Food Lipids: Chemistry, Nutrition, and Biotechnology

for problematic high wax contents (0.2–3.0%) and must undergo dewaxing; occasionally
canola oil also has wax problems.
Waxes can be removed by cooling the oil to 6–8�C and filtering or centrifuging
at cold temperatures, a process similar to winterization (described in more detail in
Sec. IV.B) [52]. To get wax crystals large enough to ease separation, cooling must
be done slowly over 4 hours, and the crystals should be allowed to mature for another
6 hours [40]. The oil is then carefully heated to 18�C and filtered.
Sometimes, dewaxing is accomplished simultaneously with removing the gums
and/or soapstock by carrying out the centrifugation at cool temperatures. Sunflower
seed oil is often predewaxed (from 1500 to 400 ppm) by cooling to 25�C for 24
hours and then degumming with a centrifuge at this temperature. Alternatively, sunflower
seed oil may be simultaneously dewaxed and alkali-refined. After neutralization,
as already described, the oil–soapstock mixture is cooled to 5–8�C and held
there for 4–5 hours under gentle mixing; then the oil is mixed with 4–6% of water
heated to 18�C. The soapy water phase wets and causes the small wax crystals to
form a heavy suspension in soapy water. The soapy suspension is centrifuged to
produce a wax/soapstock fraction and a refined, dewaxed oil [40]. Sometimes sodium
lauryl sulfate is added to help wet the crystals [53].
H. Deodorization
The final step in refining fats and oils is deodorization (Figs. 18 and 19). Oils that
are converted by a variety of processes are done so before deodorizing. The primary
objective of deodorization is to remove compounds responsible for undesirable odors
and flavors, such as residual free fatty acids (especially low molecular weight fatty
acids), aldehydes, ketones, and alcohols. Deodorization also removes peroxide decomposition
products; freshly deodorized oil should have a perioxide value of zero
and free fatty acid content of