Chocolate milk with different carrageenans (kappa appa and lambda) and sugar concentrations was heat treated indirectly at 145 degrees C for 6 s using a bench-top UHT plant. The temperature of the milk in the preheating and sterilizer sections, and the milk flow rate were determined to evaluate the overall heat transfer coefficient (OHTC) for monitoring fouling during UHT processing. Kappa-carrageenan was more effective than lambda-carrageenan in providing stability against fouling during UHT processing. By optimizing concentrations of K-carrageenan and sugar, fouling could be minimized during UHT processing. The apparent viscosity and sedimentation of UHT-processed chocolate milk increased with increasing concentration of carrageenan and sugar. (C) 2009 Elsevier Ltd. All rights reserved.