Indirect and direct heating are common technologies used in the dairy industry especially for UHT milk. Often direct heating is chosen to keep sensitive ingredients more intact while ensuring sufficient microbial inactivation as a result of its ‘shorter and higher’ time–temperature profile. A view on the technical principles of these processes exposes further differences, resulting namely from mixing of product and steam, hydrodynamic forces, removal of gasses and volatiles, product dilution and fouling. The implications of these on design of processing units and their impact on milk constituents is discussed along with the gaps.

中文翻译：

---

牛奶的直接和间接加热——超越时间-温度曲线的技术视角

间接和直接加热是乳制品行业使用的常用技术，尤其是 UHT 牛奶。通常选择直接加热以保持敏感成分更完整，同时确保充分的微生物灭活，因为其“更短和更高”的时间-温度曲线。对这些工艺技术原理的看法揭示了进一步的差异，即产品和蒸汽的混合、流体动力、气体和挥发物的去除、产品稀释和结垢。这些对加工单元设计的影响及其对牛奶成分的影响与差距一起讨论。