Guest guest Posted June 23, 2002 Report Share Posted June 23, 2002 A few times people have mentioned oils going rancid. I've got a question about topical application of oils. I've used almond oil on myself and kids during the winter months. Its just in a plastic bottle in the bathroom. It doesn't have any " smell " to make me think its bad, but its been there over a year. Is it rancid? If so, is there a shelf life of different oils? How about the olive, sesame, safflower oils in my cupboard. How long do they last? Should I be refrigerating them? Thanks for your input. Braun @... Quote Link to comment Share on other sites More sharing options...
Guest guest Posted June 24, 2002 Report Share Posted June 24, 2002 Here is some info from the Spectrum Naturals website. It comes from the FAQ and Vegetable Oil Terminology in the Natural Food Industry under Oil Facts on the Spectrum Naturals page. www.spectrumnaturals.com Do Oils Go Rancid? Oils spoil (become rancid) after prolonged contact with oxygen, light, and/or heat. You can identify a rancid oil by its unusually strong odor and sharp or bitter flavor. The off-odors are gases produced by the reactive fatty acid molecules; it's nature's way of letting you know the oil is past its prime. Spoilage in refined oils is harder to detect because these oils have had their flavor and odor bodies removed. This makes refined oils far less susceptible to damage from light, heat or oxygen exposure. Although their shelf-life is long (usually 24-30 months), deterioration can occur. Certainly, if you notice an unpleasant odor or flavor in a refined oil, it is a sign of rancidity. To protect your oils from spoilage, store them in a cool, dry place, out of harsh light. Alternatively, keep the oils you use daily in the refrigerator (note that to dissolve the solids in cold, unrefined oils, you can just set the bottle in a bowl of warm tap water). Freezing is a good way to extend shelf life, especially with the super-reactive supplement oils (with essential fatty acids) sold in plastic containers. Be careful, however, if you store glass bottles in the freezer, because the glass will become fragile. It's also wise to purchase oils in small sized bottles, because fresher oils are healthier oils. Some Oils Need Lots of Shelter Proper packaging by the manufacturer and careful storage at home are both important to preserve nutrients and prevent rancidity in oils. Heat, oxygen, and light are the most common damaging elements for vegetable oils. The more natural an oil, the more protection it needs. Oils properly sealed in glass containers, without oxygen trapped at the top (oxygen initiates deterioration), are quite stable until opened. Breaking the seal allows atmospheric oxygen to begin breaking down the oil. You can slow this process dramatically by refrigerating your oils once you've opened them. Light can damage unrefined oils by reacting with chlorophyll and other bioactive components in the oil. Light-induced deterioration, combined with oxidation, can rapidly affect the status of Vitamin E, carotenes (Vitamin A precursors), and other nutritive components of an oil. So, even if an attractive label tempts you to keep a bottle of oil on the counter, remember that it's best to keep the oil in the dark. Refined oils, however, are far less susceptible to light-induced damage. Rigorous protection is necessary for the nutrient-rich, super-sensitive supplement oils, which is why Spectrum Essentials Veg-Omega 3 Flax Oil and other Spectrum Essentials products are sold in opaque, air-tight and light-protected packages. Storage Guide To safeguard the nutritive value and longevity of your oils, keep them in a cool (40? F to 72? F), dark cupboard until opening, and then store them in your refrigerator. Storage under these conditions provides a shelf life of 10-14 months for unrefined oils, and 14-20 months for refined oils. Freezing can extend an oil's shelf life. Spectrum Essentials packages supplement oils in plastic bottles to give you this option (but be careful if you try freezing oil in glass bottles. To protect Veg-Omega 3 Oil in capsules, Spectrum Essentials uses gelatin coating that provides nearly seed-like protection for the oil. Again, refrigeration is not required but does improve shelf life. Oxidation Oxidation is a chemical reaction involving the combination of single oxygen molecules randomly drawn from the atmosphere and combined with a reactive triglyceride molecule. Spoilage usually results from oxidative stress in foods. In oils, rancidity results in the formation of peroxides as a consequence of the free radical phenomena. Peroxidized levels past 100 megs/per kg are declared rancid by Department of Agriculture standards, and are a fraction of that level in supplement oils (usually not exceeding 5.0 PV in super unsaturated fatty acids). On the other hand, olive oil, which is deemed marketable at a starting PV of 20 experiences high levels of peroxide formation and still can be considered safe and edible. Prior to being at a PV level of 20, the oil is considered immature and green. Peroxide values vary dramatically with different types of oil. The oil's intrinsic stability properties determine what the safety levels are. Sesame contains sesamin and sesamol, two very strong inhibitors which keep this oil naturally stable for very long periods of time. It is impossible to apply one standard for all oils as oils have very different properties, with different natural compounds that affect stability, taste and utility. Each oil has to be measured and tested on its own merits. Peroxide Number (PV) Peroxide value is a measure of the extent of oxidative absorption and entrainment of oxygen in a fat or oil. To properly interpret PV's, the age and handling history of the fat or oil must be known as peroxide values rise and fall on a bell curve with absorption and remission of oxidative levels in the oil, depending on the age of the oil. High peroxide usually indicates high degree of oxygen absorption. This value coupled with high free fatty acid (FFA) values indicates increased rancidity. If the value starts low, goes high and drops, and the second benchmark value continues to increase, the oil has become or is fully rancid and inedible. Peroxides can be lowered by reaction to bleaching, deodorization and alkali refining steps. Photon Decay Light is a form of energy and imparts chemical reactions in oils. Unrefined oils are more light sensitive as the chromaphores (color bodies) convert light/oxygen into free radicals through chlorophyll synthesis which is still active in the unrefined oil. This action continues to create lipase reactions and the ensuing breakdown product creates off flavors. Ketones, aldehydes and acetones are breakdown products producing off flavors in vegetable oils. The free radical process is most identified with light or photon decay and oxygen. Free radical formation is present throughout the process of decay and occurs as either alpha or beta types of oxidation. Alpha oxidation is oxygen drawn from the atmosphere, beta oxidation occurs from the entrained oxygen that is systematically present and produces reactions in the oil even while completely protected from outside influences such as heat, light and atmospheric oxygen. Long chained essential fatty acids are especially prone to light sensitivity and heat damage. Fully refined oils do not have the same potential because the trigger mechanisms of the chromaphores (color bodies) have been removed. Increasing free radical synthesis occurs with natural pigments in the oil. Refined oils have few or none and therefore have a much longer shelf life as compared to an unrefined pigment rich oil. Rancidity Rancidity is characterized by the development of off flavors, odors and colors. Rancidity in oils will usually result in a gag reflex if consumed by humans. Rancid oils have a bitter, high acrid after-taste which is easy to distinguish. Oxidative and hydrolytic stress also breakdown oils and speeds rancidity. Rancidity is measured as PV 100 meg/kg of sample tested. Quote Link to comment Share on other sites More sharing options...
Guest guest Posted July 7, 2002 Report Share Posted July 7, 2002 Thank you! ----- Original Message ----- From: Food From Afar Sent: Monday, June 24, 2002 8:02 AM Subject: RE: rancid oils Here is some info from the Spectrum Naturals website. It comes from the FAQ and Vegetable Oil Terminology in the Natural Food Industry under Oil Facts on the Spectrum Naturals page. www.spectrumnaturals.com Do Oils Go Rancid? Oils spoil (become rancid) after prolonged contact with oxygen, light, and/or heat. You can identify a rancid oil by its unusually strong odor and sharp or bitter flavor. The off-odors are gases produced by the reactive fatty acid molecules; it's nature's way of letting you know the oil is past its prime. Spoilage in refined oils is harder to detect because these oils have had their flavor and odor bodies removed. This makes refined oils far less susceptible to damage from light, heat or oxygen exposure. Although their shelf-life is long (usually 24-30 months), deterioration can occur. Certainly, if you notice an unpleasant odor or flavor in a refined oil, it is a sign of rancidity. To protect your oils from spoilage, store them in a cool, dry place, out of harsh light. Alternatively, keep the oils you use daily in the refrigerator (note that to dissolve the solids in cold, unrefined oils, you can just set the bottle in a bowl of warm tap water). Freezing is a good way to extend shelf life, especially with the super-reactive supplement oils (with essential fatty acids) sold in plastic containers. Be careful, however, if you store glass bottles in the freezer, because the glass will become fragile. It's also wise to purchase oils in small sized bottles, because fresher oils are healthier oils. Some Oils Need Lots of Shelter Proper packaging by the manufacturer and careful storage at home are both important to preserve nutrients and prevent rancidity in oils. Heat, oxygen, and light are the most common damaging elements for vegetable oils. The more natural an oil, the more protection it needs. Oils properly sealed in glass containers, without oxygen trapped at the top (oxygen initiates deterioration), are quite stable until opened. Breaking the seal allows atmospheric oxygen to begin breaking down the oil. You can slow this process dramatically by refrigerating your oils once you've opened them. Light can damage unrefined oils by reacting with chlorophyll and other bioactive components in the oil. Light-induced deterioration, combined with oxidation, can rapidly affect the status of Vitamin E, carotenes (Vitamin A precursors), and other nutritive components of an oil. So, even if an attractive label tempts you to keep a bottle of oil on the counter, remember that it's best to keep the oil in the dark. Refined oils, however, are far less susceptible to light-induced damage. Rigorous protection is necessary for the nutrient-rich, super-sensitive supplement oils, which is why Spectrum Essentials Veg-Omega 3 Flax Oil and other Spectrum Essentials products are sold in opaque, air-tight and light-protected packages. Storage Guide To safeguard the nutritive value and longevity of your oils, keep them in a cool (40? F to 72? F), dark cupboard until opening, and then store them in your refrigerator. Storage under these conditions provides a shelf life of 10-14 months for unrefined oils, and 14-20 months for refined oils. Freezing can extend an oil's shelf life. Spectrum Essentials packages supplement oils in plastic bottles to give you this option (but be careful if you try freezing oil in glass bottles. To protect Veg-Omega 3 Oil in capsules, Spectrum Essentials uses gelatin coating that provides nearly seed-like protection for the oil. Again, refrigeration is not required but does improve shelf life. Oxidation Oxidation is a chemical reaction involving the combination of single oxygen molecules randomly drawn from the atmosphere and combined with a reactive triglyceride molecule. Spoilage usually results from oxidative stress in foods. In oils, rancidity results in the formation of peroxides as a consequence of the free radical phenomena. Peroxidized levels past 100 megs/per kg are declared rancid by Department of Agriculture standards, and are a fraction of that level in supplement oils (usually not exceeding 5.0 PV in super unsaturated fatty acids). On the other hand, olive oil, which is deemed marketable at a starting PV of 20 experiences high levels of peroxide formation and still can be considered safe and edible. Prior to being at a PV level of 20, the oil is considered immature and green. Peroxide values vary dramatically with different types of oil. The oil's intrinsic stability properties determine what the safety levels are. Sesame contains sesamin and sesamol, two very strong inhibitors which keep this oil naturally stable for very long periods of time. It is impossible to apply one standard for all oils as oils have very different properties, with different natural compounds that affect stability, taste and utility. Each oil has to be measured and tested on its own merits. Peroxide Number (PV) Peroxide value is a measure of the extent of oxidative absorption and entrainment of oxygen in a fat or oil. To properly interpret PV's, the age and handling history of the fat or oil must be known as peroxide values rise and fall on a bell curve with absorption and remission of oxidative levels in the oil, depending on the age of the oil. High peroxide usually indicates high degree of oxygen absorption. This value coupled with high free fatty acid (FFA) values indicates increased rancidity. If the value starts low, goes high and drops, and the second benchmark value continues to increase, the oil has become or is fully rancid and inedible. Peroxides can be lowered by reaction to bleaching, deodorization and alkali refining steps. Photon Decay Light is a form of energy and imparts chemical reactions in oils. Unrefined oils are more light sensitive as the chromaphores (color bodies) convert light/oxygen into free radicals through chlorophyll synthesis which is still active in the unrefined oil. This action continues to create lipase reactions and the ensuing breakdown product creates off flavors. Ketones, aldehydes and acetones are breakdown products producing off flavors in vegetable oils. The free radical process is most identified with light or photon decay and oxygen. Free radical formation is present throughout the process of decay and occurs as either alpha or beta types of oxidation. Alpha oxidation is oxygen drawn from the atmosphere, beta oxidation occurs from the entrained oxygen that is systematically present and produces reactions in the oil even while completely protected from outside influences such as heat, light and atmospheric oxygen. Long chained essential fatty acids are especially prone to light sensitivity and heat damage. Fully refined oils do not have the same potential because the trigger mechanisms of the chromaphores (color bodies) have been removed. Increasing free radical synthesis occurs with natural pigments in the oil. Refined oils have few or none and therefore have a much longer shelf life as compared to an unrefined pigment rich oil. Rancidity Rancidity is characterized by the development of off flavors, odors and colors. Rancidity in oils will usually result in a gag reflex if consumed by humans. Rancid oils have a bitter, high acrid after-taste which is easy to distinguish. Oxidative and hydrolytic stress also breakdown oils and speeds rancidity. Rancidity is measured as PV 100 meg/kg of sample tested. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You are posting as a guest. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.