| Pulsed electric field (PEF) is an important kind of non-thermal processing technology. However, pulse electric field treatment were in view of the continuous phase fluid currently, but our laboratory found that PEF can be used for non-continuous phase of solid material. In the transportation of raw materials and pretreatment process can be treated by electric fields, to realize the industrialization of large-scale processing. Regarded as naturally nutritive, due to rich in unsaturated fatty acid and superior in nutrition and health care function, is the oil from the cultivar of both low in erucic acid and glucosinolate (double-low) Qinyou No.7. This research adopts the PEF rapeseed preprocessing of preset water directly, taking the pulse voltage, residence time of material, pulse frequency and pulse width as variables, to a rate of oil and rapeseed protein structure and functional properties as the indexes, get to know the effect of PEF operating conditions on the oil yield and quality and rapeseed protein molecular structure and functional properties. In order to provide theoretical basis for the comprehensive utilization of rapeseed. The main results are as follows:(1) PEF treatment increased the rapeseed oil yield. The four factors of PEF, pulse voltage, material residence time, pulse frequency and pulse width had significant effects (P< 0.05) on rapeseed oil yield, and the regression equations had high correlation (R2=0.9960) by the design of response surface optimization, the optimum conditions for:voltage 35 kV, material residence time 185 s, pulse frequency 806 Hz, pulse width 8μs. At this time, compared with the untreated group, the rapeseed oil yield from 71.60%up to 95.21%.(2) The pretreatment of PEF to rapeseed material influences the the quality of rapeseed oil. PEF pretreatment significantly (P< 0.01) increases the AV, POV and p-AV of the rapeseed oil and decreases the IV significantly (P< 0.01), while dose not significantly affect the saponification value. PEF darkens the oil significantly (P< 0.05) as the Y value and R value go larger than those of the control and change with the storage period. After PEF pretreatment, the AV, POV and p-AV of oils altered slower than those of the control. PEF does not change the category of the fatty acids, but increases the amount of saturated fatty acids and decreases that of the unsaturated ones. PEF increased both the functional components, total phenolics, α-tocopherol and y-tocopherol significantly (P< 0.01) in the oil. PEF could significantly (P< 0.05) increase the ability of the rapeseed oil to eliminate free radicals DPPH-, OH· and O2-·, therefore, increase the antioxidation stability of rapeseed oil.(3) PEF treatment changed the rapeseed protein functional properties. PEF treatment on rapeseed protein functional properties were significantly (P< 0.05). In addition, the protein fractions also has a significant effect on the functional properties of protein, performance in albumin solubility, water holding capacity and emulsification and emulsion stability and foamability and foam stability was significantly better than the whole protein and globulin. It was also found that there was a positive correlation between rapeseed oil yield and protein function properties, under different conditions of PEF.(4) PEF treatment changed the molecular structure of rapeseed protein. Through the analysis electrophoresis, near infrared spectroscopy, sulfhydryl content and the hydrophobicity index, the results showed that the color of two subunits of albumin after PEF treatment becomes shallow, no bands disappeared; globulin subunit one with lighter color, no bands disappeared; and the PEF group whole protein is more one subunit band than the control groups. PEF changed the rapeseed protein secondary structure, under certain conditions, the peptide chains unwinding, the rapeseed protein from ordered to disordered state transition. PEF treatment on rapeseed protein tertiary structure of hydrophobicity and sulfhydryl contents were significantly (P< 0.05). At the same time the hydrophobicity of albumin was significantly higher than that of whole protein and globulin, and globulin in total and free sulfhydryl group was higher than that of albumin. |
