A pilot scale study on the effects of various temperature and time conditions on milk quality using direct and indirect heating systems

Abstract

Effects of various heating temperatures (124, 129, 134, 140 or 143 °C) and holding times (1 and 4 s) on milk quality using direct and indirect heating systems at pilot scale were investigated. Vitamin degradation was observed for both direct and indirect heating and the degradation increased with increasing temperature and holding time, however, no difference could be seen between heating systems. Slight increase in pH and decrease in ionic calcium for direct heating occurred. An increase in fat globule size and aggregate formation were noted for direct heating with more pronounced effects with increasing temperature. Physical stability of milk was unaffected on day of production; however, after 28 days of storage instability was more apparent for indirect heating. No effect of heating system was observed on colour. This suggests that heating may influence milk quality, however, no clear differences between direct and indirect heating were observed for the quality parameters investigated.