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

A stirred column simulating a continuous scraped surface heat exchanger under steady-state conditions was devised and used to study the influence of mechanical mixing, gas input rate and a gas sparger on the foaming capacity of a model food. The bubble size distribution was measured simultaneously. Foaming capacity depended on the number of paddles inside the column and on the gas flow rate. Rotation speed improved the foaming capacity up to 1000 rpm. The average bubble diameter defined as the Sauter diameter was independent of operating conditions. Material balances on the gas phase showed that gas within the foamed product is under pressure so that bubbles increase in diameter when the product is maintained at atmospheric pressure.