Comparison of polysaccharide degradations by dynamic high-pressure homogenization A. Villay a , F. Lakkis de Filippis b , L. Picton b , D. Le Cerf b , C. Vial a , P. Michaud a, * a Clermont Université, Université Blaise Pascal, Laboratoire de Génie Chimique et Biochimique, Polytech’ Clermont Ferrand, 24 avenue des Landais BP 206, 63174 Aubière cedex, France b Université de Rouen, Laboratoire Polymères, Biopolymères, Surfaces, CNRS-UMR 6270 & FR3038, 76821 Mont Saint-Aignan, France article info Article history: Received 15 July 2011 Accepted 5 October 2011 Keywords: High-pressure homogenization Polysaccharide Critical overlap concentration abstract The mechanical degradation of polysaccharides was investigated using dynamic high and ultra-high- pressure homogenization (HPH). The objectives were to reduce the molar mass of polymer chains, and simultaneously, the apparent and intrinsic viscosity of polysaccharides in solution. The influence of homogenization pressure (up to 200 MPa) and cycles was compared on polysaccharides with different physical and structure properties: namely, guar gum, hydroxyethylcellulose (HEC), sodium carboxy- methylcellulose (Na-CMC), sodium alginate (Na-alginate) and gum arabic. HPH was applied on semi- dilute solutions. The apparent changes in molar mass, gyration radius and intrinsic viscosity were deduced from size exclusion chromatography coupled on-line with multi-angle laser light scattering, differential viscometer detector and differential refractive index detector (SEC/MALS/DV/DRI), while the evolution of the critical overlap concentration (C * ) was obtained by viscosimetry. A method based on a succession of homogenization cycles and polymer pre-concentration steps was developed to determine the minimum molar mass achieved at constant pressure. Molar mass, and intrinsic viscosity were shown to fall simultaneously while logically C * increased during HPH for all polysaccharides, except gum arabic, probably because of its globular and branched structure. This highlights that the differences of poly- saccharide structures and conformation (linear, branched.) exhibit a stronger impact on HPH treat- ments than polymer charge or molar mass. Finally, via an empirical approach linking the decrease of both molar masses and viscosities, we have evidenced a specific scaling exponent that should characterize the flexibility of the treated polymer (i.e. its ability to be degraded by HPH). Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Polysaccharides are defined as polymers of monosaccharides linked by glycosidic bonds and exhibiting a degree of polymeriza- tion higher than 10. These macromolecules, reaching sometimes several millions of Da, present a large structural variability and have been described as composed of neutral (pentoses and hexoses) and/or anionic monosaccharides (uronic acids) substituted or not by non-sugar compounds. For example, they may exhibit homo- polymeric or heteropolymeric structures and linear or ramified conformations. These features lead to specific behaviours and different architectures in solution, resulting in spirals, sheets, and also single, double and triple helices (Rinaudo, 2004; Sutherland, 2007). The molar-mass distribution of polysaccharides is the primary parameter that influences directly their physicochemical properties in solution, such as apparent viscosity. This is the reason why many attempts to make the molar-mass distribution of poly- saccharides more uniform and to control their average molar mass have been developed in the recent literature. These are based on the degradation of polysaccharides; the most popular of them are, namely, enzymatic, chemical and physical methods. First, polysaccharide lyases and hydrolases (Cantarel et al., 2009) have been successfully used to depolymerize polysaccharides with a high level of specificity (Akpinar, Erdogan, & Bostanci, 2009; Kashyap, Vohra, Chopra, & Tewari, 2001; Vishu Kumar, Gowda, & Tharanathan, 2004). These techniques are simple but often limited by the commercial availability of enzymes, their cost and their sensitivity to denaturation. Chemical degradations after acidic and alkaline treatments or free radical mechanisms have also been frequently described for the preparation of oligosaccharides and low-molar-weight polysaccharides (Guilloux, Gaillard, Courtois, Courtois, & Petit, 2009; Jinglin, Shijun, Fengmin, Sun, & Yu, 2009; Rota et al., 2005). For example, acidic hydrolysis led to the effec- tive degradation of polysaccharides, but generated a large amount * Corresponding author. Tel.: þ33 (0)473407425. E-mail address: philippe.michaud@univ-bpclermont.fr (P. Michaud). Contents lists available at SciVerse ScienceDirect Food Hydrocolloids journal homepage: www.elsevier.com/locate/foodhyd 0268-005X/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodhyd.2011.10.003 Food Hydrocolloids 27 (2012) 278e286