Headshot of Anne Hood

Author: Anne Hood | Major: Food Science | Semester: Fall 2024

Hi, my name is Anne Hood, and I am a senior food science major in the Bumpers College of Agricultural, Food, and Life Sciences. During the Spring 2025 semester, I continued my honors thesis research in Dr. Scott Lafontaine’s brewing science lab, investigating the sensory thresholds of iron sulfate (FeSO₄) and iron (III) chloride (FeCl₃) in nonalcoholic beer. The goal was to determine the point at which iron becomes detectable to consumers, a key question for improving beverage flavor and quality.

Flavor stability is critical in nonalcoholic beer, and trace metals like iron can contribute to off-flavors. However, no established thresholds currently exist in beer-like matrices. Using triangle testing protocols developed by the American Society of Brewing Chemists (ASBC), I conducted sensory tests with 27 participants to try to determine when the metallic taste of iron becomes noticeable. I paired these tests with ICP-OES analysis to verify iron concentrations in each triangle sample.

I first became interested in brewing science after taking Dr. Lafontaine’s introduction to brewing science course during my sophomore year. When it came time to choose a thesis topic, I reached out to him, and he proposed several research options. I selected this project because it aligned with my interests in sensory science, chemistry, and real-world food applications. It also offered the opportunity to explore an area of research that had not yet been clearly defined in the literature.

Each participant completed seven triangle tests during the December trials, with each set containing two control samples and one spiked sample presented in randomized order. However, after analyzing the data from that round, several participants’ thresholds were found to be inconclusive. To address this, those individuals were invited back in the spring for retesting using an expanded range of iron concentrations to better determine their detection thresholds. All samples were labeled with randomized three-digit codes and tracked using individualized Qualtrics surveys, ensuring blind, accurate, and consistent data collection throughout the process.    One major challenge was managing the logistics of testing. Each participant’s sample set required precise coordination, over 1,000 cups were labeled, filled, and matched to the correct survey version. After early results showed inconclusive thresholds, I adjusted the dilution schemes and conducted a second round of testing with higher concentrations, which produced more meaningful results. I also had to balance participant availability, lab space, and timing to ensure each session ran smoothly.

This project taught me the intricacies of experimental design, data management, and human subject testing. I discovered how much I enjoy hands-on scientific problem-solving and how to adapt protocols when data falls short of expectations. I also learned the importance of flexibility and persistence in research, skills I’ll carry forward in any scientific or clinical setting.

Dr. Lafontaine was instrumental throughout the project, helping refine the design and interpret results. Graduate students in the lab, especially PhD student Bernardo Pontes-Guimaraes, helped prepare sample bottles, manage the sensory room, and support testing logistics. Their teamwork made the project far more manageable and helped me stay focused on accuracy and analysis.

All testing took place on campus at the University of Arkansas in the Food Science building, where I was able to set up for testing, utilize lab tablets for data collection, and have my samples analyzed using ICP-OES. Although the project did not involve travel, the resources and support available provided everything necessary to conduct a professional, high-quality research study.

Ultimately, our findings showed that iron thresholds in beer are well above naturally occurring concentrations, suggesting that iron alone is unlikely to cause metallic off-flavors. These results align with similar findings in water, providing valuable context for the brewing industry. This work contributes new sensory data to the field and strengthened my appreciation for the scientific method as I prepare for a hopeful future in the dental field.