Susan E. Duncan

Cyclodextrin Inclusion Complex Formation and Solid-State Characterization of the Natural Antioxidants α-Tocopherol and Quercetin

Cyclodextrin (CD) complexation procedures are relatively simple processes, but these techniques often require very specific conditions for each individual guest molecule. Variations of the coprecipitation from aqueous solution technique were optimized for the CD complexation of the natural antioxidants alpha-tocopherol and quercetin. Solid inclusion complex products of alpha-tocopherol/beta-CD and quercetin/gamma-CD had molar ratios of 1.7:1, which were equivalent to 18.1% (w/w) alpha-tocopherol and 13.0% (w/w) quercetin. The molar reactant ratios of CD/antioxidant were optimized at 8:1 to improve the yield of complexation. The product yields of alpha-tocopherol/beta-CD and quercetin/gamma-CD complexes from their individual reactants were calculated as 24 and 21% (w/w), respectively. ATR/FT-IR, 13C CP/MAS NMR, TGA, and DSC provided evidence of antioxidant interaction with CD at the molecular level, which indicated true CD inclusion complexation in the solid state. Natural antioxidant/CD inclusion complexes may serve as novel additives in controlled-release active packaging to extend the oxidative stability of foods.

Controlled release of α-tocopherol, quercetin, and their cyclodextrin inclusion complexes from linear low-density polyethylene (LLDPE) films into a coconut oil model food system.

Polymer additive migration into a food product is dependent upon numerous factors including the original concentration of the additive in the polymer, its solubility in the food, its diffusion coefficient in the polymer, its partition coefficient between the polymer and food, temperature, and time. The limited solubility of quercetin in linear low-density polyethylene (LLDPE) did not allow release from the film due to phase segregation of the quercetin in the bulk polymer. Increasing the molecular weight of α-tocopherol by β-cyclodextrin inclusion complexation can greatly reduce its diffusion coefficient in LLDPE. Ziegler–Natta and metallocene LLDPE contain different crystalline structure morphologies and diffusion path networking arrangements that allow for differences in additive release rates. Effective controlled-release packaging should combine β-cyclodextrin complexation of additives and polymer morphology control to target delivery of an optimal antioxidant concentration to achieve prolonged activity, resulting in extended shelf life foods.

Controlling light oxidation flavor in milk by blocking riboflavin excitation wavelengths by interference.

Milk packaged in glass bottles overwrapped with iridescent films (treatments blocked either a single visible riboflavin [Rb] excitation wavelength or all visible Rb excitation wavelengths; all treatments blocked UV Rb excitation wavelengths) was exposed to fluorescent lighting at 4 degrees C for up to 21 d and evaluated for light-oxidized flavor. Controls consisted of bottles with no overwrap (light-exposed treatment; represents the light barrier properties of the glass packaging) and bottles overwrapped with aluminum foil (light-protected treatment). A balanced incomplete block multi-sample difference test, using a ranking system and a trained panel, was used for evaluation of light oxidation flavor intensity. Volatiles were evaluated by gas chromatography and Rb degradation was evaluated by fluorescence spectroscopy. Packaging overwraps limited production of light oxidation flavor over time but not to the same degree as the complete light block. Blocking all visible and UV Rb excitation wavelengths reduced light oxidation flavor better than blocking only a single visible excitation wavelength plus all UV excitation wavelengths. Rb degraded over time in all treatments except the light-protected control treatment and only minor differences in the amount of degradation among treatments was observed. Hexanal production was significantly higher in the light-exposed control treatment compared to the light-protected control treatment from day 7; it was only sporadically significantly higher in the 570 nm and 400 nm block treatments. Pentanal, heptanal, and an unidentified volatile compound also increased in concentration over time, but there were no significant differences in concentration among the packaging overwrap treatments for these compounds.

Antioxidant activities of Vine Tea (Ampelopsis grossedentata) extract and its major component dihydromyricetin in soybean oil and cooked ground beef.

Antioxidant activities of Ampelopsis grossedentata extract (EXT) and its major component dihydromyricetin (DHM) were analysed and compared with BHA in two model systems, soybean oil and cooked ground beef. Oxidation of soybean oil samples was measured using peroxide value, anisidine value, headspace volatiles and headspace oxygen content. TBARS (thiobarbituric acid reactive substances) test was used to measure the oxidation of cooked beef. DHM was more potent than BHA in preventing soybean oil oxidation. EXT was not as effective as BHA or DHM in soybean oil. In cooked beef, all three antioxidants significantly lowered oxidation compared to control, but there were no differences between the three. Mechanisms and potentials of EXT and DHM as natural food antioxidants need to be studied on a case-by-case basis.

Age-associated variation in sensory perception of iron in drinking water and the potential for overexposure in the human population.

Humans interact with their environment through the five senses, but little is known about population variability in the ability to assess contaminants. Sensory thresholds and biochemical indicators of metallic flavor perception in humans were evaluated for ferrous (Fe(2+)) iron in drinking water; subjects aged 19-84 years participated. Metallic flavor thresholds for individuals and subpopulations based on age were determined. Oral lipid oxidation and oral pH were measured in saliva as potential biochemical indicators. Individual thresholds were 0.007-14.14 mg/L Fe(2+) and the overall population threshold was 0.17 mg/L Fe(2+) in reagent water. Average thresholds for individuals younger and older than 50 years of age (grouped by the daily recommended nutritional guidelines for iron intake) were significantly different (p = 0.013); the population thresholds for each group were 0.045 mg/L Fe(2+) and 0.498 mg/L Fe(2+), respectively. Many subjects >50 and a few subjects <50 years were insensitive to metallic flavor. There was no correlation between age, oral lipid oxidation, and oral pH. Standardized olfactory assessment found poor sensitivity for Fe(2+) corresponded with conditions of mild, moderate, and total anosmia. The findings demonstrate an age-dependent sensitivity to iron indicating as people age they are less sensitive to metallic perception.

Dairy Intake and Related Self-Regulation Improved in College Students Using Online Nutrition Education

BACKGROUND Dairy intake by college students is markedly lower than recommendations. Interventions to improve dairy intake based on Social Cognitive Theory (SCT) have potential to successfully change behavior by improving mediators that influence dietary choices. OBJECTIVE We aimed to use SCT to improve social support, self-efficacy, outcome expectations, self-regulation, and behavior related to dairy intake in college students. DESIGN We conducted a randomized nutrition education intervention. PARTICIPANTS/SETTING Participants included 211 college students (mean age 20.2 ± 0.1 years; 63% women and 37% men) recruited from a university campus. Participants in the intervention group (n=107) and comparison group (n=104) received an 8-week dairy intake or stress management intervention, respectively, via electronic mail. Data collection included dairy intake from 7-day food records and SCT variables from questionnaires administered during January 2008 and April 2008. MAIN OUTCOME MEASURES Changes in dairy intake and SCT variables (ie, social support, self-efficacy, outcome expectations, and self-regulation). STATISTICAL ANALYSES PERFORMED Multivariate analysis of covariance, with age and sex as covariates (P<0.05). RESULTS Ninety-one percent of participants (n=97 intervention, n=94 comparison) provided data; complete data were analyzed for 85% of participants (n=90 intervention, n=89 comparison). Participants in the intervention group reported higher intake of total dairy foods (P=0.012) and improved use of self-regulation strategies for consuming three servings per day of total dairy (P=0.000) and low-fat dairy foods (P=0.002) following the intervention. CONCLUSIONS Nutrition education via electronic mail based on an SCT model improved total dairy intake and self-regulation. Participants reported increased dairy intake and better use of self-regulation strategies. Future interventions should focus on benefits of consuming low-fat vs higher-fat dairy foods.

Effect of fermentation, aging and thermal storage on total glycosides, phenol-free glycosides and volatile compounds of White Riesling (Vitis vinifera L.) wines

There is growing recognition of the significance of the products of glycoside hydrolysis to varietal wine aroma. White Riesling wines were produced from four strains of Saccharomyces cerevisiae. Wines underwent conventional aging or anaerobic thermal storage (20 days at 45°C) either 2 or 40 months post-fermentation to quantify influences on total glycosides, phenol-free glycosides and selected volatiles. Glycoside and free volatile concentrations were estimated by analysis of glycosyl-glucose and gas chromatography/mass spectrometry, respectively. Thermal storage of wines 2 months post-fermentation reduced the total glycosides by an average of 33% for all yeasts and increased the concentration of free benzyl alcohol while decreasing the concentration of free linalool and geraniol. Conventional aging for 40 months reduced the total and phenol-free glycosides equally among yeasts by an average of 60%, with phenol-free glycosides averaging 80% of the total. Thermal storage of aged wines reduced the total glycoside concentration by an additional 29%. The effect of thermal storage on selected volatile phenols, higher alcohols, esters, acids, terpenes, carbonyl compounds, C-13 norisoprenoids and six-carbon alcohols was variable depending upon the component.

Predictive model with improved statistical analysis of interactive factors affecting the growth of Staphylococcus aureus 196E

The growth of pathogenic bacteria in foods is affected by several factors which may interact to enhance or inhibit microbial growth. A model to predict the growth of Staphylococcus aureus 196E in microbiological media was developed using a modified Gompertz function and response-surface methodology. The predictive equation required the estimation of 23 parameters which describe singular and interactive effects of the growth factors studied. S. aureus 196E was inoculated into brain heart infusion broth formulated with either 0.5, 4.5, or 8.5% NaCl, adjusted to pH 5.0, 6.0, or 7.0, and incubated aerobically at 12, 20, or 28°C. Several interactive relationships between time, temperature, pH, and NaCl concentration were significant. The model adequately predicted the growth of S. aureus 196E. Predicted responses to multiple-factor interactions were displayed with three-dimensional and contour plots. A second model developed from a smaller subset of the growth data demonstrated that models could be produced with much less data collection. This methodology can provide important information to food scientists about the growth kinetics of microorganisms and prediction ranges or confidence intervals for growth parameters. Consequently, the effects of food formulations and storage conditions on the growth kinetics of foodborne pathogens or spoilage microorganisms could be predicted.

Role of Lipid Oxidation, Chelating Agents, and Antioxidants in Metallic Flavor Development in the Oral Cavity

This study investigated the production of metallic flavor, which is a combination of taste and retronasal odor. Chemical reactions in the oral cavity and saliva of healthy subjects were investigated after ingesting iron and copper solutions above and near threshold levels. Significant increase in lipid oxidation (p < 0.001) occurred after metal ingestion, detected as TBARS values. Ferrous ion caused the greatest flavor sensation and lipid oxidation, followed by cupric and cuprous ions. Ferric ion did not cause metallic sensation. Occurrence of oxidation was supported by damage to salivary proteins, detected as protein-carbonyls, and by a significant increase of odorous lipid oxidation related aldehydes. Sensory evaluation demonstrated that antioxidants (vitamins E and C) minimally reduced metallic flavor but that chelating agents (EDTA and lactoferrin) removed the metallic flavor. The role of lipid oxidation is essential for the production of a metallic flavor from ingestion of ferrous, cupric, and cuprous ions.

Focus Groups Identified Women's Perceptions of Dairy Foods

ABSTRACT Focus groups were conducted with 39 Caucasian women (ages 30–55 years) to gain insight regarding their thoughts and feelings toward dairy foods. Women resided in Virginia; all had at least a high school education. Themes characterizing the group discussions were identified. Women knew that dairy foods were a good source of calcium and discussed it in relation to osteoporosis. Although many knew the risk factors related to osteoporosis, most were confused about measures to prevent it. Many used calcium supplements or vitamin/mineral supplements to help meet calcium requirements. Most thought dairy foods were high in fat. Women also discussed the sensory attributes of dairy foods as well as convenience and cost of dairy foods in relation to their dairy food choices.