Yejun Zhong

Effects of aleurone layer on rice cooking: A histological investigation

Understanding how aleurone layer (AL) affects rice cooking behaviour is important for rice processing. Individual effects of AL on rice cooking behaviour were evaluated and histological characters of AL before and after cooking were investigated. AL slightly affected rice cooking quality (optimum cooking time, water absorption, volume expansion ratio and total solids loss) while remarkably affected rice texture (hardness and adhesiveness) and peak viscosity. Histological investigation showed that channels were formed in AL during cooking. The channels facilitated the penetration of water, which could explain why AL exhibited slight effects on rice cooking quality. In addition, thick cell walls and thermally stable aleurone grains were widely distributed in AL. Leached components accumulated on them and formed a reinforced coated film on rice surface during cooking, which may be a possible mechanism accounting for the remarkable effect of AL on rice texture. Histological characters of AL are closely related with rice cooking behaviour.

Molecular and Functional Properties of Protein Fractions and Isolate from Cashew Nut (Anacardium occidentale L.)

Some molecular and functional properties of albumin (83.6% protein), globulin (95.5% protein), glutelin (81.3% protein) as well as protein isolate (80.7% protein) from cashew nut were investigated. These proteins were subjected to molecular (circular dichroism, gel electrophoresis, scanning electron microscopy) and functional (solubility, emulsification, foaming, water/oil holding capacity) tests. Cashew nut proteins represent an abundant nutrient with well-balanced amino acid composition and could meet the requirements recommended by FAO/WHO. SDS-PAGE pattern indicated cashew nut proteins were mainly composed of a polypeptide with molecular weight (MW) of 53 kDa, which presented two bands with MW of 32 and 21 kDa under reducing conditions. The far-UV CD spectra indicated that cashew proteins were rich in β-sheets. The surface hydrophobicity of the protein isolate was higher than that of the protein fractions. In pH 7.0, the solubility of protein fractions was above 70%, which was higher than protein isolate at any pH. Glutelin had the highest water/oil holding capacity and foaming properties. Protein isolate displayed better emulsifying properties than protein fractions. In summary, cashew nut kernel proteins have potential as valuable nutrition sources and could be used effectively in the food industry.

Modification of potato starch by using superheated steam

Conventional hydrothermal modification of starches is a time- and energy-consuming process. In this study, superheated steam (SS) at different temperatures (100-160 ℃) was used to modify the structural and physicochemical properties of potato starch (PS). The long- and short-range molecular structures were disrupted without affecting the granular structure of PS and the degree of disruption could be regulated by simply changing the treatment temperature. The swelling power, solubility, transparency, peak viscosity and breakdown of PS were positively correlated with each other and were significantly decreased by SS treatment, while the pasting temperature, final viscosity and setback were significantly increased. Considerable amount (>9%) of slowly digestible starch was converted to resistant starch by SS treatment at 100 and 120 °C. Considering the high thermal efficiency of SS and the short treatment time (1 h) used in this study, SS treatment could be a superior alternative to conventional hydrothermal modification.