PARTICLE-SIZE DISTRIBUTION IN TOMATO CONCENTRATE AND EFFECTS ON RHEOLOGICAL PROPERTIES

The particle size distribution of a tomato concentrate was determined by wet sieving. Wet sieve fractions were then investigated by microsco py and a method based on laser diffraction. Both methods showed that t he size of many particles was considerably larger (up to two to three times) than the diameter of the pores through which they have passed d uring wet sieving. This was explained by the deformability of the toma to cell wall. Effects of particle size distribution on rheological pro perties were studied by standardizing wet sieve fractions (dry matter, pH). Highest values for yield stress and apparent viscosity were foun d for the 90-125 and 125-180 mu m wet sieve fractions.