I recently wanted to know how long it takes for vegetable oil to be shipped to a store. I was unable to find and confirm the ‘year’ fact that I had previously read but I did find a fascinating if kind of gross look at vegetable and animal fat shipping on the high sea on this blog.
I did not realize that a third of all of the chemical tanker trade is in shipping vegetable oils. It might comfort readers to know that chemical tanker captains are pretty concerned to keep oils and fats at the right temperatures for shipping. Not necessarily for the quality of the oil and the safety of the people who eat it, although that comes into it, but because the the ship itself can be damaged if the oil gets too hot or too cold. Oils that have cooled too far and solidified will not come out of a ship and the whole thing will have to be scrapped. Oils that get too hot will start fires and kill crew members.
Still, contamination and oxidation are always an issue. In fact the author basically says contamination is almost unavoidable. “It is quite probable that some residue from the previous cargo can remain in the tank and it’s associated pipework after cleaning and also may be absorbed onto the tank bulkheads.” What else do tankers carry? Anything liquid: gasoline, crude oil, herbicides, pesticides, fertilizers, even food byproducts such as corn syrup.
The captain goes on to say that there are international and country laws that regulate what can and cannot be carried as cargo on a tanker before a cargo of food grade fat is carried. These are known allergens and other substances known to be hazardous to human health. Still considering what has been said above I have to wonder how long allergens and hazardous substances persist in these large tanks and if one or two changes of cargo are really going to make that big of a difference to the transfer of contaminants into food grade oils.