Recipient Organization
UNIVERSITY OF KENTUCKY
500 S LIMESTONE 109 KINKEAD HALL
LEXINGTON,KY 40526-0001
Performing Department
Animal & Food Sciences
Non Technical Summary
Food materials undergo oxidative changes throughout the entire food chain leading to quality deterioration, food waste and enormous economic loss. As a consequence, analytical procedures for quality assurance are employed to monitor the oxidation of proteins, lipids and vitamins. Peroxides are ubiquitous products from the negative impact of organic radicals in foods, thus the monitoring of such molecules is useful to predict the overall quality of the product.In edible fats and oils the most widely accepted method for measuring hydroperoxides is the peroxide value (PV). This titration technique was first developed for nonfood applications in the 1880's. In 1931, the iodometric method for the determination of peroxides in edible fats and oils by heating fat with powdered potassium iodide in a mixture of chloroform-acetic acid. This mixture was then titrated with sodium thiosulfate solution to measure the liberated iodine. The next year, the method was updated by adding starch as an indicator. In 1949, PV was adopted as the official method by the American Oil Chemists Society (AOCS), and with the exception of the replacement of chloroform with isooctane in the 1990s, it has remained essentially the same. In addition to the AOCS official methods for measuring PV in edible (Official Method Cd 8b-90), other organizations use a similar technique. The aforementioned titration procedures, although utilized for decades, have several disadvantages: including requiring a laboratory titration station, being highly empirical, dependent on strict control of reaction conditions, lack of sensitivity and poor endpoint determination, and requires the use of flammable and toxic solvents that are expensive to purchase and dispose after use. This project is designed to replace this method with a safer and less costly technique.
Animal Health Component
50%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Goals / Objectives
This proposed research is designed to characterize, and elucidate the mechanism of photon emissions from a novel structured semiconductor material upon reaction with organic hydroperoxides. The primary application of this technology will be to measure hydroperoxides in oxidized edible fats and oils; however, there are numerous other potential applications.The primary objectives of this project are designed to further develop the structured semiconductor technology for use in measuring hydroperoxides in edible fats and oils. These objectives include 1) to characterize light emissions from the reaction of hydroperoxides and "light emitting crystals" (LECs), 2) to elucidate the reaction mechanism that generates light from the reaction of hydroperoxides and LECs, and 3) to further develop both the composition and structure of LECs to improve their practical use for industrial and analytical applications.
Project Methods
Atomic Absorption Spectroscopy of select components in the structured semiconductor materials will be analyzed using an AAnalyst 200 atomic absorption spectrometer (PerkinElmer Inc., Waltham, MA, USA). Samples will be dry ashed followed by wet decomposition. About 1 g of sample is weighed into a crucible and ashed in an ash oven at 580 ºC for 48 h. The residue is solubilized in 5 mL 6 N HCl, heated on a hot plate to evaporate, and then re-solubilized and soaked for one hour in 10 mL 0.1 N HNO3. The resulting solution is quantitatively transferred and diluted to 25 mL with deionized water in a volumetric flask. Manganese, copper, and iron (for example) will be analyzed at 279.48 nm (slit 1.8/0.6 mm), 324.75 nm (slit 2.7/0.8 mm), and 248.33 nm (slit 1.8/1.35 mm), respectively. The mineral concentrations in the samples will be calculated based on a standard curve analyzed along with the samples.Luminescence Assays A Promega Glomax 20/20 luminometer sensitive to the spectral range of 350-650 nm, or a Biotek Synergy H1 Hybrid Multi-Mode microplate reader with a spectral range of 200-850 nm, will primarily be utilized for general measurements of chemically-stimulated luminescence. Briefly, 80 mg of structured compound semiconductors will be reacted with 1.5 mL of sample and the chemically-stimulated luminescence will be monitored. Examples of samples in addition to edible fats and oils include solvents (water, methanol, isooctane, or chloroform) containing different levels of peroxides (hydrogen or cumene). All blank readings will be obtained with solutions eventually free of peroxides. Data points from each reaction, either one or ten every second, will be recorded and the values will be expressed as arbitrary units (a.u.). Characterization of chemically-stimulated luminescence spectra (e.g., primary wavelengths) and luminescence quantum yield will be measured on a Horiba Scientific, PTI QuantaMaster spectrofluorometer. In order to investigate the wavelength distribution of the light emitted from the chemically-stimulated luminescence from structured compound semiconductors, optical filters will be utilized.Autoxidation of soybean oil and estimation of peroxide value. The edible oil samples, which usually exhibit a maximum peroxide value of 0.4 meq/kg when fresh, will be autoxidized utilizing a water bath set at 70 °C in addition to synthetic air bubbling at 270 mL/min during 5 days. In predetermined intervals (in the range of 0.8 to 50 PV) an aliquot of edible oil will be collected for the determination of peroxide value based on American Oil Chemists Society (AOCS) method Cd 8b-90 (AOCS, 1989).Electron Paramagnetic Resonance. EPR spectroscopy will be performed at 20 °C on a Bruker EMX EPR. Typical parameters to be used are 31.65 mW microwave power; microwave frequency of 9.86 GHz; receiver gain 3.17 × 104; modulation amplitude 16.74 G; modulation frequency 100 kHz; time constant 327.68 ms; conversion time 183.84 ms; field sweep of 4,200 G; and center field of 2,500 G. Spin concentrations may be estimated using a standard curve of powdered K3CrO8 in K3NbO8 and diluted with powdered KCl. The Cr(V) spin concentrations will be calculated from the EPR signal of Fremy's salt (dipotassium nitrosodisulfonate) solutions (Boatright et al., 2008). Data analysis will be conducted on the Bruker WINEPR Processing Software. The investigation of the electron distribution of the synthesized material (especially for the manganese components) will provide additional information to characterize the observed chemically-stimulated luminescent phenomena.Cyclic voltammetry This potentiodynamic electrochemical analysis will be utilized to examine the oxidation potential of the structured compound-semiconductor, and correlate that with organic radical reduction potentials.Powder diffraction X-ray diffraction technique will be employed to characterize the micro- nano-structure of the synthesized materials. A Bruker-AXS D8 DISCOVER diffractometer is available at the University of Kentucky.Spectroscopic analysis A Thermo Nicolet 6700 FTIR coupled with Attenuated Total Reflectance accessory will be utilized to investigate the chemical structure of the synthesized materials. In addition, a Horiba Scientific, PTI QuantaMaster spectrofluorometer will be employed to investigate the wavelength distribution of the chemically-stimulated luminescence. The excitation light beam will be blocked, or the light source will be deactivated, during the whole experiment to avoid photo-stimulated luminescence. UV-Vis-NIR spectral analysis will be used for both to examine the emission of luminescence wavelengths as well in the examination of colormetric reactions from peroxidase assay analytes.GC/MS of Hydroperoxide Degradation Luminescence and products of colormetric reactions are the result of the reaction of LECs with hydroperoxides. To further correlate these reaction outputs with the degradation of hydroperoxides a time-course examination of the disappearance of hydroperoxides and the corresponding appearance of degradation products will be accomplished. The typical technique uses a combination of sample derivatization and gas chromatography/mass spectroscopy or high performance liquid chromatography.Data analysis Pearson correlation and linear regression analysis between total luminescence and peroxide value content will be investigated at 95% of confidence level utilizing SigmaPlot 13.0 (Systat Software Inc., San Jose, CA). Factors and their levels will be considered significant to the synthesis by investigating the r-squared, standard error, and P-value of linear regression coefficients between chemically-stimulated luminescence and peroxide value. In addition, ANOVA at 95% of confidence level followed by Tukey's test will be utilized to differentiate means with a minimum number of replications for each data point of three (n≥3).