Antioxidant activity of fresh and processed edible seaweeds

The antioxidant activity of aqueous/organic extracts of processed and raw edible seaweeds was determined using three methods, namely (a) free radical (DPPH·) scavenging, (b) ferric‐reducing antioxidant power (FRAP) and (c) inhibition of copper‐catalysed in vitro human low‐density lipoprotein (LDL) oxidation. Scavenging activity correlated well (r = 0.73) with the corresponding total polyphenolic content measured by the Folin–Ciocalteu procedure and expressed as phloroglucinol equivalents (PGE). Of the seaweeds tested, Fucus showed the highest antioxidant activity in two of the test methods used (1 g (dry matter) had a DPPH· activity and a FRAP value equivalent to those 0.18 and 0.07 mmol of Trolox respectively) and the highest total polyphenolic content (41.4 gPGEkg^?1 dry matter). The antioxidant activity and the content of phenolic compounds decreased with processing and storage in the seaweeds tested. In addition, Fucus showed good efficiency in the in vitro inhibition of LDL oxidation. © 2001 Society of Chemical Industry     

Nonextractable polyphenols,usually ignored,are the major part of dietary polyphenols: A study on the Spanish diet

Scope: Dietary polyphenols (PP) can be divided into two groups: extractable polyphenols (EPP) or compounds solubilized by aqueous organic solvents, and nonextractable polyphenols (NEPP) or compounds that remain in their corresponding extraction residues. Most studies on food polyphenols and dietary intakes address exclusively EPP. The objective of this work was to determine the actual amount of PP, including NEPP, in food and in a whole diet. Methods and results: HPLC‐MS analyses were performed to identify EPP in methanol–acetone extracts and NEPP in the acidic hydrolyzates of their extraction residues in cereals, fruits, vegetables, nuts, and legumes. NEPP contents, estimated as hydrolyzable PP plus nonextractable proanthocyanidins (PA), ranged from 880 mg/100 g dry weight in fruits to 210 mg/100 g in cereals and were substantially higher than the contents of EPP. NEPP intake (day/person) in the Spanish diet (942 mg) is higher than EPP intake (258 mg) fruits and vegetables (746 mg) are the major contributors to the total PP intake (1201 mg). Conclusion: Non extractable polyphenols are the major part of dietary polyphenols. The knowledge of intakes and physiological properties of NEPP may be useful for a better understanding of the potential health effects of dietary PP.     

Free radical scavenging capacity of selected red,rosé and white wines

The free radical scavenging capacity of selected red, rosé and white Spanish wines from different grape varieties was determined by the 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH^·) method using a new methodology developed at our laboratory. The amount of sample necessary to decrease by 50% the initial DPPH^· concentration (EC₅₀), the time needed to reach the steady state at EC₅₀ concentration (T_EC50) and the antiradical efficiency (AE = 1/EC₅₀T_EC50) were determined in the wine samples. Some differences between rosé wines made with Garnacha and Tempranillo grape varieties were observed in the UV‐vis spectra and in the free radical scavenging parameters, those from Garnacha variety having the highest antioxidant activity. The antiradical efficiency of the wines followed a decreasing order: red wines (22.44 × 10⁻⁶) > rosé wines (4.90 × 10⁻⁶) > white wines (1.88 × 10⁻⁶). There was a correlation between antiradical efficiency and total polyphenol (TP): AE = −3.33135 + 0.0180535TP; the correlation coefficient was r = 0.951454. © 1999 Society of Chemical Industry     

Levels of cadmium, lead and zinc protoporphyrin absorption in different risk groups

We studied groups of workers, of pregnant women and of neonates exposed and unexposed to cadmium and lead at their place of work or in the environment. A total of 118 exposed and 28 unexposed workers were studied, together with 90 exposed and 100 unexposed pregnant women and neonates. Concentrations of cadmium and lead in the blood were determined by atomic absorption spectrophotometry. There were significant differences in cadmium concentrations between workers and neonates, and significant differences in lead concentrations between workers and pregnant women. We believe these differences are due mainly to high levels of pollution in the area studied.     

Antioxidant capacity of walnut (<Emphasis Type="Italic">Juglans regia</Emphasis> L.): contribution of oil and defatted matter

Several studies have concluded that walnut exhibits greater antioxidant capacity than any other nuts. However, the contribution to antioxidant capacity of the two major fractions of walnut (defatted matter and oil) is unknown, and the aim of the present work is to elucidate it. Antioxidant capacity was evaluated in walnut oil, defatted matter, and whole walnut. The results showed that the defatted matter provided the bulk of the antioxidant capacity (estimated about 332 μmol Trolox/g dm) of this nut, a major proportion derived from insoluble tannins. The contribution of walnut oil to the overall antioxidant capacity of walnut (FRAP and ABTS assays) is less than a 5%. It was observed that oil interfered in the determination of antioxidant capacity of whole walnut, a fact that could affect the data reported in the literature. Separate determination of oil and defatted mater antioxidant capacity is recommended.     

Heat resistance of Listeria monocytogenes in semi-skim milk supplemented with vanillin

The kinetics of destruction of Listeria monocytogenes Scott A in semi-skim milk heated at 55, 58, 60 and 62°C without and with addition of 900, 1400 and 1800 ppm of vanillin was studied. Survival curves displayed an initial shoulder phase followed by an accelerating killing phase. Addition of vanillin to semi-skim milk heated between 55 and 62°C reduced the heat resistance of L. monocytogenes, effect that was more evident at the lowest temperatures. Two kinetic inactivation models were used to fit the data: the shoulder+log-linear model and the Weibull model. The presence of vanillin increased the death rate and reduced the shoulder length of L. monocytogenes in milk when working at low temperatures, while at the highest temperatures, this effect was less evident. Weibull model also showed that at lower temperatures 55°C-58°C, the population was inactivated at different treatment times, leaving a larger proportion of resistant microorganisms. Increasing the heating temperature to 60°C and 62°C, the biggest proportion of the population was destroyed in a very short time, while a very little proportion with higher resistance remained viable. Results suggest that the use of subinhibitory concentrations of vanillin added in combination with mild heat treatment could be used to enhance the inactivation of L. monocytogenes in semi-skim milk.