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.

中文翻译：

---

使用直接和间接加热系统进行不同温度和时间条件对牛奶质量影响的中试研究

使用直接和间接加热系统进行中试，研究了不同加热温度（124、129、134、140 或 143 °C）和保持时间（1 和 4 秒）对牛奶质量的影响。在直接和间接加热中都观察到维生素降解，并且降解随着温度和保温时间的增加而增加，但是，在加热系统之间没有看到差异。直接加热时，pH 略有增加，钙离子减少。直接加热会导致脂肪球尺寸和聚集体形成增加，并且随着温度升高效果更显着。生产当天牛奶的物理稳定性不受影响；然而，储存 28 天后，间接加热的不稳定性更加明显。没有观察到加热系统对颜色的影响。这表明加热可能会影响牛奶质量，但是，对于所研究的质量参数，直接加热和间接加热之间没有观察到明显差异。