Modified ferrous oxidation-xylenol orange method to determine lipid hydroperoxides in fried snacks

Two separate mechanisms are involved in membrane permeabilization during lipid oxidation

Lipid oxidation is a universal degradative process of cell membrane lipids that is induced by oxidative stress and reactive oxygen and nitrogen species (RONS) in multiple pathophysiological situations. It has been shown that certain oxidized lipids alter membrane properties, leading to a loss of membrane function. Alteration of membrane properties is thought to depend on the initial membrane lipid composition, such as the number of acyl chain unsaturations. However, it is unclear how oxidative damage is related to biophysical properties of membranes. We therefore set out to quantify lipid oxidation through various analytical methods and determine key biophysical membrane parameters using model membranes containing lipids with different degrees of lipid unsaturation. As source for RONS, we used cold plasma, which is currently developed as treatment for infections and cancer. Our data revealed complex lipid oxidation that can lead to two main permeabilization mechanisms. The first one appears upon direct contact of membranes with RONS and depends on the formation of truncated oxidized phospholipids. These lipids seem to be partly released from the bilayer, implying that they are likely to interact with other membranes and potentially act as signaling molecules. This mechanism is independent of lipid unsaturation, does not rely on large variations in lipid packing, and is most probably mediated via short-living RONS. The second mechanism takes over after longer incubation periods and probably depends on the continued formation of lipid oxygen adducts such as lipid hydroperoxides or ketones. This mechanism depends on lipid unsaturation and involves large variations in lipid packing. This study indicates that polyunsaturated lipids, which are present in mammalian membranes rather than in bacteria, do not sensitize membranes to instant permeabilization by RONS but could promote long-term damage.

Stability of Fried Fish Crackers as Influenced by Packaging material and Storage Temperatures

The objective of the study was to determine the stability of fried fish crackers during storage at different temperatures. The physicochemical properties and lipid stability were examined at 25, 40 and 60°C for three months. Fried fish crackers were packed into two types of packaging with four different layers; (i) polyethylene terephthalate-polyethylene-aluminium-linear low density polyethylene (PET-PE-ALU-LLDPE), and (ii) oriented polypropylene-polyethylene-metallized polyethylene terephthalate-linear low density polyethylene (OPP-PE-MPET-LLDPE). The linear expansion and oil absorption in control fried fish cracker was 75.67 ± 5.86% and 27.86 ± 0.79%, respectively. The initial moisture of cracker ranged from 4.41 to 5.40% and decreased to 2.76 to 3.75%. There were also reductions in water activity of crackers from 0.503 to 0.243. For color, the loss occurred gradually within the storage time from 64 to 47% (L*), from 27 to 19% (b*), and increased from 4 to 9% (a*) due to lipid degradation. For both packaging, the hardness of crackers decreased significantly at 25°C and 40°C, but increased at 60°C. Regardless of temperatures and types of packaging, crispiness increased significantly throughout the storage. This textural changes were possible cause by a decrease in moisture content. The lipid yield of the cracker was not stable within the storage time and the concentration of conjugated dienes and thiobarbituric acid reactive substances (TBARS) showed a gradual increase. These results showed that fried fish crackers in the storage study had undergone lipid oxidation where changes in physical and chemical properties were observed.

Impact of nitrogen flushing and oil choice on the progression of lipid oxidation in unwashed fried sliced potato crisps

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Storage stability of unwashed potato crisps fried in sunflower oil’s was compared.

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Oxidation products were determined, with and without flushing with nitrogen gas.

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Crisps fried in SO were the least stable and those using HOSO the most stable.

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Presence of nitrogen gas slowed down the oxidation rate after frying.

Unwashed, sliced, batch-fried potato crisps have a unique texture and are growing in popularity in the UK/EU premium snack food market. In this study, the storage stability of unwashed sliced (high surface starch) potatoes (crisps) fried in regular sunflower oil (SO) or in high oleic sunflower oil (HOSO) was compared over accelerated shelf life testing (45 °C, 6 weeks); with and without nitrogen gas flushing. Primary oxidation products (lipid hydroperoxides) were measured with a ferrous oxidation-xylenol orange (FOX) assay and volatile secondary oxidation products (hexanal) were quantified by using solid phase micro-extraction gas chromatography mass spectrometry (HS-SPME-GC/MS). Results revealed that crisps fried in SO were the least stable. Flushing the stored crisps with nitrogen gas proved to be effective in slowing down the oxidation rate after frying with sunflower oil, significantly stabilizing the crisps. However, crisps fried in HOSO were the most stable, with the lowest rate of development of oxidation markers, and this has previously not been shown for crisps with a high free starch content.

Estimation of Lipid Hydroperoxide Levels in Tropical Marine Macroalgae

The incipient levels of lipid hydroperoxides (LHPOs) were determined in selected green, brown, and red macroalgae by the FOX assay using hydroperoxy HPLC mix. The LHPOs contents varied between the investigated species and showed relatively low values in this study. Among the greens, it varied from 12 ± 6.2 μg · g(-1) (Codium sursum) to 31.5 ± 2.8 μg · g(-1) (Ulva lactuca), whereas in reds, from 5.7 ± 1.6 μg · g(-1) (Gracilaria corticata) to 46.2 ± 6 μg · g(-1) (Sarconema filiforme), and in browns, from 4.6 ± 4.4 μg · g(-1) (Dictyota bartayresiana) to 79 ± 5.0 μg · g(-1) (Sargassum tenerrimum), on fresh weight basis. These hydroperoxides represented a minor fraction of total lipids and ranged from 0.04% (S. swartzii) to 1.1% (S. tenerrimum) despite being a rich source of highly unsaturated fatty acids. The susceptibility of peroxidation was assessed by specific lipid peroxidazibility (SLP) values for macroalgal tissues. The LHPO values were found to be independent of both the PUFAs contents and their degree of unsaturation (DBI), as evident from the PCA analysis. SLP values were positively correlated with the LHPOs and negatively with DBI. The FOX assay gave ≥20-fold higher values for LHPOs as compared to the TBARS method for all the samples investigated in this study. Furthermore, U. lactuca cultured in artificial seawater (ASW) enriched with nutrients (N, P, and NP) showed a sharp decline in LHPOs contents relative to those cultured in ASW alone P ≤ 0.05. It is inferred from this study that the FOX assay is an efficient, rapid, sensitive, and inexpensive technique for detecting the incipient lipid peroxidation in macroalgal tissues.

Autoxidation of unsaturated lipids in food emulsion

Unsaturated lipids having various physiological roles are of significance in biochemistry, nutrition, medicine, and food. However, the susceptibility of lipids to oxidation is a major cause of quality deterioration in food emulsions. The reaction mechanism and factors that influence oxidation are appreciably different for emulsified lipids and bulk lipids. This article gives a brief overview of the current knowledge on autoxidation of oil-in-water food emulsions, especially those that contain unsaturated lipids, which are important in the food industry. Autoxidation of unsaturated lipids in oil-in-water emulsion is discussed, and so also their oxidation mechanism, the major factors influencing oxidation, determination measures, research status, and the problems encountered in recent years. Some effective strategies for controlling lipid oxidation in food emulsion have been presented in this review.

Moderately oxidized oils and dietary zinc and α-tocopheryl acetate supplementation: effects on the oxidative stability of rabbit plasma, liver, and meat

The aim of this study was to assess the alterations in plasma, liver, and meat oxidative stability and α-tocopherol content when moderately oxidized sunflower oils were added to feeds and when feeds were supplemented with α-tocopheryl acetate (100 mg/kg) and Zn (200 mg/kg). The effects of cooking the meat and its subsequent refrigeration were also studied. When the content of primary oxidation compounds of the oil was high, rabbit plasma, liver, and meat α-tocopherol content was reduced and meat susceptibility to oxidation increased. The addition of oil with a high content of secondary oxidation compounds (oil heated at 140 °C, 31 h) to feed also led to an increase in meat susceptibility to oxidation, although it presented an α-tocopherol content similar to that of nonheated oil. Feed supplementation with α-tocopheryl acetate increased tissue α-tocopherol content and improved the oxidative stability of liver and meat. However, in the latter, it was less effective when oil heated at 55 °C was added.

Assessment of the levels of degradation in fat co- and byproducts for feed uses and their relationships with some lipid composition parameters

This paper discusses the levels of degradation of some co- and byproducts of the food chain intended for feed uses. As the first part of a research project, "Feeding Fats Safety", financed by the sixth Framework Programme-EC, a total of 123 samples were collected from 10 European countries, corresponding to fat co- and byproducts such as animal fats, fish oils, acid oils from refining, recycled cooking oils, and other. Several composition and degradation parameters (moisture, acid value, diacylglycerols and monoacylglycerols, peroxides, secondary oxidation products, polymers of triacylglycerols, fatty acid composition, tocopherols, and tocotrienols) were evaluated. These findings led to the conclusion that some fat by- and coproducts, such as fish oils, lecithins, and acid oils, show poor, nonstandardized quality and that production processes need to be greatly improved. Conclusions are also put forward about the applicability and utility of each analytical parameter for characterization and quality control.

Effect of heated sunflower oil and dietary supplements on the composition, oxidative stability, and sensory quality of dark chicken meat

A factorial design was used to study the effect of dietary oxidized sunflower oils (fresh, heated at low temperatures, and heated at high temperatures), DL-alpha-tocopheryl acetate (0 or 100 mg/kg), and Zn supplementation (0 or 600 mg/kg) on the composition, oxidative stability, and sensory quality of dark chicken meat with skin from animals fed with a Se supplement (Se-enriched yeast, 0.6 mg of Se/kg). The positional and geometrical isomers of linoleic acid were increased in raw meat from chickens fed oils oxidized at high temperatures. In addition, supplementation with alpha-tocopheryl acetate increased the alpha-tocopherol content, whereas 2-thiobarbituric acid (TBA) values and lipid hydroperoxide content were reduced. Likewise, TBA values, rancid aroma, and rancid flavor also decreased in cooked dark meat. However, none of the dietary factors studied affected consumer acceptability scores of cooked meat. Furthermore, Zn supplementation increased the Se content in raw meat.