Abstract There are five stages in acid coagulation of milk and most studies miss out on a stage or two depending on the experiments performed. Dielectric studies of milk and various physico-chemical studies on the formation of yogurt are well studied and established. However, most of the papers deal with either a limited range of frequencies in the dielectric studies and hence are unable to reflect all the mechanisms of coagulation that occur, or are done as stand-alone experiments, with no correlations to other physico-chemical processes. In this paper, we discuss the broadband dielectric spectroscopy of lactic-acid coagulation of milk, identify the various stages, and compare it with pH, zeta potential, particle size and microscopy. We establish the superiority of dielectric spectroscopy in the identification of all stages of coagulation, the indifference of the process to fat content. Further a strong correlation between tan δ and pH is seen, that is an indicator of the five different stages of lactic-acid induced coagulation. Penetration depth is calculated as milk coagulates and it is seen to be decreasing with coagulation. Broadband dielectric spectroscopy is seen to reveal the onset of coagulation much earlier than other experimental techniques discussed here.

中文翻译：

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介电光谱法在鉴别牛奶乳酸凝固各个阶段开始的有效性

摘要 牛奶的酸凝过程有五个阶段，根据所进行的实验，大多数研究会错过一两个阶段。牛奶的介电研究和酸奶形成的各种物理化学研究都得到了很好的研究和确立。然而，大多数论文要么涉及介电研究中有限的频率范围，因此无法反映发生的所有凝结机制，要么作为独立实验完成，与其他物理化学过程没有相关性. 在本文中，我们讨论了牛奶乳酸凝固的宽带介电光谱，确定了各个阶段，并将其与 pH 值、zeta 电位、粒度和显微镜进行比较。我们确立了介电光谱在识别凝固所有阶段的优越性，该过程对脂肪含量的冷漠。进一步观察到 tan δ 和 pH 值之间的强相关性，这是乳酸诱导凝血的五个不同阶段的指标。渗透深度是在牛奶凝固时计算的，并且可以看到它随着凝固而减少。宽带介电光谱被认为比此处讨论的其他实验技术更早地揭示了凝血的开始。