Physical Properties of Cooked Wheat Grains as Affected by Cooking Temperature and Duration

The physical properties of soft and hard wheat grains, cooked with steam under pressure, were investigated. These included water uptake, rheological properties as observed by modulus of elasticity (E) and maximum compressive contact stress (S_max), color in CIE L*a*b* system and pasting properties by Rapid Visco Analyzer (RVA). Four cooking temperatures (110, 120, 130 and 1408 C) and six cooking durations (20, 40, 60, 80, 100 and 120 min) for each temperature were studied. Water uptake (WU) and rheological properties were analyzed immediately after cooking conditions were achieved. For color and pasting properties, cooked wheat grains were dried at low temperature and ground before analysis. It was found that WU increased proportionally with cooking temperatures and durations. Hard wheat grains tended to absorb more water than soft wheat grains. Both E and S_max decreased rapidly when wheat grains were cooked. Such decreases were found to be more rapid in hard wheat grains. Wheat grains became darker when cooked, resulting in the decrease of L* values and increase of a* and b* values. Cooked wheat grains lost their natural pasting properties compared to uncooked grains, resulting in the decrease of viscosity in their RVA profiles. The experimental data fitted well in second-order polynomial models (p # 0.0001). The built models were sufficiently accurate for most of the studied properties (R² ranging from 0.58–0.97).     

Simple techniques to increase the production yield and enhance the quality of organic rice bran oils

This study develops simple techniques for increasing production yield and refining of crude RBO (CRBO). It was found that pre-heating of rice bran by hot air oven to reach 60°C before being extracted by screw press machine increased the yield from 4.8 to 8.3%w/w. This paper suggested three simple steps for refining of organic CRBO: (1) filtering using filter papers (2) sedimentation by adding 4%w/v fuller's earth and (3) bleaching by running through a packed column of activated carbon. These steps significantly enhanced the qualities of RBO when compared to CRBO before treatment. It was found that the lightness of oil as indicated by color value (L*) increased from 22.8 to 28.7, gum and wax decreased from 3.6 to 1.3%w/w. However, the simple refining method had no effect on peroxide value and free fatty acid content. Moreover, it slightly induced the loss of oryzanol content from 2.8 to 2.2%w/w.     

Physicochemical properties,resistant starch content and enzymatic digestibility of unripe banana,edible canna,taro flours and their rice noodle products

Unripe banana, edible canna and taro flours, which have been reported to contain significant amounts of fibre, were investigated for their physicochemical properties, resistant starch (RS) content and in vitro starch digestibility, and compared with commercial high‐fibre‐modified starches from corn and tapioca. Differential scanning calorimetry showed a single endothermic peak located around 70–83 °C for the samples except the modified starches, which exhibited no transition enthalpy. The samples showed different pasting behaviours in the Rapid Visco‐Analyser (RVA) ranging from full to restricted swelling. The RS content varied from 1–26 g per 100 g dry sample, and the estimated glycaemic indices (GIs) of the samples were from 67% to 99%. Generally, samples with high RS were low in GI values. The starches produced acceptable rice noodles but with reduced rate of starch digestion and GI. The effects of the unripe banana, edible canna and taro flours on starch digestibility were either comparable or better than the commercial modified starches. These flours can substitute commercial modified starches to lower GIs of noodles and identical foods.     

Microstructural changes of starch in cooked wheat grains as affected by cooking temperatures and times

The changes of starch microstructure in soft and hard wheat grains after cooking in a pressure cooker were investigated using a scanning electron microscope (SEM) and a light microscope (LM) in conjunction with image analysis. The conditions studied included variation of the cooking times (20-120 min) at the constant temperature (120 °C) and with variable temperatures (110-140 °C) for constant time (40 min). SEM images showed that steam induced changes in the intact starch granules of cooked wheat grains, with the microstructure becoming more in mud-like structure, with increased cooking time or temperature. The swelling and gelatinization of starch granules could contribute to this change. Suspensions of cooked wheat flour were selectively stained with iodine, for observation using the LM. The image analysis software was used for quantitative analysis of the images captured from the LM, providing both the number and area of the starch granules (determined from the dark-blue spots) per fixed image size. With increased cooking time or temperature, the number of starch granules decreased and the area increased as a result from the swelling and melting of starch granules. This study demonstrated the use of SEM and LM for the investigation of starch granules in cooked wheat grains without prior starch isolation.