Sean F. O'Keefe

Optimizing the Extraction of Phenolic Antioxidants from Peanut Skins Using Response Surface Methodology

Peanut skins are a byproduct of peanut blanching operations and contain high levels of phenolic antioxidants. The effect of solvent type (methanol MeOH, ethanol EtOH, and water), concentration (0, 30, 60, 90%), temperature (30, 45, 60 degrees C), and time (10, 20, 30 min) on total phenolic content (TPC), oxygen radical absorbance capacity (ORAC) level, and resveratrol content of peanut skins was investigated. Response surface methodology was used to estimate the optimum extraction conditions for each solvent. EtOH extracts had the highest TPC followed by MeOH and water. The maximum predicted TPC under the optimized conditions (30.8%, 30.9 degrees C, 12 min) was 118 mg of gallic acid equivalents (GAE)/g of skins. MeOH extracts had the highest ORAC activity of 2149 micromol of TE/g followed by EtOH and water under the optimized conditions of 30% MeOH, 52.9 degrees C and 30 min. Resveratrol was identified in MeOH extracts but was not found in samples extracted with EtOH or water.

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.

Storage water activity affects flavor fade in high and normal oleic peanuts

Abstract Studies were conducted on roasted high oleic (HOP) and normal oleic peanuts (NOP) to investigate the effect of storage water activity on flavor changes. Peanuts were stored for 0–7 weeks at 0.19 and 0.60 water activities ( a w ). Volatile flavor compounds were analyzed using solid phase microextraction–gas chromatography. HOP had better oxidative stability compared to NOP, which had peroxide values 7–10 times higher. Sensory evaluation showed HOP retained roasted peanutty characteristics and resisted off-flavor development during storage better than NOP. Pyrazines remained at higher levels after storage in HOP, which also formed lower levels of aldehydes. Oxidation and sensory changes were higher at low a w .

Conversion of Nitrogen to Protein and Amino Acids in Wild Fruits

Protein content of plant tissues is usually estimated by multiplying total nitrogen by a conversion factor of 6.25. This technique assumes that all nitrogen originates from protein. When applied to fruit pulp, it overestimates protein content because pulp typically contains free amino acids and many nitrogenous secondary metabolites. At issue is the extent of error and, consequently, what the conversion factor between nitrogen and protein should be. We calculated a conversion factor based on pulp samples from 18 species collected in the southeastern United States. We also report a new and simple method of estimating protein and free amino acids in fruit pulp. Because previous studies have found high variation in protein and secondary metabolite content among fruit species, use of a single conversion factor for all species will generate error. In an attempt to reduce such error, we calculated protein contents and conversion factors separately for two common fruit types: lipid-rich/carbohydrate-poor and lipid-poor/carbohydrate-rich. We found no difference between these types of fruit and hence combined results in calculating an average conversion factor of 5.64. Use of an accurate conversion factor is important in estimating protein consumption by wild animals and in formulating diets of captive animals. It can also reveal whether loss of body mass in captive animals on fruit diets is due to insufficient protein consumption, secondary metabolite toxicity, or an imbalance of amino acids.

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.

Enhancement of Plant Essential Oils' Aqueous Solubility and Stability Using Alpha and Beta Cyclodextrin

Sodium benzoate has been shown to produce benzene in combination with ascorbic acid. This has led to research for safe alternatives from plant essential oils and parabens that have shown some antimicrobial activity, but many of these compounds exhibit poor solubility in aqueous solutions. Cyclodextrins can increase the solubility of many compounds. This work aimed to investigate the solubility of 23 plant essential oils and 4 parabens in water and an apple juice medium. Four of these compounds were chosen for their low aqueous solubility to determine if complexing the compound with α- and β-cyclodextrin would increase solubility. Three of the complexes were dissolved in an acidified aqueous solution and then studied in glass and polyethylene terephthalate (PET) to determine if storage material would affect the stability. Solubility of the 27 compounds in distilled water ranged from 1.6 mg/L to 2460.6 mg/L and the solubility of 18 of the compounds decreased from 2.5 to 84.7% in apple juice medium (pH = 3.4, 12-13 °Brix). Complexation with cyclodextrin dramatically increased the solubility of the compounds, up to 10-fold. Packaging material had no effect on concentration of compounds present over 7 days. Cyclodextrins were able to increase solubility of these compounds to more suitable concentrations, and may lead to viable natural alternatives to sodium benzoate.

The Effect of High-Pressure Processing on Infectivity of Cryptosporidium parvum Oocysts Recovered from Experimentally Exposed Eastern Oysters (Crassostrea virginica)

Abstract. Shellfish have been identified as a potential source of Cryptosporidium infection for humans. The inactivation of Cryptosporidium parvum and other pathogens in raw molluscan shellfish would provide increased food safety for normal and at‐risk consumers. The present study identified the efficacy of a non‐thermal alternative food‐processing treatment, high hydrostatic pressure processing (HPP), on the viability of C. parvum oocysts in the Eastern oysters Crassostrea virginica. Oysters were artificially exposed to 2 × 107 oocysts of the Beltsville strain of C. parvum in seawater and subjected to HPP treatments. The effects of the treatments were evaluated by inoculation of the processed oyster tissues into neonatal mice. High‐pressure processing of shucked Eastern oysters at all pressures tested (305, 370, 400, 480, and 550 MPa) was significantly effective (P<0.05) in reducing the numbers of positive mouse pups fed treated oyster tissues exposed to C. parvum oocysts. A dose of 550 MPa at 180 s (s) of holding time produced the maximum decrease in numbers of C. parvum positive mouse pups (93.3%). Measurement of tristimulus color values of HPP‐treated raw oysters at extended processing times from 120 s to 360 s at 550 MPa showed a small increase in whiteness of oyster meat. This non‐thermal processing treatment shows promise for commercial applications to improve safety of seafood and reduce public health risks from cryptosporidiosis.

Effect of α-Cyclodextrin–Cinnamic Acid Inclusion Complexes on Populations of Escherichia coli O157:H7 and Salmonella enterica in Fruit Juices

Cinnamic acid (CA), a naturally occurring organic acid found in fruits and spices, has antimicrobial activity against spoilage and pathogenic bacteria, but low aqueous solubility limits its use. The purpose of this study was to determine the effectiveness of solubility-enhancing alpha-cyclodextrin-CA inclusion complexes against Escherichia coli O157:H7 and Salmonella enterica serovars suspended in apple cider or orange juice at two different incubation temperatures (4 and 26 degrees Celsius). Two concentrations (400 and 1,000 mg/liter) of alpha-cyclodextrin-CA inclusion complex were aseptically added to apple cider inoculated with E. coli O157:H7 (7 log CFU/ml) and orange juice inoculated with a cocktail of six Salmonella enterica serovars (7 log CFU/ml). Samples were extracted at 0 min, at 2 min, and at 24-h intervals for 7 days, serially diluted in 0.1 % peptone, spread plated in duplicate onto tryptic soy agar, and incubated at 35 degrees Celsius for 24 h. Populations of E. coli O157:H7 in apple cider were significantly reduced (P < or = 0.05) during the 7-day sampling period in all solutions regardless of temperature. Compared with the controls, populations were significantly reduced by the addition of 400 and 1,000 mg/liter inclusion complex, but reductions were not significantly different (P > or = 0.05) between the two treatment groups (400 and 1,000 mg/liter). Salmonella was significantly reduced in all solutions regardless of temperature. There were significant differences between the control and each inclusion complex concentration at 4 and 26 degrees Celsius. Coupled with additional processing steps, alpha-cyclodextrin-CA inclusion complexes may provide an alternative to traditional heat processes.

Interaction of copper and human salivary proteins.

Interaction of taste molecules with saliva is the first step in the flavor perception process. Saliva is assumed to influence copper-induced sensation by controlling the copper solubility or causing astringency via binding of proteins with copper. This study was performed to identify the nature of copper-protein interactions in relation to the sensory perception of copper. Saliva was treated with CuSO4 x 5H2O at levels of 0, 2.5, 5, 10, 20, or 40 mg/L, and changes in salivary proteins were analyzed using high performance liquid chromatography (HPLC) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Protein peaks that showed changes in HPLC were characterized with SDS-PAGE. HPLC analysis revealed that copper treatment up to 40 mg/L decreased several proteins, including the dominant peak, by 70%. This peak was composed of alpha-amylase, a secretory component, and basic proline-rich proteins. SDS-PAGE results showed that salivary proteins of molecular weight 29 kDa and 33 kDa precipitated when copper was added at concentrations > or =10 mg/L. This study provides biochemical information for understanding perception mechanisms of copper sensation.