低温等离子快速提高糖基化花生分离蛋白溶解性及乳化性

为进一步提高花生蛋白的溶解特性,扩大花生蛋白在食品工业中的应用。采用低温等离子(Non-Thermal Plasma,NTP)诱导花生分离蛋白-葡聚糖(Peanut Protein Isolate-Dextran,PPI-Dex)湿法糖基化反应,研究NTP在处理0、0.5、1.5、2.0、3.0 min的情况下,反应时间对花生分离蛋白与葡聚糖糖基化反应的影响。在低温等离子处理功率为70 W,反应液温度为60℃的状态下,随着NTP处理时间的延长,PPI-Dex的接枝度增加,在处理时间为1.5 min时,PPI-Dex接枝度达最大为21.62%,与超声波接枝PPI-Dex需要40 min,传统湿接枝需要24 h相比,缩短了接枝时间。PPI-Dex接枝后,接枝物溶解度和乳液稳定性显著增强,与未接枝相比,溶解度提高了22.28%。通过测定其分子量、氨基酸含量、红外图谱及表面疏水性变化分析NTP处理对花生分离蛋白结构影响。分析结果表明,NTP处理1.5 min后,花生分离蛋白与葡聚糖发生糖基化反应形成偶联物,偶联物中羟基特征峰3000~3500 cm^-1及1000~1260 cm^-1的吸光度与未处理时相比增加,赖氨酸和苯丙氨酸相对含量显著降低(P<0.05);同时,α-螺旋含量降低,β-折叠向β-转角转变,蛋白的有序结构被破坏,结构变松散,PPI构型向亲水型转变;接枝物的表面疏水性指数降低。花生分离蛋白与葡聚糖发生糖基化反应,反应位点可能为Lys和Phe。结果表明,低温等离子处理是一种快速促进蛋白与多糖接枝的有效方法。

Rapid improvement in solubility and emulsification of glycation peanut protein isolate with non-thermal plasma (NTP)

Peanuts known as important oil crops are widely planting for a high yield in China.As an energy dense food,peanut contains a large amount of fat,proteins,carbohydrate,vitamins,minerals,and phytochemicals.Peanut protein is one of valuable byproducts from the oil extraction due to its excellent nutritional source of high-quality protein,while a low dose of anti-nutritive factors.However,low aqueous solubility and emulsification occurred in peanut protein compared with soybean protein.It is necessary to improve the functional properties of peanut protein for the better applications in food industry.Recently,protein glycation has become a safe method most commonly used to produce non-health-hazardous byproducts during protein modification.Protein glycation involves the formation of covalent bonds between proteins(free amine groups,i.e.,terminal or side chain)and polysaccharides(reducing terminal carbonyl group)via the Maillard reaction.This study aims to improve the solubility of Peanut Protein Isolate(PPI)using Non-Thermal Plasma(NTP)treatment for glycation of peanut protein isolate–dextran.NTP has become an emerging technique to treat many high energy radicals,such as atomic oxygen(O),superoxide(O2·^-),nitric oxide(·NO),and hydroxyl radicals(·OH),while the treatment can be fast,nonthermal,operationally flexible,and nonhazardous.During treatment,these obtained particles can break the covalent bonds to trigger various chemical reactions.Therefore,an experiment has been conducted to investigate the effect of NTP treatment time(0、0.5、1.5、2.0、3.0 min)on the glycation of PPI and Dextran(Dex).Under the NTP power of 70 W and solution temperature of 60℃,the Degree of Grafting(DG)of PPI-Dex increased with the extension of NTP treatment time,where the maximum DG of PPI-Dex was 21.62%at 1.5 min.The grafting time of PPI-Dex was greatly reduced,when compared with ultrasonic grafting of 40 min,and the traditional wet grafting of 24 h.After PPI-Dex grafting,there was a remarkable increase in the solubility and emulsification of PPI-Dex conjugates,where the solubility increased by 22.28%compared with that of untreated.A systematic analysis has been carried out to measure molecular weight,amino acid content,infrared spectrum and protein surface hydrophobicity index(Ho),in order to evaluate the effects of NTP treatment on the structure and functional properties of peanut protein.Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis(SDS-PAGE)analysis confirmed the coupling of PPI with dextran to form conjugates.The amino acid content analysis revealed a decrease in the content of lysine and phenylalanine,indicating that lysine and phenylalanine can be involved in glycosylation during NTP treatment.Fourier Transform Infrared(FTIR)showed an increase in the absorption of the characteristic hydroxyl peaks at 3000-3500 cm^-1 and 1000-1260 cm^-1 of PPI-Dex grafts,when NTP treatment time at 1.5 min,compared with that of untreated,and a decrease in the content ofα-helix andβ-sheets,while an increase in the content ofβ-turns.A significant decrease in Ho of PPI indicated the increase of hydrophilicity of PPI surface.This variation in the reaction can attribute to the alteration of PPI structure from compact/hydrophobic to dense/hydrophilic during NTP treatment.When PPI was glycosylated with Dex,the reaction sites can be lysine and phenylalanine.The finding demonstrated that the NTP method can be successfully applied to accelerate the graft reactions of peanut protein isolate for the peanut food production.