Periodic cooking of eggs

Abstract

Egg cooks are challenged by the two-phase structure: albumen and yolk require two cooking temperatures. Separation or a compromise temperature to the detriment of food safety or taste preference are the options. In the present article, we find that it is possible to cook albumen and yolk at two temperatures without separation by using periodic boundary conditions in the energy transport problem. Through mathematical modeling and subsequent simulation, we are able to design the novel cooking method, namely periodic cooking. Comparison with established egg cooking procedures through a plethora of characterization techniques, including Sensory Analysis, Texture Profile Analysis and FT-IR spectroscopy, confirms the different cooking extents and the different variations in protein denaturation with the novel approach. The method not only optimizes egg texture and nutrients, but also holds promise for innovative culinary applications and materials treatment.

Fig. 1. Simulation of periodic cooking.

Results of the simulation of the cooking of an egg with the periodic cooking method: a periodic time-varying BC imposed, b evolution of the thermal profile over time, c evolution of the degree of cooking over time at different distances from the center of the egg and d evolution of the cooking rate over time at different distances from the center of the egg. The distances from the center selected to construct the graphs of figures c and d are identified by the lines in figure b. The precise legend for figures c and d is given only in figure d.

Fig. 2. Simulation of hard-boiling, soft-boiling and sous vide cooking.

Results of the simulation of the hard-boiling (red), soft-boiling (yellow) and sous vide cooking (green) of an egg: a, c, e temperature values over time at different distances from the center of the egg; b, d, f degree of cooking values over time at different distances from the center of the egg. The distances selected to construct these graphs are identified by the lines in Fig. 1b. The precise legend for all the figures a–f is given in figure a.

Fig. 3. Overview of the spectroscopic analysis conducted on raw and cooked eggs.

a IR spectra of raw egg albumen (light gray) and yolk (orange) over the whole IR range (4000–650 cm⁻¹). b Cooking index derived through the FT-IR spectroscopic analysis for all cooking techniques in the case of egg albumen and yolk. The different colors of the bars evidence the different cooking methods: hard-boiling (red), soft-boiling (yellow), sous vide cooking (green) and periodic cooking (blue). c IR spectra of raw and hard-boiled albumen (light and dark gray, respectively) and (e) of raw and hard-boiled yolk (orange and red, respectively) over the whole IR range. A close up on band no. 4 and 5 (amide I region) is displayed for both albumen (d) and yolk (f) with addition of the difference spectrum magnified ×5 (purple) and the baseline used for area quantification in the Amide I region (black dashed line). The purple arrow indicates in both cases the appearance of the aggregation band.

Fig. 4. Sensory analysis evaluation.

a Photographs of the raw, hard-boiled (red), soft-boiled (yellow), sous vide (green) and periodic (blue) eggs. Results of the Sensory Analysis performed on b albumen and c yolk. Significant differences (p = 95%) are identified between: hard-boiled and periodic yolk (in Astringency, Softness, Wetness, Meltability, Sweetness and Umami); soft-boiled and periodic yolk (in Shininess, Wetness and Sweetness); sous vide and periodic yolk (in Shininess, White color, Softness, Wetness and Meltability); hard-boiled and periodic albumen (in Shininess, Orange color, Density/body, Wetness, Solubility, Pastiness, Adhesiveness, Powderiness, Sweetness and Umami); soft-boiled and periodic albumen (in Density/Body, Wetness, Sweetness and Saltiness). No significant differences are found between sous vide and periodic yolk.

Fig. 5. Hardness of egg albumen and yolk as measured with TPA.

Hardness evaluated through TPA for albumen and yolk. The color legend is the same of Fig. 4 and indicates the different cooking techniques: hard-boiled (red), soft-boiled (yellow), sous vide (green) and periodic (blue). Each box of the box plot displays (bottom to top) minimum, first quartile, median, third quartile, and maximum.

Fig. 6. Nutritional aspects of cooked eggs.

PC1 vs. PC2 biplot of the PCA model calculated using (a) both albumen and yolk extracts analyzed by ¹H-NMR and (b) yolk extracts analyzed by MS analysis and spectrophotometric assays. Acronyms used in the graphs are reported in Table 3.