Lwt - Food Science and Technology 

Abstract: The antiradical activities of various antioxidants were determined using the free radical, 2,2-Diphenyl-1-picrylhydrazyl (DPPH*). In its radical form. DPPH* has an absorption band at 515 nm which dissappears upon reduction by an antiradical compound. Twenty compounds were reacted with the DPPH* and shown to follow one of three possible reaction kinetic types. Ascorbic acid, isoascorbic acid and isoeugenol reacted quickly with the DPPH* reaching a steady state immediately. Rosmarinic acid and δ-tocopherol reacted a little slower and reached a steady state within 30 min. The remaining compounds reacted more progressively with the DPPH* reaching a steady state from 1 to 6 h. Caffeic acid, gentisic acid and gallic acid showed the highest antiradical activities with a stoichiometry of 4 to 6 reduced DPPH* molecules per molecule of antioxidant. Vanillin, phenol, γ-resorcylic acid and vanillic acid were found to be poor antiradical compounds. The stoichiometry for the other 13 phenolic compounds varied from one to three reduced DPPH* molecules per molecule of antioxidant. Possible mechanisms are proposed to explain the experimental results.

Abstract: The reaction mechanisms of three antioxidants are proposed in order to explain experimental results obtained from a kinetic study using the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH . ) method, previously adapted in our laboratory. In its radical form, DPPH . shows an absorbance maximum at 515 nm which disappears upon reduction by an antiradical compound. BHT, a synthetic antioxidant, slowly reacts with DPPH . reaching a steady state within 5 h. This 2.8-stoichiometric complete reaction follows a 1.5-order with respect to DPPH . and 0.5 to BHT. The kinetic rate constant, k, is estimated to be 5.0 L/(mol·s) at 20 °C and the energy of activation, Ea , is equal to 35 kJ/mol in methanol. Eugenol reacts with DPPH . reaching a steady state within 2 h. This 1.9-stoichiometric reaction follows a 2-order with respect to both DPPH . and eugenol, k and Ea are estimated to be 5.4 × 10 10 L 3 /(mol 3 ·s) at 20 °C and 30 kJ/mol, respectively. The eugenol mechanism may involve a dimerization between two phenoxyl radicals. The reaction with isoeugenol is rapid and reversible, with a stoichiometry of 1.1. It is first order with respect to isoeugenol with k (direct reaction) equal to 8.9 × 10 −2 s −1 at 10 °C. This reaction is consistent with a pseudo-monomolecular mechanism.

Abstract: Microbial adhesion to surfaces and the consequent biofilm formation has been documented in many different environments. Biofilms constitute a protected mode of growth that allows microorganisms to survival in hostile environments, being their physiology and behavior significantly different from their planktonic counterparts. In dairy industry, biofilms may be a source of recalcitrant contaminations, causing food spoilage and are possible sources of public health problems such as outbreaks of foodborne pathogens. Biofilms are difficult to eradicate due to their resistant phenotype. However, conventional cleaning and disinfection regimens may also contribute to inefficient biofilm control and to the dissemination of resistance. Consequently, new control strategies are constantly emerging with main incidence in the use of biosolutions (enzymes, phages, interspecies interactions and antimicrobial molecules from microbial origin). The present review will focus on describing the mechanisms involved in biofilm formation and behavior, deleterious effects associated with their presence, and some of the current and emergent control strategies, providing new insight of concern for food industry.

Abstract: Dietary antioxidants, such as water-soluble vitamin C and phenolic compounds, as well as lipid-soluble vitamin E and carotenoids, present in vegetables contribute both to the first and second defense lines against oxidative stress. As a result, they protect cells against oxidative damage, and may therefore prevent chronic diseases, such as cancer, cardiovascular disease, and diabetes. Brassica vegetables, which include different genus of cabbage, broccoli, cauliflower, Brussels sprouts, and kale, are consumed all over the world. This review focuses on the content, composition, and antioxidant capacity both lipid- and water-soluble antioxidants in raw Brassica vegetables. The effects of post-harvest storage, industrial processing, and different cooking methods on stability of bioactive components and antioxidant activity also are discussed.

Abstract: In this study, the antioxidant activity of water and ethanol extracts of fennel (Foeniculum vulgare) seed (FS) was evaluated by various antioxidant assay, including total antioxidant, free radical scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, metal chelating activities and reducing power. Those various antioxidant activities were compared to standard antioxidants such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and α-tocopherol. The water and ethanol extracts of FS seeds showed strong antioxidant activity. 100 μg of water and ethanol extracts exhibited 99.1% and 77.5% inhibition of peroxidation in linoleic acid system, respectively, and greater than the same dose of α-tocopherol (36.1%). The both extracts of FS have effective reducing power, free radical scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, and metal chelating activities. This antioxidant property depends on concentration and increasing with increased amount of sample. In addition, total phenolic compounds in the water and ethanol extracts of fennel seeds were determined as gallic acid equivalents. The results obtained in the present study indicated that the fennel (F. vulgare) seed is a potential source of natural antioxidant. Although, the tests presented here show the usefulness of FS extracts as in vitro antioxidants it still needs to be that this extracts show their activity in emulsions, biological systems, health implications or dry foods.