Effects of natural antioxidants on the lipid profile of electron beam‐irradiated beef burgers

The purpose of this study was to assess the efficacy of rosemary and oregano extracts in avoiding oxidative changes in beef burgers, and to evaluate the fatty acid profile of these products after electron beam exposition. Extracts, individually or in combination, were added to beef burgers and compared to synthetic antioxidants commonly used in food (butylated hydroxytoluene, butylated hydroxyanisole). The ground beef were submitted to electron beam irradiation at doses of 0, 3.5 and 7 kGy, and stored for 90 days. At regular time intervals, lipid oxidation and fatty acid composition were evaluated through measurement of thiobarbituric acid‐reactive substances (TBARS) and gas chromatography, respectively. The results indicate that, although the irradiation process triggers an increase in the lipid oxidation ratio expressed by TBARS values, great changes in the fatty acid profiles were not observed; instead, they continued to present characteristics very similar to that of non‐irradiated beef. Thus, as irradiation doses of up to 7 kGy for frozen meat can make foods safe from foodborne pathogens, natural antioxidants derived from spices are able to reduce and avoid lipid changes that may cause a deterioration of the sensory quality of these foods, and these natural extracts offer a good choice for replacing synthetic additives.     

The antioxidant effect of natural substances on lipids during irradiation of chicken legs

Entire fresh chicken legs were subjected to three pretreatments (packaged in air; packaged under vacuum; or marinated in natural plant extracts and packaged in air) followed by irradiation (0, 3, or 5 kGy). The control and irradiated chicken legs were stored at 4°C and analyzed for FA composition and sensory quality at predetermined intervals. Irradiation dose had a significant (P<-0.01) effect on FA derived from phospholipid but less than on FA derived from a neutral lipid. In general, levels of unsaturated FA decreased as the radiation dose increased; however, for marinated chicken legs irradiated with 5 kGy, levels of linoleic acid (C_18∶2) and arachidonic acid (C_20∶4) derived from the phospholipid fraction were significanlty (P≤0.05) higher than those irradiated in air or under vacuum. The concentration of FA also decreased significantly (P≤0.05) as storage time increased. For chicken legs packaged in air or marinated and then packaged in air, significant (P≤0.01) inverse correlations existed between high-carbon-number PUFA and lower-carbon-number (≤17) saturated FA; this relationship was not apparent in samples irradiated under vacuum. A processing combination of marinating and vacuum packaging might better control lipid oxidation and degradation in irradiated chicken. Panelists found no significant difference (P>0.05) in the flavor and oder intensity of cooked irradiated chicken legs and their nonirradiated equivalents.     

Oil quality characteristics of irradiated sunflower and maize seed

The characteristics of oils extracted from gamma‐irradiated sunflower (Halianthus annuus) and maize (Zea mays) seeds at absorbed doses of 2, 4, 6, 8, and 10 kGy were investigated. Gamma irradiation did not affect the lipid, protein, fiber, and ash contents of neither sunflower nor maize seeds significantly (p>0.05). No significant changes were observed for the values of refractive index and density between the control and irradiated sunflower and maize oils. Peroxide value, acid value, para‐anisidine value, and conjugated dienes and trienes contents increased, while iodine values decreased in the irradiated oils as compared to those of control oils (p<0.05). A small decrease in the contents of α‐, γ‐, and δ‐tocopherols of both sunflower and maize oils was noted by radiation treatment up to 6 kGy, however, the decline was more pronounced at higher dosages. The effects of irradiation on the fatty acid composition of sunflower oil showed a significant (p<0.05) change in the amounts of stearic, oleic, and linoleic acids, while the concentration of palmitic acid was unaffected even at 10 kGy. Similar trends in the fatty acid profile were found for both the sunflower and maize oil.     

Analysis of lipids from cooked beef by thin-layer chromatography with flame-ionization detection

Lipids were extracted from cooked ground beef with methylene chloride/methanol (2:1). The lipids were separated on a silicic acid column, into neutral and polar fractions by elution with methylene chloride, followed by methanol. These fractions were analyzed by Iatroscan thin-layer chromatography with flame-ionization detection instrumentation on Chromarods S-III (silica gelcoated quartz rods). Comparison of cooked beef stored for 0, 4 and 7 d at 4°C indicated that storage caused a decrease in total lipids, an increase in neutral lipids and a decrease in polar lipids, specifically in phosphatidylcholine. These changes in the lipid fraction were associated with meat flavor deterioration and an increase in lipid oxidation.     

The Synergism of Biochemical Components Controlling Lipid Oxidation in Lamb Muscle

Lipid oxidation of M. longissimus lumborum in fresh or vacuum packaged (aged) lamb meat stored at 3 °C for 0 or 4 weeks, respectively and displayed under refrigerated conditions for a further 4 days was assessed by measuring the concentration of malondialdehyde (MDA) in meat using the thiobarbituric acid reactive substances procedure. The effects of vitamin E, heme iron and polyunsaturated fatty acids (n-6 and n-3) on lipid oxidation were examined. Results showed a strong positive relationship between heme iron, n-6 and n-3 fatty acids and lipid oxidation when vitamin E was below 2.95 mg/kg muscle. When lipid oxidation was related to vitamin E concentration and the other three variables, respectively, any increase in heme iron or n-6 or n-3 fatty acids concentration did not influence lipid oxidation. Management of diet to elevate muscle vitamin E concentration above 3.45 mg/kg muscle is beneficial to maintain the level of lipid oxidation below 2.4 mg MDA/kg muscle in meat stored for up to 4 weeks. This demonstrates that vitamin E concentration in muscle has a greater influence on controlling lipid oxidation in muscle tissues than do heme iron or polyunsaturated fatty acids.     

Chlorophyll breakdown by gamma irradiation in a model system containing linoleic acid

The possible breakdown of chlorophyll by irradiation was investigated. Chlorophyll b standard (3 ppm) was added to a methanol solution containing 1% linoleic acid. Irradiation up to 20 kGy was performed with or without N₂-bubbling, and nonirradiated control was also prepared. Residual chlorophyll b content was analyzed by HPLC and UV-visible spectra after irradiation, and color was measured during 6 h of light exposure (3,300 lux, light intensity) to induce photooxidation. The added chlorophyll b was destroyed by irradiation at 20 kGy with or without N₂-bubbling. With N₂-bubbling the oil sample did not develop lipid oxidation during irradiation, and irradiated samples did not develop photooxidation during storage under light. Without N₂-bubbling, irradiated oil samples had higher PV than nonirradiated samples. The Hunter color a-value of oil increased and the b-value decreased with irradiation at 20 kGy. UV-visible spectra also supported the break-down of chlorophyll b in solution by irradiation. Irradiation at 2.5 kGy or above destroved all added chlorophyll b. The results indicate that irradiation technology could be applied to reduce or eliminate the residual chlorophyll in oil processing without developing lipid oxidation during the irradiation process, which would prolong the shelf life of oil products by protecting them from photooxidation during display.     

Gamma radiation induced oxidation and tocopherols decrease in in-shell, peeled and blanched peanuts

In-shell, peeled and blanched peanut samples were characterized in relation to proximate composition and fatty acid profile. No difference was found in relation to its proximate composition. The three major fatty acids were palmitic acid, oleic acid, and linoleic acid. In order to investigate irradiation and storage effects, peanut samples were submitted to doses of 0.0, 5.0, 7.5 or 10.0 kGy, stored for six months at room temperature and monitored every three months. Peanuts responded differently to irradiation, particularly with regards to tocopherol contents, primary and secondary oxidation products and oil stability index. Induction periods and tocopherol contents were negatively correlated with irradiation doses and decreased moderately during storage. α-Tocopherol was the most gamma radiation sensitive and peeled samples were the most affected. A positive correlation was found among tocopherol contents and the induction period of the oils extracted from irradiated samples. Gamma radiation and storage time increased oxidation compounds production. If gamma radiation is considered an alternative for industrial scale peanut conservation, in-shell samples are the best feedstock. For the best of our knowledge this is the first article with such results; this way it may be helpful as basis for future studies on gamma radiation of in-shell crops.     

Quantitation of cholesterol oxidation products in unirradiated and irradiated meats

A method to detect 7-ketocholesterol, cholesterol-5β,6β-epoxide, cholesterol-5α,6α-epoxide, 4-cholesten-3-one, 4,6-cholestadien-3-one and 4-cholestene-3,6-dione in unirradiated and irradiated beef, pork and veal was developed by use of chloroform-methanol-water extraction, solid-phase extraction, column separation, thin-layer chromatography and gas chromatography. This method recovered 78–88% of the cholesterol oxidation products and detected the cholesterol oxidation products at 10 ppb or higher. Irradiation of the meats to a dose of 10 kGy increased these compounds, except 4,6-cholestadien-3-one for all three types of meat, over unirradiated, and except cholesterol-5α,6α-epoxide and 4-cholesten-3-one for the pork. All the cholesterol oxidation products in the unirradiated meats increased during storage at 0–4°C for 2 wk with some exceptions for the pork. The increases of cholesterol oxidation products in stored irradiated meats were greater than those in the unirradiated.     

Studies on changes in fatty acid composition and content of endogenous antioxidants during γ irradiation of rice seeds

Accelerated aging effects, induced by y irradiation, were investigated on the fatty acid composition of lipids and on the content of endogenous antioxidants of four Indica and four Japonica rice seeds with and without intact hull. While the linoleic acid content of the phospholipids decreased gradually with the increase in irradiation doses, there was a corresponding increase in the linoleic acid content of the free fatty acids. Such changes were drastic, especially in the case of Japonica rice seeds irradiated without intact hull. However, the neutral lipids were found to be resistant to γ irradiation. The α-tocopherol content was found to decrease (markedly) in rice seeds irradiated with or without hull, especially in the Japonica rice seeds. At a dose of 15 kGy only traces of a-tocopherol could be detected in Japonica and Indica rice seeds irradiated with and without intact hull. Oryzanol, a relatively weaker anti-oxidant, was found to be more resistant to oxidative damage than a-tocopherol. At 15 kGy, the oryzanol content ranged from 59 μg to 170 μg/g lipid in rice seeds irradiated with intact hull, while the corresponding value for rice seeds irradiated without hull was 52 μg to 153 μg/g lipid. The overall susceptibility to oxidative damage was less in Indica rice seeds, indicating that the antioxidative defense system offered better protection in overcoming oxidative stress in Indica rice hull than in Japonica rice hull.     

Formation of Trans Fatty Acids Induced by Radicals in Irradiated Ground Beef and Liquid Egg

This study was conducted to investigate the possible formation of trans fatty acids due to gamma-irradiation of ground beef and liquid egg via a radical path. The effects of irradiation on trans fatty acids in ground beef and liquid egg were evaluated by GC analysis. The control sample of ground beef had higher concentrations of total trans fatty acids than the liquid egg. C18:1-11t was the major trans fatty acid detected in non-irradiated ground beef. The results showed that irradiation led to a significant increase of total trans fatty acid content in both of the two food items with an absorbed dose range between 6.743 and 11.472?kGy (P?<?0.05). The change in C18:1-9t content was the most significant compared with other trans fatty acids. Additionally, gamma-irradiation caused a higher rate of trans fatty acid formation in liquid egg compared with ground beef. However, a slight decrease in the total trans fatty acid amount was observed in ground beef with an absorbed dose at 21.113?kGy. The increase in trans fatty acid content was negligible in liquid egg under the same absorbed dose. This result may be due to the oxidation of unsaturated configurations of both cis and trans fatty acids.     

Improvement of Physicochemical Properties of Rubber Blends Between Nonirradiated and Irradiated Rubber Latexes by Radiation Vulcanization

Abstract

Nonirradiated natural rubber latex (NRL) and irradiated (12 kGy) rubber latex were blended in ratios of 100:0, 85:15, 65:35, 50:50, 35:65, 15:85, and 0:100 (v/v) to improve properties of the rubber latex. The blends were irradiated using different irradiation doses (0–20 kGy) in the presence of a radiation vulcanization accelerator (RVA), normal butyl acrylate (n-BA). The physicochemical properties of the nonirradiated latex, irradiated latex, and blend films were determined after leaching with distilled water. It was observed that the tensile strengths of the blend films increases with an increase in the content of the irradiated proportion and radiation doses. The composition of the blends and the doses of radiation were optimized. The maximum tensile strength (31.41 MPa) was found for the 50:50 composition of the blend with a 5 kGy radiation dose. The 100:0 blends, when irradiated, give the highest tensile strength (27.69 MPa) with 12 kGy but a 15:85 nonirradiated blend gives the tensile strength of 26.18 MPa.     

Effect of Gamma Irradiation on Biochemical Properties of Grape Seeds

In the present study, grape seed samples (Alicante Bouschet, Cabernet Franc, Cinsault, Merlot, Shiraz) were treated with 1.0, 3.0, 5.0, and 7.0 kGy of gamma radiation. Effect of irradiation dose on free fatty acids (FFA), peroxide value (PV), sterol, fatty acid composition, phenolic content, antioxidant activity of the seed oils, and chemical (dry matter, fat, ash, total sugar, invert sugar) changes of grape seeds were determined. Regarding fatty acid composition, oleic acid (C18:1) and linoleic acid (C18:2) levels decreased. β-sitosterol content with a highest percentage among sterols in grape seed oils decreased due to gamma irradiation. Generally gamma irradiation increased free fatty acids and peroxide value of the oils; however, phenolic content and antioxidant capacity of grape seeds decreased.     

Effect of low-dose γ-radiation on individual phospholipids in aqueous suspension

A series of individual phospholipids (phosphatidylcholines, phosphatidylethanolamines, phosphatidylserines and phosphatidylglycerols) containing either saturated or unsaturated fatty acid chains was irradiated at 9.66 kGy and 0–4°C in aqueous suspension. The phospholipids were analyzed by normal-phase high-performance liquid chromatography on a silica column with an evaporative light scattering detector. Phospholipid disappearance and production of two radiolytic products, phosphatidic acid and the lysophospholipid, after irradiation were quantitated from calibration curves of synthetic standards. Dipalmitoylphosphatidic acid and monopalmitoylphosphatidylcholine from irradiated dipalmitoylphosphatidylcholine were identified by liquid secondary-ion mass spectrometry.     

Detection of Hydrocarbons in Irradiated Chilled Beef by HS-SPME–GC–MS and Optimization of the Method

The hydrocarbons 1,7-hexadecadiene (1,7-C16:2) and 8-heptadecene (8-C17:1), which are used as markers for identifying irradiated chilled beef, were easily detectable in chilled beef irradiated at 0.5 kGy or higher by using a new method of headspace solid-phase microextraction, gas chromatography and mass spectrometry (HS-SPME–GC–MS). The conditions for using SPME were optimized in this study for qualitative and quantitative determination of 1,7-C16:2 and 8-C17:1 produced by γ-radiation in chilled beef. The relationship between irradiation dose and production of hydrocarbons was also studied, which showed good linear correlation with the coefficients of 0.9942 and 0.9943 for 1,7-C16:2 and 8-C17:1, respectively. HS-SPME–GC–MS is a simple and sensitive method for the analysis of hydrocarbons in irradiated chilled beef.     

Formation kinetics of radiolytic lipid products in model food–lipid systems with gamma irradiation

Irradiation processes can change the lipid composition of foods. The major lipid radiolysis products are known to be 2-alkylcyclobutanones and hydrocarbons, the formation kinetics of which is determined by the chemical nature of the inherent lipids. This information can be used to evaluate the irradiation history of lipid-rich foods. A solid-phase microextraction (SPME)-assisted gas chromatography–mass spectrometry (GC–MS) technique was used to study the formation of volatile hydrocarbons and 2-dodecylcyclobutanone (2-DCB), a cyclobutanone formed from the esters of palmitic acid, in irradiated (0–50 kGy) tripalmitin and chicken fat. Thirty-three volatile compounds (hydrocarbons, aldehydes, ketones) increased with irradiation dose to varying extents. Six major lipid radiolysis products were selected to analyze their formation kinetics: tridecane, 1-tetradecene, tetradecane, 1-pentadecene, pentadecane, and 2-DCB. The concentration of the selected compounds increased linearly with irradiation dose following zeroth-order kinetics, except for tridecane and tetradecane in tripalmitin, formation of which followed first-order kinetics. The formation rate of hydrocarbons was higher in tripalmitin than in chicken fat (5× higher for pentadecane), while 2-DCB formed faster (3.5×) in chicken fat than in tripalmitin. This difference was related to the diversity in the natural fatty acid composition of chicken fat as compared to the homogeneous structure of tripalmitin. The results of this study indicate that the concentrations of palmitic acid radiolysis products linearly increase with irradiation dose in general to offer potential to back-trace irradiation dose in lipid-rich foods.     

Encapsulation of Long-Chain n-3 Polyunsaturated Fatty Acids Using Egg Yolk

Egg yolk is well known for its excellent emulsifying property. In this article, egg yolk was used as the encapsulating matrix to prevent the oxidation of n-3 long-chain polyunsaturated fatty acids from fish oil. A 2 × 2 × 5 complete block design with three replications was used. Two levels of fish oil (1% and 5%) and two levels of esterification type (triglycerides or ethyl esters) of eicosapentaenoic/docosahexaenoic fatty acids were used. Time was considered a fixed factor with five levels. Emulsions were prepared by homogenization and stored for up to 4 weeks at 4–6 °C, with weekly sampling. Emulsions were analyzed for particle size and distribution, encapsulation efficiency, and surface oil. The oxidative stability of the emulsions was evaluated before and after cooking at 150–170 °C for 75 s. The addition of triglycerides resulted in a larger average particle size (234 ± 12.4 nm). All emulsions achieved 100% encapsulation efficiency and showed no significant change in the surface oil concentration during storage. After 4 weeks of storage, the concentration of eicosapentaenoic + docosahexaenoic fatty acids in nonencapsulated fish oil triglycerides and ethyl esters decreased by 20.32% and 14.74%, respectively, while the emulsions showed no significant differences. In addition, no peroxide or propanal formation was detected in raw emulsions over the storage period. Propanal formation was negligible in cooked samples, and the peroxide value showed no differences between the egg yolk control and the emulsions. Therefore, egg yolk was observed to be an efficient encapsulating food matrix that protects n-3 polyunsaturated fatty acids against oxidation and degradation.     

Dragon Fruit (Hylocereus spp.) Seed Oils: Their Characterization and Stability Under Storage Conditions

Oil was extracted from the seeds of white-flesh and red-flesh dragon fruits (Hylocereus spp.) using a cold extraction process with petroleum ether. The seeds contained significant amounts of oil (32–34 %). The main fatty acids were linoleic acid (C18:2, 45–55 %), oleic acid (C18:1, 19–24 %), palmitic acid (C16:0, 15–18 %) and stearic acid (C18:0, 7–8 %). The seed oils are interesting from a nutritional point of view as they contain a large amount of essential fatty acids, amounting to up to 56 %. In both dragon fruit seed oils, tri-unsaturated triacylglycerol (TAG) was mainly found while their TAG composition and relative percentage however varied considerably. Therefore, they showed a different melting profile. A significant amount of total tocopherols was observed (407–657 mg/kg) in which the α-tocopherol was the most abundant (~72 % of total tocopherol content). The impact of storage conditions, cold and room temperatures, on the oxidative stability and behavior of tocopherols was monitored over a 3-month storage period. During storage, the oxidative profile changed with a favorably low oxidation rate (~1 mequiv O₂/week) whilst tocopherols decreased the most at room temperature. After 12 weeks, the total tocopherol content, however, still remained high (65–84 % compared to the initial oils). Hereto, the dragon fruit seed oils can be considered as a potential source of essential fatty acids and tocopherols, with a good oxidative resistance.     

Effect of microencapsulation and spray drying on oxidative stability of flaxseed oil and its release behavior under simulated gastrointestinal conditions

Flaxseed oil is one of the richest sources of omega-3 fatty acid (α-linolenic acid, ALA). It contains high amounts of polyunsaturated fatty acids, making it extremely susceptible to oxidation. In the present study, flaxseed oil was stabilized using microencapsulation followed by spray drying and studied for its oxidative stability in terms of peroxide value (PV), thiobarbituric acid, and p-anisidine value at room temperature (35 ± 1°C) and low temperature (4–7°C) storage for 6 months. Results revealed that the developed flaxseed oil powder was stable throughout the storage period and PV remained below to the maximum permissible limit (≤5 mEq/kg oil) prescribed by the Codex Alimentarius Commission. The fatty acids profile measured by gas–liquid chromatography indicated a 14.28–15.13% decrease in ALA content in flaxseed oil as a result of microencapsulation and storage at room temperature. In vitro digestion behavior of microcapsules showed 4.39 ± 0.53 to 19.87 ± 0.47% release of flaxseed oil under simulated gastric continued, whereas under gastrointestinal conditions it was 20.00 ± 3.66 to 59.99 ± 9.29%.     

Influence of heating time and oxygen availability on lipid oxidation in meat emulsions

The aim of the present study was to investigate the effect of heating time and oxygen availability on lipid oxidation during chill storage, using different step indicators, in a meat emulsion model. Lipid oxidation was measured by conjugated dienes, hydroperoxides and 2‐thiobarbituric acid reactive substances formation on raw and cooked meat emulsion at 80 °C in different oxygen availability bags, at 0 °C during 35 d. The results obtained showed that heat treatment and oxygen availability affected conjugated dienes, hydroperoxides and 2‐thiobarbituric acid reactive substances formation during chill storage. Besides cooked meat emulsion did not have a similar behaviour to that of raw samples. Thus, is very important to follow primary and secondary products of oxidative deterioration to understand the effect of heat treatment and oxygen availability overall lipid oxidation process in meat emulsion.     

A Single Bout of Exercise Increases the Expression of Glucose but not Fatty Acid Transporters in Skeletal Muscle of IL-6 KO Mice

IL-6 is a biologically active cytokine released during exercise by contracting skeletal muscles. It appears to be highly involved in the regulation of muscles energy substrate utilization. Whether an ablation of IL-6 (IL-6 KO) in mice subjected to a single bout of exercise affects lipid and/or glucose metabolism is currently unknown. In the present study we examined fatty acid (FAT/CD36, FABPpm, FATP-1, FATP-4) as well as glucose (GLUT-1, GLUT-4) transporters expression in IL-6 KO mice. In addition, intramuscular glycogen and lipid content was also evaluated. The expression of all fatty acid transporters (FAT/CD36: +25 %; FATP-1: +31 %; FABPpm: +12.7 %; FATP-4: +7.2 %) was increased in muscles from IL-6 KO mice compared to wild type (WT) mice. Accordingly intramuscular lipid content was also increased in these muscles (FFA: +38 %; DAG: +36 % and TAG: +160 %). Interestingly, IL-6 deficiency had only minor effect on glucose transporters expression (GLUT-1: ?4 %, and GLUT-4: ?5.1 %), with no apparent difference in muscular glycogen content. A single bout of exercise increased the glucose transporters (GLUT-1: +8 %; GLUT-4: +15 %) as well as FA transporters (FAT/CD36: +13 %; FABPpm: +4.5 %; FATP: +2.5 %, FATP-4: +10 %) expression but only in WT skeletal muscles. In muscles from IL-6 KO mice exercise induced changes only in glucose (GLUT-1: +20 %; GLUT-4: +35 %) but not in the content of FA transporters. Concomitantly, IL-6 KO mice displayed shorter time toward exhaustion with more pronounced reductions in intramuscular lipid and glycogen content. We may speculate, that IL-6 deficiency provokes more pronounced glucose utilization over lipid oxidation during a single bout of exhausting exercise.