Rabiha Sulaiman

ABSTRACT A modified Brookfield viscometer equipped with a data acquisition system was used to study gelatinizing behavior of native corn starch. Data for the dependent variable (continuous torque), and independent variables were collected. The independent variables were time–temperature history, shear history, and temperature, corresponding to the three main regions in a pasting curve. Parameters were estimated simultaneously using both ordinary least squares, and the sequential method. The model fit well as shown by RMSE of approximately 2% of full scale, and relative standard error of all parameters estimated less than 11%. Scaled sensitivity coefficients showed that the most important parameters were time–temperature history, followed by shear history, and the temperature parameter was the least important. This work is the first to show that starch-pasting curve parameters can be estimated simultaneously and sequentially, and can be used to predict pasting curves in other systems (RVA) well.

Central composite rotatable design (CCRD) was used to optimize the settings for the roasting conditions of jackfruit (Artocapus hetrophyllus) seed (JFS). The response variables studied were; color attributes L*, a*, and b*, browning intensity, and fracturability. The colors L*, a*, b* and browning intensity were well predicted by a second-order polynomial model. Fracturability was predicted by a first-order polynomial. The determination coefficients for colors L*, a*, b*, browning intensity, and fracturability were 0.81, 0.96, 0.93, 0.92, and 0.74 respectively. The fitted models were checked for adequacy using analysis of variance (ANOVA). The optimum roasting conditions were established at a temperature of 153.36 °C, 34.36 min, and pH of 6.34 with composite desirability value of 0.95. Micro-structural studies of both raw and roasted JFS at different roasting levels (i.e., low, medium, and high) were also investigated using scanning electron microscope (SEM). JFS starch granules fell in the B-type category with semi-oval to bell-shaped granules (5-9 μm in diameter). In addition, Fourier Transform Infrared analysis was carried out on both raw and roasted JFS. The IR spectra was in the 4000-1000 cm(-1) region which is described by five main modes; O-H, C-H, C = O, (C-H) CH3, and C-O.

The seeds of Terminalia catappa from Malaysia were analyzed for their physicochemical properties. The following values were obtained: moisture 6.23 ± 0.09 %, ash 3.78 ± 0.04 %, lipid 54.68 ± 0.14 %, protein 17.66 ± 0.13 %, total dietary fibre 9.97 ± 0.08 %, carbohydrate 7.68 ± 0.06 %, reducing sugar 1.36 ± 0.16 %, starch 1.22 ± 0.15 %, caloric value 593.48 ± 0.24 %. Studies were also conducted on amino acid profile and free fatty acid composition of the seed oil. Results revealed that glutamic acid was the major essential amino acid while methionine and lysine were the limiting amino acids. The major saturated fatty acid was palmitic acid, while the main unsaturated fatty acid was oleic acid followed by linoleic acid. In addition, the seed was rich in sucrose and had trace amount of glucose and fructose. Briefly, the seed was high in proteins and lipids which are beneficial to human.

ABSTRACT The apparent viscosity profile of starches during gelatinization varies with different amylose content. This study focused on the influence of amylose content on the kinetic parameters of a starch viscosity model for corn starches. The five parameters were: gelatinization rate constant (kg), gelatinization activation energy (Eg), relative increase in apparent viscosity during gelatinization (Aα), relative decrease in apparent viscosity during shearing (B), and viscous activation energy (Ev). The parameters were estimated at different amylose content using both ordinary least squares nonlinear regression and the sequential method. The mixer viscometry approach was used to measure apparent viscosity. The first part of this paper presents parameter estimation results for waxy corn starch. The model was validated by using the parameters to predict viscosity for the same starch in a different measuring system, i.e., the RVA. The second part of this paper presents the estimated parameters for corn starch blends at different amylose content. The following parameters were significantly affected by amylose content: kg and Eg both decreased with amylose content by an power-law relationship. Activation energy of gelatinization ranged from 121 to 1169 kJ/mol. The other parameters Aα, B, and Ev were not significantly influenced by amylose content. In summary, the gelatinization parameters kg and Eg dramatically decreased as amylose increased from 3% to 35% (waxy corn starch blends).

ABSTRACT A modified Brookfield viscometer equipped with a data acquisition system was used to study gelatinizing behavior of native corn starch. Data for the dependent variable (continuous torque), and independent variables were collected. The independent variables were time–temperature history, shear history, and temperature, corresponding to the three main regions in a pasting curve. Parameters were estimated simultaneously using both ordinary least squares, and the sequential method. The model fit well as shown by RMSE of approximately 2% of full scale, and relative standard error of all parameters estimated less than 11%. Scaled sensitivity coefficients showed that the most important parameters were time–temperature history, followed by shear history, and the temperature parameter was the least important. This work is the first to show that starch-pasting curve parameters can be estimated simultaneously and sequentially, and can be used to predict pasting curves in other systems (RVA) well.