Validation of a quantitative assay for the total content of lipophilic and hydrophilic antioxidants in foods

One of the main methods used to assess total antioxidant content in foods is the Ferric Reducing Ability of Plasma (FRAP) assay. The FRAP assay has previously not been extensively validated. In the present study, 39 pure compounds, such as different polyphenols, ascorbic acid, tocopherols, tocotrienols and carotenoids dissolved in water/methanol, water/2-propanol and 2-propanol, were tested. Our results demonstrate that the FRAP assay can quantitate satisfactorily most hydrophilic and lipophilic compounds with antioxidant properties. The reaction was followed for 60 min. The most extensive reaction occurred within the first 4 min for most compounds and foods. The lipophilic tocopherols and tocotrienols were easily quantitated and reached endpoint within 4 min while carotenoids were somewhat more demanding due to low solubility and slower reaction kinetics. We conclude that the FRAP assay, with 4 min reaction time, is suitable for high-throughput screening of total antioxidant content of edible items.     

Vitamin K2 in different bovine muscles and breeds

Meat is a natural source of vitamin K, a vitamin associated with reduced bone loss and prevention of osteoporosis. Whether vitamin K content varies between breeds and muscles in cattle is not known. In the present study, contents of vitamin K1 (phylloquinone) and K2 (menaquinone, MK) were analysed in three different muscles from steers of two different breeds, Norwegian Red and Jersey, respectively. Results showed that MK4 was the most dominant of the vitamin K2 analogues, while only traces were found of MK6 and MK7. Both breeds had higher levels of MK4 in M. biceps femoris (BF) and M. longissimus dorsi (LD) compared to M. psoas major (PM). The results also showed significantly higher MK4 levels in muscles from Jersey compared to Norwegian Red. Furthermore, MK4 was not associated with intramuscular fat, suggesting a physiological role for MK4 in skeletal muscle cells. There were no association between vitamin K content and tenderness.     

Analysis of Early Lipid Oxidation in Salmon Pâté with Cod Liver Oil and Antioxidants

ABSTRACT: Analytical methods that can detect early stages of lipid oxidation in complex food matrixes are highly needed, and the interest in rapid methods is great. In the present study, sensory analysis, dynamic headspace/gas chromatography-mass spectrometry (GC-MS), front-face fluorescence spectroscopy, and an electronic nose were used to detect early lipid oxidation in salmon pâté. The pâté was enriched with cod liver oil to increase the n-3 content, and citric acid (CA) or calcium disodium ethylenediamine tetraacetate (EDTA) were used as metal chelators. The sensory panel, GC-MS, and fluorescence methods detected oxidative changes in the pâté after 4 wk of storage. The fluorescence intensity increased with time. More volatile lipid oxidation products were formed in pâté with cod liver oil than in pâté without oil, but no differences were found between the batches with regard to rancid odor and flavor. CA and EDTA slightly promoted formation of volatile oxidation products. EDTA had a small positive impact on the sensory perception of the samples, whereas CA did not work favorably. With better packaging and antioxidant protection, n-3 enriched salmon pâté could be viable. Front-face fluorescence and dynamic headspace/GC-MS could be well suited to monitor lipid oxidation in such products.     

Functional characterisation of potato starch modified by specific in planta alteration of the amylopectin branching and phosphate substitution

Potato starch was modified in planta by antisense of the starch branching enzyme I (SBE I), and the starch branching enzyme II (SBE II) both simultaneously and individually generating B group starches. Another group of starches, G group starches, was generated by over expression of the E. coli glycogen branching enzyme (E. coli glgB). The content of covalently esterified phosphate increased in the B group starches and decreased in the G group starches. The content of phosphate correlated with length of debranched amylopectin chains measured by HPAEC-PAD, and with gelatinisation mid temperature (T_m) and change in enthalpy (ΔH) measured by differential scanning calorimetry (DSC). Freeze/thaw stability measured by ¹H pulse-NMR and cohesiveness measured by texture profile analysis (TPA) was in the same range in all starch samples, whereas gel hardness was inversely correlated to phosphate content. No correlations between the pasting properties measured by rapid visco analysis (RVA), gel strength (G′) measured by small deformation oscillation testing or any structural parameter could be revealed. The data set was mined using multivariate statistics. Based on this data starch samples could be separated into the two groups B and G, in accordance with their original transformation strategy.     

Fucosterol Causes Small Changes in Lipid Storage and Brassicasterol Affects some Markers of Lipid Metabolism in Atlantic Salmon Hepatocytes

Several feeding trials with Atlantic salmon fed naturally high phytosterol concentrations due to dietary rapeseed oil inclusion have shown changes in lipid metabolism and increased hepatic lipid storage in the fish. An in vitro trial with Atlantic salmon hepatocytes was, therefore, performed to study the possible direct effects of phytosterols on lipid storage and metabolism. The isolated hepatocytes were exposed to seven different sterol treatments and gene expression, as well as lipid accumulation by Oil Red O dyeing, was assessed. Fucosterol, a sterol found in many algae species, had an effect on the size of individual lipid droplets, leading to smaller lipid droplets than in the control without added sterols. A sterol extract from soybean/rapeseed led to an increase in the percentage of hepatocytes with visible lipid droplets at 20× magnification, while hepatocytes of both the sterol extract‐treated groups and fucosterol‐treated groups had a larger proportion of their area covered with lipids compared to control cells. Brassicasterol, a sterol characteristic of rapeseed oil, was the only sterol treatment leading to a change in gene expression, affecting the expression of the nuclear receptors, peroxisome proliferator‐activated receptor gamma (pparg) and retinoid X receptor (rxr). The current study thus shows that phytosterols can have direct, although subtle, effects on both hepatic lipid storage and gene expression of Atlantic salmon in vitro.     

Trans-Membrane Uptake and Intracellular Metabolism of Fatty Acids in Atlantic Salmon (<Emphasis Type="Italic">Salmo salar</Emphasis> L.) Hepatocytes

To elucidate if the trans-membrane uptake of fatty acids is protein-mediated, the uptake of oleic acid (18:1n-9), linoleic acid (18:2n-6), alpha-linolenic acid (18:3n-3), eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3) was investigated in vitro in Atlantic salmon (Salmo salar L.) primary hepatocytes. Firstly, optimal fatty acid incubation time and concentration were established for trans-membrane 18:n-9 uptake. Based on saturation kinetics, a 2-h incubation time and 37.5 μM were used for the following experiments. Secondly, in order to identify whether trans-membrane fatty acid uptake in hepatocytes was mainly passive or protein mediated, hepatocytes were pre-incubated with membrane protein inhibitors followed by 2 h of incubation with [1-¹⁴C] labelled 18:1n-9, 18:2n-6, 18:3n-3, 20:5n-3 and 22:6n-3. Fatty acid uptake into hepatocytes was highest with 20:5n-3 and 22:6n-3 and lowest with 18:1n-9. Phloretin was the most potent fatty acid uptake inhibitor, inhibiting uptake in the following order: 20:5n-3 > 18:3n-3 = 22:6n-3 > 18:2n-6 > 18:1n-9. The uptake of FA in Atlantic salmon hepatocytes seem to be due to both saturable and inhibitable protein mediated uptake, as well as passive uptake processes with more unsaturated and long fatty acids (20:n-3 > 22:6n-3 = 18:3n-3 > 18:2n-6) being more dependent on membrane protein mediated uptake compared to 18:1n-9.     

A Fixed-Bed Reactor Study of Catalytic Partial Oxidation over Rh/Al2O3: An Indication of a Direct Pathway to CO

Catalytic partial oxidation (CPO) of CH₄ in air was investigated over Rh/Al₂O₃ catalysts (0.01, 0.05, 0.1 and 1 wt% Rh⁰) in co-feed modus in laboratory scale fixed-bed reactors. Main focus was on catalyst stability and selectivity at low temperatures (<700 °C). A particularly high selectivity to CO was observed, indicating existence of a direct pathway.     

Risk and food: environmental concerns and consumer practices

Environmental risks related to food consumption produce needs among consumers to handle such risks through their consumption practices. Consumers' ways of coping with risks are dependent on the social relations of everyday life, of which consumption practices are a part. Risk-handling in food consumption is socio-culturally broader than the cognitive rationality assumed in expert knowledge and administrative procedures on risk and risk-handling. Likewise, risk-handling in food consumption is also characterized by ambivalences. The objective of the article is to show that an important social and cultural source of ambivalence in consumers' handling of risk in food consumption comes from food consumption practices being caught in the tension between desire and control. The article proposes a heuristic theoretical device, called 'the contested space of the body', which is used to discuss the bodily dimension of consumer risk-handling. This is based on a Danish empirical study of parents with small children. A typology of consumers' risk-handling is presented which differs from traditional typologies of consumer segments by allowing for overlaps and shifts between the individual positions in the typology. The three types of risk-handling are the worried, the irritated and the pragmatic. The results suggest that in worried risk-handling control marginalizes desire, in irritated risk-handling desire is openly in conflict with control, and in pragmatic risk-handling relief from the contested space of the body is attempted.     

Characterization of a Monolithic Concatenated SOA/SA Waveguide Device for Picosecond Pulse Amplification and Shaping

In this paper, a monolithic waveguide device, named IRIS, is presented. The device consists of an array of concatenated semiconductor optical amplifiers and saturable absorbers. We have fabricated the devices in InP-InGaAsP bulk gain material and we have experimentally investigated picosecond pulse transmission through these devices. Operated as an optical amplifier the IRIS devices show a decreased temporal pulse broadening and decreased amplified spontaneous emission noise generation as compared to a semiconductor optical amplifier of equivalent length. Used as a nonlinear element to increase the optical bandwidth of a picosecond pulse train, the spectra obtained with IRIS devices show an increased broadening and smoothness as compared to a semiconductor optical amplifier. We have set up a theoretical model to describe spectral and temporal pulse shaping by the IRIS device. Agreement between the simulations and the experiments is obtained.