Document Type

Dissertation - Open Access

Award Date

2016

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry and Biochemistry

First Advisor

Douglas Raynie

Abstract

Food safety has become a top concern in our society. The public in general is increasingly concerned about the safety of the food products they consume every day as more and more food contamination incidents and widespread recalls arise. It is necessary to trace any presence and/or the concentration levels of contaminants, pesticides, herbicides, or other harmful substances in food samples. Sample preparation is a crucial step in a food analytical method, as it takes up most of the total analysis time, contributing highly to the total cost of analysis and greatly influencing the results of the analysis. Traditional extraction methods for food samples such as liquid-liquid extraction and Soxhlet extraction are involved time-consuming and large solvent consumption steps. In recent years, some extraction techniques have been developing as the substitutions to the conventional sample preparation methods. Accelerated solvent extraction (ASE) and solid phase extraction (SPME), which are considered “green” sample preparation techniques, are among the most studied sample preparation techniques. They have advantages over traditional extraction methods, such as shortened extraction time, reduced solvent consumption, increased pollution prevention, and reduced cost. This dissertation reported the studies on method developments for food safety and quality analyses using these modern sample extraction techniques. Perfluorooctanoic acid is an organofluorine compound that is synthetically produced and primarily used as an emulsifier in the production of polytetrafluoroethylene (PTFE or Teflon). These polymers provide oil and water repellency as well as stain resistance, which make them ideal coating materials for non-stick cookware. PFOA is bioaccumulative, persistent, and potentially harmful to humans. PFOA is not supposed to be found in the final products of non-stick cookware after processing. A method for determination of the leaching of PFOA from the cookware under simulated cooking conditions was presented. To simulate cooking conditions, PTFE-coated cookware was extracted with ethanol/water mixtures using accelerated solvent extraction (ASE). The extraction parameters such as pressure, cycle, and purge time were optimized. The resulting extracts were analyzed by liquid chromatography tandem mass spectrometry (HPLC-MS/MS). Good recoveries, precision, and linearity were obtained. Limits of detection (LOD) were as low as 0.03 and 0.02 μg/L, corresponding to 5.0 pg/cm2 and 3.3 pg/cm2, for PFOA analysis under watery- and fatty-food-simulation conditions, which are lower than the reported methods by approximately 80%. The method was successfully applied to analyze PFOA from used and new cookware under simulated cooking conditions. The results demonstrated that PFOA were detectable in all pan samples extracted with both watery-and fatty-food-simulation conditions. It is assumed that PFOA breaks down from fluoropolymer-coated cookware (new or used) may leach into foods under common cooking conditions (175 °C and 20 min). However, no attempt was made to correlate this data to PFOA levels found in fried foods or the average diet. Overall, the proposed method was an efficient, accurate, and precise method that can be applied to analyze contaminants and harmful substances from food contact materials and samples. A headspace-solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) method was developed to identify and quantify the flavor component allyl isothiocyanate (AITC) and related compounds in horseradish products. Solvent extraction, headspace sampling, and HS-SPME were compared, and HS-SPME gave acceptable accuracy and precision for the quantification of AITC and related compounds in horseradish. The optimized conditions for HS-SPME were 0.8 g sample size in a 4-mL vial at 30 °C for 20 min with one minute desorption in the GC injector at 250 °C. A calibration curve was generated in the concentration range of 50-3200 ppm of allyl isothiocyanate using the internal standard method. The validated method resulted in intraday and interday precision (% RSD) and accuracy (% recovery) of less than 10% and 80-120%, respectively. The method was applied to analyze allyl isothiocyanate in horseradish samples. Seven constituents were identified and the major constituents were allyl isothiocyanate (97.58%) and phenylethyl isothiocyanate (1.65%), representing 99.23% of the pungent components in prepared horseradish sample. The HS-SPME-GC-MS method presented is simple, accurate, and sensitive. Manufacturer, processors, and regulatory authorities can use this method to evaluate quality of flavored products before and after production. Horseradish (Armoracia rusticana) is mostly used as a condiment in food due to its characteristic strong pungent smell and taste. Allyl isothiocyanate is responsible for the pungency of horseradish. In this study, a sensory analysis was carried out through the development of a method for studying the correlation between the level of allyl isothiocyanate and the perceived pungency in horseradish products. Sensory pungency analysis of 14 commercial horseradish products from 8 manufacturers was carried out by a trained panel. The level of allyl isothiocyanate in horseradish products was quantified by the validated HS-SPME-GC-MS method. Differences due to water content are noted, but the impact of other sample ingredients is more complex. Both the sensory data and analytical results showed that there were differences in pungency among the 14 horseradish product samples. Panelists exhibited no significant difference in overall preferences among the 14 samples, with the average overall preference ratings ranging from 4.3-5.4. Some differences in terms of expectation, acceptability, and interpretation of sensory characteristics of horseradish might be present among the panelists. Due to the limited number of panel participants and samples, the information obtained from this study should be considered preliminary. For future study, a larger group of panelists is needed to better understand the links between sensory testing and instrumental analysis. Additionally, it will gain more insight if the influence of food components and masking effects are better understood.

Library of Congress Subject Headings

Food -- Analysis.
Extraction (Chemistry)
Food -- Quality.
Food contamination.

Description

Includes bibliographical references (page 91-112)

Format

application/pdf

Number of Pages

130

Publisher

South Dakota State University

Rights

Copyright © 2016 Changling Qui

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