Factors affecting water uptake of rice grain during soaking

Effects of soaking and acidification on physicochemical properties of calcium-fortified rice

BACKGROUND

Calcium-fortified rice was prepared by soaking milled rice in calcium lactate solution, steaming and drying, and physicochemical properties were determined to evaluate effects of calcium concentration (0, 30, 50 g L(-1) ), soaking temperature (ambient temperature, 40 °C, 60 °C) and acidification.

RESULTS

Calcium-fortified rice had less lightness. More total solid loss was observed, especially at high soaking temperature. Harder texture was detected with increased calcium concentration. Calcium fortification lowered pasting viscosity of milled rice. Panelists accepted all fortified rice; however, only rice soaked at 50 g L(-1) concentration could be claimed as a good source of calcium. Increasing of soaking temperature induced more penetration of calcium to rice kernels but calcium was lost more easily after washing. With addition of acetic acid to the soaking solution, enriched calcium content was comparable to that of high soaking temperature but with better retention after washing and calcium solubility was improved. Acid induced reduction of lightness and cooked rice hardness but increased total solid loss and pasting viscosity. Although the taste of acetic acid remained, panelists still accepted the fortified rice.

CONCLUSION

Calcium-fortified rice (190.47-194.3 mg 100 g(-1) ) could be successfully produced by soaking milled rice in 50 g L(-1) calcium lactate solution at 40 °C or at ambient temperature with acidification. © 2015 Society of Chemical Industry.

Effect of presoaking high hydrostatic pressure on the cooking properties of brown rice

Effects of presoaking-high hydrostatic pressure (PHHP) on cooking time, hardness, gumminess, springiness, and microstructure of brown rice were evaluated. Compared with traditional soaking treatment, PHHP significantly shorten the cooking time of brown rice from 34 to 14 min. The hardness of brown rice treated by PHHP reduced remarkably, which is lower than that treated by soaking process and similar to that of white rice. The gumminess and springiness of brown rice dramatically decreased under pressure above 500 MPa. However, the water uptake capacity of brown rice treated by PHHP was not obviously affected, whose moisture contents were much lower than that of soaked samples. The analysis of thermal properties revealed that the enthalpy of brown rice was influenced by PHHP, and the denaturation of brown rice components generated. These results and microstructure analysis revealed that the structures of pericarp and aleurone layer of brown rice were damaged by PHHP, which allows water to be easily absorbed by the rice kernel during cooking process. PHHP treatment could be a potentially applicable pretreatment for improving cooking properties of brown rice.

Hydration kinetics and physical properties of split chickpea as affected by soaking temperature and time

In this study, some physical properties (principal dimensions, mean diameters, sphericity, area, density and electrical conductivity) of split chickpea were measured as function of soaking time (up to 360 min) and temperature (25-65 °C). Initially, the water absorption rate was high and then it showed a progressive decrease at all temperatures, whereas solid loss exhibited a power function of temperature (P < 0.05). The Peleg model was predicted well the kinetic of split chickpea soaking. No significant difference (P < 0.05) was observed in Peleg rate constant (K1) and Peleg capacity constant (K2) at all temperatures except for K1 at 25 °C. The discrepancy for K1 was in relation to permeability characteristics of split chickpea at temperature of 25 °C. As temperature increased from 25 to 65 °C, the K1 value decreased from 0.04620 to 0.00945 g h(-1), whereas the K2 value increased from 0.08597 to 0.11320 g(-1). Plot for K1 exhibited a slope changes around 45 °C corresponding to gelatinization temperature of split chickpeas. The effect of temperature and time on physical properties of split chickpea during soaking was monitored by regression equations. It was concluded that physical properties of split chickpea affected by its water absorption especially at higher temperatures.

Temperature dependence on hydration kinetic model parameters during rehydration of parboiled rice

A study was carried out to relate the hydration behaviour with processing conditions of low amylose content parboiled rice which was dried at various temperatures (40, 50 and 60 °C). The rehydration characteristics of the parboiled rice (dehusked only) was then studied at various soaking temperatures (30, 40 and 50 °C) and time ( upto 3 h at every 30 min interval) and equilibrium moisture content of rehydration (EMC) was determined. The data were tested on three hydration equations viz., Peleg's, Exponential and Weibull equations. The experimental data were used to determine the model parameters. The goodness of fit for the models were evaluated by coefficient of determination (R(2)) and sum of square error (SSE). The results were indicated that the Weibull model fits better than the exponential model and Peleg's equation. Also, water transfer to paddy, was described by applying the Fick's diffusion model and the moisture diffusivity (D) was calculated. The Diffusivity values varied between 1.06 and 4 × 10(-11) m(2)/s.

Enzymatic polishing of cereal grains for improved nutrient retainment

Consumer acceptance of food products is largely driven by the dietary and functional quality of their ingredients. Though whole cereal grains are well known for bioactive components, scientists are facing dire need for better technologies to prevent the nutritional losses incurred through the conventional food processing technologies. Application of enzyme for depolymerisation of carbohydrates present in bran layer of grain is becoming an efficient method for phenolic mobilization and dietary fiber solubilisation. The present article emphasizes deep insights about the application of enzyme as an alternative technology for cereal grain processing to improve the product quality while forbidding the nutritional losses in an eco-friendly manner.

Ultrasound assisted hydration of navy beans (Phaseolus vulgaris)

The use of ultrasound to enhance the transport phenomena in food processes has been well recognised in recent times. The objective of this study was to evaluate the effect of sonication on hydration rate and pasting profile of navy beans. The hydration kinetics for control and ultrasound assisted soaking was mathematically described using mechanistic (Fickian diffusion) and empirical (Peleg's equation, Weibull model and First Order equation) models. Ultrasound enhanced the rate of hydration which was evident from the plot of kinetic data and model parameters. The effective diffusivities for water transport without and with ultrasound application were estimated to be 1.36×10(-10) m(2)/s and 2.19×10(-10) m(2)/s respectively, considering Fickian diffusion. The Weibull model was concluded to best predict the hydration kinetics of navy beans in an ultrasonic field. Significant increase in peak viscosity of sonicated bean powder was observed compared to control.