Abstracts from the College of Agriculture and Marine Studies
Undergraduate Summer Research Symposium August 14, 2003

Ordered alphabetically by student's last name


Extraction and Quantification Methods for Heterocyclic Amines 

Deidre L. Blackwell1 and Catherine G A Davies2
1Department of Chemistry & Biochemistry and 2Department of Animal & Food Science

Heterocyclic amines are formed in cooked meats produced by a reaction between creatine, free amino acids, and sugars.  Five of these amines, 2-amino-1-methyl-6-phenlyimidazo[4,5-b]pyridine (PhIP), 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), and 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMeIQx), were used to develop extraction and quantitative methods for heterocyclic amines. The clean up of the samples was performed by solid-phase extraction (SPE).  Quantitative analysis was carried out using HPLC with an TSK-gel ODS 80TM column.  A UV detector was used and the mobile phase consisted of a triethylamine-phosphate buffer (pH 3.20) and acetonitrile.  Caffeine has been selected as the internal standard.  The calibration curve of caffeine shows what concentration of caffeine will be detected in the peak area range of the heterocyclic amine mixture

A Study of Nodule Formation Through the Comparison of Wild Type Medicago truncatula and Mutant Medicago truncatula 

Carol A. Carlson, Janine G. Haynes, and D. Janine Sherrier
Department of Plant and Soil Science and Delaware Biotechnology Institute

Nitrogen fixing nodules are formed through a symbiotic relationship between the bacteria S. meliloti and the plant Medicago truncatula.  We are evaluating nodule development in wild type (A-17) and mutant plants (CC1& CC2) whose mutation is in their nitrogen fixing ability.  Our objectives are to evaluate root infection and nodule development including cell invasion and infection thread formation by electron microscopy (EM), and confocal light microscopy (CLM).  Plants are grown aeroponically and inoculated with bacteria to induce nodule formation and are harvested at 5,10,&15 days post inoculation for EM study and 18,25,&28 days post inoculation for CLM study.  Thus far infected roots have been fixed and embedded for EM, but the study is not complete. Our confocal study has shown that both CC1 and CC2 are defective in nodule formation.  In CC1 we observed a delayed and sparse growing of nodules with infection threads in abnormal locations within the root.  We found an unusual plant defense response in CC2 as well as aberrant and extensive thread formations.  Work is ongoing to replicate and verify the findings of our initial experiments.  This work is funded by UD Life Science Scholars and USDA.

The Effect of Sodium Chloride on Maillard Browning in Model Systems

Catherine Connelly and Catherine G A Davies
Department of Animal and Food Sciences

The Maillard reaction between carbonyls and amines produces color, flavor, and aroma compounds associated with cooked and processed food. The objective of this study was to determine the potential inhibitory effect, of sodium chloride (NaCl) on Maillard browning. Two types of model systems were studied: glucose-glycine-sodium acetate (GGA) and glucose-lysine-sodium acetate (GLA), each with various concentrations of NaCl (0 M, 0.5 M, and 1 M), pH 5.5.  Solutions were incubated at 60°C.  The rate of the browning reaction was assessed by measuring the absorbance of the solutions at 420 nm at timed intervals. The rates for browning were 0.042, 0.042, 0.039, 0.115, 0.095, and 0.098 units per hour for GGA without NaCl, GGA with 0.5 M NaCl, GGA with 1 M NaCl, GLA without NaCl, GLA with 0.5 M NaCl, and GLA with 1 M NaCl, respectively.   While this suggests that NaCl does have an inhibitory effect (at some concentrations) on the rate of browning, it was not significant under the reaction conditions.  Further experiments are in progress to determine if NaCl impacts browning in model solutions with different concentrations of sugar, amino acid, and buffer. 

Purification of Dissolved and Secreted Proteins from Environmental Samples.

Steve Fatula and Thomas Hanson
College of Marine Studies and Delaware Biotechnology Institute

The experiments presented here are part of a project designed to determine if proteomic techniques can be applied to environmental samples.  This study focused on secreted and dissolved proteins because they should limit the complexity of environmental proteomes.  Additionally, secreted and dissolved proteins may be stable and highly informative about the physiological state of natural communities.  However, it is not clear that secreted and dissolved proteins can be recovered from the environment in a state useful for proteomic analysis.  A protocol utilizing filtration steps of steadily decreasing pore sizes was applied to control samples and water samples collected from the Chesapeake Bay.  The resulting concentrated samples were analyzed for protein content and recovery followed by SDS-PAGE.  The results indicated that there was not enough protein recovered for 2D-SDS PAGE from the Chesapeake Bay samples using the current protocol.  The results suggest larger initial volumes should be collected and that concentration should be stopped at a larger final volume to avoid protein aggregation.  1D-SDS PAGE indicated protein differences between different sites.  The conclusion is that secreted and dissolved proteins can be recovered from the environment and will be amenable to proteomic analysis with an improved purification protocol. Funded by BRIN Project to Delaware Biotechnology Institute.

A New Method to Measure Viscosity in Food Using a Flaxseed Meal Model System

Adaora Ikwuagwu1, Edmund Nowak, Annette Shine, and Catherine G A Davie
1Delaware State University and Department of Animal and Food Science, University of Delaware

Batters containing flaxseed meal increase in viscosity over time. The objective of this study is to investigate the effect of flaxseed on viscosity using different measurements of viscosity. The aim was to determine if a new method using a magnetostrictive resonator (MSR) was appropriate to measure viscosity change in food systems. Viscosity was measured using a Brookfield Viscometer, a Cenco Consistometer and the MSR. Two model systems were developed: Flaxseed meal-water (FW), and flaxseed meal-water-oil-eggbeaters (FWOE). Both model system showed an increase in viscosity over 5 h using the Brookfield and Consistometer. The biggest increase was in the 1st hour, after which there was no significant change. FW increased its viscosity from approximately 3458cP to 6421cP while FWOE increased approximately from 535cP to 1198cP. The change in viscosity of FWOE was also determined with the MSR. Viscosity data from the MSR was shown to be complementary to the Brookfield data and allowed for more frequency measurements to be made. The change in viscosity is linear for the first hour and is probably caused by the diffusion of water into the flaxseed meal, resulting to gelation of gums. AI was funded by the HHMI Undergraduate Science Education Program.


Links: Summer 2002 Undergraduate Research Symposium, Symposium Abstracts from other Colleges and Departments,
Undergraduate Research Summer Enrichment ProgramUnversity of Delaware Undergraduate Research Program, Howard Hughes Undergraduate Program.
Created 8 August 2003. Last up dated 22 August 2003 by Hal White
Copyright 2003, University of Delaware