I am sitting on a large quantity of oil which I don't want to go rancid. I expect to do a lot of baking this winter, so I was thinking of hydrogenating it. But I've heard that it's hard to do at home and not that good for the health?
Far from it. Don't be put off by what you read in the news about trans fats; when done right, hydrogenation can improve the quality and taste of oil and keep it in a waxy solid form that will last years, even when used daily for deep-frying.
Long a mainstay in the food industry, more and more consumers are choosing to harden their own fat at home, especially with the recession crimping food budgets. Although there are companies and labs that will hydrogenate fats for you, prices vary and you can't be sure that they specialize in culinary hydrogenation -- equipment being used now to hydrogenate a winter supply of oil may have been used for methanol in the spring or petrochemicals in the summer.
At the same time, many hobbyists have found that fat hardening can be a feasible and rewarding weekend project. Not only does DIY save money on by-the-gallon batch jobs, people who have a favorite flavoured oil they don't use every day might opt to harden it into an "heirloom margarine" for special occasions for generations to come.
To turn that messy, unwieldy oil into that beautiful, lustrous hard fat fit for the table or the next batch of melt-in-your-mouth (and only in your mouth) confection, you'll need to pass hydrogen through it at extremely high pressure. The two essential pieces of equipment are a hydrogen tank (here zeppelin hobbyist shops can be a good resource) and a piston compressor that is capable of compressing the gas to 30-40 bar. That may sound like a tall order, but if you live in a university town or larger city, you may be able to scrounge around the academic labs -- also keep your eyes peeled when a university advertises a new equipment procurement; sometimes piston compressors are disposed of.
Some contrarians like the New York Times' Mark Bittman say dihydronaphthalene or dihydroanthracene can be used just as well for hydrogenation, but most feel the pure bottled hydrogen gas gives the best flavour.
When Jamie Oliver "hydrogenates for his mates", he uses a Haug piston compressor with a nickel catalyst. Emeril -- who makes a "Cajun Crisco" from local artisan oils, prefers ruthenium and a much lower pressure. Whichever recipe you try, remember to play it safe. A mass spectrometer, if you have one in your kitchen, can be a good way to check to see if you have hydrogenated the right chemical bonds, and that the output is not toxic. Although it's inevitable that most of the catalysts and residues will end up in your first couple batches, don't be overly worried about these -- just be sure to use them only in lower-fat recipes. Most people find that their second or third batch is already quite successful.
As well as delicious.