pH对水酶法大豆乳状液稳定性影响的机理研究
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摘要
以水酶法大豆乳状液为研究对象,通过激光共聚焦、红外光谱、荧光光谱等手段研究p H对水酶法乳状液粒径、Zeta电位、微观结构及其中蛋白质性质的影响,研究pH对乳状液稳定性影响的机理。结果表明:随着乳状液pH的增加(2～10),乳状液的Zeta电位显著降低,且当p H为4. 5～4. 7范围内时乳状液的Zeta电位接近0;当pH在蛋白质等电点附近,乳状液的粒径最大,乳状液中蛋白质的表面疏水性最低,相对分子质量最大,荧光强度最低,三级结构更加松散,二级结构中有序的α-螺旋含量最低,而无规卷曲含量最高。表明pH在蛋白质等电点附近时,乳状液是最不稳定的,在此环境下更容易破除乳状液。
With aqueous enzymatic soybean emulsion as material,the effects of pH on the particle size,Zeta potential and microstructure of emulsion and properties of protein in emulsion were studied by laser confocal microscopy,infrared spectroscopy and fluorescence spectroscopy to explore the mechanism of effect of p H on stability of emulsion. The results showed that with the increase of emulsion p H from 2 to10,the Zeta potential of the emulsion significantly reduced,and approached to zero when the p H was in the range of 4. 5-4. 7. When the pH was near the isoelectric point of the protein,the particle size of emulsion was the largest,and the surface hydrophobicity of the protein in the emulsion was the lowest with the largest relative molecular weight,the lowest fluorescence intensity,more loose tertiary structure,the lowest ordered α-helix content and the highest random coil content in the secondary structure. So when p H was near the isoelectric point,the emulsion was the most unstable and easier to be broken.
With aqueous enzymatic soybean emulsion as material,the effects of pH on the particle size,Zeta potential and microstructure of emulsion and properties of protein in emulsion were studied by laser confocal microscopy,infrared spectroscopy and fluorescence spectroscopy to explore the mechanism of effect of p H on stability of emulsion. The results showed that with the increase of emulsion p H from 2 to10,the Zeta potential of the emulsion significantly reduced,and approached to zero when the p H was in the range of 4. 5-4. 7. When the pH was near the isoelectric point of the protein,the particle size of emulsion was the largest,and the surface hydrophobicity of the protein in the emulsion was the lowest with the largest relative molecular weight,the lowest fluorescence intensity,more loose tertiary structure,the lowest ordered α-helix content and the highest random coil content in the secondary structure. So when p H was near the isoelectric point,the emulsion was the most unstable and easier to be broken.
引文
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[2]YUSOFF M M,GORDON M H,NIRANJAN K. Aqueous enzyme assisted oil extraction from oilseeds and emulsion deemulsifying methods:a review[J]. Trends Food Sci Technol,2015,41(1):60-82.
[3]郝莉花,陈复生,殷丽君,等.水酶法乳状液的稳定性及其破乳方法研究进展[J].粮食与油脂,2017,30(3):13-16.
[4]迟延娜,张文斌,杨瑞金,等.顽固乳状液的破乳处理提高花生游离油提取率[J].农业工程学报,2014,30(8):257-264.
[5]LI P F,ZHANG W B,HAN X,et al. Demulsification of oil-rich emulsion and characterization of protein hydrolysates from peanut cream emulsion of aqueous extraction processing[J]. J Food Eng,2017,204,64-72.
[6]崔健,郦金龙,王盼,等.温度、p H和盐对乳清蛋白乳状液稳定性的影响[J].食品工业科技,2010,31(11):84-87.
[7]CHABRAND R M,KIM H J,ZHANG C,et al. Destabilization of the emulsion formed during aqueous extraction of soybean oil[J]. J Am Oil Chem Soc,2008,85(4):383-390.
[8]胡森,齐宝坤,孙禹凡,等.大豆乳状液的组成成分及相关性质的研究[J].中国油脂,2019,44(1):41-46.
[9]王瑛瑶,王璋,罗磊.水酶法提花生油中乳状液性质及破乳方法[J].农业工程学报,2008,24(12):259-263.
[10]尹寿伟.芸豆蛋白的物化修饰及相关构效机理研究[D].广州:华南理工大学,2009.
[11]KATO A,NAKAI S. Hydrophobicity determined by a fluorescence probe method and its correlation with surface properties of proteins[J]. Biochim Biophys Acta,1980,624(1):13-20.
[12]XIONG W F,REN C,TIAN M,et al. Emulsion stability and dilatational viscoelasticity of ovalbumin/chitosan complexes at the oil-in-water interface[J]. Food Chem,2018,252:181-188.
[13]XIONG W F,REN C,JIN W,et al. Ovalbumin-chitosan complex coacervation:phase behavior,thermodynamic and rheological properties[J]. Food Hydrocolloid,2016,61:895-902.
[14]LI P F,GASMALLA M A A,LIU J J,et al. Characterization and demusification of cream emulsion from aqueous extraction of peanut[J]. J Food Eng,2016,185:62-71.
[15]PUPPO M C,SPERONI F,CHAPLEAU N,et al. Effect of high-pressure treatment on emulsifying properties of soybean proteins[J]. Food Hydrocolloid,2005,19(2):289-296.
[16]MORR C V. Current status of soy protein functionality in food systems[J]. J Am Oil Chem Soc,1990,67(5):265-271.
[17]MCCLEMENTS D J. Theoretical analysis of factors affecting the formation and stability of multilayered colloidal dispersions[J]. Langmuir,2005,21(21):9777-9785.
[18]YANG H S,XU W,LIU B Y,et al. Effect ofγ-irradiation on the physiochemical properties of mixed soy protein isolate/starch material[J]. African J Biotechnol,2012,11(28):7238-7246.
[19] LIU J H,RU Q M,DING Y T. Glycation a promising method for food protein modification:physicochemical properties and structure,a review[J]. Food Res Int,2012,49(1):170-183.
[20]XU J,MUKHERJEE D,CHANG S K C. Physicochemical properties and storage stability of soybean protein nanoemulsions prepared by ultra-high pressure homogenization[J]. Food Chem,2018,240:1005-1013.
[21]VISEU M I,CARVALHO T I,COSTA S M. Conformational transitions inβ-lactoglobulin induced bycationic amphiphiles:equilibrium studies[J]. Biophys J,2004,86(4):2392-2402.