摘要：
The lipoxygenase (LOX) in grass carp can catalyze the oxidation of polyunsaturated fatty acids even their esters, resulting in rancidity deterioration of grass carp and its products during the process and storage. Preliminary purification, quantitative determination and distribution of grass carp muscular LOX were investigated in the present study. LOX activity of the grass carp muscle was measured to be 35.17 KU/g and its molecular weight was 95.71 kDa identified by SDS-PAGE. Using previously reported extraction methods such as twice salting-out and once dialysis, the LOX protein content in the crude muscular LOX extraction is about 28%. When salted with graded saturation of ammonium sulfate, we found once salting-out was enough for LOX extraction and the effective percentage saturation of ammonium sulfate for LOX extraction was 40%. Under this condition, the LOX protein content in the crude muscular LOX extract was doubled. The LOX distribution in fish was gradually increased from skin and muscle, gill, viscera to blood, which indicates that it is very important to remove the viscera and bleed fish completely during fish product processing to decrease the risk of lipid oxidation caused by LOX.
摘要：
The effects of germination on the bio-functional components in the germ-remaining polished rice have been investigated. The bio-functional components in the raw GRPR, brown rice and germinated brown rice were also characterized as the comparison. The results showed that a decrease in amylose content and an increase in reducing sugar were observed after germination. The germinated GRPR contains much more bio-functional components (GABA and dietary fiber) than GRPR and brown rice, and slightly less than germinated brown rice. The results also demonstrated that germinated GRPR contained less phytic acid than other three kinds of rice. Consequently, the nutritional value of GRPR had been improved by germination. Germination of GRPR would be a promising processing method to enhance the germinated rice consumption.
关键词：
DEAMIDATION;GLUTAMINASES;GLUTELINS;HYDROLASES;MODIFICATION;PH;PROTEINS CEREAL;RICE;SOLUBILITY;STRUCTURE;Catering;speciality and multi-component foods;Protein isolates
摘要：
The effects of glutaminase on deamidation of rice glutelin were investigated. Water-insoluble rice glutelin was deamidated to the extent of deamidation degree 52.29% in 200 mmol/L sodium phosphate buffer (pH 7.0) at 37 degrees C for 48 h. Zeta potential analysis indicated that the glutamines of rice glutelin were deamidated into glutamic residues. Size exclusion chromatography results demonstrated that glutaminase deamidation broke the hydrophobic, hydrogen and some intermolecular disulfide bonds in rice glutelin and thereby rearranged the molecular weight distributions without serious cleavage of the peptide bonds. Fourier transform infrared analysis revealed the transformation of alpha-helix to random coil and beta-turn by deamidation and suggested that deamidated rice glutelin maintained more flexible or extended forms. Solubility properties of rice glutelin in mildly acid (pH 5) and neutral buffers (pH 7) were remarkably improved by glutaminase deamidation. These new features of deamidated rice glutelin suggested that glutaminase could be a potential tool for enhancing the usability of rice protein in the food industry. (C) 2011 Elsevier Ltd. All rights reserved.
关键词：
Acid-deamidation;Microstructure;Rheology;Rice protein
摘要：
Microstructure and theological properties of mixtures of acid-deamidated rice protein (ADRP) and dextran were studied. The microstructures of the ADRP/dextran mixtures were described using confocal laser scanning microscopy (CLSM), which revealed the effective association among ADRP and formation of a protein network-like structure in the mixture with higher protein concentration. Mechanical properties of the mixtures were observed by rheometer. The steady shear measurements showed a correlation with the CLSM results via a marked increase in the viscosity of the mixtures with protein association. Frequency sweeps further evidenced the build-up of the gelled network-like structure. The differences in fracture forces observed by textural measurements between mixture and single ADRP gel also suggested the difference in microstructures. The formation of network-like structure appeared to have occurred through a phase separation of ADRP and dextran. (c) 2009 Elsevier Ltd. All rights reserved.
