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Gel properties of hydrogel-forming by Ala-Lys dipeptide (AK) and iota-carrageenan (ι-C) were investigated by rheological behavior, fourier transform infrared analysis, cryo-scanning electron microscopy, low field-NMR relaxometry and magnetic resonance imaging. Iota-carrageenan was changed from a liquid to a gel with the addition of AK, and the existence of AK significantly increased the storage modulus (G') of ι-C from 590.4 to 1077.8 Pa. In the ι-C/AK gel, the blue-shift of O H stretching and water deformation were observed, meanwhile, the presence of amide I band at 1682 cm−1 was observed. The network of ι-C/AK gel showed a dense honeycomb structure with flocculating continuous phase and rough entanglement morphology. After adding AK, the water free in the pores of ι-C entered the ι-C/AK gel matrix, and the binding capacity of bound water was enhanced. These scenarios proved that the AK as the cationic dipeptide could control the conversion of negatively charged ι-C from an original random structure to a helical structure due to electrostatic interactions and hydrogen bonds. This study provides a new opportunity for the peptides into carbohydrate-based gel matrices, which could provide insights for the further application of ι-C/AK gels in the fields of food industry, tissue engineering and drug delivery. • AK dipeptide enhanced the gel properties of iota-carrageenan. • Electrostatic interactions was the main force in AK/ ι-C gel. • The hydrogen bond stabilized the AK/ι-C gel structure. • AK induced regular and homogenous network structure in the ι-C gel. [ABSTRACT FROM AUTHOR]

In the present study, the effects of corn starch (CS) on the properties of Chinese shrimp (Fenneropenaeus chinensis) powder (SP) were characterized to explore the feasibility of developing dysphagia diet. The SP/CS gels were prepared by adding CS at different concentrations. The SP/CS mixture presented low gel properties at CS concentrations ranging from 12 to 48 mg/mL, but did demonstrate gelation behavior with the highest G′ value of 1134.2 Pa and a water holding capacity of 90% at 60 mg/mL. As the CS concentration increased, the stability of the SP/CS mixture also improved, as evidenced by the significantly reduced relaxation times T 22 and T 23 , enhanced gel network formation, and the presence of hydrogen bonding and electrostatic interactions between SP and CS. Furthermore, the international dysphagia diet standardisation initiative (IDDSI) swallowing level of the SP/CS mixtures were 2, 3, 4, and 5 at CS concentrations of 12, 24, 36, 48 and 60 mg/ml, respectively. The SP/CS-60 mixture gel was considered suitable for dysphagia patients. These findings suggest that the gel properties of SP can be modified by CS, and that the SP/CS mixture gels have the potential to be used as a texture-modified diet with high-quality protein for dysphagia patients. [Display omitted] • The gel properties of SP/CS were positively correlated with the concentration of CS. • CS increased the elasticity and water holding capacity of SP. • CS promoted water migration to bound water in SP and enhanced the gel network. • SP/CS (each at 60 mg/mL) gel was suitable for dysphagia patients. [ABSTRACT FROM AUTHOR]

Roes are the main byproducts during the processing of large yellow croaker (Pseudosciaena crocea) and have not been well utilized. Heat-induced gels were prepared by using P. crocea roe protein isolates (pcRPI), and the influence of pH on the gel properties was also investigated. pcRPI could not form a gel at pH 4–6 but showed gelation behaviors at pH 7–9. The pcRPI gels prepared at pH 8 had a lower gel point (84 °C), and their G ′ reached 535.4 Pa. Moreover, pcRPI gels formed at pH 8–9 had a more continuous network structure with a shorter T 2 relaxation time than those at other pH conditions. Additionally, vitellogenin and vitellogenin B and C in pcRPI easily formed protein complexes during heating. The hydrophobic interactions, which were the main force between protein molecules during heating, as shown by molecular dynamics simulation, also contributed to gel formation. pcRPI has the potential to be used as a novel hydrogel product in food and other fields. • The optimum pH of P. crocea roe protein isolates (pcRPI) to form gels was pH 8. • The water holding ability of pcRPI gels was enhanced as pH increased. • The pcRPI gels had smoother surface and continuous network structure at pH 8–9. • Hydrophobic interactions were the main forces in the formation of pcRPI gels. [ABSTRACT FROM AUTHOR]