New research reveals how time-controlled temperature cycles can solve the age-old egg-cooking dilemma—creating a perfectly set white and a creamy yolk without sacrificing nutrition or taste.
Study: Periodic cooking of eggs. Image Credit: Pixel-Shot / Shutterstock
In a recent study published in the journal Communications Engineering, researchers used mathematical modeling, simulations, and a combination of advanced characterization techniques, including FT-IR spectroscopy and texture profile analysis, to develop a novel egg-cooking method. Named 'periodic cooking,' the method uses short (~2 min) alternating bouts of heat (boiling water) and cold (lukewarm water) to cook both egg yolk and albumen uniformly. This results in a unique texture for both egg components while preserving key bioactive compounds, such as polyphenols and amino acids, better than conventional methods.
Notably, this cooking method does not require cooking egg yolk and albumen separately and eliminates the need for complex handling steps, though it requires multiple hot-cold cycles amounting to 32 minutes of cooking time. While longer than soft or hard boiling, it is still faster than sous vide (1 hour). Periodic cooking also addresses the sous vide challenge of undercooked albumen and potential food safety concerns. The implications of these findings may extend beyond the kitchen into the realms of material science and engineering due to the insight gained in agglutination, curing, and foaming.
Background
Eggs are some of the most popular and widely consumed food items known to humanity. While global egg consumption is increasing, reports estimate that 161 eggs are consumed per person annually (2018). This number continues to rise at unprecedented rates – global egg production increased almost 10% between 2017 (80.1 million tonnes) and 2019 (88 million tonnes) – driven by the growing human population and nutrition research, the latter of which speaks volumes about eggs' functional and nutritional benefits.
Unfortunately, eggs are composed of two main parts: the yolk and the albumen. Each part comprises several proteins not found in the other, all with unique agglutination and coagulation temperatures. The optimal cooking temperature for the egg yolk is 65 °C, while the egg albumen requires at least 85 °C.
This discrepancy in optimal cooking temperatures forces chefs to choose one of two options – either cook each component separately (requiring removal of the eggshell and numerous complicated steps) or use the novel sous vide egg technique (low temperature, long-duration cooking).
About the Study
The present study addresses this conundrum by leveraging the 'time-varying boundary conditions' (BCs) principle from the research team's previous work to develop a novel 'periodic egg' cooking method. The experiment aims to identify a novel technique that evenly and sufficiently cooks the egg yolk and albumen without losing either the component's flavor or key nutritional qualities.
"…the idea is to place the raw shell-on egg alternatively in hot water (Th) and cold water (Tc) for relatively short periods of time (th and tc, respectively) and repeat these cycles N times until the cooking of both the yolk and the albumen is reached."
To identify the ideal cooking temperatures, the study used a mathematical model with four assumptions:
- Both egg components are isotropic and homogeneous;
- The starting temperatures are uniform between all experimental eggs (T = 20 °C);
- Thermal conductivity and density are a function of temperature for both egg components; and
- Model calculations do not include natural convection, air bubbles, and moisture within eggs.
Computational Fluid Dynamics (CFD) software was used to model the mathematical model, the results of which were experimentally verified. Verification experiments were performed using a kitchen pan (filled with tap water) and a heater. A food thermometer measured water temperatures (hot = 100 °C, cold = 30 °C). Four egg cohorts were compared:
- Hard-boiled eggs (hot water for 12 minutes),
- Soft-boiled eggs (hot water for 6 minutes),
- Sous vide eggs (65 °C for 1 hour), and
- Periodic eggs (alternative hot and cold water for 2 minutes each, 8 cycles, totaling 32 minutes).
On completion of the experiment, eggshells were removed, and characterization was undertaken:
- Fourier transform infrared (FTIR) spectroscopy for protein denaturation estimations,
- Texture Profile Analysis (TPA),
- Quantitative Descriptive Analysis (QDA), and
- Metabolomic Analysis (High-Resolution Mass Spectrometry [HRMS] & hydrogen-1 Nuclear Magnetic Resonance [1H-NMR]) for biochemical and nutritional profiling.
Study Findings
Both components of hard-boiled eggs were found to attain 100 °C by the end of their cooking cycle. In contrast, soft-boiled eggs only attained 100 °C in albumen layers close to the shell, while the rest of the egg displayed uneven and insufficient cooking. Surprisingly, the reverse was noted in sous vide eggs, wherein the egg yolk receives sufficient cooking, but the albumen never attains adequate temperatures for its proteins to denature and aggregate.
In periodic cooking, the albumen was found to attain temperatures of 87-100 °C (hot cycle) and 30–55 °C (cold cycle), with the yolk experiencing a constant and ideal 67 °C, as predicted in simulations. This allowed for a unique and favorable texture and confirmed minimal loss of essential amino acids and polyphenols compared to all other cooking techniques. Characterization experiments confirmed these findings, highlighting the improved denaturation and aggregation of periodic cooked eggs compared to conventional cooking techniques.
Conclusions
The present study used physics-based mathematical modeling, simulations, and experimental verification to develop a novel 'periodic cooking' technique for the effective cooking of eggs while maintaining their nutritional integrity. The method uses short (2 mins, 8 cycles, totaling 32 minutes) alternating periods of hot (100 °C) and cold (30 °C) temperatures to achieve consistent and sufficient cooking of both egg yolk and albumen.
This technique can not only be used to develop nutritious recipes but may also have broader applications in materials science, particularly in controlled structuring, crystallization, and curing processes.