Elucidating causes of fouling of canned black coffee manufacturing equipment

Fouling of processing equipment remains a crucial challenge in canned black coffee manufacturing. In this study, a small flow-type heat exchanger was developed to simulate stain formation on stainless steel surfaces. Effects of coffee pH (5.4-6.6) and processing temperatures (30-85°C) on deposition behavior were examined. Fourier transform infrared spectroscopy indicated that the stain consisted mainly of calcium phytate. Hydrophilic interaction liquid chromatography was used to quantify calcium phytate deposition, which varied significantly with temperature and pH. Deposition was markedly higher at pH 5.7 (85°C) and pH 6.2 (60°C), whereas no detectable deposition was observed at pH 5.5 and 30°C. The non-monotonic dependence on pH and temperature suggested that fouling was governed by a balance between surface-mediated nucleation and growth of calcium phytate crystals and bulk crystallization followed by crystal deposition. These findings provided a mechanistic basis for fouling control in coffee and other phytate-containing food processing systems.