The thermodynamic basis for the Relative Water Demand Model that describes non-Fickian water diffusion in starchy foods

Water Holding Capacity Profile that Governs Water Migration in Starchy Food During Boiling

“…It was found that the transient water content profile in the dough slab during boiling was well described in its outline by using RWC model with water diffusivity of 5x 1010 m2/s and WHC profile proposed. The breaking points that emerge at three levels of water content (m= 0.85, 1.1, and 1.6 kg-water/kg-solid) in the measured against expansion due to water sorption [13,14].…”

“…It was found that some of the changes could not be explained using Fick's Law of diffusion [10][11][12]. We recognized that this irregular behavior was caused by the fact that some kinds of food, such as starchy foods, change from single-phase to multiphase during boiling [13,14]. This is because water holding capacity of a food body changes as starch gelatinization proceeds during boiling; namely, the distribution of water holding capacity becomes uneven throughout the body [15].…”

“…Since Fick's diffusion law is applicable only to homogeneous systems, it cannot be applied to such a multiphase system. The Relative Water Content (RWC) model was proposed as an alternative model that is able to describe water migration in a multiphase food system [13,14]. In the RWC model (Eq.1), water migration is driven by the gradient of water content divided by the water holding capacity (WHC), m/m*, whereas it is driven by the gradient of water content, m, in Fick's law.…”

Modelling Processes and Products in the Cereal Chain

“…Other evidence of the relationship comes from the equilibrium water content, as native starch in the rice grain can only contain a limited amount of water, around 0.5 kg/kg, while the completely gelatinized starch can absorb an amount of water equal to nine times its original dry weight [ 93 ]. A possible integration of the two phenomena is presented in [ 94 ], where the water demand driving force is introduced. The water demand depends on a local maximum water content, which in turn is a function of the local degree of starch gelatinization.…”

Use of microwave heating to control the degree of starch gelatinization in noodles

“…Recently, they reported the modified water demand model, i.e. relative water demand model (Watanabe et al, 2007). In their work, the driving force of water migration was the gradient of water content divided by the WHC.…”