LIPID OXIDATION IN TURKEY MEAT AS INFLUENCED BY SALT,METAL CATIONS AND ANTIOXIDANTS1

Turkey breast or thigh muscle was mixed with 2% pure salt, rock salt, or pure salt plus 50 ppm of one or a combination of copper, iron or magnesium. Efficacy of 2 antioxidants was tested. Lipid oxidation was monitored during refrigerated and frozen storage of raw and cooked turkey by the thiobarbituric acid (TBA) test. TBA results indicated that the most significant prooxidant effect was caused by salt plus Cu²⁺ and Fe²⁺ followed by salt plus Fe³⁺ or Cu²⁺ alone. Tenox 6 was an effective antioxidant in the presence of copper and iron ions. Thigh meat was more susceptible to oxidation than breast meat. Cooking had a significant prooxidant effect as measured by TBA.     

Potential mechanism of kaempferol against Cu2+-induced oxidative stress through chelating activity and regulation of nuclear factorerythroid-2-related factor 2 signaling

Metal ions play important roles in various biological processes of living systems. However, the generation of reactive oxygen species (ROS) is also closely linked with the participation of redox-active metal ions such as copper, iron, chromium, and cobalt ions. Excessive production of ROS by redox-active metal ions can cause oxidative stress and further oxidative stress-related diseases. This study shows the results of the antioxidant activity of kaempferol in both ORAC_OH· and Cu²⁺-treated HepG2 cells. Preventive mechanism of kaempferol in Cu²⁺-treated HepG2 cells is also elucidated. These results suggest that both cellular Cu²⁺-chelating activity and expression of phase II detoxifying enzymes such as HO-1 and GSTA2 through activating Nrf2 are required for cellular antioxidant activity of kaempferol in Cu²⁺-treated HepG2 cells. Our findings provide the scientific evidence for the development of Nrf2 targeting dietary antioxidant to prevent oxidative stressrelated conditions.     

Effects of metal ions on growth, β-oxidation system,and thioesterase activity of Lactococcus lactis

The effects of divalent metal ions (Ca²⁺, Mg²⁺, Fe²⁺, and Cu²⁺) on the growth, β-oxidation system, and thioesterase activity of Lactococcus lactis were investigated. Different metal ions significantly influenced the growth of L. lactis: Ca²⁺ and Fe²⁺ accelerated growth, whereas Cu²⁺ inhibited growth. Furthermore, Mg²⁺ inhibited growth of L. lactis at a low concentration but stimulated growth of L. lactis at a high concentration. The divalent metal ions had significant effects on activity of the 4 key enzymes of the β-oxidation system (acyl-CoA dehydrogenase, enoyl-CoA hydratase, L-3-hydroxyacyl-CoA dehydrogenase, and thiolase) and thioesterase of L. lactis. The activity of acyl-CoA dehydrogenases increased markedly in the presence of Ca²⁺ and Mg²⁺, whereas it decreased with 1 mmol/L Fe²⁺ or 12 mmol/L Mg²⁺. All the metal ions could induce activity of enoyl-CoA hydratase. In addition, 12 mmol/L Mg²⁺ significantly stimulated activity of L-3-hydroxyacyl-CoA dehydrogenase, and all metal ions could induce activity of thiolase, although thiolase activity decreased significantly when 0.05 mmol/L Cu²⁺ was added into M17 broth. Inhibition of thioesterase activity by all 4 metal ions could be reversed by 2 mmol/L Ca²⁺. These results help us understand the effect of metal ions on the β-oxidation system and thioesterase activity of Lactococcus lactis.     

Influence of dietary phenolic acids on redox status of iron: Ferrous iron autoxidation and ferric iron reduction

We investigated the effect of dietary phenolic acids on the oxidation of Fe²⁺ caused by molecular oxygen. All phenolic acids bearing 3,4-dihydroxy (catechol) or 3,4,5-trihydroxy (galloyl) moiety formed chelates with ferric iron and significantly increased the rate of Fe²⁺ autoxidation. The carboxylate group and catechol substitution instead of galloyl moiety facilitated the ferrous ion oxidation more effectively. Caffeic acid and protocatechuic acid, the strongest accelerators of Fe²⁺ autoxidation, were able to facilitate autoxidation at concentrations lower than 1% of the initial amount of Fe²⁺. Therefore chelates of these catecholic acids with iron displayed ferroxidase-like activity. Conversely, when we started from ferric ions, catechols partially formed ferrous ions in the presence of ferrozine. Thus, catecholic acids formed stable chelates with iron, in which ferric ion is the dominant species, but the redox cycling of iron between Fe²⁺ and Fe³⁺ in chelates probably plays a crucial role in the catalysis of ferrous iron autoxidation. Interestingly, 3-hydroxybenzoic acid, 4-hydroxybenzoic acid and vanillic (4-hydroxy-3-methoxybenzoic) acid protected ferrous ions from autoxidation as effectively as ascorbic acid and cysteine. These monophenolic acids, differently from ascorbic acid and cysteine, were not able to reduce ferric ions. Syringic (3,5-dimethoxy-4-hydroxybenzoic) acid did not alter the redox state of iron, only in a large excess over metal, syringic acid slightly inhibited ferrous ions autoxidation and partially reduced ferric ions. Therefore, the effects of syringic acid at high concentration were similar but much lower to those of ascorbic acid and cysteine. The biological importance of ferroxidase-like activity of polyphenols, especially the influence on iron absorption, is also discussed.     

Growth Inhibition of Listeria monocytogenes by Sodium Polyphosphate as Affected by Polyvalent Metal Ions

Sodium polyphosphate (SPP, average chain length = 13) increased the lag time of L. monocytogenes Scott A (Lm) in brain-heart infusion broth (BHI). Polyvalent metal ions (1–10 mM) reversed inhibition of Lm growth by 0.5% SPP (nominal 3.6 mM). 10 mM Ca²⁺ or Mg²⁺, 5 mM Fe³⁺, 2 mM Mn²⁺ or 1 mM Zn²⁺ added to SPP-containing BHI, pH 6.0, at 19°C resulted in growth comparable to control cultures. Fe²⁺ partially restored growth; Ni²⁺, Co²⁺, Cu²⁺ or Al³⁺ were ineffective. SPP inhibited growth at 28°C in BHI, pH 5.0, and Lm grew upon addition of Ca²⁺, Mg²⁺ or Mn²⁺, but not Zn²⁺ or Fe³⁺. Addition of 0.5% SPP to mineral-rich foods, such as pureed beef, green beans or sweet potatoes, did not delay growth.     

The interaction of metal ions with Maillard reaction products in a lactose–glycine model system

The influence of Cu²⁺, Fe²⁺ and Zn²⁺-ions on Maillard model reactions was studied by heat treatment of lactose/glycine model solutions. The presence of metals affected the intensity of browning. Fe²⁺-ions stimulated the accumulation of colored compounds at all concentrations (20–100 mg/L) tested, Cu²⁺ and Zn²⁺ only at the lowest concentrations applied (1 and 5 mg/L, respectively) but to a higher extent. Cu²⁺ and Zn²⁺-ions at the highest concentrations applied (5 and 25 mg/L, respectively) suppressed browning of the model mixtures. The relative amounts of metal ions incorporated into the high molecular weight melanoidin fraction increased initially with the reaction time, but near the end of the reaction time studied (5 h, reflux conditions) Cu²⁺ and Fe²⁺-ions were released again from the melanoidins. The amounts of metal ions incorporated into the lactose–glycine melanoidins and their influence on Maillard browning of the different fractions depended on the time of interaction and the nature and concentration of the incorporated metals.     

The Effect of Proanthocyanidins on Growth and Alcoholic Fermentation of Wine Yeast under Copper Stress

Proanthocyanidins (PAs) derived from the grape skin, as well as from grape seeds, grape stems, are an important group of polyphenols in wine. The aim of this study was to understand the effect of PAs (0.1, 1.0 g/L) on growth and alcoholic fermentation of 2 strains of Saccharomyces cerevisiae (commercial strain FREDDO and newly selected strain BH8) during copper‐stress fermentation, using a simple model fermentation system. Our results showed that both PAs and Cu²⁺ could pose significant inhibition effects on the growth of yeast cells, CO₂ release, sugar consumption, and ethanol production during the initial phase of the fermentation. Compared to PAs, Cu²⁺ performed more obvious inhibition on the yeast growth and fermentation. However, adding 1.0 g/L PAs increased in the vitality and metabolism activity of yeast cells at the mid‐exponential phase of fermentation in the mediums with no copper and 0.1 mM Cu²⁺ added, shortened the period of wine fermentation, and decreased the copper residues. It indicated that PAs could improve the ability of wine yeast to resist detrimental effects under copper‐stress fermentation condition, maintaining cells metabolic activity, and fermentation could be controlled by manipulating PAs supplementation.     

Effects of metal ions (Cu,Fe and Fe) on HPLC analysis of catechins

Catechins [(−)-epicatechin (EC), (−)-epigallocatechin (EGC), (−)-epicatechin gallate (ECG) and (−)-epigallocatechin gallate (EGCG)] were analysed by HPLC using an ODS column, an electrochemical detector (0.75 V vs. Ag/AgCl) and an eluting solvent composed of water containing buffer (84% v/v), acetonitrile (12% v/v) and ethylacetate (4% v/v) in the presence of metal ions (Cu²⁺, Fe²⁺ and Fe³⁺). HPLC peaks were affected by metal ions: the peak intensities of ECG and EGCG decreased, but the peak intensities of EC and EGC were not affected seriously. Fe²⁺ most markedly decreased the peak intensities of EGCG. EDTA was added to mask metal ions and an optimum condition was proposed. The effects of the metal ions on HPLC analysis are discussed from the viewpoints of metal complex formation with catechins and oxidation of catechins on the basis of ultraviolet–visible (UV–vis) spectrophotometry, electrospray ionisation mass spectrometry (ESI-MS) and cyclic voltammetry (CV).     

High levels of copper retard the growth of Saccharomyces cerevisiae by altering cellular morphology and reducing its potential for ethanolic fermentation

Previous research has shown that high levels of Cu²⁺ inhibit the growth of yeast and induce sluggish fermentation, resulting in a decrease in alcohol production. Little data are available on the effects of copper on the cell morphology, especially the surface elasticity of Saccharomyces cerevisiae. This work investigated the effects of Cu²⁺ (0.5, 1.0 and 1.5 mm ) on the growth, surface characteristics and elasticity of two strains of S. cerevisiae in a low sugar model synthetic medium. The results indicated that high levels of Cu²⁺ retarded the growth rate of S. cerevisiae and reduced the utilisation of reducing sugars. Cells showed intercellular adhesion, became small and deformed, and the surface was uneven and rough after the adsorption of Cu²⁺. The Young's modulus also decreased with an increase in the concentration of Cu²⁺, indicating that the cells had softened. This study reveals the response mechanism of S. cerevisiae under copper stress by altering cellular morphology and mechanical properties.     

红曲甜米酒生产过程中红曲色素稳定性研究

通过固态发酵的方法,制备红曲米,并从中提取出天然红曲色素。以色价为指标,研究光照、温度、受热时间及金属离子对红曲色素稳定性的影响。结果表明:光照条件对红曲色素稳定性影响的大小顺序为日光紫外灯避光处,其中,日光对红曲色素稳定性的影响最为明显;另外随着温度的升高,红曲色素的稳定性越来越差,加热时间越长,色价损失越大;金属离子中,Fe~(3+)对红曲色素的影响最大,而Cu~(2+)和Zn~(2+)影响不显著。     

Pea mitochondrial lipids and their oxidation during mitochondria swelling

The composition and oxidation of lipids in pea mitochondria induced by swelling in presence of some transitional metal ions and ascorbic acid has been studied. Among the major mitochondrial lipids found were phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol and diphosphatidylglycerol. The major fatty acids present in these lipids were linoleic, oleic and palmitic acids. The average unsaturation for mitochondria total fatty acids, expressed as Double Bond Index was 1.44, while the unsaturation for fatty acids of individual lipids varied between 1.02 and 1.73 being highest for an unidentified phospholipid and 1.44 for phosphatidylcholine present in mitochondria as the major lipid. Mitochondria isolated from pea seeds germinated for 4 days were found to be tightly coupled and to have an ADP/O ratio of 1.3. The swelling assay in 0.1 M-KCl for 1-day-old mitochondria has shown a swelling ability matching those of 4 and up to 8 days of age. Isolated mitochondria aged for 24 h at 2–4º C showed a swelling comparable to that of the fresh preparation. Swelling in the presence of ascorbic acid did not induce mitochondrial lipid oxidation. However, this was brought about in the presence of Cu²⁺ ions. The presence of Fe²⁺ ions induced the highest degree of oxidation, and instead of a concurrent swelling, it induced contraction. At the same level of ions, Fe²⁺ was more effective than Fe³⁺. Contrary to iron used at 4% of its physiological level, Mn²⁺ and Co²⁺ used at 12 to 24% of their levels found in pea seeds were ineffective in inducing oxidation. Nevertheless, the degree of mitochondrial swelling was highest in the medium containing KCl, lower in the presence of Co²⁺ and ascorbic acid and lowest in the presence of Fe³⁺. These results suggested that mitochondrial lipid oxidation does not depend on the degree of swelling. The lipid peroxides formed within mitochondria, up to 8 mg of mitochondrial protein, could not be detected by dropping mercury electrode polarography but were readily determined colorimetrically using thiobarbituric acid reagent.     

Preparation of Amylose-g-Poly (Styrene)

A study on the grafting of styrene on amylose has been made using H₂O₂ as an initiator and Cr³⁺, Fe²⁺, Co²⁺, Cu²⁺, Zn²⁺, and Ag⁺ ions as catalyst. It has been shown that with Fe²⁺ ions maximum grafting yield was obtained. The optimum conditions for the preparation of amylose-g-poly (styrene) have been set up.     

Assessing the antioxidant and pro-oxidant activity of phenolic compounds by means of their copper reducing activity

The antioxidant or pro-oxidant activity of some dietary phenolic compounds has been determined by their reducing activity over Fe³⁺ and Cu²⁺. The FRAP method has shown that phenolic acids exert a high reducing activity that give rise to a decrease in linoleic acid oxidation mediated by Fe³⁺, measured as TBARS. However, the reducing activity of phenolic compounds over Cu²⁺ leads to linoleic acid oxidation. Reducing capability against copper has been measured by a new approach called CRAI (Copper Reducing Activity Index), and results agreed with the degree of hydroxylation of the studied compounds. Sensibility and reproducibility of the method have been checked by measuring the inter-day and intra-day variation (1.08 and 1.89%, respectively). Possible pro-oxidant activity of phenolic compounds should be considered when the overall antioxidant activity in Cu naturally rich or Cu-enriched foodstuffs for dietetic purposes has to be evaluated.     

Purification and characterisation of β‐mannanase from Lactobacillus plantarum (M24) and its applications in some fruit juices

β‐Mannanase was purified 2619.05‐fold from the Lactobacillus plantarum (M24) bacterium by ammonium sulphate precipitation and ion exchange chromatography (DEAE‐Sephadex). The purified enzyme gave two protein bands at a level of approximately 36.4 and 55.3 kDa in the SDS‐PAGE. The purified mannanase enzyme has shown its maximum activity at 50 °C and pH 8, and it has been also determined that the enzyme was stable at 5–11 pH range and over 50 °C. The V_max and K_m values have been identified as 82 mg mannan mL^?1 and 0.178 mm , respectively. The effects of some metal ions such as Fe²⁺, Ca²⁺, Co²⁺, Ni²⁺, Mn²⁺, Cu²⁺ and Zn²⁺ on the mannanase enzyme have been also investigated, and it has been determined that all metal ions had significant effects on the activation of the mannanase enzyme. In addition, the effectiveness of the purified mannanase enzyme on the clarification of some fruit juices such as orange, apricot, grape and apple has been investigated. During the clarification processes, the enzyme was more effective than crude extracts on the clarification of the peach juice with a ratio of 223.1% at most.     

Application of beech sawdust for removal of heavy metals from water: biosorption and desorption studies

In this work the efficiency of applying non-modified beech sawdust for the removal of Cu²⁺ and Cr³⁺ heavy metal ions from water solutions was examined. Parameters taken into consideration in the analysis of environment conditions were influence of sorbent concentration, initial concentration of metal ions, temperature effect, presence of additional substances in solution (NaCl and MgCl₂ inorganic salts and anionic and cationic surface-active compounds). Results of kinetic experiments were described by two models: pseudo-first-order and pseudo-second-order; equilibrium results were approximated with five non-linear isotherm models. Maximum sorption capacity at a temperature of 20 °C and pH 5.0 was 30.22 mg g^?1 for Cu²⁺ ions and 41.86 mg g^?1 for Cr³⁺ ions. The positive value of the thermodynamic parameter ΔH° indicates the endothermic nature of the process. Application of 0.1 M HCl as the eluent enables effective desorption of precious metals and reuse of sorbent for purifying water solutions of Cu²⁺ and Cr³⁺ ions.     

Modified barley straw as a potential biosorbent for removal of copper ions from aqueous solution

Barley straw (BS), a very low-cost material, has been utilized as a biosorbent material for the removal of copper (Cu²⁺) ions from aqueous solutions after treatment with citric acid. Barley straw was thermochemically modified with citric acid (CA–BS) for the purpose of improving the Cu²⁺ ion sorption capacity of the straw. Biosorption studies have been carried out to determine the effect of pH, adsorbent concentration, contact time, extent of modification, and adsorbate concentration on the biosorption capacity of Cu²⁺ ions by the esterified straw. The equilibrium sorption capacities of Cu²⁺ were 4.64 mg/g and 31.71 mg/g for BS and CA–BS, respectively. The optimum pH for the removal of Cu²⁺ ions by CA–BS was around pH 7.0 and the removal of Cu²⁺ ions was 88.1%. Langmuir, Freundlich, Scatchard and D–R (Dubinin–Radushkevich) isotherms have been used to characterize the observed biosorption phenomena of Cu²⁺ ions on CA–BS. The carboxyl groups on the surface of the modified barley straw were primarily responsible for the sorption of Cu²⁺ ions.     

Ranking the efficacies of selected red wine phenolic anti-oxidants using reversed-phase HPLC

Several studies have assessed total anti-oxidant activity of wine or individual components in isolation using chemical-based assays. In this study, a quantitative approach was developed to assess the relative anti-oxidant efficacies of selected red wine phenolics via peak reduction, using reversed-phase HPLC. Both intact red wine and phenolic standard solutions were challenged with five oxidant model systems as follows: (1) hydrogen peroxide (H₂O₂); redox-active metal ions (2) Fe³⁺ and (3) Cu²⁺; and the Fenton reagents (4) H₂O₂ + Fe²⁺; and (5) H₂O₂ + Cu⁺. Treatment with oxidants (1–3) resulted in loss of 47–60% of phenolic standards, which increased to 66–89% for treatment with the Fenton systems, with quercetin exhibiting the optimal anti-oxidant activity. For intact red wine, treatment with oxidants (1–3) led to all phenolic compounds being oxidised (27–77% loss), with caffeic acid and quercetin as the most effective anti-oxidants. For both Fenton systems (4–5), activities in red wine were considerably enhanced for caffeic acid and quercetin, which exhibited the highest anti-oxidant efficacies with 100% peak reduction, while p-coumaric acid and gallic acid were less effective anti-oxidants with peak reductions of 60–68%. The ranking, facilitated by this new quantitative approach, allows comparison of the individual efficacies of the anti-oxidants in a complex matrix.     

Wheat-bug damage in New Zealand wheats: Some properties of a glutenin hydrolysing enzyme in bug-damaged wheat

Some properties of a glutenin hydrolysing enzyme present in bug (Nysius huttoni) damaged wheat (Triticum aestivum) were examined using a modified SDS sedimentation test reported previously. The enzyme appears to be a water-soluble alkaline protease with an activity optimum at pH 9.0. It is relatively heat stable, but the temperature optimum for activity is quite low (35–40°C). The enzyme is not inhibited by EDTA or N-ethylmaleimide, but is inhibited by the metal ions Co²⁺, Mn²⁺ and Fe²⁺.     

Resistance of Lactobacillus casei KCTC 3260 to Reactive Oxygen Species (ROS): Role for a Metal Ion Chelating Effect

The antioxidative capacity of 4 Lactobacillus strains, isolated from a milk product, was evaluated by measuring total antioxidative ability (TAA) and resistance to reactive oxygen species (ROS). Both intact cells and intracellular cell‐free extracts of Lactobacillus casei KCTC 3260 demonstrated the highest antioxidative activity and inhibited lipid peroxidation by 46.2% and 72.9%, respectively. To evaluate the resistance of 4 Lactobacillus strains to ROS, we tested the survival under conditions of 1 mM hydrogen peroxide, 0.4 mM hydroxyl radicals, and 10 mM paraquat‐induced superoxide anions. L. casei KCTC 3260 was viable even after 8 h in the presence of 1 mM hydrogen peroxide and after 7 h in 0.4 mM hydroxyl radicals. Moreover, this strain was not influenced by superoxide anions, indicating that it has resistance to superoxide anions. To define the antioxidative mechanism, superoxide dismutase (SOD) and metal ion chelating activity were determined. All tested strains did not possess detectable SOD activity except Lactobacillus rhamnosus GG, but L. casei KCTC 3260 had the higher level of chelating activity for both Fe²⁺ and Cu²⁺ ions at 10.6 ppm and 21.8 ppm, respectively. These results suggested that the antioxidative capacity of L. casei KCTC 3260 may be caused by chelating metal ions instead of SOD activation.     

Accumulation of Iron in Lactic Acid Bacteria and Bifidobacteria

Lactobacillus acidophilus, L. delbrueckii var. bulgaricus, L. plantarum and Streptococcus thermophilum, all used extensively in the food industry, were tested for their ability to internalize and/or oxidize ferrous iron (Fe²+). For comparison some experiments were performed with bifidobacteria, B. thermophilum and B. breve. All organisms except L. bulgaricus could transport Fe²⁺ into the cell, where it was partially oxidized to the ferric form (Fe(III)). In addition, L. acidophilus and L. bulgaricus could oxidize Fe²⁺ to Fe(III) extracellularly through the elaboration of H₂O₂ into the medium when the experiments were carried out in air. L. bulgaricus elaborated H₂O₂ only in the presence of glucose, whereas L. acidophilus released H₂O₂ in absence of glucose. We concluded that lactic acid bacteria, like bifidobacteria, can exert some beneficial effects in animal organisms, or in food processing and storage, by making Fe²⁺ unavailable to harmful microorganisms.