Functional properties esterification

Functional properties of proteins are closely related to their size, structural conformation, and level and distribution of ionic charges. Chemical treatments, which could cause alteration of these properties, include reactions that either introduce a new functional group to the protein or remove a component part from the protein. Consequently, reactions such as acylation, phosphorylation, esterification, glycation, limited hydrolysis, and deamidation have been used to impart improved functional properties to the dairy proteins. 

Improvement of functional properties of milk proteins by esterification... 

As natural milk proteins have acidic isoelectric points, they have low solubility at acid pH and this compromises many of their functional properties in acidic environments. Esterification of proteins increases the net negative charge and raises the isoelectric point of proteins, making them more functional at acidic pHs. 

This selective review, which deals primarily with the chemical modification of soy proteins, is further limited to nondestructive chemical reactions which alter physical and biochemical properties of importance in food systems. Soy protein products have been modified by various chemical reactions including (a) treatment with alkalies and adds, (b) acylation, (c) alkylation and esterification, and (d) oxidation and reduction. In most instances these reactions have been applied to heterogeneous protein mixtures containing nonprotein impurities, and often to proteins of unknown prior history. Nonetheless, these reactions indicate that protein functional properties of value in food fabrication can be altered significantly through reaction with chemical reagents. It is recognized that chemically modified proteins must be critically evaluated for food safety. 

Over the last two decades, there has been an increasing interest in the industrial use of plant proteins for non-food applications because of their renewabiUty or biodegradability Plant proteins ve thus been used for the fabrication of materials such as films and coatings, adhesives, thermoplastics and surfactants. However, for many applications, it is necessary to confer and/or to improve some specific properties by chemical modification of the native proteins. Particularly, the esterification of their carboxyl and amide groups by a fatty alcohol (Fig 1) could lead to a protein-derivative with improved functional properties. Such modification would result into a lower water sensitivity of the protein-based products and it would therefore offer... 

EsterificaticMi with a fatty alcohol modified the functional properties of proteins, particularly their solubility in alkaline water. For wheat gluten and sunflower esterified proteins, solubility at basic pH decreased compared to native proteins, indicating thus a hydrophobation effect Fig 4 shows the effect of esterification on solubility of sunflower proteins. The solubility of unmodified sunflower proteins increased significantly in alkaline media and... 

Proteins valorization as thermoplastic or thermosetting materials has been performed by chemical modifications [212]. Improved functional properties can be obtained by esterification of protein carboxyl and amide groups by fatty alcohol that lead to a protein-derivative with improved functional properties which would result into a lower water sensitivity. For example sunflower and wheat gluten have been esterified by octanol in the presence of an acid catalyst. Esterified protein result less soluble at basic pH compared to native proteins, indicating a hydrophobation effect [213]. 

The degree of esterification largely influences the functional properties solubility, gel formation and gel properties. 

Stewart" proposed a parallel between the rate of esterification of 2-substituted benzoic acids and the molecular weights of the substituents. The nitro group deviated strongly from this relationship. It is the first work to attempt to relate the steric effect of a group to some property that might at least in part be a measure of size. Kindler made the first attempt at defining a set of steric parameters. These parameters were later shown to be a function of electrical effects. The first successful parameterization of the steric effect is due to Taft, who defined the steric parameter Es for aliphatic systems by equation 27 ... 

Finally, Lecomte and coworkers reported the synthesis of mikto-arm star-shaped aliphatic polyesters by implementing a strategy based on click chemistry (Fig. 36) [162]. Firstly, the polymerization of sCL was initiated by a diol bearing an alkyne function. The chain-ends were protected from any further undesired reaction by the esterification reaction with acetyl chloride. The alkyne was then reacted with 3-azidopropan-l-ol. The hydroxyl function located at the middle of the chain was then used to initiate the ROP of sCL and y-bromo-s-caprolactone. Finally, pendant bromides were reacted successfully with sodium azide and then with N, N-dimethylprop-2-yn-l-amine to obtain pendant amines. Under acidic conditions, pendant amines were protonated and the polymer turned out to exhibit amphiphilic properties. 

Reactivity of Functional Groups. The reactivity of the functional groups of liquid prepolymers significantly affects the processing, cure behavior, and the ultimate mechanical properties of the cured binder and propellant. The reactivity of carboxyl groups of CTPB can be determined by the rate of reaction with n-butyl alcohol. The rate of esterification is measured from the rate of water evolution from the alcohol—carboxylic acid reaction, and a plot of water evolved vs. time then permits the calculation of the corresponding rate constants. 

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