The neutralisation of acid casein with a twin-screw cooking extruder was studied using sodium bicarbonate as the neutralising agent. The effects of sodium bicarbonate concentration, moisture content in the feed and mass temperature on the properties of the product powder were tested. An NaHCO3 concentration of 4% gave greater expansion ratios than did 2.3 or 6%. Moisture content in the feed in the range 20-30% did not have a significant influence on the expansion ratio but had an effect on the solubility of the ground product. With a moisture content of 20% in the feed and an NaHCO3 concentration of 4% the solubility was 83%, whereas with moisture contents of 23-29° it was 97-100%. The mass temperature had a significantly greater influence on the expansion ratio than did the moisture content. The expansion ratio increased with a decrease of the mass temperature, reaching the highest value at 65-73°C within the range tested. The Iysinoalanine concentration in the product remained low ( < 30 μg/g) with an NaHCO3 concentration of 4%. a mass temperature of 65-93°C and a moisture content of 20-30% in the feed. The ground extrudate had a coarse structure which was less porous than that of spray-dried powders. This gives the product a high particle density and good dispersibility.
|Journal||Lebensmittel-Wissenschaft & Technologie|
|Publication status||Published - 1986|
|MoE publication type||A1 Journal article-refereed|