Gel properties of blue round scad (Decapterus maruadsi) mince as influenced by the addition of egg white powder.

The use of egg white powder (EWP) to enhance the physicochemical properties, molecular structure, and thermal stability of Decapterus maruadsi mince gels was investigated. The thermal stability was analyzed by adding spray-dried EWP (0, 0.2, 0.4, 0.6, 0.8, and 1%) to the mince, and mince gels were prepared to study the changes in their fracture constant, water distribution, microstructure, and protein conformation of mince gels. In addition, the stress-strain curve of the EWP-mince gel was measured to obtain its compressive modulus (E). The formation of the mince gel was promoted by EWP, and the whiteness, fracture constant, water-holding capacity (WHC), and immobilized water were all enhanced. At 0.8% addition of EWP, the fracture constant increased from 176.715 ± 2.463 N/m to 348.631 ± 3.144 N/m (p < .05), which was a nearly twofold improvement. Additionally, the WHC increased from 75.21% to 79.99%, and the percentage of immobilized water increased from 94.03% to 94.91%. The EWP-mince gel network structure was the most uniform and dense, and there were increases in hydrogen bonds, disulfide bonds, ß-sheets, and ß-turns in mince gels, as well as the storage modulus (G') and enthalpy (ΔH). In contrast to the control group, the relative content of α-helixes decreased from 53.34% to 37.09% and transformed into other secondary structures, and the bulk water and cooking loss also decreased to 2.41% and 8.51%, respectively. Consequently, EWP effectively improved the quality of mince products, and the effect was most apparent when 0.8% was added.

Changes of water state and gel characteristics of Hairtail (Trichiurus lepturus) surimi during thermal processing.

This study examined the changes of water state and gel characteristics of Hairtail surimi during thermal processing including two steps. The results showed that there were four content of water in Hairtail surimi gels. Water-holding capacity (WHC) and T23 relaxation time of water and gel strength increased from 47.01 to 78.97% and from 64.23 to 51.52 ms, respectively, and whiteness decreased from 63.87 to 55.22 during the entire thermal processing. Meanwhile, the texture properties including hardness, gumminess, and chewiness declined from 402.42 to 130.41 g, from 294.39 to103.70 g, and from 233.68 to 43.60 g, respectively, during the first step, and then increased markedly during the second step from 130.41 to 2,301.87 g, from 103.70 to 1,250.99 g, and from 43.60 to 978.51 g, respectively. Furthermore, the WHC and textural profile had positive correlation, and changes in protein secondary structure were interesting, with the α-helices decreasing significantly from 26.40 to 14.12%, while the ß-sheet and the random coil structure increasing significantly from 36.28 to 44.03%, and from 10.89 to 14.31%, respectively, and ß-turn structure increasing form 26.44 to 27.98% during the first step and then declining markedly during the second step, moreover ß-sheet had a fine positive correlation with WHC hardness and chewiness. Overall, dense, porous and compact three-dimensional network gel structure gradually formed. In a word, during thermal processing. WHC of Hairtail surimi increased, and protein secondary structure of protein became orderly, and a fine, dense gel formed during thermal processing. Water is considered as the highest and most important chemical constituent in surimi products. During surimi gelation, water molecules exist as bulk water and motionally restricted water on the protein surface. In order to gain more insights into the surimi heating-induced gelation processing, and improve the surimi gel properties, and give same advice to manufacturing enterprise, this work was conducted to study the structural changes of protein and water state during surimi gelation processing and performed along with the monitoring of the texture, WHC and other physical characteristics of surimi gel, as well as the microstructure of surimi gel.