Retrogradation inhibition and intragranular distribution in cooked rice by addition of α-glucosidase (AG) and branching enzyme (BE).

The effect of inhibiting retrogradation and changes in chain length distribution by AG and BE, which are texture-modifying enzymes, has been clarified. To ascertain in which part of the rice grain retrogradation occurs and which enzymes is most effective, the degree of retrogradation in each part of the rice grain was measured from the surface to the core of the same rice grain using a synchrotron radiation X-ray beam with a beam size of 100 µm. Retrogradation was effectively suppressed at all measurement sites by enzyme addition, although the effect of enzymes was greater at the surface. Rice grain sections were stained with iodine and eosin. A starch layer that does not easily form a complex with iodine was observed inside the protein layer at the surface of cooked rice. A starch layer with a long molecular chain that forms complexes with iodine was observed inside the rice grain.

Effects of Dual Modification with Succinylation and Annealing on Physicochemical, Thermal and Morphological Properties of Corn Starch.

The objective of this study was to investigate the effects of annealing, succinylation, and a dual modification process (succinylation⁻annealing) on the physicochemical, thermal, and morphological properties of corn starch. Specifically, the properties of interest were the water-binding capacity (WBC), swelling power, paste clarity, solubility, pasting properties, stability ratio, and thermal and morphological characteristics. The dual modification process increased the physicochemical properties (WBC, swelling power, peak viscosity, and paste clarity) and increased the gelatinization temperature and gelatinization enthalpy (∆H), but had no effect on the morphological properties and X-ray diffraction patterns. A comparison of samples, made using each of the processes, showed that dual modification increased the stability ratio (more stable viscosity under thermal and shear stress), which was 0.69 for dual modified starch, compared with 0.64, 0.58 and 0.44 for native, succinylated, and annealed starches, respectively. The findings of the present study are of potential use in the food industry.

Kinetic Analysis of Freeze-Thaw Stability of Mayonnaise.

Kinetic analysis was used to study the destabilization of mayonnaise by focusing on the fat crystals. Mayonnaise prepared from rapeseed oil and soybean oil was stored at temperatures ranging from −20 to −40 °C. The destabilization kinetic parameters were measured by observing oil separation over time. The destabilization rate constant, kd, increased with decreasing temperature. The highest value of kd was 1.28 × 10−3 min−1 at −40 °C for rapeseed oil mayonnaise (RoM) and the lowest was 1.95 × 10−6 min−1 at −20 °C for soybean oil mayonnaise (SoM). At each temperature, the kd value in RoM was higher than that in SoM. However, the order of destabilization, n, followed no specific pattern. The crystallization rate constant, Kc, and Avrami constant, n, were calculated using microscopic images of the fat crystals. The increase in crystallization kinetic parameters with decreasing temperature revealed changes in crystal behavior. Both the destabilization rate constant, kd, and the crystallization rate constant, Kc, depended on the temperature. This temperature dependency behavior showed a correlation between kd and Kc, suggesting that the destabilization rate depended on the rate of growth of fat crystals during the freeze-thawing of mayonnaise.

Airflow resistance measurement for a layer of granular material based on the Helmholtz resonance phenomenon.

A Helmholtz resonance technique was employed to predict the airflow resistance of layers of granular materials, namely glass beads, brown rice, soybean, adzuki beans, and corn kernels. Each granular sample was placed on the tube mouth of an open-type Helmholtz resonator. The resonant frequency was determined by measuring the electric impedance of a loudspeaker that was installed in the resonator and driven by a chirp signal linearly sweeping from 90 to 220 Hz for 6.0 s. For a changing sample layer thickness, the resonant frequency was measured, and the specific airflow resistance was calculated by measuring the static pressure drop required for N2 gas to flow through the layer at a constant velocity of 0.042 m/s. When the thickness of the layer was fixed, the Helmholtz resonant frequency decreased as the specific airflow resistance increased, regardless of the kind of granular material.

The effects of water absorption and roasting conditions on fracture properties and internal structure of sesame seeds.

We investigated the effects of soaking, residence time before roasting and roasting conditions on the fracture properties and structure of the cross-section of sesame seeds. Soaking time affected only the size of the side voids of the seed cross-section. The fracture force and strain of the roasted seeds decreased as residence time increased. The center void of the roasted seeds, important for seed crispness increased as residence time increased. In contrast, the side void of the roasted seeds only increased with residence time during the first 10 min. Seeds roasted at higher temperatures had smaller fracture forces and larger central voids than those roasted at lower temperatures. During roasting at 300 °C, the fracture force and strain decreased as the center void ratio increased. Overall, both a sufficient time for moisture diffusion in the seeds and a high roasting temperature were necessary to produce crisp roasted seeds.