Well Jason my boy, you`ve opened a can of worms here. Geeeze, it's only been six months since you asked this question. I'd like to have a crack at the answer anyway. I'm surely no expert, but shucks, you can always throw tomatoes at me if you don`t like my answer.
Deterioration of lipids has always been a significant problem in the storage of oils and fats wherever sausage makers are concerned. I wonder how much has been thrown out and just how many folks have been sickened by the degradation process in lipids. The natural process of decomposition or degradation, has often been called rancidity
and is the hydrolysis
(or both) of oil or fat. The increase of rancidity is associated with by a discernible increase in the acid value of fat, normally tested using two basic laboratory tests: Peroxide Value
(PV) and Anisidine Value
Reacting with air or moisture (and/or other elements), the process of degradation converts fatty acid esters of oils into free fatty acids. Triglycerides
(95 percent of all dietary fats), are included and are naturally occurring esters of three fatty acids and glycerol. By the way, doctors will tell you that heart attack victims have high triglycerides... but will not say that those having high triglycerides will have heart attacks.
Some oils, such as conjugated linoleic acid (CLA) or saw palmetto, are naturally high in free fatty acids. The degradation of these lipids become so severe, that they eventually reach the point of becoming either unpalatable or unhealthy to ingest, indeed being linked with the development or. Ingestion of rancid lipids has been linked to the development or intensification of such diseases as atherosclerosis, cataracts, diarrhea, kidney disease and heart disease. Worse, they can cause cellular membrane damage, neurodegeneration, and carcinogenesis.
Ok pard, which of the oils would you think would turn rancid more quickly? Believe it or not, vegetable oils tend to be less stable and turn rancid more quickly than do animal fats. Not only that but they can also become several times more rancid
than animal fats. Almost unbelievably this may occur before the human sense of smell can detect it! Unsaturated fats are more susceptible to oxidation than are saturated fats. This means that the more polyunsaturated a fat is, the sooner it will become rancid. Why? It`s due to having more unstable double bonds
, which allow more oxygen to react at those points. Now any cowboy worth his salt would say, "that`s catawampously exfluncticatin"!
Oils slowly become more oxidized over time - they don`t suddenly become rancid. And just what causes rancidity in stored edible oil? If it is oxidative the process is known as autoxidation and it occurs when oxygen is absorbed from the environment. Also, in the presence of UV (ultraviolet radiation), most lipids will break down, degrade, and form other compounds. Ok, now get this... oxygen is eight times more soluble in fats than it is in water.
No kidding! This exposure is the main cause of the autoxidation process, increasing the saturation of the oil.
If the rancidity is hydrolytic rather than oxidative, the process is called hydrolysis
or "enzymatic oxidation
" and it occurs in the absence of air yet having moisture present. This is normally accomplished through something the big guys call "enzymatic peroxidation
Wow, did you get that? Oh, stop worrying. It just means that it takes place where enzymes
are found naturally in plant oils. Examples are lipoxygenase
. In animal fats, the enzyme lipase
may catalyze reactions between water and oil.
Whoa hoss! There`s one more degradation process - microbial rancidity
. This process takes place whenever micro-organisms such as bacteria, molds and yeast use their enzymes to break down chemical structures in oil, producing unwanted odors and flavors. Sound familiar sausage makers? Do you remember Brocotrix Thermosphacta
? In this type reaction, water needs to be present for microbial growth to occur.
What controls the speed and severity of the degradation or "rancidity" processes? It all depends upon elements of nature including temperature, time, light, water, and catalysts. Light? Yes, in the presence of oxygen, light promotes oxidation of unsaturated fatty acids. And what catalysts? Hmmmm, that would be trace metal ions, metalloproteins, and inorganic salts. You know... "catalysts"
How does it all take place? Lipid peroxidation, the oxidative deterioration of unsaturated fatty acids, occurs in three phases
. The first, "induction
" phase takes place when unsaturated fatty acids combine with molecular oxygen to produce hydroperoxides and peroxyl free radicals - both highly unstable and most reactive. Next, "propagation
" takes place where these unstable free radicals react with other lipids to initiate a continuing "free radical lipid peroxidative chain", if you will. Whew! This is autoxidation and results in a continuing or cyclical oxidative degradation process, breaking down the lipid.
Are you following me Jason? Pay attention!
Quiz at 5:30! C'mon... There`s only one more process to go.
The final phase is "termination
" and it`s recognized by the slowing and stoppage of the other reactions, completing the formation of unreactive compounds such as amides, aldehyedes, hydrocarbons, alcohols, keytones, etc., whenever an antioxidant is either added or encountered.
Ok, it gets a little "hinky" from here. BTW, did you see "The Fugitive"? Tommy Lee Jones (Inspector Girard) told Cosmo that he wouldn`t talk to anyone who used the word "hinky
Anyway for further information about primary oxidation byproducts, including peroxides (ROO) and hydroperoxides (ROOH) or secondary oxidation products occurring when ROOH further degrades into other substances, I recommend a qualified course of study. This is where the stuff becomes volatile, including various acidic compounds. Interesting stuff in all. Over time, these compounds have been known to start fires upon reaching "auto-ignition" temperature and condition. In other words, clean up all your old messes and rags!
A completely separate topic may be mentioned here. It is how to measure rancidity. Again, a course of study would reveal measurements incorporating units of milliequivalents (meq), normally reported as millimole (mmol) of hydroperoxide. Yikes! Did you get that? The boys who discuss that stuff won`t even speak to me! What the heck - my horse won`t speak to me either. Come to think of it, some of those boys remind me of the back end of my hoss!