Microcapsules based on glycinin–sodium dodecyl sulfate complex coacervation

Microcapsules processed by complex coacervation were prepared using hexadecane for the oil phase and glycinin (a soybean storage protein)-sodium dodecyl sulfate (SDS) as the main wall-forming material. The study underlines the essential role of SDS, which, by the way of [glycinin(+)-SDS(-)] insoluble complex formation, allowed the precipitation of proteins around oil droplets. Moreover, particular attention was attributed to the study of suitable conditions of glycinin cross-linking with glutaraldehyde. The reticulation step was performed at pH 4.0 and it was observed that the precipitated state of proteins increased considerably the efficiency of the cross-linking reaction. Analysis of the reactional medium after each main step of the process (emulsification, complex coacervation, cross-linking) allowed the follow-up and characterization of microcapsule formation. Optimization of different process parameters such as glycinin concentration, glycinin/SDS/glutaraldehyde ratios, pH and the kinetics of cross-linking allowed the encapsulation of the totality of oil and the use of more than 98% of initially introduced proteins for the microcapsule wall formation.

Characterisation and foaming properties of hydrolysates derived from rapeseed isolate

Two hydrolysis methods used to obtain rapeseed isolate derivates were compared: chemical hydrolysis performed under alkaline conditions and pepsic proteolysis performed under acidic conditions. The mean molecular weights obtained for the hydrolysates varied from 26 to 2.5 kDa, depending on the level of hydrolysis. Further characterisation showed that, at the same level of hydrolysis, the chemical hydrolysates differed by their charges and hydrophobicity from those derived from enzymatic digestion. Analysis of the foaming properties showed, for both cases, that a limited degree of hydrolysis, around 3%, was sufficient to optimise the foaming properties of the isolate despite the different physicochemical properties of the peptides generated. The study of foaming properties at basic, neutral and acidic pHs showed that the hydrolysate solutions yielded dense foams which drained slowly and which maintained a very stable volume under the three pH conditions tested.

Soy glycinin microcapsules by simple coacervation method

Encapsulation of a dispersed oil phase (hexadecane) was realized by simple coacervation method using soy glycinin as the wall forming material. Suitable emulsification and coacervation conditions, that favor the formation of microcapsules wall, were identified and investigated. Mild acid (pH 2.0) and heat (55 degrees C) treatments of the reaction medium during the emulsification step enhanced significantly the deposition of coacervated glycinin around oil droplets. A pronounced correlation between glycinin concentration in the continuous phase, specific surface of the dispersed phase and the microencapsulation efficiency was also observed. Coacervation step study concerned the morphology and the stability of microcapsules. Controlled initiation of the coacervation, by slow readjustment of the pH, allowed a homogeneous precipitation of glycinin around oil droplets as well as the absence of aggregation phenomena. Since the morphology of microcapsules was considerably affected by a prolonged stirring of the reaction medium, the coacervation and reticulation time were optimized in order to preserve the homogeneity of the microcapsules size distribution and the microencapsulation efficiency.