AimsThis study aimed to evaluate in vitro antioxidant capacity of olive leaf extract (OLE), Olea europaea L., and its protective effect on peroxyl radical-induced oxidative damage in human erythrocytes.Main methodsThe OLE was evaluated by the following assays: i) total phenolic and flavonoid content; ii) oleuropein content; iii) Ferric reducing antioxidant power (FRAP); iv) antioxidant activity against ABTS•+, DPPH• and reactive oxygen and nitrogen species: superoxide anion (O2·−), hypochlorous acid (HOCl) and nitric oxide (NO•) and v) protective effect on peroxyl radical-induced oxidative damages in human erythrocytes as hemolysis, thiobarbituric acid reactive substances (TBARS) formation and oxyhemoglobin oxidation.Key findingsTotal phenolic and flavonoid contents were 131.7 ± 9.4 mg gallic acid equivalents/g dry weight (dw) and 19.4 ± 1.3 mg quercetin equivalents/g dw, respectively. Oleuropein content was 25.5 ± 5.2 mg/g dw. FRAP analysis was 281.8 ± 22.8 mg trolox equivalent/g dw and OLE inhibited ABTS•+ (50% effective concentration (EC50) = 16.1 ± 1.2 μg/mL) and DPPH• (EC50 = 13.8 ± 0.8 μg/mL). The extract demonstrated effective ability to scavenge O2·− (EC50 = 52.6 ± 2.1 μg/mL), NO• (EC50 = 48.4 ± 6.8 μg/mL) and HOCl (EC50 = 714.1 ± 31.4 μg/mL). The extract inhibited peroxyl radical-induced hemolysis (EC50 = 11.5 ± 1.5 μg/mL), TBARS formation (EC50 = 38.0 ± 11.7 μg/mL) and hemoglobin oxidation (EC50 = 186.3 ± 29.7 μg/mL) in erythrocytes.SignificanceOLE is an important source of natural antioxidants; it has effective antioxidant activity against different reactive species and protects human erythrocytes against oxidative damage.

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This study aimed to evaluate the use of 1 Hz pulsed magnetic field (PMF) in the preservation of fresh ground beef during aerobic refrigerated storage. Supraspinatus muscle from Angus cattle was ground and aerobically packaged into 21 portions. These portions were divided into three treatment groups: not exposed to PMF (control); exposed to PMF for 2 h (PMF-2h) and exposed to PMF for 12 days (PMF-12d). Packages from all groups were stored for 12 days in the dark at 48C. One package from each group was used for microbiological assays and analyses of pH, instrumental color, myoglobin and lipid oxidation. Results have shown that exposure to PMF for 12 days did not alter the preservation and quality of ground beef compared to the control. However, samples exposed to PMF for 2 h reduced the microorganism growth and metmyoglobin content in relation to the control group. However, pH, instrumental color and lipid oxidation of samples exposed to PMF for 2 h did not change during storage compared to the control. We concluded that PMF could be used for fresh meat preservation. However, more studies are needed to understand the mechanisms of action of the magnetic field. PRACTICAL APPLICATIONSIn the present study, the use of a moderate pulsed magnetic field for preservation of fresh beef looks promising for preventing microbial growth, without changing some parameters such as pH, color or lipid oxidation. However, this mild and nonthermal technology needs more studies to evaluate some factors such as the exposure time to the magnetic field. In general, the use of the magnetic field in food preservation may be a viable alternative to the traditional technologies, and can be used alone or in combination with traditional methods in order to increase their efficiency.

This study aimed to evaluate the use of low intensity pulsed magnetic field (PMF) in the preservation of microbiological quality, color and oxidative stability of ground beef during aerobic refrigerated storage. Ground beef samples of chuck tender (Supraspinatus muscle) were exposed to PMF for 2 hours at frequencies of 1, 30 and 60 Hz or, in another step, they were exposed to a 1 Hz PMF for 2 hours or continuously for 12 days. Control samples were not exposed to PMF. Samples were stored at 4 o C for up to 12 days, and evaluated every six days through microbiological analysis of total aerobic mesophilic bacteria count, and every two days through physicochemical and biochemical analysis of pH, instrumental color (CIELAB scale), myoglobin and lipid oxidation. Exposure to 1 Hz PMF for 2 hours reduced the growth of aerobic mesophiles in relation to the control by 1.3 logarithmic cycles in the 12th day of refrigerated storage. Metmyoglobin content of samples exposed to the PMF for 2 hours, regardless of the pulse frequency, were significantly lower compared to the control in the 6th day of refrigerated storage. The other quality parameters did not change significantly during storage compared to the control and it was not observed effect of different PMF frequencies. We concluded that low intensity pulsed magnetic field (order of mili Tesla) has the potential to be used as innovative technology, in combination with refrigeration, in fresh meat preservation. However, more studies are needed to better understand the mechanisms of action of magnetic field, mainly in foods.

.1 ± 1.2 g/mL, respectively. In relation to the antioxidant activity against reactive species of biological importance, the OLE showed high ability to inhibit O 2 • (IC 50 = 52.6 ± 2.1 g/mL) and NO • (IC 50 = 48.4 ± 6.8 g/mL), when compared to ascorbic acid. However, inhibition of HOCl was not as efficient (IC 50 = 714.1 ± 31.4 g/mL). The OLE inhibited induced erythrocyte hemolysis in a concentration dependent manner (IC 50 = 7.8 ± 1.1 g/mL) as well as lipid peroxidation and the formation of methemoglobin, with IC 50 values of 38.0 ± 11.7 and 186.3 ± 29.7 g/mL, respectively. The results suggest that olive leaf extract has effective antioxidant activity in biological systems, based on its scavenging effect of certain reactive species that participate in biochemical processes, and the prevention of oxidative damage in human erythrocytes. So, the intake of olive leaf extract may be related to the prevention of in vivo oxidative stress, with health benefits.