Like oxidation, thermal failure results in a change in oil color, although typically early thermal failure causes a color change sooner than oxidative failure. The color change is due to the formation of carbon and oxide insolubles - chemical by-products of base oil breakdown, which are suspended in the oil. A number of tests including a simple patch test using a 0. FTIR is also an effective tool for providing an early warning sign, or for confirming active thermal degradation.
However, because few oxygenated by-products are formed in early stage thermal failure, looking at the characteristic cm-1 region is unlikely to show problems.
Instead, the focus should be around the to cm-1 region of the spectrum Figure 4. In this region, the by-products of thermal base oil degradation, specifically nitrogenous molecules, adsorb. Peaks in this region are often referred to as FTIR nitration peaks. A significant increase in the FTIR nitration region can point toward thermal failure as the dominant mechanism of base oil degradation. In some circumstances, where thermal heating is severe and prolonged, such as in heat transfer oils and quench oils, the base oil molecules can experience thermal cracking.
Perhaps more useful is a slightly more sophisticated test termed gas chromatography GC. While GC has many and varied uses in oil analysis, GC is perhaps most useful in its ability to separate similar molecules like hydrocarbon oil molecules based on their molecular size. A gas chromatogram from a thermally cracked oil would hence show a higher than normal level of light-end fractions smaller sized molecules in the degraded oil, compared to a new oil chromatogram.
Beyond mineral oils and SHCs, there are many different types of base oils, from vegetable-based oils such as canola and soybean oils, to phosphate ester , polyol ester, diesters, polyalkylene glycols and silicone fluids. While the chemical structure and mechanism of degradation will vary based on environmental stressing factors, hydrolysis is perhaps the most noteworthy degradation pathway.
Hydrolysis is simply the chemical reaction of the base oil molecule with water. Ester type base oils are perhaps most prone to hydrolysis. Their ester chemical linkages make them potentially susceptible to hydrolysis under certain conditions, resulting in a breakage of the ester bond. Under these circumstances, the typical reaction by-products are acidic in nature, which not only cause an increase in corrosivity, but can also catalyze further reaction. Whether simply trying to trend the onset of base oil oxidation for a condition based oil change, or looking for signs of thermal failure due to compressive heating, it is vital that the fundamental chemistry of base oil degradation be understood so that the telltale signs can be identified using well-selected oil analysis test slates.
We encourage you to read our updated Privacy Policy Hide. Toggle navigation Toggle search. Magazine Subscribe Today! Current Issue Archive Advertise. Understanding the Mechanism of Oil Degradation Aside from the effects of radiation on base oils a topic that is beyond the scope of this article , hydrocarbon base oils - both mineral and synthetic - degrade in one of three ways Figure 1.
Oxidation Oxidation is perhaps the most common chemical reaction, not just in lubrication chemistry, but also in nature as a whole. The Effects of Oxidation - What to Look for on an Oil Analysis Report While controlling temperature and using higher-quality base oils can help limit the degree and rate of oxidation, the eventual breakdown of the base oil molecules due to oxidative processes is inevitable.
Thermal and Compressive Base Oil Degradation Unlike oxidation, the effects of thermal or compressive heating are commonly far less understood than oxidation. Related Articles. Product Unboxing - Luneta Bowl. Case Study: Using Industry 4. Featured Videos. Atten2 S Oil Wear 2. Featured Whitepapers. The temperatures required to hot-fill are widely believed to be very damaging to vitamins and even more damaging to probiotics.
For probiotics, the drinks must be taken to market through the cold channel at considerably higher costs or not at all. One popular probiotic-fortified beverage, Kevita owned by Pepsi was recently the subject of a class action lawsuit for false labelling claims as any naturally occurring probiotic cultures were all destroyed when the product was pasteurised to extend its shelf-life. Within the last decade, probiotics have risen beyond specialty and niche markets to become a mainstream ingredient.
Ganeden BC 30 the probiotic strain used in all Karma products was the first strain of Bacillus coagulans for which safety data was published in a peer-reviewed journal. To deliver health benefits, probiotic bacteria must overcome several challenges present in food processing. Furthermore, ensuring that probiotics remain viable throughout shelf-life is a formidable challenge. Like this story? Subscribe to Nutraceutical Business Review magazine for incisive analysis, the latest news and expert-written articles from the functional food and drink industries.
For more information click here. Oxidation in water causes water-soluble vitamins and probiotics to degrade with time. Just as nails rust in damp air and apples turn brown when cut open, water soluble vitamins and probiotics degrade when exposed to water and oxygen. This happens naturally in the atmosphere but putting the vitamins or probiotics in a water medium facilitates and accelerates the process — sometimes quite significantly. Vitamin C, also known as ascorbic acid, is an example of a water-soluble vitamin and is common in natural fruits and as a supplement.
The effects of oxidation are similar on other water-soluble vitamins, such as thiamine vitamin B1 , riboflavin vitamin B2 , niacin vitamin B3 , vitamin B6 pyridoxine , folate folic acid , vitamin B12, biotin and pantothenic acid. Acidity low pH causes faster degradation … and many common beverages have pH levels low enough to cause significant degradation.
Again, the effect of a typical hydration beverage on a delicate active ingredient such as folic acid is quite significant Figure 2. For probiotics, the effects are similar. Probiotics are bacteria and yeast colonies that are believed to have beneficial effects on digestion and other areas.
Schwanhausser, Nature, , The lifetime of mRNA molecules is usually short in comparison with the fundamental time scale of cell biology defined by the time between cell divisions. As shown in Figure 1A, for E. The experiments leading to these results were performed by inhibiting transcription through the use of the drug rifampicin that interacts with the RNA polymerase and then querying the cells for their mRNA levels in two minute intervals after drug treatment.
In particular, the RNA levels were quantified by hybridizing with complementary DNAs on a microarray and measuring the relative levels of fluorescence at different time points. This reflects the fleeting existence of some mRNA messages. Given such genome-wide data, various hypotheses can be explored for the mechanistic underpinnings of the observed lifetimes. For example, is there a correlation between the abundance of certain messages and their decay rate?
Are there secondary structure motifs or sequence motifs that confer differences in the decay rates? One of the big surprises of the measurements leading to Figure 1A is that none of the conventional wisdom on the origins of mRNA lifetime was found to be consistent with the data, which revealed no clear correlation with secondary structure, message abundance or growth rate. The short answer is not very.
Whereas the median mRNA degradation lifetime is roughly 5 minutes in E. Interestingly, a clear scaling is observed with the cell cycle times for these three cell types of roughly 30 minutes E. As a rule of thumb, these results suggest that the mRNA degradation time scale in these cases is thus about a fifth of the fast exponential cell cycle time.
Messenger RNA is not the only target of degradation. Protein molecules are themselves also the target of specific destruction, though generally, their lifetimes tend to be longer than the mRNAs that lead to their synthesis, as discussed below. Because of these long lifetimes, under fast growth rates the number of copies of a particular protein per cell is reduced not because of an active degradation process, but simply because the cell doubles all its other constituents and divides into two daughters leaving each of the daughters with half as many copies of the protein of interest as were present in the mother cell.
To understand the dilution effect, imagine that all protein synthesis for a given protein has been turned off while the cell keeps on doubling its volume and shortly thereafter divides. This mechanism is especially relevant in the context of bacteria where the protein lifetimes are often dominated by the cell division time.
The statement that protein lifetimes in rapidly growing bacteria are longer than the cell cycle itself is supported by measurements already from the s where radioactive labeling was used as a way to measure rates. In this case, degradation of labeled proteins was monitored by looking at the accumulation of radioactive amino acids in a rapidly exchanged perfusate.
More recently, studies showed specific cases of rapid degradation including some sigma factors, transcription factors, and cold shock proteins, yet the general statement that dilution is the dominant protein loss mechanism in bacteria remains valid.
Figure 3: Measured half lives of proteins in budding yeast and a HeLa human cancer cell line.
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