Degradation of methylcellulose during ultra-high pressure homogenisation

Initially developed for the dairy industry, the very high pressure homogeni sation (>100 MPa) is now also applied in the pharmaceutical sector and in b iotechnology (breaking cells for biomass extraction). The use of this techn ology to make fine food emulsions and to modify functional properties of ma cromolecules seems to be promising. Thus the objective of this study was to understand the effect of homogenisation forces on the mechanical degradati on of a model polymer extensively used in food, cosmetic and pharmaceutical preparations: the methylcellulose. Degradation of the polymer was studied in a pressure range in the homogenising valve from 20 to 350 MPa. It was ob served that as the pressure imposed by the homogeniser increased, the intri nsic viscosity decreased. Intrinsic viscosity decrease was correlated to ap parent changes in the average molecular weight of the polymers obtained by size exclusion chromatography coupled on-line with multiangle laser light s cattering and refractive index detection (SEC/MALLS/RI). The strong elongat ional flow encountered by the polymer at the entrance of the valve of the h igh pressure homogeniser device may bring sufficient energy to disrupt cova lent bonds. Consequently, as shown by flow behaviour the thickening propert ies of this polymer were also reduced. (C) 2001 Published by Elsevier Scien ce Ltd.