Removing environmental contaminants:comparing multi-stage thin-film evaporation with gas stripping and short-path distillation

摘要

Most edible oils undergo four basic processing steps:refining/neutralization,bleaching,winterization,and deodorization(O'Brien et al.,2000).The last step,deodorization,is basically a stripping process that uses steam to remove undesirable odors or flavors along with other impurities,such as peroxides,carboxylic compounds,and free fatty acids(FFAs).Deodorization also partially removes environmental contaminants and destroys color compounds,which has somewhat of a bleaching effect on the oil.Depending on the type of oil being processed,most deodorizers operate at temperatures above 200°C,and pressures between 2 and 5 torr.FFAs are typically reduced to 0.2 to 0.5% by weight,but this also varies based on the type of oil.Desirable compounds,such as tocopherols and other antioxidants,are also removed.Deodorization can reduce the content of tocopherols in the final RBD(refined,bleached,and deodorized)oil by as much as 60%(Norris,1985).Typically,a small amount of tocopherols is added to the final product to prevent oxidation after deodorization.