Rice Gel Research Articles

Study on creep properties of indica rice gel

Rice gels from 16 various types of indica rice were prepared. Their rheological parameters based on creep behavior were determined and the effect of the chemical compositions on the rheological parameters of rice gel was assessed. The creep process of rice gel consisted mainly of retarded elastic deformation, ε 2, and viscosity flow deformation, ε 3. The retarded elastic modulus, E 2, relaxation time, τ, and the viscosity coefficient, η 3, of the rice gel were estimated according to the Burger model. The creep parameters of indica rice gel were related to rice variety. The complex of protein or lipid with amylose and embedment in gel network made an important contribution to the state of the network structure formed by starch molecular chain, and that affected the creep properties of rice gel. Correlation analysis indicated that the creep properties showed a dependence on the chemical compositions. The retarded elastic modulus, E 2, had positive correlations with amylose ( P = 0.004) and fat content ( P = 0.066). The relaxation time, τ, had negative correlations with amylose ( P = 0.006) and fat content ( P = 0.012). The viscosity coefficient, η 3, was positively correlated to both amylose ( P = 0.079) and protein content ( P = 0.089).

Characters of rice starch gel modified by gellan, carrageenan, and glucomannan: A texture profile analysis study

Mixed gel was prepared with rice starch (indica, japonica, or sticky rice starch), polysaccharides (gellan, carrageenan, or konjac glucomannan), CaCl 2, and deionized water. Rice starch, deionized water, and CaCl 2 were kept constant; a mixture design was used to study the effects of varieties of rice starch, polysaccharides and its concentration on the quality of the mixed gel by texture profile analysis (TPA) method. The texture profile of the rice starch–polysaccharides mixed gel was dependent not only on the variety of rice and polysaccharides, but also on the concentration of the polysaccharide. The addition of the non-suitable polysaccharide or non-proper concentration would lead to deterioration of the gel. Only the suitable polysaccharide at a proper concentration would endow the gel with the excellent quality. Low concentration (<0.2% (w/w)) of carrageenan and high concentration of gellan (>0.3% (w/w)) could increase the hardness and adhesiveness significantly; the indica rice starch–polysaccharides always owned the largest hardness, adhesiveness, and chewiness. Considering the economic factor, adding 0.2% (w/w) carrageen to the indica rice starch was found to be valuable for improving the texture of rice gel food, when a higher adhesiveness/hardness ratio was needed, 0.3% (w/w) gellan could be added to indica rice starch. The konjac glucomannan could not improve the adhesiveness, chewiness, and hardness significantly for any kinds of rice starches. The three varieties of rice starch, polysaccharides and their concentration had no significant effect on the springiness of the mixed gel.

Utilization of Hydroxypropylated Waxy Rice and Corn Starches in Korean Waxy Rice Cake to Retard Retrogradation

ABSTRACTA traditional waxy rice gel cake in Korea, Injulmi, was prepared with hydroxypropylated waxy rice and corn starches (molar substitutions 0.13 and 0.11, respectively), and the textural and retrogradation characteristics of the cake were compared with a conventional cake made of waxy rice flour. In the pasting viscogram, hydroxypropylated starches exhibited reduced pasting temperatures, but increased peak viscosities compared with the unmodified starches. Under differential scanning calorimetry, the Tg′ and ice melting enthalpy of the starch gel cakes were reduced by hydroxypropylation, which indicated that the modified starches had higher water‐holding capacity than the unmodified starches. The degree of retrogradation, as measured by the hardness of the gel cake and the melting enthalpy, was significantly reduced by hydroxypropylation and hydroxypropylated waxy rice starch was more effective in retarding the retrogradation than hydroxypropylated waxy corn starch

VISCOELASTIC CHARACTERIZATION OF RICE GEL

Rice flour dispersions with 15–25% solids were subjected to microwave heating for 0–75 s and samples were subjected to oscillatory frequency sweep between 0.01–10 Hz. The initial rapid increase in storage modulus (G1) with frequency decreased to a plateau at higher frequencies. An increase in G1 and complex viscosity (η*) with an increase in the time of treatment or concentration of solid indicate the extent of sol‐gel transformation. The sensory data on hardness, elasticity and stickiness also followed similar trend. Principal component analysis (PCA) of the sensory results indicate that a minimum treatment time of 45 s is needed to achieve a rice gel with acceptable sensory characteristics. The G' values were modeled (0.936 ≤ r ≤ 0.988, P ≤ .01) by the 4‐element spring‐dashpot model.

PHYSICOCHEMICAL PROPERTIES OF THREE RICE VARIETIES

ABSTRACTPhysicochemical properties of three rice varieties were studied. Textural properties of gels from La Grue, Bengal, and S201, were investigated using the Universal Texture Analyzer, and pasting characteristics by Brabender Visco/amylography. Gels from La Grue (long grain) had higher fracturability, hardness, amylographic consistency, and setback viscosity (P&lt;0.05). Gels from S201, a short grain variety, were harder and had higher fracturability values than those from Bengal, a medium grain variety. Analysis of texture profiles of rice gels could be an alternative to Brabender viscoamylographs for differentiating among rice varieties. Tests on in‐vitro starch digestibility showed that La Grue had lower maltose released than S201 or Bengal during the first 15 and 45 min of hydrolysis with human salivary α‐amylase.

BASIC RESEARCH FOR RICE DRYING WITH SILICA GEL

ABSTRACT Using silica gel as a desiccant, rice drying tests were carried out under two elemental drying systems. In the first system ( a divided particle bed system ), a rough rice bed was directly put on a silica gel bed in an airtight cylinder. In the second system ( a mixed particle bed system ). an intimate mixture of rice grains and silica gel particles was sealed in airtight bottles. Experimental results showed that the first system was not appropriate as a practical drier because of moisture inequalities in the rice bed. However, the second system which was assumed to have uniform moisture content was considered to be applicable to use in a practical drier because of reasonable drying rate and product rice quality. An empirical equation for predicting required amount of silica gel was given as a function of initial moisture content of both the rice and silica gel.