Pressure Gradients Application for Accelerating Corn Hydration

Abstract

Three varieties of corn kernels were hydrated under pressure gradients in the range of 96 to 136 cm Hg, and at atmospheric pressure for comparison. Hydration at atmospheric pressure was modeled by the first order kinetics model and by the Fick's second law of diffusion. Rate constants of 0.192, 0.184 and 0.141 h −1 , and water effective diffusivity of 5.4 ×10 −11 , 3.6 ×10 −11 , and 1.9 ×10 −11 m 2 s −1 were obtained for blue, yellow and white corn kernel, respectively. Significant polynomial equations described the corn kernels hydration under pressure gradients, as a function of vacuum pressure, vacuum time and hydration time. Hydration rates of the studied grains were significantly enhanced using the pressure gradients, compared to the conventional method. Pressure gradient soaking required 60% less time than the conventional soaking, to reach a water content of 45% in corn kernels. The hydration extent of corn kernels determined the levels of solutes leaching, in both soaking treatments. Minimum hydration levels for initiating leaching of soluble solids were observed.

A Preliminary Study on the Effect of the Instant Controlled Pressure Drop Technology (DIC) on Drying and Rehydration Kinetics of Maize Kernels (Zea mays L.)

“…Moreover, to obtain an average final moisture content of 0.7121 g H 2 O/g dry matter, DIC 17 and DIC 18 required 2 h instead of 17 h for controls. Similar results were found by Martínez-Garza [ 42 ] for blue, yellow, and white non-treated maize kernels which required 15 h of rehydration to achieve equilibrium moisture contents of 0.5270, 0.5000, and 0.5040 g H 2 O/g dry matter, respectively. This result reflects that DIC treatment intensified both rehydration stages, the starting accessibility and diffusional stages.…”

“…However, this process used to be long which could cause microbial spoilage, swelling, and physical destruction of the food [ 41 ]. According to Martínez-Garza [ 42 ], obtaining a complete rehydrated grain sometimes requires 16–36 h, indicating that new technologies are needed to accelerate this process. In this respect, this study showed that the DIC technology could significantly improve the rehydration of maize kernels.…”

Study Of The Rehydration Kinetics Of Nixtamalized Corn By Using Two Nixtamalization Methods

“…The Control samples showed a Deff value of 0.091 x 10 -9 ± 0.016 x 10 -9 m 2 /s. The obtained results were higher than reported by Martínez-Garza, et al [27] for white corn with Deff of 0.019 x 10 -9 m 2 /s, it is possible because of the different maize variety. Compared to control, the Deff value was significantly (p > 0.05) higher for ash treatment, it increased the Deff in about 354% (Table I).…”

“…The kinetic parameter of first-order model (𝑘 6 ) indicates the rate of rehydration, which is proportional to a temporary driving force. The 𝑘 6 values for Control samples (0.003 min -1 ) were between the values reported by Martínez-Garza, et al [27] for white corn (0.0024 min -1 ) or for yellow corn (0.0046 min −1 ) reported by Miano, et al [33]. Compared to Control, only the 𝑘 6 value for ash treatment was significantly different and was the highest, indicating higher rehydration rate in these samples.…”

Heat transfer simulation in corn kernel during nixtamalization process

“…The temperature measurement has been commonly carried out on the alkaline solution and its control is important due to its effect on quality parameters such as moisture and texture of masa, moisture and texture of tortilla, percentage and diffusion of calcium and solids loss (Sahai et al, 2001). Some reports have focused on mass transport phenomena in hydration of the corn kernel (Martínez-Garza et al, (2018)), and nixtamalization process, during cooking and steeping (Ruiz-Gutiérrez et al, 2010;Gutiérrez-Cortez et al, 2016); however, there are no studies about the behavior of temperature and heat transfer inside the corn kernel subjected to the nixtamalization process. In this operation, two unsteady state heat transfer mechanisms are involved: conduction inside the corn kernel and convection by the alkaline solution at the surface.…”