MECHANICAL ASPECTS OF GAS DISPERSION IN CONTINUOUS FOAMING FOOD PROCESSES USING SCRAPED SURFACE HEAT-EXCHANGERS

A stirred column simulating a continuous scraped surface heat exchange r under steady-state conditions was devised and used to study the infl uence of mechanical mixing, gas input rate and a gas sparger on the fo aming capacity of a model food. The bubble size distribution was measu red simultaneously. Foaming capacity depended on the number of paddles inside the column and on the gas flow rate. Rotation speed improved t he foaming capacity up to 1000 rpm. The average bubble diameter define d as the Sauter diameter was independent of operating conditions. Mate rial balances on the gas phase showed that gas within the foamed produ ct is under pressure so that bubbles increase in diameter when the pro duct is maintained at atmospheric pressure.