Evolution of oxidative and structural characteristics of proteins, especially lipid transfer protein 1 (LTP1) in beer during forced‐ageing

Abstract

Summary The evolution of oxidative and structural characteristics of proteins, especially lipid transfer protein 1 (LTP1), in beer during forced‐ageing was examined. The oxidative characteristics of beer and proteins were evaluated by DPPH radical scavenging activity and ABTS radical cation scavenging activity. Results showed that the levels of proteins, thiols, LTP1 and antioxidant activity decreased gradually. This was accompanied by the degradation of macromolecular proteins in beer during forced‐ageing. Results from circular dichroism (CD), Fourier‐transform infrared spectroscopy (FTIR), surface hydrophobicity (S0) and ζ‐potential further indicated that the secondary and tertiary structure of LTP1 changed drastically during forced‐ageing, with the reduction of the S0, α‐helix and β‐sheet contents and the increase in negative ζ‐potential and random coil. Thus, the proteins, especially LTP1, might play important roles in maintaining oxidative stability of beer.

Effect of Egg White Protein and Soy Protein Isolate Addition on Nutritional Properties and In-Vitro Digestibility of Gluten-Free Pasta Based on Banana Flour

“…The ABTS radical scavenging assay was based on the method of Cai et al [23]. ABTS •+ was prepared by reacting colourless ABTS stock solution (7 mM in water) with 2.45 nM potassium persulfate and allowing the reaction to stand for 16 hours in the dark at room temperature.…”

Effect of dissolved oxygen on the oxidative and structural characteristics of protein in beer during forced ageing

“…By 7 days of forced ageing, all protein bands with a DO of 6 mg L À1 almost disappeared. Among them, the protein Z had a molecular weight range of 35-55 kDa, and the LTP1 with the molecular weight around 10 kDa (Cai et al, 2019). The increase in DO in beer caused the disappearance of the LTP1 band under the same ageing condition, which clearly demonstrated that the DO could damage the protein subunit of LTP1.…”

“…After forced ageing for 7 days, the protein content in beer samples with DO of 0.5, 2, 4 and 6 mg L À1 decreased by 15.42%, 16.93%, 20.59% and 22.42%, respectively. The results indicated that the increase of DO might accelerate protein degradation or precipitation, and cause more serious damage to beer when compared with thermal ageing (Cai et al, 2019). Previous studies have shown that the initial DO concentration had a decisive effect on the level of reactive oxygen species (ROS) in beer.…”

“…The beer samples (twenty four bottles) without addition of highpurity oxygen was used as a control with a DO of 0.5 mg L À1 . Then, all beer samples were aged at 60°C for 7 days according to the method of Yao et al (2018) and Cai et al (2019).…”

Micro‐encapsulation of gurum (Citrullus lanatus Var. Colocynthoide) seed oil maintains functional quality characteristics during accelerated storage

“…The high PUFA content of gurum seed oil makes it unstable and prone to oxidation, especially when exposed to light, oxygen and moisture. This oxidative degradation is an issue with vegetable oil products (Cai et al., 2019; Atay & Altan, 2021; Meng et al., 2021) and the nutritional quality of gurum seed oil, affecting its shelf life and sensory properties. In order to overcome these disadvantages, gurum seed oil can be microencapsulated to reduce the oxidation rates, which converts the oil into a powder that can be utilised in food supplements.…”