Karen M. Schaich

Methods of measurement and evaluation of natural antioxidant capacity/activity (IUPAC Technical Report)*

The chemical diversity of natural antioxidants (AOXs) makes it difficult to separate, detect, and quantify individual antioxidants from a complex food/biological matrix. Moreover, the total antioxidant power is often more meaningful to evaluate health beneficial effects because of the cooperative action of individual antioxidant species. Currently, there is no single antioxidant assay for food labeling because of the lack of standard quantification methods. Antioxidant assays may be broadly classified as the electron transfer (ET)- and hydrogen atom transfer (HAT)-based assays. The results obtained are hardly comparable because of the different mechanisms, redox potentials, pH and solvent dependencies, etc. of various assays. This project will aid the identification and quantification of properties and mutual effects of antioxidants, bring a more rational basis to the classification of antioxidant assays with their constraints and challenges, and make the results more comparable and understandable. In this regard, the task group members convey their own experiences in various methods of antioxidants measurement.

Factors affecting DNA damage caused by lipid hydroperoxides and aldehydes

Single (SSB) and double strand breaks (DSB) in supercoiled plasmid DNA pBR322 reacted with linoleic acid hydroperoxides (LOOH) were followed by agarose gel electrophoresis to obtain definitive information about factors affecting LOOH interaction with DNA. In water, LOOH induced extensive DSB, which were metal mediated and increased with incubation time. Adventitious metal bound to DNA was sufficient to decompose LOOH to reactive radicals, activity that was not readily inhibited by chelators DTPA and desferrioxamine. Added Fe2+ and Fe3+ increased SSB and DSB, although the effects of Fe2+ were more extensive. Above 100 microM both valences inhibited DNA damage. Strand breakage by LOOH proceeded via lipid alkoxyl and peroxyl radicals. Aldehydic lipid peroxidation products induced strand breaks via oxidation of double bonds, not by reactions of the carbonyl groups. Lipophilic antioxidants BHA, BHT, and alpha-tocopherol were about 20 times more effective than hydrophilic free radical scavengers sodium benzoate, inositol, DMSO, and mannitol in preventing LOOH-induced strand breaks, supporting lipid phase localization of the damage.

Extrusion chemistry of wheat flour proteins : I. Free radical formation

ABSTRACT Electron paramagnetic resonance (EPR) spectroscopy was used to study free radical production in hard red wheat flours extruded according to a two-level fractional factorial experimental design (11 and 14% protein content, 160 and 185°C, 16 and 20% moisture, 300 and 500 rpm screw speed, and mass flow rate of 225 and 400 g/min). All spectra showed dominant broad singlets (g = 2.0053–2.0059) from nitrogen-centered radicals originating from heat-induced peptide scission and reactions of lipid radicals with side-chain amino groups. At 77 K, sulfur-oxyl or peroxyl radicals (g = 2.008–2.018), thiyl radicals (g = 2.025), and disulfide radical species (g = 2.032–2.035 and 2.05–2.06), resulting from intra- and intermolecular electron migration and shear-induced scission of disulfides, sometimes were present. The strongest EPR signals occurred under conditions of maximum free radical production and minimum opportunity for radical recombination: high protein flour (14%), high die temperature (180°C), and low...

Extrusion Chemistry of Wheat Flour Proteins: II. Sulfhydryl-Disulfide Content and Protein Structural Changes

ABSTRACT Effects of twin-screw extrusion conditions on wheat flour proteins were studied, using a two-level fractional factorial experimental design (11 and 14% protein content, 160 and 185°C, 16 and 20% moisture, 300 and 500 rpm screw speed, mass flow rate of 225 and 400 g/min). Total protein detectable by solid-phase bicinchoninic acid assay decreased slightly after extrusion, with greatest protein loss at 16% moisture and 160°C. Sulfhydryl content of both flours increased after extrusion at 185°C and 16% moisture with moderate specific mechanical energy (SME ≈ 400–600 kJ/kg) or 160°C and 16% moisture with high SME (SME > 1,000 kJ/kg). Disulfide bonds increased under comparable conditions but with moderate shear (SME = 510–540 kJ/kg). At 20% moisture and either temperature, sulfhydryl and total thiol contents decreased without corresponding increases in disulfides. Reversed-phase HPLC indicated gliadins were the fractions most affected by extrusion; high molecular weight glutenin subunits also were affe...

Immunochemical and Electrophoretic Analysis of the Modification of Wheat Proteins in Extruded Flour Products

ABSTRACT Antibodies specific for wheat proteins were used to identify protein fractions modified during extrusion of Hard Red Spring wheat flour (14% protein) under four different combinations of extrusion conditions (18 and 24% feed moisture and 145 and 175°C die temperature). Antibody binding was assessed on immunoblots of proteins extracted from flour and extrudates separated by SDS-PAGE. Antibodies to high molecular weight glutenin subunits (HMW-GS) and to B-group low molecular weight glutenin subunits (LMW-GS) recognized intact subunits from both flour and extrudates. Antibodies to C-group LMW-GS had diminished binding to extruded proteins. Glutenin-specific antibodies also recognized protein in the extrudates migrating as a smear at molecular weights higher than intact subunits, indicating cross-linked proteins. Antibodies recognized albumins or globulins in flour but not in extrudates, evidence that these fractions undergo significant modification during extrusion. Acid-PAGE and antibody reaction o...

Rapid method for preparation of pure veratryl alcohol for the assay of lignin peroxidase

We present a simple method for the rapid preparation of veratryl alcohol by reducing commercially available veratraldehyde with sodium borohydride resulting in high-purity veratryl alcohol. The lag period in the activity of lignin peroxidase from Phanerochaete chrysosporium that is associated with use of commercial preparations of the substrate is eliminated with the use of pure veratryl alcohol. The compound affords also estimation of low enzymatic activity.

Red/Green Currant and Sea Buckthorn Berry Press Residues as Potential Sources of Antioxidants for Food Use

The potential for using extracts of press residues from black, green, red, and white currants and from sea buckthorn berries as sources of antioxidants for foods use was investigated. Press residues were extracted with ethanol in four consecutive extractions, and total Folin–Ciocalteu (F–C) reactive material and authentic phenolic compounds were determined. Radical quenching capability and mechanisms were determined from total peroxyl radical-trapping antioxidant capacity (TRAP) and oxygen radical absorbance capacity (ORAC) assays and from diphenylpicrylhydrazyl (DPPH) kinetics, respectively; specific activities were normalized to F–C reactive concentrations. Levels of total F–C reactive materials in press residue extracts were higher than in many fruits and showed significant radical quenching activity. Black currant had the highest authentic phenol content and ORAC, TRAP, and DPPH reactivity. Sea buckthorn grown in northern Finland showed extremely high total specific DPPH reactivity. These results suggest that berry press residues offer attractive value-added products that can provide antioxidants for use in stabilizing and fortifying foods.

Effects of CD36 Genotype on Oral Perception of Oleic Acid Supplemented Safflower Oil Emulsions in Two Ethnic Groups: A Preliminary Study: Effects of CD36 genotype…

Abstract Previous studies demonstrate humans can detect fatty acids via specialized sensors on the tongue, such as the CD36 receptor. Genetic variation at the common single nucleotide polymorphism rs1761667 of CD36 has been shown to differentially impact the perception of fatty acids, but comparative data among different ethnic groups are lacking. In a small cohort of Caucasian and East Asian young adults, we investigated if: (1) participants could detect oleic acid (C18:1) added to safflower oil emulsions at a constant ratio of 3% (w/v); (2) supplementation of oleic acid to safflower oil emulsions enhanced perception of fattiness and creaminess; and (3) variation at rs1761667 influenced oleic acid detection and fat taste perception. In a 3‐alternate forced choice test, 62% of participants detected 2.9 ± 0.7 mM oleic acid (or 0.08% w/v) in a 2.8% safflower oil emulsion. Supplementation of oleic acid did not enhance fattiness and creaminess perception for the cohort as a whole, though East Asians carrying the GG genotype perceived more overall fattiness and creaminess than their AA genotype counterparts (P < 0.001). No differences were observed for the Caucasians. These preliminary findings indicate that free oleic acid can be detected in an oil‐in‐water emulsion at concentrations found in commercial oils, but it does not increase fattiness or creaminess perception. Additionally, variation at rs1761667 may have ethnic‐specific effects on fat taste perception.