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Paste made from eight types of cereal grains (low fiber containing grains [LF grains]: rice, sticky rice, black rice, and millet; and high fiber containing grains [HF grains]: wheat, buckwheat, oat, and barley), and four types of legumes (soybean, red bean, kidney bean, and mung bean), were studied in terms of particle size, rheological, and tribological properties. Sticky rice and soybean pastes showed lower yield stress, viscosity and consistency coefficient than other pastes. Most cereal pastes showed a major peak at approximately 160 µm except for oat and barley, while legume pastes showed mono modal profiles except for soybean. Tribological results showed that starch tended to develop type A friction profiles, showing a typical Stribeck curve; bran/fiber tended to develop type B profiles, showing an ascent curve with clear onset of hydrodynamic regime; protein and lipids promoted type C profiles, showing a flat plateau shaped curve. Water soluble polysaccharides in grains or legumes could improve the paste lubrication. In general, 5% of the black rice paste and sticky rice in the LF grain group, and the soybean paste in the legume group, showed a low friction coefficient (μ) in the entire entrainment speed range; barley paste and oat paste in the HF grain group showed relatively low μ at low entrainment speed (0.5 mm/s) and medium entrainment speed (5 and 10 mm/s), respectively.

In this study, mung beans were added to rice porridge as supplementary cereal at 0%, 25%, 50%, 75%, and 100% (beans/100 g total mixture), respectively to investigate the effect of mung beans on the rheological and frictional properties of rice porridge. During the frequency scanning experiment, the storage modulus (G’) of all samples was more substantial than the loss modulus (G’’). Moreover, the data obtained from the creep-recovery tests were modeled using Berger’s model. The addition of mung beans also increased the instantaneous elastic modulus (E1) and retarded elastic modulus (E2) values. In tribology test, the friction curves of the mung bean-rice porridge did not resemble the traditional Stribeck curve and with the increase of mung bean addition ratio and it was more difficult for the fluid (porridge) to enter the next zone. Furthermore, the sensory evaluation indicated that the rice porridge containing 25% and 50% mung beans represented the highest overall preference among evaluators. This study provided theoretical support for finding the relationship between rheology and sensory characteristics of porridges.