The other day I wrote a post on the subject of the shelf life of cooking oils, since then I have been doing some additional research on this subject and have found some additional useful information.
In a 1999 article Oscar A. Pike, a noted researcher in food storage at BYU (Brigham Young University) published the following information on the shelf life of fats and cooking oils “Cooking oil is very susceptible to deterioration by light, so it is a good idea to store your cooking oil in a dark location”. He then went on to expound on the dangers of temperature on the shelf life.
A more recent study dated 11/11/2010 by Christine Nicole Shearer shows that they may be a correlation between the shelf life of cooking oils and the types of plastic bottles the oils are stored in.
Here is the abstract on her study on the shelf life of cooking oils
Vegetable oil is an important commodity; however, the majority of commercially available vegetable oils have a fairly short shelf life, which limits their usefulness for long term food storage, disaster relief, space travel, food aid programs, and military rations. Vegetable oils with high oleic acid and reduced linolenic acid contents, especially with added antioxidant combinations, were previously found to have significantly longer oil stability index (OSI) values than traditional vegetable oils. This study used accelerated shelf life testing to estimate the ambient shelf life of high oleic sunflower oil (HOSUN) and high oleic canola oil (HOCAN), each containing 1,000 ppm ascorbyl palmitate, 200 ppm tertiary butyl hydroquinone, and 200 ppm mixed tocopherols.
Oils were stored in the dark in low density polyethylene (LDPE), or polyethylene terephthalate (PET) bottles at 30, 40, 50, and 60°C. Control samples were stored in the dark in glass bottles at -50°C. Testing included peroxide values, qualitative headspace volatile analysis, descriptive sensory analysis, and consumer sensory acceptance. The estimated shelf life was calculated from the change in overall acceptance score over time using the Q10 method. The stabilized HOCAN in PET bottles was estimated to have a shelf life at ambient temperature of 6.8 years, while oil stored in LDPE bottles had an estimated shelf life of only 2.7 years. The estimated shelf life of HOSUN at room temperature in PET is 2.6 years and in LDPE is 0.88 years.
Here is a link to the complete study Accelerated Shelf Life Determination of Antioxidant Stabilized High Oleic Sunflower and Canola Oils in Plastic Bottles
Pet bottles have the recycling number 1 and LDPE is number 4. These numbers will be located in a small triangle normally on the bottom of the bottle. However, they will all have it somewhere on the bottle.
Based on this information I will check the recycling number when I purchase cooking oils. Hopefully this will help to improve the shelf life of cooking oils in my storage.
Howard
When I was in Italy I asked my host about olive oil, which is a staple there. He told me that olive oil sold in Italy may ve packaged only in glass bottles, metal tins or PET bottles or jugs. While clear glass or PET is preferred for consumer retail packaging, commercial sized containers used in the food service industry and instiutional users such as schools, hospitals, the prison system and military are always packaged in metal tins, the typical size being a 5L rectangular can with screw cap, plastic pouring spout and handle. Once opened, a 5L tin should be kept in a cool, dark place, not over 30 degs. C, and used within a year. He says that in typical rural Italian households, it would certainly be used within that time.
I wonder if the shelf life increases if the oils are in glass bottles. I have refined walnut oil, purchased in glass bottles. They don’t even seem to have an expiration date on them. So far, I haven’t noticed any rancidity. I didn’t think to date them when I purchased them, so I don’t know how old they actually are, though, either.
Based on a cursory reading of the complete study one might conclude that repackaging the oil you by into dark colored beer bottles (not the screw top kind) might be a good way to store your cooking oils. I gotta think some more about this. I have plenty of bottles, caps, and a capper.
Hangtown Frank
The problem is finding cooking oils in glass bottles. I used to be able to find olive oil occasionally in glass bottles, but everything seems to be in plastic. I’m in Oklahoma. Any suggestions on brands or stores?