Evaluation of the ability of antioxidants to counteract lipid oxidation: Existing methods, new trends and challenges

Development of a Method Suitable for High-Throughput Screening to Measure Antioxidant Activity in a Linoleic Acid Emulsion

An improved system for measuring antioxidant activity via thiobarbituric acid reactive substances and ferric thiocyanate assays is reported, on the basis of oxidation of a linoleic acid (LA) emulsion. Oxidation times were reduced from 20 h to 5 h by increasing the reaction temperature from 37 °C to 50 °C and with an acceptable precision of <10% coefficient of variation (CV). Antioxidants varying in polarity and chemical class—250 µM Trolox, quercetin, ascorbic acid and gallic acid—were used for method optimisation. Further reductions in reaction time were investigated through the addition of catalysts, oxygen initiators or increasing temperature to 60 °C; however, antioxidant activity varied from that established at 37 °C and 20 h reaction time—the method validation conditions. Further validation of the method was achieved with catechin, epicatechin, caffeic acid and α-tocopherol, with results at 50 °C and 5 h comparable to those at 37 °C and 20 h. The improved assay has the potential to rapidly screen antioxidants of various polarities, thus making it useful in studies where large numbers of plant extracts require testing. Furthermore, as this assay involves protection of a lipid, the assay is likely to provide complementary information to well-established tests, such as the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay.

31 P NMR assessment of the phosvitin-iron complex in mayonnaise

Lipid oxidation is the main reason for the limited shelf life of mayonnaise. One of the main catalysts of this process is iron, which is introduced in its ferric (Fe(III)) form via phosvitin, an egg yolk phosphoprotein rich in phosphoserines. The binding of Fe(III) to phosvitin and its ability to establish a redox couple with Fe(II) is believed to determine the oxidation rate of unsaturated lipids. In this work, a ³¹ P NMR based method was developed to quantify loading of phosvitin with Fe(III) and its reductive release. Both features could be quantified in model phosvitin solutions by exploiting the paramagnetic broadening of ³¹ P NMR signal of phosphoserine residues by Fe(III). This method was then successfully applied to quantify the phosvitin-Fe(III) loading in mayonnaise water phase by liquid NMR, whereas ³¹ P NMR MAS could only provide a qualitative measure. The ³¹ P NMR method showed a direct relation between loading of the Fe(III)-phosvitin complex and lipid oxidation.

Essential oils and their bioactive compounds as green preservatives against fungal and mycotoxin contamination of food commodities with special reference to their nanoencapsulation

Fungal and mycotoxin contamination of stored food items is of utmost concern throughout the world due to their hazardous effects on mammalian systems. Most of the synthetic chemicals used as preservatives have often been realised to be toxic to humans and also cause adverse environmental effects. In this respect, use of different plant products especially essential oils (EOs) and their bioactive compounds has been recognized as a green strategy and safer alternatives to grey synthetic chemicals in view of their long traditional use. The current nanoencapsulation technology has strengthened the prospective of EOs and their bioactive compounds in food preservation by enhancing their bioactivity and mitigating other problems regarding their large-scale application. Although, the antimicrobial potential of EOs and their bioactive compounds has been reviewed time to time by different food microbiologists, but very less is known about their mode of action. Based on these backgrounds, the present article provides an account on the antifungal and antimycotoxigenic mode of action of EOs as well as their bioactive compounds. In addition, the article also deals with the application of currently used nanoencapsulation approach to improve the stability and efficacy of EOs and their bioactive compounds against mycotoxigenic fungi causing deterioration of stored food items so as to recommend their large-scale application for safe preservation and enhancement of shelf life of food items during storage.

Effect of gentisic acid on the structural-functional properties of liposomes incorporating β-sitosterol

Multifunctional liposomes incorporating β-sitosterol were developed for delivery of gentisic acid (GA). The interactions of both compounds with phospholipid bilayer were interpreted viaeffects of different β-sitosterol content (0, 20 and 50 mol %) and different gentisic acid to lipid ratio (n_GA/n_lip from 10^-5 to 1) on membrane fluidity and thermotropic properties. Multilamellar vesicles of phosphatidylcholines (with size range between 1350 and 1900 nm) effectively encapsulated GA (54%) when n_GA/n_lip was higher than 0.01. Suppression of lipid peroxidation was directly related to concentration of GA. The resistance to diffusion of gentisic acid from liposomes increased for ˜50% in samples incorporating 50 mol % β-sitosterol compared to sterol-free liposomes. Finally, simulated in vitro gastrointestinal conditions showed that the release was mainly affected by low pH of simulated gastric fluid and the presence of cholates in simulated intestinal fluid, rather than by enzymes activity.

Effects of plasma treatment on the oxidative stability of vegetable oil containing antioxidants

Plasma, the fourth stage of matter, is a partially or wholly ionized state of gas. Degree of lipid oxidation and effects of antioxidants were evaluated in bulk oils at plasma treatment. Significant changes in the conjugated dienoic acid were induced after 10 min of plasma treatment, which corresponded to treatment for 2.5 h at 100 °C and 48 h at 60 °C. Tocopherol stability in the stripped corn oil was significantly higher than that in medium-chain triacylglycerol after the plasma treatment. The antioxidant capacities of 10 μM of α-tocopherol and sesamol were higher than that of β-carotene, and synergistic effects among α-tocopherol, sesamol, and β-carotene were not observed. Added α-tocopherol and sesamol decreased CDA formation by 33 and 30% compared to control samples after plasma treatment. Moisture content in oils decreased significantly about 20% moisture after 6 min plasma treatment. Lipid oxidation could be an important issue in plasma-treated lipid-rich products.

Organic solvent-free extraction of carotenoids from carrot bio-waste and its physico-chemical properties

The bio-wastes (like peels, seeds, etc.) from food industry are rich source of bio-active components, but are poorly managed. In present study, carotenoids were extracted from carrot pomace using ultrasonication and high shear dispersion techniques and flaxseed oil as green solvent (green biorefinery approach). Various combinations of time and temperature were used and final selection was made on the basis of maximum recovery of carotenoids. High shear disperser yielded maximum carotenoids (recovery 94.8 ± 0.08%). The total carotenoid content, antioxidant activity as ABTS, DDPH and FRAP and β-carotene of carotenoid rich extract from carrot pomace (CREP) were 82.66 ± 0.06 μg/g, 1596.04 ± 69.45 μg Trolox eq./ml, 380.21 ± 39.62 μg Trolox eq./ml, 941.20 ± 19.91 μM Trolox eq./ml, 78.37 μg/g, respectively were significantly higher (p < 0.05) when compared with the extracting medium. The L*, a* and b* values of CRE were 18.65 ± 0.037, 19.42 ± 0.21, 27.947 ± 0.65 and were significantly higher than extracting medium. The CRE could be used as a natural source of β-carotene and natural colorant for food applications.

Use of grape residue flour in lactating dairy sheep in heat stress: Effects on health, milk production and quality

The objective of this study was to evaluate the effects of grape residue flour (GRF) on antioxidant activities, biochemistry variables, components of the immune system and milk production and quality of Lacaune sheep in heat stress. Twenty-seven multiparous lactating sheep [50 ± 1.8 days (d) milking] were stratified by initial body weight, age, date of lambing and milk production and assigned randomly to 1 of 3 treatments (9 sheep/treatment): no GRF supplementation (control group) or supplementation at 1% (10 g/kg GRF) or 2% (20 g/kg GRF) of GRF (bark and seed) in the concentrate (grains and minerals mixture). Each ewe received 0.8 kg/d of concentrate, 3.6 kg/d of corn silage, and 0.25 kg/d of Cynodon spp hay. Milk production along with blood and milk samples were collected on d 1, 10 and 15. The 2% GRF sheep had increased serum concentrations of superoxide dismutase and glutathione peroxidase activity on d 15 compared to control sheep. Over time (d 10 to 15), lipid peroxidation was reduced in 2% GRF sheep. Total serum antioxidant capacity was greater in 2% GRF sheep compared to control sheep on d 10 and 15. Superoxide dismutase and glutathione peroxidase activity in milk samples were greater in 2% GRF sheep compared to control sheep. Supplementation with GRF did not affect milk production but GRF sheep were more efficient compared to control sheep. Protein and lactose concentrations were similar between treatments, but total solids and fat concentrations were greater in 2% GRF sheep compared to control sheep on d 15. Somatic cell count was reduced in GRF sheep compared to control sheep. In summary, supplementation with 2% GRF in dairy sheep in heat stress resulted in antioxidant and anti-inflammatory responses, which improved milk quality and reduced somatic cell count and lipid peroxidation.

Antioxidant properties and potential mechanisms of hydrolyzed proteins and peptides from cereals

Cereals like wheat, rice, corn, barley, rye, oat, and millet are staple foods in many regions around the world and contribute to more than half of human energy requirements. Scientific publications contain evidence showing that apart from energy, the regular consumption of whole grains is useful for the prevention of many chronic diseases associated with oxidative stress. Biological activities have mostly been attributed to the presence of glucans and polyphenols. In recent years however, food proteins have been investigated as sources of peptides that can exert biological functions, promote health and prevent oxidative stress. This review focuses on the role of hydrolyzed proteins and peptides with antioxidant properties in various models and their mechanisms which include hydrogen or electron transfer, metal chelating, and regulation of enzymes involved in the oxidation-reduction process.

Analysis of Oxidative Carbonyl Compounds by UPLC-High-Resolution Mass Spectrometry in Milk Powder

Long-chain polyunsaturated fatty acids are highly susceptible to lipid oxidation which causes undesirable odors and flavors in food. We present the development, validation, and application of a semiquantitative screening method to monitor volatile and nonvolatile carbonyl compounds generated from lipids oxidation after 7-(diethylamino)-2-oxochromene-3-carbohydrazide (CHH) derivatization using liquid chromatography high-resolution mass spectrometry. An inclusion list containing eligible compounds was used in full scan mode to identify potential oxidative markers. In an antioxidants study using lecithin and tocopherols, the proposed method was successfully used to monitor the docosahexaenoic acid (DHA)-specific oxidative markers in a model milk powder system enriched with fish oils. The results showed that lecithin inhibits oxidation by reducing the peroxidation rate, while δ-tocopherol delays the oxidation with distinct induction periods. Here, we explore the optimum concentration of soy lecithin and δ-tocopherol needed to limit lipid oxidation in a complex food matrix such as milk powder.

Extracts of Peels and Seeds of Five Varieties of Brazilian Jabuticaba Present High Capacity to Deactivate Reactive Species of Oxygen and Nitrogen

Jabuticaba has a high concentration of phenolic compounds, which have a significant antioxidant capacity. Methodologies have been developed to evaluate the ability of plant extracts to fight free radicals such as H₂O₂, O₂^•-, HOCl, ONOO- and ROO^•. Thus, the capacity of deactivation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in peel and seed extracts of five varieties of jabuticaba was evaluated. Sabará peel (SFP) deactivated HOCl with IC₅₀ 9.24 μg. mL^-1; Paulista seed (PF) deactivated O₂^•- with IC₅₀ 16.15 μg. mL^-1; Coroada seed (CFP) deactivated ONOO- with IC₅₀ 3.84 μg. mL^-1; the peel of CFP deactivated ONOO- with IC₅₀ 5.88 μg. mL^-1; the peel of SFP deactivated the ROO^• at 918.16 μmol TE. g^-1; and Sabará seed deactivated H₂O₂ with 49.11% inhibition at a concentration of 125 μg. mL^-1 of extract. These results demonstrate the high antioxidant potential of this fruit, indicating that it could be extremely beneficial to human health.

Oil nanoencapsulation: development, application, and incorporation into the food market

Oils are very important substances in human nutrition. However, they are sensitive to oxygen, heat, moisture, and light. In recent years, there has been a growing interest in the modification technology of oils. Methods that modify oil characteristics and make oils suitable applications have been increasingly studied. Nanotechnology has become one of the most promising studied technologies that could revolutionize conventional food science and the food industry. Oil nanoencapsulation could be a promising alternative to increase the stability and improve the bioavailability of nanoencapsulated compounds. The occurrence of oil nanoencapsulation has been rapidly increasing, especially in the food industry. Conventional nanoencapsulation technologies applied in different oils exert a direct impact on oil nanoparticle synthesis, influencing parameters such as zeta potential, size, and the polydispersity index; these characteristics might limit the use of oils in different industries. This review summarizes oil nanoencapsulation in the food industry and highlights the technologies, advantages, and limitations of different techniques for obtaining stable oil nanocapsules; it also illustrates key opportunities for and the benefits of technological innovations and analyzes the protection of this technology through patent applications. In the last 20 years, oil nanoencapsulation has grown considerably in the food industry. Although nanoencapsulated oil products are not currently found in the food industry, there are numerous articles in the food science area reporting that oil nanoencapsulation will be a market trend. Nevertheless, different areas can apply nanoencapsulated oils, as demonstrated via patent applications.

Characterisation of peroxidation products arising from culinary oils exposed to continuous and discontinuous thermal degradation processes

High-resolution NMR analysis has been used, for the first time, to identify, putatively, two new secondary aldehydic lipid oxidation products in culinary oils.

Effect of methanolic Prosopis farcta extract on storage stabilization of canola oil

The aim of the present study was to evaluate the effect of methanolic Prosopis farcta extract (PFE; 0, 200, 400, 600, 800 and 1000 ppm) on storage stabilization of canola oil during 24 days of accelerated storage. The canola oil was mainly comprised of oleic acid (65.01%), linoleic acid (19.56%), linolenic acid (8.11%) and palmitic acid (4.48%). The 1, 1-diphenyl-2-picrylhydrazyl radical scavenging activity and β-carotene bleaching ability of the PFE were 1.16 μg/ml and 0.09 mg/ml, respectively. Our study showed that total phenolic content of PFE was 365.72 ± 6.21 mg gallic acid/g of dried fruit quantified by Folin-Ciocalteu's method. Peroxide value, p-anisidine value and thiobarbituric acid value exhibited that PFE at concentration levels of 400, 600, 800 and 1000 ppm in canola oil had good antioxidant effect. According to the results of the present study. The induction periods of treated samples were significantly increased with increasing of PFE concentration. Indeed, the induction periods of oil were improved from 1.99 (control) to 3.32, 4.56, 8.32, 9.89 and 13.34 h by addition of 200, 400, 600, 800 and 1000 ppm of PFE, respectively.

Phenolic compounds can delay the oxidation of polyunsaturated fatty acids and the growth of Listeria monocytogenes: structure-activity relationships

BACKGROUND

Phenolic compounds present a potential solution to ensure food quality and safety. Indeed, they can limit oxidation reactions and bacterial growth in food products. Although their antioxidant mechanisms of action are well known, their antibacterial ones are less well understood, especially in light of their chemical structures. The aim of this study was first to quantify both aspects of a series of natural phenolic compounds and then link these activities to their chemical structure.

RESULTS

We evaluated antioxidant activity by measuring the capacity of phenolic compounds to delay free linoleic acid oxidation caused by the action of a hydrophilic azo-radical initiator (AAPH). We evaluated antibacterial activity by measuring the growth inhibition of Listeria monocytogenes and determining the non-inhibitory and minimum inhibitory concentrations for each compound. Compounds with ortho-diphenolic structures were the best antioxidants, whereas those belonging to the simple phenol category were the best antibacterial compounds.

CONCLUSION

The physico-chemical properties of the compounds influenced both activities but not in the same way. The chemical environment of the phenolic group and the presence of delocalization structures are the most important parameters for antioxidant activity, whereas the partition coefficient, logP, is one of the most important factors involved in antibacterial activity. © 2018 Society of Chemical Industry.

Inhibition of Lipid Peroxidation of Kiwicha (Amaranthus caudatus) Hydrolyzed Protein Using Zebrafish Larvae and Embryos

Amaranth protein concentrate (APC) was hydrolyzed under in vitro gastrointestinal conditions. APC proteins were partially degraded by pepsin at pHs 1.2, 2.0, and 3.2. During the intestinal phase (pepsin/pancreatin enzymes at pH 7.0), no polypeptide bands were observed in the gel, suggesting the susceptibility of amaranth proteins to the action of digestive enzymes. The potent in vitro inhibition of lipid peroxidation, shown by the gastric and intestinal digests, was confirmed in the zebrafish larvae, with a 72.86% reduction in oxidation of lipids in the presence of the gastric hydrolysate at pH 2.0, compared to a 95.72% reduction in the presence of the gastrointestinal digest. APC digests were capable of reducing reactive oxygen species (ROS) production in the zebrafish embryo model with a value of fluorescence of 52.5% for the gastric hydrolysate, and 48.4% for the intestinal hydrolysate.

A new perspective on lipid research in age-related macular degeneration

There is an urgency to find new treatment strategies that could prevent or delay the onset or progression of AMD. Different classes of lipids and lipoproteins metabolism genes have been associated with AMD in a multiple ways, but despite the ever-increasing knowledge base, we still do not understand fully how circulating lipids or local lipid metabolism contribute to AMD. It is essential to clarify whether dietary lipids, systemic or local lipoprotein metabolismtrafficking of lipids in the retina should be targeted in the disease. In this article, we critically evaluate what has been reported in the literature and identify new directions needed to bring about a significant advance in our understanding of the role for lipids in AMD. This may help to develop potential new treatment strategies through targeting the lipid homeostasis.

Comparison of the antioxidant effects of carnosic acid and synthetic antioxidants on tara seed oil

Background

In the present study, tara seed oil was obtained by supercritical fluid extraction and used to investigate the antioxidant strength of carnosic acid (CA) compared with conventional synthetic antioxidants.

Methods

The antioxidants were added to the tara seed oil at 0.2 mg of antioxidant per gram of oil. The samples were then submitted to at 60 °C 15 days for an accelerated oxidation process, with samples taken regularly for analysis. After oxidation, the samples were analyzed to determine the peroxide value, thiobarbituric acid reactive substances, conjugated diene content, and free fatty acid content. CA was investigated at three purity levels (CA20, CA60, CA99), and compared with three synthetic antioxidants (butylatedhydroxyanisole, butylatedhydroxytoluene, and tert-butylhydroquinone).

Results

The oxidation indicators showed that CA was a strong antioxidant compared to the synthetic antioxidants. The antioxidant activities decreased in the order: tert-butylhydroquinone > CA99 > CA60 > CA20 > butylatedhydroxyanisole > butylatedhydroxytoluene. These results show that CA could be used to replace synthetic antioxidants in oil products, and should be safer for human consumption and the environment.

Effects of dietary hop (Humulus lupulus L.) β-acids on quality attributes, composition and oxidative stability of pork meat

BACKGROUND

The effects of dietary levels of hop β-acids on physical attributes, lipid oxidation and chemical composition of pork meat were evaluated. Thirty-two castrated male pigs obtained from a complete block design feeding experiment (6.23 ± 0.42 kg initial body weight (BW) to 20.45 ± 0.95 kg final BW) and fed diets supplemented with 0, 120, 240 or 360 mg kg^-1 hop β-acids during 35 days were slaughtered to sample longissimus dorsi muscle for meat analysis.

RESULTS

No effects (P > 0.05) of dietary hop β-acids were observed on meat physical attributes. Quadratic effects (P < 0.05) of hop β-acids were observed on lipid and protein contents and on thiobarbituric acid-reactive substance (TBARS) values of meatballs, whose equations allowed the estimation of dietary hop β-acid levels of 176, 169 and 181 mg kg^-1 to provide up to 16.20% lipid reduction, 1.95% protein accretion and 23.31% TBARS reduction respectively.

CONCLUSION

Dietary hop β-acids fed to pigs might reduce lipid, increase protein and reduce lipid oxidation without affecting physical attributes of the pork meat. © 2017 Society of Chemical Industry.

Investigation of the composition and antioxidant activity of acetone and methanol extracts of Daphne sericea L. and Daphne gnidioides L

The compositions of methanol and acetone extracts obtained from Daphne sericea L. and Daphne gnidioides L. were investigated. The antioxidant activities of each extract were determined by various test methods. Phenolic composition profile analysis by HPLC-DAD showed that D. gnidioides extracts contain more phenolic compounds than D. sericea extracts. Among the components, syringic acid was found to be the most abundant one in D. gnidioides extracts (42.8 and 38.4 mg per g dry extract of methanol and acetone, respectively). Total flavonoid, total phenolic and total carotenoid contents of methanolic D. gnidioides extracts were found to be 244.5 mg rutin/g dry weight of extract, 1219.3 mg GAE/g dry weight of extract and 11.9 mg/g dry weight of extract, respectively. DPPH^·, ABTS^·+ and O₂^·- assays were applied to plant extracts as radical scavenging activity tests. Methanolic extracts of D. sericea and D. gnidioides showed the highest radical scavenging activities according to DPPH^· and ABTS^·+ tests (61.6 and 147.2 in terms of IC₅₀, respectively). Antioxidant activity tests for measuring lipid oxidation inhibiting capacity were carried in low density lipoprotein (LDL) and bovine brain extract (BBE). Methanolic extracts of D. gnidioides and D. sericea demonstrated remarkable lipid oxidation inhibiting capacity in LDL and BBE tests.

Non-Destructive Spectroscopic Techniques and Multivariate Analysis for Assessment of Fat Quality in Pork and Pork Products: A Review

Fat is one of the most important traits determining the quality of pork. The composition of the fat greatly influences the quality of pork and its processed products, and contribute to defining the overall carcass value. However, establishing an efficient method for assessing fat quality parameters such as fatty acid composition, solid fat content, oxidative stability, iodine value, and fat color, remains a challenge that must be addressed. Conventional methods such as visual inspection, mechanical methods, and chemical methods are used off the production line, which often results in an inaccurate representation of the process because the dynamics are lost due to the time required to perform the analysis. Consequently, rapid, and non-destructive alternative methods are needed. In this paper, the traditional fat quality assessment techniques are discussed with emphasis on spectroscopic techniques as an alternative. Potential spectroscopic techniques include infrared spectroscopy, nuclear magnetic resonance and Raman spectroscopy. Hyperspectral imaging as an emerging advanced spectroscopy-based technology is introduced and discussed for the recent development of assessment for fat quality attributes. All techniques are described in terms of their operating principles and the research advances involving their application for pork fat quality parameters. Future trends for the non-destructive spectroscopic techniques are also discussed.

Searching for an absolute kinetic scale of antioxidant activity against lipid peroxidation

The inhibition properties of a number of antioxidants against peroxidation, started by a 2,2'-azobis[2-(2-imidazolin-2-yl)propane] radical initiator, of linoleic acid in sodium dodecyl sulfate micelles, have been determined in terms of oxygen consumption by a Clark electrode in an oxygen-tight cell. For the 31 antioxidants investigated at variable concentrations, the experimental results well fit the kinetic equation for competitive reactions. The ratio between the initial rates, monitored in the absence and in the presence of antioxidants, depends linearly on their concentration. From the slopes of these straight lines, an absolute scale of inhibition properties of the lipid peroxidation can be devised. Furthermore, the little difference of the time of complete oxygen consumption on concentration of different antioxidants has been found, indicating a restricted difference towards chemical structure and stoichiometric ratio. Some considerations regarding the mechanisms of inhibition of the lipid peroxidation in micelles, in view of bibliographic data, have been made.

Reactivity of peptides within the food matrix

Numerous biological activities have been reported for peptides or peptide-rich fractions from hydrolyzed food proteins. Some of the properties of peptides include antioxidant, antimicrobial, anti-inflammation, antihypertensive, and immune system modulation. To evaluate the efficacy of peptides in vivo, foods have been used as carrier vehicles. However, there are many molecules in foods that can react or interact with peptides, thereby reducing the bioavailability or bioactivity of these peptides. The Schiff base reactions of peptides with reducing sugars are well established. Peptides can also react with oxidized lipids or reactive oxygen species. Secondary metabolites such as quinones in foods, can react as well with amine or thiol groups of peptides. All these reactions affect the concentration of peptides. This review summarizes and discusses some of the implication of those reactions on the availability of bioactive peptides within the food matrix. PRACTICAL APPLICATIONS: Bioactive peptides possess specific effects on foods like preventing oxidative rancidity. In human, they may lower blood pressure or reduce inflammation. The knowledge on the type of reactions these peptides may encountered when foods are used as transport vehicles is essential. This will prevent variability in intake and ensure proper dosage and reproducible results.

Effects of Pro-Oxidants and Antioxidants on the Total Antioxidant Capacity and Lipid Oxidation Products of Milk During Refrigerated Storage

Oxidized flavor is a major problem that affects the dairy industry because of its adverse effect on milk acceptability. The objectives of this research were to examine the roles of pro-oxidants and antioxidants on the oxidative stability of whole milk. In the 1st experiment, the effect of light (2300 Lux) and/or cupric sulfate (0, 0.5, and 1.0 mg/kg) as pro-oxidants in milk were investigated during an 11-d refrigerated storage period. The effects of added retinyl palmitate (1.16 mg/L; 2113 IU Vitamin A/L) and tocopheryl acetate (100 mg/kg milk fat; 5.02 IU Vitamin E/L) as antioxidants in the presence of light (2300 Lux) and light with cupric sulfate (0.05 mg/kg) during a 7-d study were investigated in the 2nd experiment. The presence of pro-oxidants significantly (P < 0.05) decreased the total antioxidant capacity (TAC) and increased the lipid oxidation products in milk during storage. Light had a greater effect in the decrease of TAC, although cupric sulfate in the presence of light significantly increased the formation of lipid oxidation products. The addition of antioxidants resulted in a significant (P < 0.05) increase in TAC on day 0. However, with exposure to light and light with cupric sulfate, the antioxidants did not result in a higher TAC in comparison to the treatments without added antioxidant. Analysis of lipid oxidation products by instrumental and sensory methods showed that the presence of light and cupric sulfate significantly (P < 0.05) increased the oxidized flavor from the control, but no significant (P > 0.05) difference in oxidized flavor intensity was detected between milk with and without added antioxidants.

PRACTICAL APPLICATION

Production and processing variables can affect the content of pro-oxidants and antioxidants in milk, which has an impact on flavor. An understanding of the role of these components in contributing to or minimizing off-flavor formation in milk, will help dairy producers to provide quality products to consumers.

Photoinduced electron transfer reaction in mitochondria for spatiotemporal selective photo-oxidation of lipids by donor/acceptor linked molecules

Donor-acceptor-linked molecules have been synthesized and utilized to induce the rapid and site-selective lipid-oxidation in mitochondria by utilizing a photoinduced intermolecular electron transfer reaction. Two water-soluble donor-acceptor molecules (1 and 2) were designed and synthesized for this purpose. 2 was prepared to modulate its affinity to cell membrane in mitochondria. Confocal laser microscopy experiments revealed that 1 and 2 possess high localization abilities in mitochondria. By the photoinduced electron transfer, 2 exhibited the remarkable oxidation ability of lipids, mainly cardiolipin. In HeLa cells, 2 triggered mitochondrial lipid oxidation, which was followed by apoptotic cell death, under illumination within a few seconds. These results show that the present molecular system is highly promising to utilize the photoinduced intermolecular electron transfer reaction in a precise spatiotemporal manner in a cell by using light.

Impact of legume protein type and location on lipid oxidation in fish oil-in-water emulsions: Lentil, pea, and faba bean proteins

Emulsion-based delivery systems are being developed to incorporate ω-3 fatty acids into functional foods and beverages. There is interest in formulating these delivery systems from more sustainable and label-friendly ingredients. The aim of this study was therefore to examine the impact of plant-protein emulsifiers on the oxidative stability of 1wt% fish oil-in-water emulsions. Fish oil emulsions stabilized by three types of legume protein (lentil, pea, and faba bean) were produced using a high-pressure microfluidizer. The formation of primary (peroxides) and secondary (TBARS) lipid oxidation products was measured when the emulsions were stored at 37°C under accelerated (+100μM iron sulfate) or non-accelerated (no added iron) conditions for 21 or 33days, respectively. The particle size, charge and microstructure of the emulsions were monitored during storage using light scattering and microscopy to detect changes in physical stability. Emulsions stabilized by whey protein isolate, a commonly used animal-based protein, were utilized as a control. The emulsions formed using whey protein had smaller initial particle sizes, better physical stability, and slightly better stability to lipid oxidation than the ones formed using plant-based proteins. The impact of protein location (adsorbed versus non-adsorbed) on the oxidative stability of the emulsions was also investigated. The presence of non-adsorbed proteins inhibited lipid oxidation, presumably by binding transition metals and reducing their ability to interact with ω-3 fatty acids in the lipid droplets. Overall, these results have important implications for fabricating emulsion-based delivery systems for bioactive lipids, e.g., they indicate that including high levels of non-adsorbed proteins could improve oxidative stability.

Comparison of Antioxidant Evaluation Assays for Investigating Antioxidative Activity of Gallic Acid and Its Alkyl Esters in Different Food Matrices

The addition of antioxidants is one of the strategies to inhibit lipid oxidation, a major cause of lipid deterioration in foods leading to rancidity development and nutritional losses. However, several studies have been reported that conventional antioxidant assays, e.g., TPC, ABTS, FRAP, and ORAC could not predict antioxidant performance in several foods. This study aimed to investigate the performance of two recently developed assays, e.g., the conjugated autoxidizable triene (CAT) and the apolar radical-initiated conjugated autoxidizable triene (ApoCAT) assays to predict the antioxidant effectiveness of gallic acid and its esters in selected food models in comparison with the conventional antioxidant assays. The results indicated that the polarities of the antioxidants have a strong impact on antioxidant activities. In addition, different oxidant locations demonstrated by the CAT and ApoCAT assays influenced the overall antioxidant performances of the antioxidants with different polarities. To validate the predictability of the assays, the antioxidative performance of gallic acid and its alkyl esters was investigated in oil-in-water (O/W) emulsions, bulk soybean oils, and roasted peanuts as the lipid food models. The results showed that only the ApoCAT assay could be able to predict the antioxidative performances in O/W emulsions regardless of the antioxidant polarities. This study demonstrated that the relevance of antioxidant assays to food models was strongly dependent on physical similarities between the tested assays and the food structure matrices.

Gallic Acid Grafted Chitosan Has Enhanced Oxidative Stability in Bulk Oils

Gallic acid (GA) was grafted in chitosan and the effects of GA grafted chitosan (GA-g-CS) on the oxidative stability in bulk oil was tested at 60 and 140 °C. To text oxidative stability in oils, headspace oxygen content, conjugated dienoic acid (CDA) value, p-anisidine value (p-AV), and acid value were determined. Chitosan itself did not show antioxidative or prooxidative effects in oils at 60 °C. However, GA-g-CS and GA acted as antioxidants at 60 °C. At 140 °C heating with moisture supplied condition, different results were observed. GA-g-CS acted as antioxidants based on the results of CDA and p-AV. However, chitosan showed the highest oxidative stability based on results of acid value and brown color formation at 140 °C. This could be due to reduction of moisture content by chitosan. GA was continuously released from GA-g-CS in bulk oil. This might have provided extra antioxidant activities to oils.