Effect of Cloud Particle Characteristics on the Viscosity of Cloudy Apple Juice

GENOVESE, DIEGO B.; LOZANO, JORGE E.

JOURNAL OF FOOD SCIENCE

Blackwell Synergy

Año: 2000 vol. 65 p. 641 - 645

0022-1147

Particle size, shape and volume fraction as well as soluble pectin content and electro-viscous effects on cloudy apple juice viscosity were investigated. Particle characteristics were micrographically determined by electron microscopy. More than 2,300 particles were digitalized and statistically analyzed. Cloudy apple juice resulted in a suspension of irregular shape particles ranging from 0.25 to 5 mm in size. A 10°Brix juice had a particle volume fraction of fo= 3.93 x 10-3. Relative viscosity values were fitted to the generalized Sudduth equation. Intrinsic viscosity resulted 5.8 times greater than the theoretical value predicted by Einstein (a = 2.5). This was attributed to the first electro-viscous effect. Results also indicate that the effect of particle non-sphericity on cloudy apple juice viscosity can be neglected. Soluble pectin was found to significantly increase juice viscosity. Combined effects result in a strong linear increase of intrinsic viscosity.