Funcitonal Properties Improvement Of Black Kidney Bean Proteins By PEGylation And Reduce Of Lectin Allergencity

In the present study,PEG-BKBPIs and PEG-LCs were prepared by PEG chemical modification using black kidney bean protein isolate(BKBPI)and lectin(LC).The functional properties and allergenicity of the BKBPI were studied before and after PEG modification.The effects of PEG-SPA with different molecular weights on the functions of lectin were analyzed.And the conditions for the PEG-SPA modification were optimized.Finally,the stability of the LC and PEG-LC was further evaluated.The main contents and results are as follows:1.Functional properties and allergenicity changes of BKBPI were investigated before and after PEGylation.The PEG modification of BKBPI was analyzed by TNBS method and infrared spectroscopy,and the functional properties and allergenicity changes of BKBPI before and after PEG modification were determined.TNBS and infrared spectroscopy analysis demonstrated that BKBPI could be modified by PEG-SC,PEG-SPA and PEG-SS effectively,and-CONH-might be the PEG conjugation bond.The solubility,fat-binding compacity,emulsifying compacity,emulsifying stability,foaming capacity,foaming stability,thermal stability and digestion stability were all improved.The hemagglutinating activity as well as allergenicity of BKBPI were significantly decreased after the PEG modification.Furthermore,the results suggested that PEG-SS and PEG-SPA might be more useful in the PEGylation of BKBPI.2.Gel properties of BKBPI were studied before and after the PEG modification.The influence of different concentration of NEM,Na CL and pre-heating on the gel ability of BKBPI was analyzed by a rheometer.Results showed that after PEGylation of BKBPI,the gelation concentration decreased from 80 to 75 mg/m L,and the gel strength significnalty increased,while the time required for gel formation was shortened.The addition of salt and NEM in the protein solution facilitaed the gelation of BKBPI and PEG-BKBPIs.When Na CL concentration reached 1.0 mol/L,the gel of BKBPIs was weakened.Moreover,after BKBPI and PEG-BKBPIs were pre-heated,the gel strength increased at least 116%.3.Effects of different molecular weight PEG-SPA modifications on LC were investigated.Different molecular weight(5 K,10 K,20 K)PEG-SPA were used as PEG modifiers of PEGylation on LC,and the protein structure and biological activity of LC before and after PEGylation were studied.The results have shown that molecular weight PEG-SPA modification did not significantly affect the secondary and tertiary structure of LC.No obvious difference was observed in the affinity activity of specific sugar for the LC and PEG-LCs,but the coagulation activity and allergenicity of PEG-LCs decreased significantly by more than 50% compared with those of LC,And the PEG-SPA(20 K)might be an effective modification on improve the safety of BKBPI.4.The modification conditions using PEG-SPA for LC were optimized.PEG-SPA(20 K)was selected as the chemical modifier according to the above sutdy.PEGylation degree and the activites of the modified products were chosen as indicators.The study indicated that the best modification reaction conditions were as follows: LC and PEG-SPA were mixed in a molar ratio of 1:10,and the reaction was at p H 7.0 and 24 ℃ for 2 h.5.The difference between the stability of LC and PEG-LC was further investigated.The native and PEG-SPA-modified LC were subjected to different acid-base treatments,heat treatments,in vitro digestion and storage experiments,respectively.The results showed that the biological activity,secondary structure and tertiary structure of LC and PEG-LC changed significantly only at p H 2.0,and remained stable under other p H conditions.Heat treatment above 80℃ destroyed the structure and biological activity of LC and PEG-LC.PEG-LC exhibited higher stability under acid,alkali,and heating treatments.Both LC and PEG-LC were digested in the simulated gastric phase,and remained stable in the simulated pancreatic phase.PEG-LC was more difficult to be digested.After a storage period of 30 days,the maximum particle sizes of protein aggregations of LC and PEG-LC were 1400 and 619 nm,respectively,and LC appeared to aggreate earlier compared with PEG-LC(within 48 h).Therefore,PEG-LC had a better storage stability.