7S球蛋白水解物对猪肉糜凝胶的影响

以大豆为原料,提取7S球蛋白,并采用碱性蛋白酶对其进行限制性酶解,控制其水解度,得到水解度为3%、6%、9%、12%、15%的酶解产物,将酶解产物与猪肉糜混合制备猪肉肠,分析添加不同水解度的酶解产物所形成的猪肉糜凝胶的化学作用力的变化。结果表明：静电作用与猪肉糜凝胶强度相关性不显著,不是维持猪肉糜凝胶网络结构的主要作用力;疏水作用与猪肉糜凝胶的回复性和咀嚼性呈现极显著的正相关性;氢键与猪肉糜凝胶的弹性呈现极显著的正相关性,二硫键与猪肉糜凝胶的弹性、内聚性和回复性呈现显著的正相关性。提示：氢键、疏水作用、二硫键是维持猪肉糜凝胶网络结构的主要作用力。扫描电镜图谱显示：随着添加的酶解产物水解度的增大,所形成的凝胶网络结构逐渐紧密,且比较均匀,无明显的空洞,猪肉糜凝胶的网络结构得到显著改善。     

The characterization of soybean varieties by fluorescence spectroscopy

Fluorescence spectroscopy was used to differentiate between β‐conglycinin (βC) and glycinin (G) fractions that were isolated from four food grade soybean varieties (Glycine max var. K1430, Hutcheson, K93‐90‐29, and KS4997) grown in the same location. The protein fractions were discriminated by using spectroscopic tryptophan fluorescence emission and synchronous scanning techniques that took advantage of the sensitivity of the chromophore to changes in the protein environment. The relative intensities of the βC and glycinin fluorescence ranged from 1.00 to 1.30 and 1.00 to 1.31 respectively. The intensities of the βC and glycinin synchronous fluorescence ranged from 1.00 to 1.45 and 1.00 to 1.30 respectively. The spectroscopic method proved to be an effective technique to differentiate between different soybean varieties.     

Functionality of soy protein produced by enzyme-assisted extraction

This study investigated the potential of enzymes to increase soy protein extractability without causing protein degradation. The aqueous extraction of protein was performed from defatted soy flakes on a laboratory-and pilot-plant scale. Yields of protein and reducing sugars were determined in the alkali extracts obtained with cellulases and pectinase, added alone or as cocktails. Using 5% (wt/g of protein) Multifect pectinase resulted in the best improvement of protein yields, which were 50 and 17% greater than the controls in laboratory- and pilot-plant-scale trials, respectively. This enhanced protein extraction was accompanied by an increased reducing sugar content in the aqueous extract compared with the control. Under the conditions tested, no enzyme cocktail markedly increased the protein yield compared with the use of single enzymes. The solubility curve for Multifect pectinase-treated soy protein isolate (SPI) was typical of SPI at pH 2–10. Its foam stability significantly improved, but the emulsification properties declined. Multifect pectinase markedly reduced the viscosity of SPI. SDS-PAGE showed that the α’ and α subunits of β-conglycinin were modified, and glycoprotein staining showed that these modifications were probably due to a protease secondary activity in the pectinase preparation. One cellulase and one pectinase were identified as effective in modifying the protein and reducing sugar extractablity from the defatted soy flakes.     

大豆β-伴球蛋白多肽抗氧化活性研究

以大豆β-伴球蛋白为原料,利用枯草芽孢杆菌进行发酵制备抗氧化肽,研究发酵时间和浓度对大豆β-伴球蛋白肽抗氧化活性影响。结果表明,发酵40 h时,大豆β-伴球蛋白肽抗氧化活力最高,抑制自由基能力最强;在此最佳发酵时间下,当大豆β-伴球蛋白肽浓度为1.6 mg/mL时,对羟自由基清除率最大;浓度为2 mg/mL时,对超氧阴离子自由基清除能力最强。