【作者】 刘岩；

【导师】 赵谋明；

【作者基本信息】 华南理工大学 ， 食品科学， 2011， 博士

【摘要】 热压榨花生粕(或脱脂花生粉)是花生榨油的副产物,其中含有43.7 %的粗蛋白,由于花生蛋白在压榨过程中变性严重,溶解性大幅降低,导致蛋白提取率下降,功能特性缺失,限制了其在食品体系中的应用。本文旨在通过物理或酶解手段,改善花生粕中热变性蛋白的溶解性及其它功能特性,探索适用于热压榨花生粕蛋白资源利用的途径。花生仁经历高温干热/湿热处理和常温脱脂后制备花生分离蛋白,研究了加热方式及不同热处理时间对其物化及功能特性的影响。由SDS-PAGE和DSC分析可知,花生球蛋白组分比花生伴球蛋白组分更加耐热;高温处理显著降低了花生脱脂粉中蛋白的回收率(p < 0.05),但所制备的花生分离蛋白在pH7.0左右的溶解性随加热时间延长而升高,其等电点随加热时间的延长向酸性偏移;花生仁经150℃干热处理60 min后,其制备的花生分离蛋白样品的乳化活性显著高于未变性的花生分离蛋白(p < 0.05),105℃湿热处理使花生分离蛋白的乳化特性降低,加热至135min,其起泡能力与未变性分离蛋白无显著差别(p > 0.05)。采用碱溶酸沉法从花生粕中提取分离蛋白,探讨了超高压微射流不同的均质压力(80 MPa,100 MPa,120 MPa,140 MPa,160 MPa)对其结构和功能特性的影响。随均质压力的增加,花生分离蛋白的乳化性、起泡性和凝胶性均有不同程度的增加(p < 0.05),微射流均质120 MPa为改善花生分离蛋白功能特性的最优条件,尤其凝胶特性提高显著,与未经微射流处理的空白对照相比,其热诱导凝胶的弹性模量(G′)从5 Pa增加至4700 Pa左右;在此均质压力下,分离蛋白具有较高的自由巯基含量和较低的变性焓值。探讨了高温强碱处理对花生粕蛋白提取率及其功能特性的影响。结果表明:高温强碱处理能够改善花生粕蛋白的溶解性,进而提高其蛋白回收率,同时显著改善其分离蛋白的功能特性。通过对高温强碱促提分离蛋白工艺的优化,其提取率由19.9 %增至54.8 %,且蛋白纯度可高达91.2 %,制备的花生粕分离蛋白的功能特性(溶解性、乳化性和起泡性)显著优于未变性花生分离蛋白和大豆分离蛋白(p < 0.05)。采用Alcalase、Protamex或Papain对花生粕蛋白限制性酶解处理,再经碱溶酸沉提取制备花生浓缩蛋白,研究了蛋白酶种类及其水解度对花生粕蛋白提取率及其制备的花生浓缩蛋白功能特性的影响。结果表明,蛋白酶优先水解花生粕中不可溶蛋白部分,由SDS-PAGE图谱可知,花生球蛋白的酸性亚基相对于球蛋白碱性亚基更易被酶解;当水解度(DH)为1.0 %时,经Alcalase酶解后制备的浓缩蛋白提取率达到最高值,约44.0 %,并表现出最优的持水性,达6.2 mL/g;当DH 8.0 %时,经Protamex和Papain酶解后制备的花生浓缩蛋白具有最高的乳化活性指数(EAI),分别为140 m2/g和160 m2/g;相对于未经酶解处理的花生浓缩蛋白,三种蛋白酶制备的浓缩蛋白起泡特性均有显著改善(p < 0.05)。以Alcalase、Protamex或Papain对花生粕蛋白限制性酶解处理,离心后上清液直接冻干制备花生蛋白粉,其纯度较低,但蛋白利用率高,Alcalase酶解产物的蛋白回收率最高,可达81.1 %;三种蛋白酶制备的花生蛋白粉,乳化活性由高到低分别为:Protamex > Papain > Alcalase;Alcalase和Protamex的酶解产物的起泡特性都有显著改善(P < 0.05)。更多还原

【Abstract】 In China, most of the defatted peanut flour (DPF), a by-product containing 47–55 % protein, are underutilized in developing countries and only used for animal feed, due to the poor functional properties caused by heat denaturation. The aim of the present study was to modify heat peanut meal protein by enzymatic hydrolysis and physics for improving its functional properties and extending utilization. Physics and hydrolysis modifications were used to modify DPF for improving its functional properties. Main results are as follows:Comparison of the dry roasting and moist heat treatments on peanut protein isolate (PPI) the impact of structural and functional properties. The results showed that the proportion of conarachin in PPI was decreased with heat time and arachin was more heat resistant than conarachin. Heat aggregation or breakdown of arachin during roasting after 30min. Roast and moist heat treatments both decreased sharply the quantity of extractable protein in defatted flour but increased significantly protein solubility of PPI in pH 7.0; the isoelectric point of peanut protein isolate shifted to acidic pH compared with control. The emulsifying properties of PPIs decreased toward 15 min and then increased; moist heat treatment from 0min to 75 min resulted in a decrease in EAI and ESI, while an increase was observed after 75 min. All of samples (including control) could not form the strong gells. On the moist heat treatment samples, the value of foaming capability was increased towards 75 min then decreased. However, for foaming stability, the value first showed a decrease, then an increase.Optimal conditions of heat and alkali extraction of peanut protein, yield of peanut protein was 54.83 %. Compared functional properties of extracted peanut protein, nature peanut protein and Commercial soy protein isolate, the solubility, emulsifying properties and foaming properties of peanut meal protein are significantly better than the other two proteins.The effects of microfluidization on functional properties as well as conformational properties of PPI were investigated by solubility and emulsifying properties, foaming properties, gel properties, DSC, free sulfhydryl and far-UV CD. When the pressure is 120 MPa, the microfluidization led to dissociation of insoluble aggregates, thus improved NSI, EAI and FA of PPI. Free sulfhydryl and far-UV CD spectrum analyses showed that both the tertiary conformation and the secondary structure of the proteins in PPI were nearly unaffected by the microfluidization treatment. DSC analysis indicated the microfluidization-treated PPI samples presented similar Td andΔH, relative to that of untreated PPI.Four proteases (alcalase, protamex, pancreatin and papain) were used to hydrolyze heat peanut meal and hydrolytic conditions were optimized. When using protamex to hydrolyze the heat peanut flour, its hydrolysate was modified slightly. The hidrolysate just had a little of low-molecular weight of peptide and most was large-molecular weight of peptide. Compared to the control, the hydrolysates of protamex just had little change of its structure. Hydrolysate of other three enzyme had large change of theirs structure and all had much low-molecular weight peptide. After hydrolyzing, the heat denaturation peanut flour protein which had no sensitive to heat was sensitive to heat. For the function characteristic, some was improved. All the hydrolysates’solubility were over 80 %, and was just little less than the control. Except the hydrolysate of papain, all the hydrolysate had improvement in foamability and the maximum was 140 % which was four times to the control. Although all the hydrolysates’foam stability was over 80 %, it was still little lower than the control. Hydrolysates of protamex whose hydrolysis degree was under 3.4 % and hydrolysates of trypsin whose hydrolysis degree was under 1.76 % had improvement on the emulsibility. But the emulsion stability was worse than the control.Peanut protein concentrate (PPC) was extracted from commercial defatted peanut flour (DPF), a severely denatured byproduct, by combined protease pretreatment and alkali solution with isoelectric precipitation. The effect of proteolysis by Alcalase, Papain and Protamex at various degree of hydrolysis (1-8 % DH) on the yield and functional properties of PPC were investigated. Alcalase was the most efficient protease for hydrolyzing of DPF, followed by Protamex and Papain. Proteolysis remarkably increased the nitrogen solubility of DPF in acidic and basic condition. Enzymatic degradation of acidic subunits (AS) of denatured and insoluble arachin was mainly responsible for the increase of nitrogen solubility index (NSI). Compared with the control, the yield of PPC was significantly increased by enzymatic pretreatment. In terms of the functional properties, PPCs prepared by Papain and Protamex at 4 % or 8 % DH were considered good emulsifiers with emulsifying activity index (EAI) larger than 120 m2/g. For all three enzymatic treatments, foaming capacity (FC) and foaming stability (FS) were significantly improved at various DH (p < 0.05). Alcalase treatment at 1 % DH could remarkably enhance water holding capacity (WHC) to 6.2 mL/g. This study demonstrated that the PP-ASIP method could be a highly effective way to obtain PPC with good functional properties from denatured DPF.更多还原