Palm thermal bleaching

Timms (21) has heat of fusion to 17.7-22.3 kcal/kg for milkfat, 24-31 kcal/kg for fully hardened milkfat, 26-29 kcal/kg for cocoa butter in the p polymorph, 22.6 kcal/kg for refined, bleached, and deodorized (RBD) palm oil, 29.7 kcal/kg for RBD palm kernel oil, 26.0 kcal/kg for RBD coconut oil, 31.6 kcal/kg for fully hardened palm kernel oil, and 31.2 kcal/kg for fully hardened coconut oil. The heat of fusion is an empirical physical property dependent on the thermal history or tempering of the oil. 

Bleaching by thermal degradation with distillation of the breakdown products is a feature of the modern process. Loncinera/. (1971) showed that the carotene content of palm oil is reduced after 40 min at 240 °C to 1% of the starting level. However, they also reported that a crude oil stored for 7 days at 75 °C in an oxygen atmosphere yielded a product of colour 3.3 Red and 35 Yellow (Lovibond SVa inch cell), whereas the colour of the control product was 1.6 Red and 18 Yellow. 

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