Antioxidative Effect of Seaweed Extracts in Chilled Storage of Minced Atlantic Mackerel (<Emphasis Type="Italic">Scomber scombrus</Emphasis>): Effect on Lipid and Protein Oxidation

In this study, antioxidant activity of absolute ethanol, 50 % ethanol and water extracts of two species of seaweeds namely, Fucus serratus and Polysiphonia fucoides were evaluated for their ability to retard lipid and protein oxidation in minced mackerel. Mackerel mince added with 0.5 g/kg of extracts was prepared. For comparison, BHT at 0.2 g/kg and a control with no added extracts were also prepared. The samples were stored at 5 °C for 8 days, and sampling was done at time 0, 1, 2, 4, 5 and 8 days. The 50 % ethanolic extracts of P. fucoides were found to be very effective in retarding lipid and protein oxidation, as it resulted in low levels of peroxide value, volatiles and carbonyl compounds and protected against the loss of α-tocopherol and tryptophan residues. In spite of the higher phenolic content, the absolute ethanol extracts of both species showed a pro-oxidative tendency in minced mackerel. Water extract with lowest phenolic content showed no antioxidant effect in minced mackerel. In conclusion, the 50 % ethanolic extracts of P. fucoides can be a potential source of natural antioxidants, as these extracts have antioxidant activities similar to synthetic antioxidants such as BHT. However, the extent of protection offered by these extracts against protein oxidation was not clear and further studies are needed to understand the nature of the interaction between proteins and these extracts.     

Isolation of Fucoxanthin from Brown Algae and Its Antioxidant Activity: In Vitro and 5% Fish Oil‐In‐Water Emulsion

Fucoxanthin, a nonprovitamin A carotenoid, is a yellowish‐brown pigment found abundantly in brown algae. Along with chlorophyll a, it is bound to proteins and acts as a light‐harvesting and a light‐transferring pigment. The occurrence of carotenoids and chlorophylls in photosynthetic tissues complicates the isolation of pure fucoxanthin. The present study deals with a method for the isolation of fucoxanthin by low‐temperature crystallization and testing its antioxidant activity both in in vitro assays and in 5% oil‐in‐water emulsion. The yield of fucoxanthin obtained with this method ranged from 0.1% to 0.5% of dried algae depending on the species. Fucoxanthin showed good α,α‐diphenyl‐β‐picrylhydrazyl radical‐scavenging and iron‐chelating properties. However, it showed low reducing power and was poor in the inhibition of lipid oxidation in a liposome model system. When tested in 5% fish oil‐in‐water emulsion with iron as an oxidation inducer, fucoxanthin showed antioxidant activity by resulting in low levels of volatile oxidation products and low tocopherol loss compared to control and butylated hydroxytoluene.     

Antioxidant Activity of Seaweed Extracts: In Vitro Assays,Evaluation in 5 % Fish Oil‐in‐Water Emulsions and Characterization

In this study the antioxidant activity of absolute ethanol, 50 % ethanol and water extracts of two species of seaweeds, namely Fucus serratus and Polysiphonia fucoides, were evaluated both in in vitro assays and in 5 % fish oil‐in‐water (o/w) emulsions. The 50 % ethanolic extracts of P. fucoides showed higher antioxidant activity both in in vitro assays and in 5 % oil‐in‐water emulsion in the presence or absence of iron. In spite of the higher phenolic content and very good antioxidant activity in some of the in vitro assays, the absolute ethanol extracts of both the species showed a pro‐oxidative tendency in 5 % fish oil‐in‐water emulsion in the presence or absence of iron. In order to investigate the reason for the higher antioxidant activity of 50 % ethanolic extracts of P. fucoides, these extracts were further fractionated into polyphenol‐rich, protein‐rich, polysaccharide‐rich and low‐molecular‐weight fractions. These fractions were tested both in in vitro and in 5 % oil‐in‐water emulsions. The results of the present study showed that the main effect was due to the phenolic compounds. In conclusion, the 50 % ethanolic extracts of P. fucoides can be a potential source of natural antioxidants as these extracts have antioxidant activities similar to those of synthetic antioxidants such as BHT.     

Supplementation of squalene attenuates experimentally induced myocardial infarction in rats

We have investigated the preventive effects of squalene against isoprenaline-induced myocardial infarction in male albino rats. Supplementation with squalene significantly prevented the isoprenaline-induced adverse changes in the levels of protein and glycoprotein components in plasma and heart tissue of experimental groups of rats. It exerted an antioxidant effect by inhibiting the isoprenaline-induced lipid peroxidation and by maintaining the level of non-enzymatic free radical-scavenger, reduced glutathione at near normalcy. Histopathological observations also confirmed the possible cardioprotective action of squalene by maintaining the normal architecture of the heart tissue. The results of the present investigation demonstrate that supplementation with squalene offers cardioprotection in experimental rats by its antioxidant and membrane- stabilizing properties.     

New natural antioxidants for protecting omega‐3 rich products

The long‐chain (LC) highly unsaturated omega‐3 fatty acids, EPA (eicosapentaenoic acid, 20:5) and DHA (docosahexaenoic acid, 22:6) are vital for a wide range of biological functions and are implicated in the prevention of numerous diseases. However, these fatty acids are highly susceptible to oxidation because of their unsaturated nature. Addition of antioxidants is one method to prevent lipid oxidation. As synthetic antioxidants may have carcinogenic effects at higher levels, the replacement of synthetic antioxidants with natural antioxidants is now in demand. We have isolated natural antioxidants from yoghurt, potato peel, fish protein hydrolysates and seaweed, which were able to protect highly unsaturated fish oil from oxidation. These antioxidant extracts may have potential for commercial exploitation.     

New control paradigm for integration of photovoltaic energy sources with utility network

The employment of an inverter to integrate a distributed generation system to the utility network is well known. In such a context, there is an increasing interest in developing an appropriate control strategy to derive a current with less distortion from the inverter. In this paper, a new current controller for inverters of this kind has been proposed. The proposed technique combines the benefits of a proportional-integral controller and a hysteresis limiter. The paper presents the development of such a controller and its structure. Inverter-output current waveforms of the proposed scheme are compared with that of a hysteresis alone and average current mode controllers. A better harmonic elimination and current tracking performance of the proposed controller is thereby established. Filter responses have also been compared to establish the superiority of the proposed approach.     

Antioxidant Activity of Potato Peel Extracts in a Fish-Rapeseed Oil Mixture and in Oil-in-Water Emulsions

The objectives of the present work were (a) to extract the phenolic fraction from the peels of two Danish varieties of potatoes, viz. Sava and Bintje, and examine their antioxidant capacity in in-vitro systems (b) to evaluate the effect of these extracts on the storage stability of a fish-rapeseed oil mixture and oil-in-water emulsions. Multiple antioxidant activity of the potato peel extracts was evident from in-vitro systems as they showed strong reducing power, radical scavenging ability, ferrous ion chelating activity and prevented oxidation in a liposome model system. The Sava variety, which showed strong antioxidant activity in in-vitro systems, was tested in oil and oil-in-water emulsions. Ethanolic extracts of Sava (≥1,600 mg/kg) prevented lipid oxidation in emulsions and in oil. Water extracts showed no antioxidant activity in oil whereas it showed pro-oxidant activity in emulsions. Thus, the results of the present study show the possibility of utilizing waste potato peel as a promising source of natural antioxidants for retarding lipid oxidation.     

Antioxidant activity of yoghurt peptides: Part 1-in vitro assays and evaluation in ω-3 enriched milk

The aim of the present study was to investigate important factors contributing to the high oxidative stability of fish-oil-enriched yoghurt, with particular emphasis on the possible antioxidative effects of peptides released during yoghurt fermentation. Yoghurt samples were stripped from sugars and lactic acid and subsequently fractionated by ultrafiltration using membranes with cut off sizes of 30 kDa, 10 kDa and 3 kDa. The fractions were tested for antioxidant activity by investigating the inhibition of oxidation in liposome model system, 1,1-diphenyl-2-picrylhydrazyl radical-scavenging activity, iron-chelating activity, and reducing power. The lower molecular weight fractions were found to be more effective antioxidants than higher molecular weight fractions. The lower molecular fractions were further tested as antioxidants in fish-oil-enriched milk. On the basis of peroxide value, volatiles, tocopherol and sensory characteristics, the lower molecular weight fractions 3–10 kDa and <3 kDa showed protection against oxidation of fish oil to the same extent as caseinophosphopeptides. The oxygen content of the yoghurt was also found to be lower than that of milk. Thus our findings suggests that the higher oxidative stability of yoghurt might be due to antioxidant peptides released during the fermentation of milk by lactic acid bacteria and/or by the lower oxygen content of yoghurt, which subsequently reduces the oxidative stress of fish oil incorporated in the yoghurt. The results show that antioxidant peptides may be used as an ingredient in foods enriched with fish oils to increase their oxidative stability.