【作者】 Nasir Mehmood Khan；

【导师】 木泰华；

【作者基本信息】 中国农业科学院 ， 农产品质量与食物安全， 2013， 博士

【摘要】 在中国,甘薯淀粉加工过程中会产生大量的废水,从废水中回收蛋白质既能实现经济效益,又能解决环境污染问题,因此越来越受到广泛的关注。甘薯蛋白(SPP)是甘薯淀粉加工后废水的主要成分,甘薯蛋白极富营养价值,它的氨基酸组成均衡、功能性质良好。研究表明SPP可作为功能性添加剂应用于食品产品的开发。为此,利用超高压技术对SPP进行适当结构修饰可增强SPP的功能性质,扩大其在食品行业的应用范围。本文研究了超高压处理(HHP)对不同浓度2%、4%和6%的SPP理化性质和乳化特性的影响。当压力从200MPa上升到600MPa时,SPP的疏水性、变性焓和溶解性会产生明显的改变(P<0.05)。当压力为400MPa时,SPP-2和SPP-6的乳化活性指数(EAI)升高；而在压力为600MPa时,所有SPP的乳化活性都显著下降(P<0.05)。当压力大于200MPa时,SPP-2和SPP-6的乳化稳定性显著下降,而SPP-4的乳化稳定性增加(P<0.05)。随着压力的升高,相比于SPP-4和SPP-6,SPP-2乳化剂的粘度急剧下降。Sporamin A和Sporamin B均被加压SPP乳化剂较好的吸收。这些结果显示HHP处理可以改变SPP的理化特性和乳化特性。本文还探讨了pH在3,7,8三个水平时HHP对SPP乳化剂理化性质的影响。在不同pH值条件下经过HPP处理后,不同乳化剂乳化活性指数(EAI)和乳化稳定性(ESI)都显著升高(P<0.05)。当压力从200MPa上升到600MPa时,油滴尺寸明显降低,而体积较小油滴的分布频率明显提升；pH为3、7、8的乳化体系中界面蛋白浓度也明显升高。在非还原条件下,pH为7的由SDS-PAGE组成的乳化体系中产生了由二硫键连接的高分子量聚合物。600MPa的超高压降低了流动指数,导致所有SPP乳化剂的水相粘度升高。pH为3和7时,经过和不经过HHP处理,SPP乳化剂都会剪切变释,而pH为8的乳化剂受到200MPa和400MPa的高压处理时则显示出牛顿流体的特性。结果表明,HHP处理所得的稳定乳化剂在食品行业中有广泛的应用前景。表面疏水性在pH为3时显著升高,而在pH为6和9时下降(P<0.05)。随着压力的增大,pH为6时乳化剂的EAI明显上升；在pH为6和9时乳化剂的ESI明显更高(P<0.05)。当pH为3和6的乳化剂经超高压处理时,会使体积较小油滴的分布频率升高,而油滴尺寸则明显下降。在pH为6和9时,经HHP处理的SPP乳化剂的粘度升高,但所有利用HHP处理的SPP乳化剂产品的假塑性均未改变。结果显示HHP能够改变SPP的结构使其具有更好的乳化性能,从而扩大其在食品行业的应用范围。相比于SPP凝胶模型,瓜尔胶中存在的SPP经HHP处理后乳化稳定性提高,乳化率降低,粘度明显提高。另外,GMS则对SPP的乳化能力产生负面影响,对乳化剂的稳定性、乳化率和粘度均产生不良影响。结果表明,HHP是改良瓜尔胶中SPP乳化能力的可靠方法。更多还原

【Abstract】 The production of proteins from sweet potato starch wastewater has attracted attention in China due to of its economic benefits and due to environmental concerns. Sweet potato protein (SPP) is one of the major components of starch wastewater generated from the processing of sweet potato starch and has nutritional benefits, a balanced amino acid composition and good functional properties. The study has shown the potential of SPP as a functional additive during food product development. Hence, the appropriate structure modification of an SPP by high hydrostatic pressure (HHPs) might lead to suitable functional properties, which could increase the applications of SPP in the food industry.The influence of high hydrostatic pressure (HHP) treatment on the physicochemical and emulsifying properties of sweet potato protein (SPP) at various concentrations, e.g.2%,4%and6%(w/v, SPP-2, SPP-4and SPP-6), was investigated. Significant differences in the hydrophobicity, enthalpy of denaturation and solubility were observed when the pressure was increased from200to600MPa (P<0.05). The emulsifying activity indexes (EAI) of SPP-2and SPP-6increased at400MPa, whereas the EAI of all SPP significantly decreased at600MPa (P<0.05). Emulsion stability (ESI) was significantly decreased for SPP-2and SPP-6, while increase in ESI was observed for SPP-4above200MPa (P<0.05). SPP-2emulsions showed sharp decrease in apparent viscosity with increase in HHP compared to SPP-4and SPP-6, while pseudo plastic flow behaviour were not changed for all of emulsions produced with HHP treated SPP. Sporamin A and sporamin B were well adsorbed in pressurised SPP emulsion without displacement. These results suggest that HHP treatment could be used to modify the physicochemical and emulsifying properties of SPP, depending on protein concentration and the pressure applied.The effect of high hydrostatic pressure (HHP) treatments on the physicochemical properties of sweet potato protein (SPP) emulsions at three pH values (3,7and8) was investigated. The emulsifying activity index (EAI) and the emulsifying stability index (ESI) of all emulsions at the different pH values were significantly increased by the HHP treatments (P<0.05). The oil droplet sizes were significantly decreased, whereas the volume frequency distribution of the smaller droplets was markedly increased when the pressure was increased from200to600MPa (P<0.05). A significant increase in the interfacial protein concentration in the pH3,7and8emulsions was observed when the pressure was increased from200to600MPa (P<0.05). Under non-reducing conditions, higher molecular weight aggregates formed by disulfide bonds were observed in the pH7emulsions by SDS-PAGE. However, HHPs did not change and/or displace the main electrophoretic bands of SPP. The600MPa HHP decreased the flow indices, which resulted in an increase in aqueous phase viscosity in all the SPP emulsions. The SPP emulsions had shear-thinning behaviors at pH3and7with and without HHP treatment, whereas a Newtonian behavior was observed in the pH8emulsion subjected to the200and400MPa treatments. These results suggest that HHP-treated emulsions stabilized by SPP could have various applications in the food industry. The CD analysis confirmed the modification of SPP secondary structure. Surface hydrophobicity was increased significantly (P<0.05) at pH3and decreased at6and9. Emulsifying activity index (EAI) at pH6was significantly increased with increase in pressure, whereas emulsifying stability index (ESI) values were significantly higher at pH6and9(P<0.05). The oil droplet sizes were significantly decreased, while the volume frequency distribution of the smaller droplets was increased for pH3and6with HHP treatment. Emulsion viscosity of HHP treated SPP were increased at pH6and9and pseudo plastic flow behaviours were not altered for all of emulsions produced with HHP treated SPP. These results suggest that HHP could be applied to modify SPP structure for better emulsifying properties, which will increase the use of SPP emulsion in food industry.SPP in presence of guar gum with HHP treatment increase the stability of emulsions decreased the creaming rate and improve in apparent viscosity compared to the control SPP-hydrocolloids model (0.1MPa). The GMS at another hand showed negative effect on the emulsifying efficiency of SPP and showed poor stability, creaming rate and viscosity of emulsions. These results suggest that HHP is reliable method for modification of emulsifying efficiency of SPP in the presence of guar gum.更多还原