Changes of hydrogen peroxide and radical-scavenging activity of raspberry during osmotic, convective, and freeze-drying

This study was conducted to investigate the influence of different drying treatments on antioxidant (AO) activity and phenolic content of raspberry (Rubus idaeus), cultivar Willamette. Whole raspberry fruits were dried convectively (air-drying), osmotically, and freeze-dried. Acetone-water extracts of fresh and dried raspberries were assessed for total phenolic content by standard Folin-Ciocalteau method. Two AO assays were applied, a recently developed direct current (DC) polarographic assay based on decrease of anodic oxidation current of hydrogen peroxide and widely used radical scavenge against the 1,1-diphenyl-2-picrylhydrazyl (DPPH). Strong correlation has been obtained between both AO assays and total phenolic content. In addition, some individual phenolic compounds present in raspberry have been assessed using DPPH and DC polarographic assay. Comparison and evaluation of drying methods has been based on preservation of AO activity and total phenolic content. Obtained results confirmed superiority of freeze-drying; convective drying caused slight changes while osmotic dehydration showed a significant decrease of phenolic compounds and AO activity.     

A Review: Biological and Technological Functions of Barley Seed Pathogenesis‐Related Proteins (PRs)

The mature barley seed proteome is dominated by proteins involved in stress responses, including the Pathogenesis‐Related proteins (PRs). PRs are currently classified into 17 families. The biochemistry of the PRs families, whose members are constitutively present in barley seed, is surveyed in this paper. These proteins are assumed to protect dormant and germinating seeds against pathogenic microorganisms and pests. The current knowledge on PRs structural and functional properties is summarized in an attempt to illustrate their importance in barley seed innate resistance. At the same time, a platform to understand PRs technological function in cereal foods and in beverage processing and quality is provided.     

Antimicrobial Activity of Malting Barley Grain Thaumatin‐Like Protein Isoforms,S and R

Two basic proteins were isolated to homogeneity from malting barley (Hordeum vulgare L.) grain. Proteins were identified as members of a Thaumatin‐Like Protein (TLP) family, by Western blot. Isoforms, assigned as TLP‐S and TLP‐R, have slightly different mobility at about 22 and 27 kDa in nonreducing and reducing conditions, and pI values of 9.5 and 9.4, respectively. The antifungal potency of malting barley grain TLPs isoforms was examined on Micrococcus lysodeikticus, Saccharomyces cerevisiae, Candida albicans and plant pathogen Fusarium sporotrichioides growth in vitro. It was found that that IC₅₀ value for TLP‐S was two fold higher. Antibacterial and antifungal activities of both isoforms were completely abolished by divalent (Ca²⁺, Mn²⁺, Mg²⁺) and monovalent (K⁺) cations, at concentrations approximating physiological ionic strength and higher. Glucanase activity was not observed; neither TLP‐S nor TLP‐R digested glucan. On the basis of these results, the importance of TLP for barley grain protection against fungal diseases has been discussed together with the mechanism of antimicrobial action.     

Barley Grain Non‐specific Lipid‐Transfer Proteins (ns‐LTPs) in Beer Production and Quality

Plant non‐specific lipid‐transfer proteins (ns‐LTPs) are known for their ability to transfer various lipids between membranes in vitro. These ubiquitous basic proteins, that all share alpha structure stabilized by four disulphide bridges, are characterized by the presence of a hydrophobic cavity able to accommodate lipid molecules. According to molecular mass, this multigene family is subdivided into two subfamilies, ns‐LTP1 (9 kDa) and ns‐LTP2 (7 kDa); both located in the aleurone layer of the cereal grain endosperm. Ns‐LTP1 is a prominent protein in barley grain, malt and beer. Numerous studies performed on its structure and function confirm its important role in grain protection, as well as brewing technology. As the major beer protein crucial for many aspects of brewing, ns‐LTP1 can affect beer production and quality. Comparatively, there is less data available on the less abundant ns‐LTP2. In this review, the focus is on recent progress on the structure, biological and technological function of barley grain ns‐LTP1 and ns‐LTP2, with an emphasis on their importance in brewing.     

Cold-Pressed Pumpkin Seed Oil Antioxidant Activity as Determined by a DC Polarographic Assay Based on Hydrogen Peroxide Scavenge

Antioxidant (AO) activity of cold pressed pumpkin (Cucurbita pepo L.) seed oil, produced from three naked and one hulled variety, was assessed using a DC polarographic assay based on a hydrogen peroxide scavenge (HPS). Results are expressed as the decrease of the anodic oxidation current of hydrogen peroxide obtained upon addition of methanolic extract of the investigated oils. Strict correlations of HPS and (1) radical scavenging capacity against the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH) (0.99), (2) the induction period estimated by a Rancimat test (0.99) and (3) total phenolic content estimated by Folin-Ciocalteu (FC) assay (0.99) were obtained. In addition, a significant correlation of HPS and the content of δ-tocopherol (0.87), squalene (0.67) and color CIE a* (−0.89) was found. Based on the results reported, the polarographic assay was found to be suitable for determination of AO activity as an indicator of the quality and oxidative stability of oil.