No abstract

In this work, protein structures and properties and physico-chemical characteristics of surimi fried at different temperatures were studied. The effect of frying on surimi protein structure was characterised by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE), intrinsic fluorescence, surface hydrophobicity, intermolecular interaction and Fourier transform infrared spectroscopy (FT-IR). SDS-PAGE analysis observed the appearance of new peptide bands and the weakening of myosin heavy-chain and actin bands after frying. In addition, frying damaged the hydrogen bond and ionic bond but promoted formation of the disulphide bond. Moreover, β-sheet and random coil were increased after frying, while α-helix and β-turn were decreased. After frying, the surface hydrophobicity of fried surimi decreased and the fluorescence maximum emission wavelength showed a red shift. The above changes indicated occurrence of protein denaturation and degradation, which were dependent on the frying temperature. Moreover, the effect of the frying temperature on physicochemical properties of fried surimi was characterised by measuring the hardness, oil absorption, porosity and water absorption capacity of fried surimi. The moisture loss, oil uptake, porosity and water absorption capacity of the fried surimi increased gradually with the frying temperature. However, the hardness of fried surimi was not positively correlated with the frying temperature but strongly dependent on the porous structure. These results showed that the physico-chemical properties of the fried surimi were dependent on not only degree of protein denaturation but also the porous structure.

Rice bran, rich in feruloyl arabinoxylan, is a good source of feruloyl oligosaccharides (FOs). To prepare FOs, bran was often hydrolyzed by amylase and protease to remove starch and protein and then hydrolyzed by xylanase, which was time-consuming and had a low yield. To solve the above problems, enzymatic extrusion was used to treat rice bran, and the effects of traditional hydrolysis, a combination of traditional extrusion and hydrolysis (extrusion-hydrolysis) and enzymatic extrusion on the yield of FOs were investigated and compared in this study. It was found that traditional extrusion and enzymatic extrusion significantly increased the yield of FOs. Particularly, the yield of FOs resulting from enzymatic extrusion was increased to 5.78%, while the yield from traditional hydrolysis was 4.23%. Microscopy analysis showed that extrusion damaged the cell wall of bran, which might increase the accessibility of xylanase to arabinoxylan and the yield of FOs. Spectroscopy analysis suggested that FOs obtained by different pretreatments had similar structures. It was obvious that enzymatic extrusion saved the time for removal of starch and protein and increased the yield of FOs. In addition, the highest yield of FOs was found at the moisture content of 30% and the screw speed of 50 rpm. This study provided an efficient method for the preparation of FOs that is suitable for industrial production.