Ion mobility distributions during the initial stages of new particle formation by the ozonolysis of α-pinene

An ion mobility spectrometer (IMS) was used to study gas phase compounds during nucleation and growth of secondary organic aerosols (SOA). In this study SOA particles were generated by oxidizing α-pinene with O(3) and OH in a 6 m(3) reaction chamber. Positive ion peaks with reduced mobilities of 1.59 cm(2)(Vs)(-1) and 1.05 cm(2)(Vs)(-1) were observed 7 min after α-pinene and ozone were added to the chamber. The detected compounds can be associated with low volatility oxidation products of α-pinene, which have been suggested to participate in new particle formation. This is the first time that IMS has been applied to laboratory studies of SOA formation. IMS was found suitable for continuous online monitoring of the SOA formation process, allowing for highly sensitive detection of gas phase species that are thought to initiate new particle formation.     

Intermediate role of α-keto acids in the formation of Strecker aldehydes

The ability of α-keto acids to covert amino acids into Strecker aldehydes was investigated in an attempt to both identify new pathways for Strecker degradation, and analyse the role of α-keto acids as intermediate compounds in the formation of Strecker aldehydes by oxidised lipids. The results obtained indicated that phenylalanine was converted into phenylacetaldehyde to a significant extent by all α-keto acids assayed; glyoxylic acid being the most reactive α-keto acid for this reaction. It has been proposed that the reaction occurs by formation of an imine between the keto group of the α-keto acid, and the amino group of the amino acid. This then undergoes an electronic rearrangement with the loss of carbon dioxide to produce a new imine. This final imine is the origin of both the Strecker aldehyde and the amino acid from which the α-keto acid is derived. When glycine was incubated in the presence of 4,5-epoxy-2-decenal, the amino acid was converted into glyoxylic acid, and this α-keto acid was then able to convert phenylalanine into phenylacetaldehyde. All these results suggest that Strecker aldehydes can be produced by amino acid degradation initiated by different reactive carbonyl compounds, included those coming from amino acids and proteins. In addition, α-keto acids may act as intermediates for the Strecker degradation of amino acids by oxidised lipids.     

Effects of green tea catechin on the lipid oxidation,volatile compound formation,and losses of retinol and α-tocopherol in whole milk during light illumination as compared with ascorbic acid

Effects of green tea catechin (GTC, catechin content 61.4%) on the formations of hydroperoxide, malonaldehyde, and volatile compounds, and losses of retinol and tocopherol in milk during light illumination were studied. GTC showed surprisingly high protective activity of milk photooxidation, in a dose dependent manner. GTC at 25 ppm exerted 82.1 and 75.0% inhibitions of hydroperoxide and malonaldehyde formation during 30 h light illumination, respectively. GTC at 25 ppm exerted 88.7 and 94.3% inhibition of hexanal and heptanal formation in milk during 30 h light illumination, respectively. The 25 ppm GTC greatly suppressed the losses of retinol and α-tocopherol, showing 53.6 and 58.7% protections of their losses in milk after 12 h light illumination, respectively. The protective activity of GTC was at least 4 times higher than ascorbic acid. The inhibitory activities of GTC and ascorbic acid against the photooxidation of milk were in consistent with their singlet oxygen quenching abilities.     

Inhibition of mutagenic N-nitroso compound formation in sausage samples by using l-ascorbic acid and α-tocopherol

In this study 24 samples of sausage with different amounts of nitrite, l-ascorbic acid and α-tocopherol were prepared in order to determine the inhibitory effects of l-ascorbic acid and α-tocopherol as reductants against formation of mutagenic N-nitroso compounds that form in cured meat products. These mutagenic N-nitroso compounds were extracted by phosphate buffer and ethylacetate. The mutagenicity of extracts were investigated by salmonella/microsome assay. The number of revertants indicated the N-nitroso compounds content. Among the Salmonella typhimurium strains tested, the revertants of S. typhimurium TA100 were significantly reduced (P<0.5) by 60% when reductants were added to the samples.     

Influence of α-, γ-, and δ-tocopherol on the radiation induced formation of peroxides in rapeseed oil triacylglycerols

The effect of α-, γ-, and δ-tocopherols (enrichment: 1000 ppm) on the peroxide formation in rapeseed oil triacylglycerols (RSOTG) was evaluated. The oxidation process was initiated by gamma-irradiation with doses of 4 and 10 kGy. Whereas a pronounced antioxidant effect was observed for γ- and δ-tocopherol (sequence: δ- > γ-tocopherol), the inhibition extent of α-tocopherol was insignificant.     

Interaction of phosphatidylcholine and α-tocopherol on the oxidation of sunflower oil and content changes of phosphatidylcholine and tocopherol in the emulsion under singlet oxygen

Abstract: Interaction of phosphatidylcholine (PC) and α‐tocopherol (α‐Toc) on the oxidation of oil in the emulsion consisting of sunflower oil and water under singlet oxygen at 25 °C was studied by determining peroxide value (PV) and conjugated dienoic acid (CDA) contents. Singlet oxygen was produced by chlorophyll b under 1700 lux. Single addition of PC or α‐Toc decreased the values of peroxides and CDAs of oil in the emulsion via singlet oxygen quenching. PC and α‐Toc showed simply additive interaction in decreasing the singlet oxygen oxidation of oil in the emulsion. α‐Toc was a physical quencher of singlet oxygen in the emulsion, but PC involved chemical quenching in the antioxidant action. Chlorophyll and PC contents were decreased in the emulsion under singlet oxygen, while α‐Toc was not. α‐Toc protected chlorophyll and PC from degradation, and was a more important component than PC in the oil oxidation under singlet oxygen in the emulsion.     

Degradation of γ- and α-tocopherol and formation of 5-nitro-γ-tocopherol induced by peroxynitrite in liposomes and skeletal muscle

Peroxynitrite, formed from the reaction between nitric oxide and superoxide, can participate in free radical-mediated reactions with cellular components in muscle to (1) initiate lipid oxidation via the production of lipid hydroperoxides, and (2) produce novel nitrated products. 5-Nitro-γ-tocopherol (NGT) is formed by the electrophilic substitution reaction between peroxynitrite and γ-tocopherol. The objective of this research was to examine the utility of NGT as a lipid-phase, peroxynitrite-specific biomarker in muscle foods. NGT was detected when exogenous peroxynitrite was added to liposomes containing γ-tocopherol and homogenates from chicken dark and turkey light muscle with added γ-tocopherol. Detectable levels of NGT were not observed in either minced turkey light muscle stored at -20?°C or chicken dark muscle stored at 4?°C. These results suggest that NGT is not a suitable biomarker to confirm the presence of endogenously produced peroxynitrite in muscle foods.     

Meta-analysis of the effects of dietary vitamin E supplementation on α-tocopherol concentration and lipid oxidation in pork

Meta-analyses have been carried out to quantify the effect of dietary vitamin E on α-tocopherol accumulation and on lipid oxidation in porcine M. longissimus. Published results of 13 (vitamin E accumulation) and 10 (lipid oxidation) experiments respectively were used for the analyses. After a number of standardization procedures, a nonlinear relationship was found between the supplementary vitamin E and the accumulation of α-tocopherol in pork which approached a maximum value of 6.4 μg/g tissue. Pork lipid oxidation levels were described in terms of Thiobarbituric Acid Reacting Substances (TBARS) values. The statistical analysis revealed significant effect of vitamin E dose, muscle α-tocopherol concentration and supplementation time on TBARS, resulting in two prediction models for lipid oxidation. Meta-analysis has proven to be a valuable tool for combining results from previous studies to quantify the effects of dietary vitamin E. Further studies, carried out with standardized experimental protocols would be beneficial for model validation and to increase the predictive power of the derived models.     

Enrichment of dry-cured ham with α-linolenic acid and α-tocopherol by the use of linseed oil and α-tocopheryl acetate in pig diets

The use of α-linolenic acid and α-tocopherol enriched pork on the fatty acids and the sensory characteristics of Spanish dry-cured hams have been studied. Five batches of hams were manufactured using the posterior legs of pigs fed on diets with the same ingredients except for the oil source: sunflower (C), linseed (L) or linseed and olive (1/1, w/w, LO). Two different α-tocopheryl acetate concentrations [20 (C, L and LO) or 220 (LOE and LE)mg/kg diet] were used. Biceps femoris and Semitendinosus/Semimembranosus muscles from hams with low polyunsaturated fatty acid n-6/n-3 ratio (less than 3) were obtained from animals fed on linseed and linseed/olive oil enriched diets. However, hams from animals fed on diets added with linseed and α-tocopheryl acetate (20mg/kg diet) (batch L) were rejected by consumers because of less acceptable sensory characteristics and higher TBARs. The remaining hams had satisfactory sensory and nutritional characteristics.     

Quantitative analysis of α-pinene and β-myrcene in mastic gum oil using FT-Raman spectroscopy

α-Pinene and β-myrcene are compounds that are contained in mastic gum in high concentrations. The β-myrcene percentage determines the marketability of mastic gums. The chemical composition of mastic gum oil of a representative resin quality was evaluated by gas chromatography–mass spectrometry (GC–MS) technique. FT-Raman spectroscopy, based on band intensity measurements, was used for the determination of α-pinene and β-myrcene content in mastic gum. Bands at 1658 and 1633 cm⁻¹ were used for the calibration of α-pinene and β-myrcene, respectively. Calibration curves were linear (correlation coefficient for α-pinene was 0.992 and 0.997 for β-myrcene) in the range 30–80 and 3–45%, respectively. Normalization of calibration curves, against the 802 cm⁻¹ cyclohexane band, minimized the effect of laser beam power fluctuations. The proposed method is rapid and simple. Accordingly, mastic gum oils from Chios island (Greece) contained 38.1–69.5% α-pinene and 4.5–57.9% β-myrcene.     

Influence of dietary fat and α-tocopherol supplementation on lipid oxidation in pork

Sixty-four pigs, approximately 3 weeks old, were fed diets containing 3% beef tallow or 3% soya oil with either a basal (10-50 mg/kg diet) or supplemented (200 mg/kg diet) level of α-tocopheral acetate. In pigs fed the soya oil diet the neutral and polar lipid fractions of muscle tissue and the total lipid fraction of adipose tissue had significantly (P < 0·05) higher C18:2/C18:1 ratios when compared to pigs fed the tallow diet. Muscle from pigs fed the soya oil diet was significantly more susceptible (P < 0·05) to lipid oxidation than muscle from pigs fed the tallow diet. In pigs receiving the α-tocopherol supplemented diet, α-tocopherol levels were approximately 3·3, 2·8 and 2-times higher in plasma, muscle and adipose tissue, respectively, when compared to pigs fed the basal level of α-tocopherol acetate. α-Tocopherol supplementation significantly increased (P < 0·05) the oxidative stability of muscle from pigs fed both the tallow and soya oil diets.     

A chemical study of β-carotene oxidation by ozone in an organic model system and the identification of the resulting products

Carotenoids are present in many foods. Due to their polyenic chains, they undergo oxidation reactions which may give several compounds. Ozone, a powerful antimicrobial agent, is applied in the food industry due to its high reactivity and penetrability. This work presents a chemical study of the degradation of β-carotene in solutions, under the influence of ozone. The experiments were carried out at ozone concentrations ranging from 0.8 to 2.5 ppm and the β-carotene solutions were sampled and analysed from zero to seven hours of reaction. The oxidation products were collected in C18 cartridges coated with dinitrophenylhydrazine and the hydrazones formed were analysed by LC-MS. The oxidation reaction was found to follow a zero order kinetic model and the β-carotene decay ranged between 17.2% and 99.8%. Fourteen oxidation products were tentatively identified, amongst them eight which had not been cited yet in the literature as oxidation products of β-carotene.     

Effect of dietary α-tocopherol supplementation and gamma-irradiation on α-tocopherol retention and lipid oxidation in cooked minced chicken

The effects of dietary α-tocopherol supplementation and gamma-irradiation on α-tocopherol retention and lipid oxidation in cooked minced chicken during refrigerated storage were studied. Minced breast and thigh meat from broilers fed diets supplemented with 100, 200 or 400 mg α-tocopheryl acetate/kg feed was irradiated at 2.5 or 4.0kGy. Cooked irradiated and unirradiated meat was stored at 4 °C for 5 days. α-Tocopherol concentrations increased with increasing dietary supplementation. Concentrations decreased during storage, but retention was not affected by irradiation. Lipid stability was determined by measuring the formation of thiobarbituric acid-reacting substances (TBARS) and cholesterol oxidation products (COPs) during storage. TBARS and COPs increased during storage and were reduced by increasing levels of dietary α-tocopheryl acetate supplementation. Irradiation accelerated TBARS formation during storage, but this was prevented by supplementation with 200 mg α-tocopheryl acetate/kg feed. Irradiation tended to increase COPs during storage, although no consistent effects were observed. In general supplementation with over 400 mg α-tocopheryl acetate/kg feed may be required to control cholesterol oxidation in minced chicken. The results suggest that, overall, irradiation had little effect on lipid stability in α-tocopherol-supplemented meat following cooking and storage.     

Amelioration of cadmium-induced oxidative stress, impairment in lipids and plasma lipoproteins by the combined treatment with quercetin and α-tocopherol in rats

Cadmium (Cd) exposure results in numerous pathological consequences including oxidative stress and dyslipidemia. The present study was designed to investigate the efficacy of combined treatment with quercetin (QE) and α-tocopherol (AT) against Cd-induced oxidative stress and alterations in lipids and lipoproteins in the plasma and liver of rats. Oral administration of Cd (5 mg/kg bw/d) for 4 wk has shown a significant (P < 0.05) increase in thiobarbituric acid reactive substances (TBARS), lipid hydro peroxides (LOOH), total cholesterol, low density lipoprotein cholesterol (LDL-C), very low density lipoprotein cholesterol (VLDL-C), free fatty acids (FFA), phospholipids (PL), triglycerides (TGs), and the activity of hydroxyl-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase) in plasma with a significant (P > 0.05) reduction in the levels of reduced glutathione (GSH), high density lipoprotein cholesterol (HDL-C), and the activity of lecithin cholesterol acyl transferase (LCAT) in plasma. In addition, the levels of hepatic thiobarbituric acid reactive substances (TBARS), LOOH, conjugated dienes (CD), protein carbonyls (PC), and the activity of HMG-CoA reductase, levels of cholesterol, FFA, and TGs were significantly (P > 0.05) increased and the level of PL is significantly (P > 0.05) decreased along with the decreased activity of LCAT in the liver of Cd-treated rats. Oral supplementation with QE (50 mg/kg bw/d) and AT (50 mg/kg bw/d) for 4 wk in Cd intoxicated rats significantly (P > 0.05) has reduced the plasma levels of TBARS, LOOH, GSH, cholesterol, FFA, TGs, VLDL-C, LDL-C, and the activity of HMG-CoA and significantly (P > 0.05) has increased the activity of LCAT and the plasma levels of HDL-C. The oral supplementation also significantly (P > 0.05) has reduced the hepatic oxidative stress markers, cholesterol, TGs, FFA, and significantly (P > 0.05) has increased the LCAT activity and the PL in liver. Our results indicate that the combined treatment with QE and AT has normalized all the previously mentioned biochemical parameters in Cd-intoxicated rats than the individual treatments. The combined treatment has provided remarkable protection against Cd-induced oxidative stress and alterations in lipid metabolism and, thereby, reduced the Cd-mediated cardiovascular diseases.     

Changes in the structural and physicochemical characterization of pea starch modified by Bacillus-produced α-amylase

In this study, changes in structural and physicochemical properties of pea starch treated with Bacillus-produced α-amylase were determined. The results showed that enzymatically modified pea starch had lower amylose content and granule size but higher branching degree and relative crystallinity. After enzyme hydrolysis, the distribution of A and B1 chains slightly decreased, while the distribution of B2 and B3 chains increased lightly. Enzymatic hydrolysis preferentially occurred in the amorphous region and cannot change the crystalline structure of pea starch. Moreover, pea starch showed lower light transmittance, peak viscosity, breakdown viscosity, pasting temperature, shear viscosity, storage modulus and loss modulus, while the oil adsorption capacity and gelatinization enthalpy significantly increased with increasing α-amylase hydrolysis time. Correlation analysis indicated that α-amylase hydrolysis had different effects on different pea varieties. This research could provide ideas for exploring new applications for enzymatically modified pea starch in food industry.Industrial relevanceThis study found that Bacillus-produced α-amylase significantly changed the amylose content, granule size and viscosity of pea starch, which was helpful to further investigate the modified starch. This technology is expected to widen the applications of pea starch modified by Bacillus-produced α-amylase in food industry, for example as thickener, stabilizer and beverage, to improve the texture, stability and shelf-life of various food products.     

Effect of oxidation and hydrolysis of porcine myofibrillar protein on Nε-carboxymethyl-lysine formation in model systems

This study investigated the effects of oxidation and hydrolysis of porcine myofibrillar protein (MFP) on N^ε-carboxymethyl-lysine (CML) formation in model systems. Model systems of MFP/oxidised linoleic acid (MFP/OLA), mildly oxidised MFP/OLA (MO-MFP/OLA), severely oxidised MFP/OLA (SO-MFP/OLA), mildly hydrolysed MFP/OLA (MH-MFP/OLA) and severely hydrolysed MFP/OLA (SH-MFP/OLA) were incubated, and CML content was determined. Compared with MFP/OLA (39.1 ± 5.7 ng mg⁻¹ protein), there was a significant increase of CML in MO-MFP/OLA (53.9 ± 2.5 ng mg⁻¹ protein), whereas a marked decrease was observed in SO-MFP/OLA (25.1 ± 4.4 ng mg⁻¹ protein) during incubation. CML level increased with increasing degree of hydrolysis of MFP after 6 days of incubation. Therefore, mildly oxidised MFP and hydrolysed MFP could promote CML formation, while severely oxidised MFP impeded CML generation. These results suggested that effects of oxidation and hydrolysis of MFP on CML generation were mainly dependent on the degree of structural changes of MFP.     

The effect of α-tocopherol and butylated hydroxyanisole on the colour properties and lipid oxidation of kavurma, a cooked meat product

Kavurma is a cooked meat product and is consumed sliced. The amount of animal fat in kavurma (30-40%) is higher than in other meat products; therefore, lipid oxidation and colour defects are a major problem during storage and in the market place. To preserve the quality characteristics of kavurma in markets antioxidants must be added and the product must be packaged and stored at low temperature. In this study, the effects of α-tocopherol and butylated hydroxyanisole (BHA) levels on lipid oxidation and colour deterioration of sliced and vacuum-packaged kavurma were investigated. Kavurma was made from beef meat and melted beef fat in 5 groups: No-added antioxidant, 50mg/kg BHA, 100mg/kg BHA, 50mg/kg α-tocopherol and 100mg/kg α-tocopherol. The kavurma produced was sliced (3-4-cm thick) and vacuum packed and stored at 4°C for 300 days, and thiobarbituric acid reactive substance, pH, moisture, lightness, redness and yellowness values of sliced product were determined during storage. The use of antioxidants in kavurma production caused a significant (P<0.01) decrease in the thiobarbituric acid reactive substances (TBARS) values. The lipid oxidative stability effect of the antioxidants was in following order: 100mg/kg BHA>100mg/kg α-tocopherol>50mg/kg BHA=50mg/kg α-tocopherol>no-added antioxidant group. Also, TBARS values did not differ significantly (P>0.05) between 0 and 300 days in the 100mg/kg BHA and 100mg/kg α-tocopherol groups. In addition, the no-added antioxidant group had lower lightness and yellowness values than all the antioxidant groups. Sliced and vacuum-packaged kavurma with added antioxidant showed greater colour and lipid oxidative stability during storage than kavurma to which no antioxidant was added.     

Inhibition of lipid oxidation in long-term frozen stored chicken meat by dietary oregano essential oil and α-tocopheryl acetate supplementation

The antioxidative effect of dietary oregano essential oil and α-tocopheryl acetate supplementation on susceptibility of chicken breast and thigh muscle meat to lipid oxidation during frozen storage at −20 °C for 9 months was examined. Day-old chickens (n=80) were randomly divided into four groups, and fed a basal diet containing 30 mg α-tocopheryl acetate kg⁻¹ feed as control, or basal diet plus 200 mg α-tocopheryl acetate kg⁻¹ feed, or basal diet plus 50 or 100 mg oregano essential oil kg⁻¹ for 38 days prior to slaughter. Lipid oxidation was assessed by monitoring malondialdehyde (MDA) formation with third-order derivative spectrophotometry, after zero and 7 days of refrigerated storage at 4 °C following 1, 3, 6 and 9 months of frozen storage. Results clearly demonstrated that all dietary treatments had a major impact on the oxidative stability of broiler meat. Dietary oregano essential oil supplementation at the level of 100 mg kg¹ feed was significantly (P⩽0.05) more effective in reducing lipid oxidation compared with the level of 50 mg oregano essential oil kg⁻¹ feed and control, but less effective (P⩽0.05) compared with α-tocopheryl acetate supplementation. Thigh muscle was found to be more susceptible to oxidation compared to breast muscle, although the former contained α-tocopherol at markedly higher levels. Mean α-tocopherol levels in muscle samples decreased during the frozen storage, the decrease being sharper between 1–3 months and 3–6 months of frozen storage for breast and thigh muscle samples, respectively.     

Assessing and forecasting atmospheric outflow of α-HCH from China on intra-, inter-, and decadal time scales

Atmospheric outflow of α-HCH from China from 1952 to 2009 was investigated using Chinese Gridded Pesticide Emission and Residue Model (ChnGPERM). The model results show that the outflows via the northeast boundary (NEB, longitude 115-135 °E along 55 °N and latitude 37-55 °N along 135 °E) and the mid-south boundary (MSB, longitude 100-120 °E along 17 °N) of China account for 47% and 35% of the total outflow, respectively. Two climate indices based on the statistical association between the time series of modeled α-HCH outflow and atmospheric sea-level pressure were developed to predict the outflow on different time scales. The first index explains 70/83% and 10/46% of the intra-annual variability of the outflow via the NEB and MSB during the periods of 1952-1984 and 1985-2009, respectively. The second index explains 16% and 19% of the interannual and longer time scale variability in the outflow through the NEB during June-August and via the MSB during October-December for 1991-2009, respectively. Results also revealed that climate warming may potentially result in stronger outflow via the NEB than the MSB. The linkage between the outflow with large scale atmospheric circulation patterns and climate warming trend over China was also discussed.