This work aimed to investigate the combined effect of ultrasound (US) treatment and κ-carrageenan (KC) addition on the gelling properties and rheological behaviors of myofibrillar protein (MP). Without US treatment, the KC incorporation promoted the gel strength and water-holding capacity (WHC) of MP gels. These properties were further improved by 20 min US treatment with gel strength of 98.61 g and WHC of 79.87 %, which was mainly attributed to changes associated with hydrophobic interactions and disulfide bonds and the transformation from α-helix to β-sheet in MP gels. In addition, US treatment for 20 min effectively resulted in a more homogeneous polymer distribution of the MP-KC mixed system, leading to lower particle size and the largest G\' and G″ values of the MP-KC mixed gels. However, longer US treatment times (30, 40 and 50 min) rendered lower gel strength, WHC, storage modulus and loss modulus of MP-KC mixed gels, which was mainly due to the formation of loose and disordered gel structures. Our present results indicated that the application of US to MP for an intermediate treatment time (20 min) combined with KC provides a potential and novel strategy to promote the gel qualities of heat-induced MP gels.

This study aimed to investigate the effects of different concentrations (0.1, 0.2, 0.3, 0.4, and 0.5% w/w) of Abelmoschus manihot gum (AMG) on the gel properties and in vitro digestibility of frankfurters. The results indicated that AMG incorporation significantly enhanced the emulsion stability and texture of frankfurters, as well as the dynamic rheological characteristics of raw meat batter, with the optimal concentration being 0.3% (p < 0.05). Furthermore, hydrogen bonds and disulphide bonds were the main molecular forces of the frankfurters in the presence of AMG. Microstructural images showed that more uniform and dense microstructures of frankfurters were formed due to AMG supplementation. In addition, AMG incorporation significantly increased the in vitro protein digestibility of frankfurters as the level of addition increased (p < 0.05). In conclusion, our results provided critical information for the practical application of AMG in the production of emulsified meat products.

Soybean proteins are limited by their low contents of methionine and cysteine. Herein, 7S globulin accumulation was reduced using RNA interference to silence CG-β-1 expression, and the content of the A2B1a subunit was largely increased under the soybean seed-specific oleosin8 promoter. The results showed that the sulfur-containing amino acid content in soybean seeds drastically improved, reaching 79.194 nmol/mg, and the 11S/7S ratio had a 1.89-fold increase compared to the wild-type acceptor. The secondary structures of 11S globulin were also altered, and the β-sheet content increased with decreasing β-turn content, which was confirmed by Fourier transform infrared spectroscopy, Raman spectroscopy and circular dichroism analysis. Our findings suggested that raising the accumulation of 11S glycinin at the expense of reducing the content of 7S globulin is an attractive and precise engineering strategy to increase the amount of sulfur-containing amino acids, and soybean proteins with A2B1a subunits of 11S isolates improved, and β-subunits of 7S fractions reduced simultaneously might be an effective new material for food production.

The influences of multi-frequency countercurrent S-type ultrasound (MFSU), with various frequency modes, on lysinoalanine (LAL) formation and conformational characteristics of rice dreg protein isolates (RDPI) were investigated. The ultrasonic operating mode with dual-frequency combination (20/40 kHz) indicated lower LAL content and higher protein dissolution rate of RDPI compared with that of other ultrasound operating modes. Under the dual-frequency ultrasound mode of 20/40 kHz, acoustic power density of 60 W/L, time of 20 min, and temperature of 35 °C, the relative reduction rate of LAL of RDPI reached the highest with its value of 26.95%, and the protein dissolution rate was 71.87%. The changes in chemical interactions between protein molecules indicated that hydrophobic interactions and disulfide bonds played a considerable role in the formation of LAL of RDPI, especially the reduction of g-g-g and g-g-t disulfide bond. Alterations in microstructure showed that ultrasonication loosened the protein structure and created more uniform protein fragments of RDPI. In conclusion, using MFSU in treating RDPI was an efficacious avenue for minimizing LAL content and modifying the conformational characteristics of RDPI.

The influences of dual-frequency slit ultrasound (DFSU) pretreatment with various working parameters on the enzymolysis efficiency and conformational characteristics of corn gluten meal (CGM) were studied. Results indicated that under the conditions of ultrasonic power density of 80 W/L, time of 30 min, ultrasonic intermittent ratio of 5:2 s/s, temperature of 30 °C, and substrate concentration of 50 g/L, the relative enzymolysis efficiency (REE) of CGM reached a maximum of 21.05%, and the protein dissolution rate was 68.50%. In addition, ultrasonication had considerable impact on the conformation of CGM and consequently improved the susceptibility to alcalase proteolysis. Changes in free sulfhydryl (SHF) and disulfide bonds (SS) groups indicated spatial conformation of CGM was altered following sonication (sonochemical) treatment. Fourier Transform Infrared Spectrum (FITR) analysis showed a reduction in α-helix and β-turn content; and an increase in β-sheet and random coil content of CGM. Alterations in the particle size, particle size distribution, microstructure and surface roughness (Ra, Rq) indicated generation of smaller and more uniform protein fragments of CGM by sonochemical pretreatment. The proposed mechanism of sonicated CGM was elaborated. Our findings suggest that using DFSU in pretreating CGM may be an efficacious approach to enhance proteolysis.