Handbook of Functional Lipids

refining) (see Figure 5.2). Refined oil is dried and bleached with activated clay to remove
color pigments and residual soap. Bleached oils are then deodorized by steam distillation
to eliminate odorous components. When the soybean oil is of good quality and the free
fatty acid (FFA) content is low, the oil can be physically refined. Physical refining
involves water washing to recover lecithin followed by phosphoric acid pretreatment
and bleaching to remove the nonhydratable gum (primarily phospholipids). After
bleaching, the oil is steam deodorized to remove the FFA. The RBD oil is used to
produce various finished products (e.g., salad and cooking oils, shortenings, and mar-
garine). Some of the finished products also require the oil to be hydrogenated, which
changes the consistency and solid content of the oil and increases stability to oxidation,
which extends the shelf life of the finished products. Also, some of the oils (e.g.,
cottonseed and sunflower) are winterized to remove the higher melting constituents or
wax. The solid fraction removed from winterization can be used in confectionery
products; the winterized oil is less likely to become cloudy in refrigerated storage.

5.2.1 P

REPARATION

FOR

XTRACTION

5.2.1.1 Storage

For optimum extraction and quality of oil, the oil-bearing material should be stored
at dry and relatively low temperature. If it is wet, it should be processed as soon as
possible after harvest. Oils in the presence of water can deteriorate rapidly due to

FIGURE 5.2

Flow diagram of edible oil processing.

Caustic Solution

Acid Activated Clay

Winterization

STEARINE

Winterization

Deodorization

Blending

SHORTENING

MARGARINE

RBHWD

(SALAD OIL)

Hydrogenation

SPENT CLAY

SOAPSTOCK

DEGUMMED OIL

Add Water/

Centrifuge

LECITHIN or

PHOSPHATIDES

DEODORIZER

DISTILLATE

DEODORIZER

DISTILLATE

DEODORIZER

DISTILLATE

Deodorization

RBWD

(SALAD OIL)

CRUDE OIL

Centrifuge

REFINED OIL

Filtration

BLEACHED OIL

Deodorization

RBD OIL

(COOKING OIL)

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