Processing Induced Changes in Food Proteins: Amyloid Formation during Boiling of Hen Egg White

Abstract

Amyloid fibrils (AFs) are highly ordered protein nanofibers composed of cross β-structure that occur in nature, but that also accumulate in age-related diseases. Amyloid propensity is a generic property of proteins revealed by conditions that destabilize the native state, suggesting that food processing conditions may promote AF formation. This had only been shown for foie gras, but not in common foodstuffs. We here extracted a dense network of fibrillar proteins from commonly consumed boiled hen egg white (EW) using chemical and/or enzymatic treatments. Conversion of EW proteins into AFs during boiling was demonstrated by thioflavin T fluorescence, Congo red staining, and X-ray fiber diffraction measurements. Our data show that cooking converts approximately 1−3% of the protein in EW into AFs, suggesting that they are a common component of the human diet.

Drying mode and hydrothermal treatment conditions govern the formation of amyloid-like protein fibrils in solutions of dried hen egg white

“…In a black 96-well plate (Greiner Bio-One), samples were prepared as in Monge-Morera et al (2020) and measured in triplicate in a Synergy Multi-Mode Microplate Reader (BioTek). The excitation and emission wavelengths were 440 nm and 480 nm, respectively.…”

“…The apparent MW distribution of (un)heated EWSD, EWSD 50°C/50% and EWSD 60°C/80% (see section 2.4) was also monitored with both UV (at 280 nm) and ThT fluorescence measurements (with 450 and 480 nm as excitation and emission wavelengths, respectively) as described in Monge-Morera et al (2020). In this case, samples (25 µl) were loaded on the same column type, eluted at 30 °C and the analysis was performed using a modular system similar to the above one.…”

“…Boiling OVA solutions for 15 min under similar conditions results in smaller (ca. 80 nm in length) worm-like fibrils (Monge-Morera et al, 2020). As the denaturation temperature of OVA is ca.…”

“…They can be formed during food processing (Jansens, Lambrecht, et al, 2019). For example, boiling induces the formation of AFs in native EW (Monge-Morera et al, 2020). In addition, processing conditions in terms of temperature, time, pH, protein concentration, ionic strength, moisture content and heating mode, such as microwave heating (Zhang et al, 2020), influence AF formation (Jansens, Lambrecht, et al, 2019).…”

Discerning amyloid network in plants

“…[27] Wheat gluten is also known to form amyloid fibrils in certain experimental conditions. [28] There have also been reports of in-vitro formation of amyloid-like fibrils by seed storage proteins of maize, wheat, pea, and soybean. [29] The seed storage proteins, interestingly, are reported to possess carbohydrate-affinity due to lectin-like activity.…”