mannitol to Lactobacillus plantarum Degradation in Green Beans Fermented with Lactobacillus cellobiosus

Mannitol, in fermented green bean juice, was converted to lactic acid by Lactobacillus plantarum when the initial pH was raised to 3.9. However, at pH 3.5, mannitol was stable to anaerobic degradation by a 10⁶ CFU/ml inoculum of 19 strains of L. plantarum and four isolated homofermentative lactobacilli. Several strains were capable of limited mannitol degradation at an initial pH 3.7. Completely fermented beans were microbiologically stable for at least 6 months under anaerobic conditions at 27°C. It is possible that heterolactic acid-fermented vegetables are microbiologically stable provided fermentable sugars are removed and the pH is lowered below pH 3.7.     

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.     

Sensitivity of spores of Bacillus subtilis and Clostridium sporogenes PA 3679 to combinations of high hydrostatic pressure and other processing parameters

The combined effects of pressure, temperature, pH and the presence of nisin or sucrose laurate on the survival of spores of Bacillus subtilis 168 and Clostridium sporogenes PA 3679 were investigated. Spore populations of PA 3679 were reduced by 2.5-log₁₀ when exposed to 404 megapascals (MPa) at 25°C, pH 4.0 for 30 min, but the same treatment at pH 7.0 resulted in a <0.5-log₁₀ reduction in spore counts. Pressurization of B. subtilis spores at 70°C, pH 6.0 or 7.0 for 15 min at 404 MPa resulted in a 5-log₁₀ reduction as compared to a <0.5-log₁₀ reduction for the same pressurization treatment at 25°C. For the inactivation of spores of B. subtilis and PA 3679, the addition of nisin to the plating medium appeared to be synergistic in some instances when combined with pressurization at elevated temperatures and reduced pH. B. subtilis 168 was resistant to 0.1% sucrose laurate, but when combined at ≤6.0 pH with a 15-min treatment of 404 MPa at 45°C, a dramatic synergistic effect eliminated spore suspensions of 1×10⁶/ml.     

Oxidation of Tryptophan by H2O2 in Model Systems

Degradation reactions of tryptophan (trp) and the dipeptides alanyltryptophan (ala-trp) and phenylalanyltryptophan (phe-trp), induced by H₂O₂, were investigated under different conditions in aqueous systems. Decreases in the content of trp as well as the formation of soluble degradation products were determined. Highest losses of trp were obtained after H₂O₂ treatment at 100°C for 2 hr at pH 8.5. Lowest losses occurred at pH 4.0, 25°C, for 30 min. The destruction of trp in ala-trp was similar, while losses of trp in phe-trp under the same reaction conditions were lower. This was indicative of a negative induction effect of the phenyl ring. The quantity of degradation products showed extensive variations, dependent upon the radical mechanism of the oxidation reaction.     

A Study of Factors Affecting Growth and Recovery of Listeria monocytogenes Scott A

The growth parameters for Listeria monocytogenes Scott A at various temperatures, pH values, water activity values, and in different carbohydrates were assessed. Growth was seen from 4°C through 45°C and at pH values from 4.7 through 9.2. Generation times were calculated for each parameter at which growth was observed. Optimum growth was defined as shortest generation time. L. monocytogenes grew optimally over the temperature range 30–37°C. The optimum pH was 7.0. Growth was demonstrated in solutions of up to 39.4% sucrose (a_w of 0.92). Carbohydrate fermentation was variable. Further studies involved examination of growth at optimal water activities (0.97) with suboptimal temperatures and pH values, and at 7.0, with suboptimal temperatures and water activities. Growth was seen when these parameters were combined.     

Effect of storage of adzuki bean (Vigna angularis) on starch and protein properties

Differential scanning calorimetry was used to evaluate the effect of storage at 10°C, 20°C and 30°C, and 40% and 65% relative humidity (RH) on adzuki bean starch gelatinisation and protein denaturation temperatures. Storage for 6 months at an elevated storage temperature (30°C) caused increases in the starch gelatinisation onset temperature (T_o) and gelatinisation peak temperature (T_p) for both Bloodwood and Erimo varieties. Storage at 40% RH resulted in higher T_o and T_p values than storage at 65% RH. The T_o of starch from Bloodwood and Erimo beans stored for up to 1.5 months at 10°C and 65% were similar to those of fresh beans.The changes in the salt-soluble protein component were less clear cut than those of the starch. Nonetheless, protein extracted from beans stored at 40% RH exhibited significantly lower T_o and T_p values compared with those stored at 65% RH. This indicates some destabilisation of the protein at the higher RH.These results suggest that detrimental changes occur in starch and, to a lesser extent protein, of adzuki beans stored under unfavourable conditions. On the basis of these results, the best storage conditions to maintain the characteristics of fresh beans are low temperatures (e.g. 10°C) and high RH (e.g. 65%).     

A comparison of effects of pH on the thermal stability and conformation of caprine and bovine lactoferrin

Thermal stability and structural changes in caprine lactoferrin (cLF) and bovine lactoferrin (bLF) at pH 2.0–8.0 were measured using thermal denaturation temperature (T_m) analysis, fluorescence spectroscopy and circular dichroism (CD). Thermal stability analysis indicated a T_m of 70 °C for bLF and 67 °C for cLF at pH 7.0. From pH 7.0 to 3.0, a gradual reduction in the T_m of both bLF and cLF was observed and reached a value of 39 °C and 30 °C, respectively. At pH 2.0–3.0, a partly unfolded structure of bLF and cLF was observed with a relatively low content of α-helix structure (3% and 7%, respectively), but still rich in β-structure (54% and 57%, respectively). A higher exposure of hydrophobic surfaces at low pH for bLF compared with cLF was proved by fluorescence studies. In conclusion, the structure of cLF was more affected by pH and showed lower temperature stability than bLF.     

Effect of Food Composition on the Heat Resistance of Yeast Ascospores

The ascospores of Saccharomyces cerevisiae were over 100-fold more resistant than vegetative cells of the same strain. The D₆₀ of spores in apple juice was 6.1 min and the z value was 3.8°C; in a Chenin blanc wine the D₅₅ was 0.57 min and the z value was 6.7°C. The presence of sugar in the heating medium increased spore resistance while alcohol reduced it; varying pH over the range 3.0 to 7.0 had little effect.     

Effects of Heat-Stable Alakaline Protease Activity of Atlantic Menhaden (Brevootii tyrannus) on Surimi Gels

Heat stable protease isolated from the sarcoplasmic fraction of menhaden (Brevoorti tyrannus) muscle tissue was characterized as to optimum temperature and pH against casein substrate and its degradative action on actomyosin and surimi during heating. The optimum conditions for activity were 60°C at a pH of 7.5 to 8.0. Activity dropped off remarkably at temperatures below 45°C or above 70°C and when pH was below 7.0 or above 8.0. The enzyme(s) was capable of degrading actomyosin as observed by sodium dodecyl sulfate electrophoresis. This implicated a causative role for this protease system in the texture degradation observed during thermal processing of menhaden surimi at temperatures of 50-70°C.     

A comparison between the properties of seed,starch, flour and protein separated from chemically hardened and normal kidney beans

The physicochemical, functional and thermal properties of starch, flour and protein isolates obtained from chemically hardened kidney beans were evaluated. A rapid chemical hardening procedure (soaking in acetate buffer, pH = 4.0, 37 °C, 6 h) was used to produce hardened kidney beans. Chemical hardening altered physicochemical, cooking, hydrating and textural properties of beans to a significant level (P < 0.05). Soaked and cooked chemically hardened beans had a higher value for different textural parameters than their normal counterparts. Chemical hardening increased cooking time (from 49 to 123 min) of beans and decreased swelling power and solubility of starch. The turbidity value of gelatinized starch suspensions from chemically hardened beans was significantly lower than that from normal beans. Chemical hardening of beans caused significant increase in transition temperatures (T_o, T_p, T_c) and enthalpy of gelatinization (ΔH_gel) of both starch and flour. Chemically hardened bean starch showed significantly higher pasting temperature (94.9 °C) as compared to normal bean starch (83.2 °C). Flour and protein isolate from chemically hardened beans showed significantly lower water absorption, oil absorption, foaming capacity and gelling ability than those from normal beans. The onset temperature (T_m), peak denaturation temperature (T_d) and heat of transition or enthalpy (ΔH) of protein isolate from hardened and normal beans did not differ significantly. Copyright © 2007 Society of Chemical Industry