The effect of lecithin addition on the gelling characteristics and oxidative stability of single-washed mackerel (Auxis thazard) surimi was investigated in this study. Surimi was chopped in the presence of 2.5% (w/w) NaCl with different concentrations of lecithin (0, 0.1, 0.5, 1, and 1.5 g/100 g surimi). The rheological behavior, gel-forming ability, microstructure, and lipid oxidation of lecithin-added surimi varied significantly depending on lecithin content. When compared to the control, lecithin at 0.1, 0.5, and 1 g/100 g improved the breaking force of the gel (p < 0.05). The breaking force of the gel decreased significantly as lecithin concentration increased (up to 1.5 g/100 g) (p < 0.05). Deformation, on the other hand, reacted differently to the lecithin than it did to the breaking force. At a lecithin level of 0.1 g/100 g, the surimi gel displayed improved deformation (p < 0.05). Nonetheless, at higher doses (0.5–1.5 g/100 g), lecithin considerably reduced surimi gel deformation (p < 0.05), and the gel containing lecithin at 1.5 g/100 g showed significantly decreased deformation. Surimi with 0.1 g/100 g lecithin had the lowest expressible drip (p < 0.05). In general, lecithin at concentrations ranging from 0.1 to 1 g/100 g reduced expressible drip (p < 0.05), but not at 1.5 g/100 g, which was equivalent to the control (p > 0.05). Adding lecithin to mackerel surimi improved its whiteness slightly, regardless of concentration. Lecithin impacted the microstructures of surimi gel in a concentration-dependent manner. Lecithin at a concentration of 0.1 g/100 g produced a densely packed network with small, jointed clusters and minimal holes within the gel. Joined clusters in the gel were reduced by 0.5–1.5 g/100 g lecithin, and continuous aggregates predominated. Surprisingly, at higher doses of lecithin, notably 1.5 g/100 g, porous structures with continuous voids were perceived. Surimi gels treated with various lecithin doses had lower thiobarbituric acid reactive substances (TBARS) levels than the control (p < 0.05). Overall, lecithin at a low concentration of 0.1 g/100 g was most effective at improving the texture, increasing water-holding capacity, lightening the color, and delaying lipid oxidation of single-washed mackerel surimi.

Dynamic viscosity and kinematic viscosity are important physical properties of a liquid. In this work, correlation of dynamic viscosity and kinematic viscosity of fatty acids (FA) are correlated to the Martin's rule of free energy additivity for estimated kinematic viscosity and dynamic viscosity from their own equations. The proposed equations for estimating viscosity and density of FA are correlated to number of carbon atoms, number of double bond(s) and temperature. Data collected from literatures were used to validate and support the proposed models. The proposed equations are easy to use and the estimated dynamic viscosity and kinematic viscosity values of FA at different temperatures agree well with the literature values. The average absolute deviation of dynamic viscosity and kinematic viscosity of FA at 288.15 and 394.25K are 4.14 and 4.37, respectively. The estimated outside temperature between 288.15 and 394.25K may be possibly estimated by this model but accuracy may be lower.

Surface tension is important to ensure the efficiency of industrial operation units involving chemical reactions and extractive processes that use these compounds as solvents. In this work, the surface tension of fatty acids (FA) is correlated to Martin's rule of free energy additivity for estimating surface tension. The proposed equations for estimating the surface tension of FAs are correlated to the number of carbon atoms (z), the number of double bond (s) (nd) and temperature (T) to γ = 69.065−1.3614z−0.13895T+0.005209zT+6.24n_d−0.01612n_dT. The proposed equations are easy to use and the estimated values of surface tension of FA at different temperatures agree well with the literature values.