Protein structure can be altered
with heat, but models which predict
denaturation show that globular proteins also spontaneously unfold
at low temperatures through cold denaturation. By an analysis of the
primary structure of pea protein using bioinformatic modeling, a mechanism
of pea protein cold denaturation is proposed. Pea protein is then
fractionated into partially purified legumin and vicilin components,
suspended in ethanol, and subjected to low temperatures (−10
to −20 °C). The structural characterizations of the purified
fractions are conducted through FTIR, ζ potential, dynamic light
scattering, and oil binding, and these are compared to the results
of commercial protein isolates. The observed structural changes suggest
that pea protein undergoes changes in structure as the result of low-temperature
treatments, which could lead to innovative industrial processing techniques
for functionalization by low-temperature processing.
Isolated anthocyanins have limited colonic bioavailability due to their instability as free forms. Thus, many methods have been fabricated to increase the stability of anthocyanins. Complexation, encapsulation, and co-pigmentation with other pigments, proteins, metal ions, and carbohydrates have been reported to improve the stability and bioavailability of anthocyanins. In this study, anthocyanins extracted from purple potatoes were complexed with four different polysaccharides and their mixture. The anthocyanin–polysaccharide complexes were characterized using a zeta potential analyzer, particle size analyzer, scanning electron microscopy, and Fourier-transform infrared spectroscopy. Complexes were subjected to simulated digestion for assessing the stability of anthocyanins. Furthermore, complexes were subjected to different pH conditions and incubated at high temperatures to monitor color changes. A Caco-2 cell monolayer was used to evaluate the colonic concentrations of anthocyanins. In addition, the bioactivity of complexes was assessed using LPS-treated Caco-2 cell monolayer. Results show that pectin had the best complexation capacity with anthocyanins. The surface morphology of the anthocyanin–pectin complex (APC) was changed after complexation. APC was more resistant to the simulated upper gastrointestinal digestion, and high pH and temperature conditions for a longer duration. Furthermore, APC restored the lipopolysaccharide (LPS)-induced high cell permeability compared to isolated anthocyanins. In conclusion, complexation with pectin increased the stability and colonic bioavailability and the activity of anthocyanins.
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