Effect of moisture content on textural attributes of dried figs

Due to their soft texture consumers prefer moist figs, which has motivated fig processors to increase the production of this product. However, as water enhances the browning reaction rate, moisture content optimisation of moist figs is very important. Processed figs must have suitable texture softness with browning kept to a minimum. The purpose of this study was to examine the effect of moisture content on the textural attributes of dried figs. Hardness, compression energy, gradient, gumminess and chewiness of fig samples decreased with moisture content exponentially, whereas the trend of springiness and cohesiveness with change of moisture content was nearly constant. Moreover, in the texture profile analysis plot of rehydrated figs, the presence of negative area is an indication of adhesiveness which was zero in control dried figs. The results of the texture profile analysis tests proved the existence of a critical moisture content of about 18.4%, above which no significant effect of moisture content on textural parameters was found. The glass-rubber transition results from differential scanning calorimeter may explain the different texture profile analysis attributes of dried figs compared with rehydrated figs

Kinetic of color and texture changes in rehydrated figs

Intermediate-moisture figs obtained by rehydration of dried figs are more suitable for direct consumption. Colour and texture are the most important quality attributes, which influence the acceptability of this product. In this research the kinetic of color and texture changes in rehydrated figs were studied as a function of time and temperature (25-90 °C). All hunter colour parameters (L*, a* and b*) were used to estimate the extent of colour change during rehydration. Results indicated that among different kinetic models, a combined kinetic model provided the best fit. Moreover, texture development kinetics over all temperature ranges were satisfactorily described by means of first-order kinetic model compared with second-order, Weibull and Peleg models. Model parameters including texture softening (k) and residual constant (A) values were calculated which also confirmed the decrease in firmness of the dried figs due to the plasticization effect of water intake. The Arrhenius model described well the temperature dependence of the reaction rate constant for colour and texture parameter

Modeling rehydration behavior of dried figs

In this research, rehydration behavior of dried figs was studied at different temperatures (25, 60, 70, 80, and 90°C). The rehydration kinetic was examined using the four most frequently used empirical models, namely, Weibull, Peleg, first-order, and exponential association models. The Weibull model gave the highest coefficient of determination (R2) and the lowest values of root mean square error (RMSE), sum of squared error (SEE), and chi-square (X2) was considered the best. In all models examined, the equilibrium moisture content showed statistically significant differences as compared to the rehydration temperature. The temperature dependence of kinetic constants was described in terms of Arrhenius relationship. The average activation energy for the four models was 24.362 kJ mol-1. During the rehydration process hardness of dried figs decreased, which was further confirmed by microscopic evaluation. Scanning electron microscopy (SEM) images of rehydrated figs indicated porous structure proposing the presence of free water

Using power ultrasound for cold gelation of kappa-carrageenan in presence of sodium ions

Usually a heating stage is required to solubilize kappa carrageenan dispersions for gel formation on cooling. This work reports cold gelation of kappa carrageenan in the presence of sodium ions using power ultrasound without using any heating stage. Carrageenan gels were prepared using ultrasound in the presence or absence of NaCl and their textural properties were compared with the gels prepared with conventional heating method. Mechanical properties of the gels strongly increased with ultrasonication time up to a certain level, and further sonication reduced mechanical characteristics. Addition of Na + ions after ultrasonication was more effective in increasing textural hardness than when Na+ is present during ultrasonication. Microscopic images demonstrated that increasing ultrasonication time up to a certain level leads to coherent gel networks and further ultrasound has a negative impact on the gel network. Solubility and intrinsic viscosity results are also presented. Moreover, Maxwell model with three elements was used to analyze stress relaxation data. Industrial relevance So far, all documented reports have indicated that to induce gelation of kappa carrageenan dispersions a preheating step is required followed by cooling. In the present work, using power ultrasound a new method for cold gelation of carrageenan dispersions is introduced. Using ultrasound, food and non-food processors can use kappa carrageenan as a viscosifying and gelling agent without using heating