Biopolymer nanoparticles can be formed by heating globular protein/polysaccharide mixtures above the
thermal denaturation temperature of the protein under pH conditions where the two biopolymers are
weakly electrically attracted to each other. In this study, the influence of polysaccharide linear charge
density on the formation and properties of these biopolymer nanoparticles was examined. Mixed
solutions of globular proteins (b-lactoglobulin) and anionic polysaccharides (high and low methoxyl
pectin) were prepared. Micro-electrophoresis, dynamic light scattering, turbidity and atomic force
microscopy (AFM) measurements were used to determine the influence of protein-to-polysaccharide
mass ratio (r), solution pH, and heat treatment on biopolymer particle formation. Biopolymer nanoparticles
(d < 500 nm) could be formed by heating protein–polysaccharide complexes at 83 C for 15 min
at pH 4.75 and r ¼ 2:1 in the absence of added salt. The biopolymer particles formed were then subjected
to pH and salt adjustment to determine their stability. The pH stability was greater for b-lactoglobulinHMP
complexes than for b-lactoglobulin-LMP complexes. The addition of 200 mM sodium chloride to
heated complexes greatly improved the pH stability of HMP complexes, but decreased the pH stability of
LMP complexes. The biopolymer particles formed consisted primarily of b-lactoglobulin, which was
probably surrounded by a pectin coating at low pH values. AFM measurements indicated that the
biopolymer nanoparticles formed were spheroid in shape. These biopolymer particles may be useful as
delivery systems or fat mimetics.