Winterization

Winterization is the refining step that pulls traces of waxes and higher-melting glycerides — stearin — out of fats and oils, keeping them clear and pourable under refrigeration. Waxes drop out with rapid chilling and filtration, while stearin needs very slow cooling so its crystals grow large enough for filtration or centrifugation to catch. Cottonseed and groundnut oils are winterized into salad oils that stay liquid and brilliant at low temperatures, while winterizing tallow and other animal fats allows the simultaneous production of oleo fractions alongside harder fats. Cooling profiles and filtration efficiency decide the clarity, and winterized oil is the standard for dressings and cold-use applications.