OIL REFINING
In the processing of food oils and fats from animal, vegetable and marine sources, it is important to produce edible oil and fat products that have a bland, neutral taste for several months after processing. To obtain an oil with these characteristics, it is essential to remove compounds that give flavor to the oil as well as compounds that are detrimental to oxidative stability. It is also desirable to significantly reduce, if not eliminate, chemical contaminants such as PCBs and pesticides.

The concentrations of objectionable compounds vary in the different oils, depending on the source. Many of the common vegetable oils contain phosphatides, colored compounds and their breakdown products, oxidation products of triglycerides, dissolved and suspended proteinaceous material, free fatty acids, pesticides, pro-oxidant metals and pesticides. Oils derived from marine sources, mammalian and fish, are very low in phosphatides and may be low in colored compounds, but proteinaceous and mucilagenous materials, breakdown products from triglyceride oxidation, and concentrations of calcium and magnesium and pro-oxidant metals are more significant, as well as pesticides. Most importantly, these oils are more sensitive to oxidative deterioration because of the highly unsaturated fatty acids present. They also contain only insignificant amounts of natural antioxidants, such as the tocopherols that are present in significant amounts in most vegetable oils. The oils of marine origin also have a very intense fishy odor and taste, which originates with protein, mucilage and triglyceride breakdown products. The odor and taste compounds and their precursors must be removed to extremely low levels to make the oil more suitable for food uses and to improve their flavor stability after processing.

BLEACHING
The seal oil is treated with a adsorptive clay for the removal of peroxides, trace heavy metals (Cd, Hg, As & Pb), colour bodies and traces of protein from the oil. An acid pretreatment is done to aid in the removal of trace metals. The acid used here is citric acid. Activated carbon is used in conjunction with bleaching clays. Activated carbon possesses an extremely high surface area. Because of this, they are used to remove high-molecular weight contaminants from oil. The activated carbon that we use is design to remove PCB, Dioxins and Furans from a oil.

DEODORIZATION
The bleached seal oil is subjected to sparging with steam at high temperature and low pressure to remove odoriferous components, pollutants, flavour components, and additional free fatty acids. Colour is also reduced by heat bleaching at elevated temperatures where the carotenoid pigments and other colorized compounds either break down or are evaporated. Deodorization is a mass transfer purification process, where the oil is exposed to surface condition (temperature and vacuum) forcing the volatiles into a vapour state. Deodorizing condition normally involve exposing a thin film of oil to a carrier gas (steam or nitrogen) at an elevated temperature and low absolute pressure. The carrier gas carries the volatiles from the deodorizer to the vapour recovery system. We deodorize seal oil at 258 - 262°C, minimal retention time and sparge steam addition of 1%. We need to deodorize seal oil at this high temperature because we have to remove pollutants (Dioxins, Furans, PCB and Organochlorinr Pesticides) to WHO specification. These pollutants are more volatile at higher temperature and vacuum. This is why we deodorizer the oil at 260C with a absolute pressure of <3.0 mmHG. After deodorization, the seal oil exceeds WHO specification for Dioxins, Furan and Dioxin like PCBs. Seal oil contains a high concentration of long chain polyunsaturated fatty acid, we have minimal retention time to minimize the damage to these fatty acids.