报告题目：Fragmented protein as Potential Steric Stabilisers and Emulsifiers in Food Colloid based Formulations 

                   碎片蛋白可作为食品胶体制剂中潜在的立体稳定剂和乳化剂

主 讲 人 ：Rammile Ettelaie博士  英国利兹大学

报告时间：2019年4月9日（周二）上午10:00

报告地点：下沙校区食品学院257学术报告厅

报告人简介

Rammile Ettelaie于1987年在英国曼彻斯特的理论凝聚态物理研究所（Theoretical Condensed Matter Physics）获得博士学位，现任职于英国利兹大学食品物理化学方向副教授；1987-1989年作为博士后研究科学家在帝国学院（Imperial College）中央电力研究实验室从事博士后研究；1989-1993年和1993-2001年分别在ICI公司胶体科学集团、威尔顿中心任高级研究科学家。2001年起在利兹大学任教，历任食品物理化学的讲师、食品化学物理高级讲师。2013年至今为食品化学物理副教授。Rammile Ettelaie教授曾是液体和复杂流体物理研究所（IOP）指导委员会成员（2001-2010）和英国皇家化学会胶体与界面科学组委员（1999-2006）。

报告摘要

Animal proteins, in particular milk-based proteins, remain the obvious emulsifiers of choice in many food emulsion formulations.  However, the increasing use of such proteins in other industries (e.g., adhesives), high costs associated with the production of animal-based proteins and the increasing preference of consumers for phasing out of certain animal products, all necessitate the development of edible, non-animal-based alternatives. Vegetable proteins, due to their rather globular and aggregated nature are not particularly efficient emulsifiers.  Furthermore, the sequence of hydrophobic and hydrophilic amino acids in vegetable proteins is often far from that expected for an ideal emulsifier or a good colloid steric stabiliser.   

It has been suggested that while native vegetable proteins may not be suited to emulsification, certain sections of such proteins may have much more favourable primary structures for this purpose.  However, the initial costs of developing the required biotechnology for producing (via selective proteolysis) and isolating such polypeptides is very high, especially given the large combinations of polypeptide fragments possible.  Thus, there is a need to pre-select and focus experimentation on a few potentially the most promising polypeptides.  To this end, we have used the Self-Consistent-Field methodology, frequently used in the fields of polymer Physics and Chemistry, to select and study the surface properties of polypeptides that in principle could be produced from various sources.  Such calculations not only provide information on the efficiency of adsorption but also the thickness and extent of the adsorbed layer.  Furthermore, it is possible to calculate the strength and the nature of interaction forces between emulsion droplets arising from the overlap of the polypeptide layers on the droplet surfaces.    

We demonstrate the principles here by comparing the surface adsorption and colloidal steric stabilising properties of a polypeptide fragment, which potentially is derivable from hydrolysis of “Soybean β-Conglycinin alpha Prime Homotrimer” protein, with that of the milk protein s1-casein.  This plant polypeptide consists of 145 amino acid residues and was deliberately chosen due to its structural resemblance to as1-casein. We find that surface properties of the fragmented protein are indeed very similar to as1-casein at appropriate pH values relative to the iso-electric point (pI) of each respective protein (The pI of the plant polypeptide is close to 7.7, whilst that for as1-casein is close to 4.6).  This potentially allows the plant protein to provide better emulsion stabilising properties than as1-casein at the relatively low pH range between 4 to 5, which is often desirable in foods.