Oils, shelf life

The resistence to oxidation was related to the high content of polyphenols removal of polyphenols greatly reduced oxidative stability [39]. The subsequent studies were devoted to identifying the compoimds which more contribute to oil stability and the mechanism of protection. Hydroxytyrosol and caffeic acid were better protection factors than BHT tyrosol and other monohydroxy phenols gave little contribution to oil stability [43] oil shelf-life was positively correlated to hydroxytyrosol / tyrosol ratio [44]. 

D. Chatteijee, P. Bhattacharjee, Comparative evaluation of the antioxidant efficacy of encapsulated and un-encapsulated eugenol-rich clove extracts in soybean oil Shelf-life and frying stability of soybean oil. J. Food Eng. 117, 545-550 (2013)... 

The concentration of heavy metal ions that results in fat (oil) shelf-life instability is dependent on the nature of the metal ion and the fatty acid composition of the fat (oil). Edible oils of the linoleic acid type, such as sunflower and com germ oil, should contain less than 0.03 ppm Fe and 0.01 ppm Cu to maintain their stability. The concentration limit is 0.2 ppm for Cu and 2 ppm for Fe in fat with a high content of oleic and/or stearic acids, e. g. butter. Heavy metal ions trigger the autoxidation of unsaturated acyl lipids only when they contain hydroperoxides. That is, the presence of a hydroperoxide group is a prerequisite for metal ion activity, which leads to decomposition of the hydroperoxide group into a free radical ... 

Antioxidants (qv) have a positive effect on oils when present in the proper concentration. Sterols and tocopherols, which are natural antioxidants, may be analy2ed by gas-Hquid chromatography (glc), high performance Hquid chromatography (hplc), or thin-layer chromatography (tic). Synthetic antioxidants maybe added by processors to improve the performance or shelf life of products. These compounds include butylatedhydroxyanisole (BHA), butylated hydroxytoluene (BHT), / fZ-butyUiydroquinone (TBHQ), and propyl gallate. These materials may likewise be analy2ed by glc, hplc, or tic. Citric acid (qv), which functions as a metal chelator, may also be deterrnined by glc. 

Butter is used in some, usually more expensive, bakery foods, and is prized for its flavor contribution. Fats are used in some products such as pie cmst, croissants, or puff pastry, up to 60%, based on flour. StabiHty of fats and oils in perishable items such as breads, cakes, or pastries is of no consequence because shelf life is so limited that rancidity does not occur. In cookies and crackers, however, stable fats must be used in the formula since prolonged shelf life could lead to product deterioration with fats that develop rancidity. 

In particular, oil spill-treating agents should have a long shelf life and should be ... 

Oxidative rancidity is not necessarily a problem unless a polyunsaturated fat such as sunflower oil has been used. Where such a fat is used oxidative rancidity can occur and, as autoxidation occurs where the reaction becomes self-catalysing as oxygen free radicals react, some very unpleasant tastes can appear very quickly. In general, the effect of oxidation on biscuits at the end of their shelf life is that a cardboard taste starts to appear. 

Enzymic action is not normally a problem since only the most heat resistant enzymes survive the cooking. Oxidation can occur, but unless some polyunsaturated material, e.g. sunflower oil, is present is unlikely to be the problem that limits shelf life. Products that have suffered oxidation tend in general to have a cardboard taste rather than any other effect. 

Employing any method compare the effect of using the same weight of a vegetable oil such as rape or soy bean oil compared with a control sample made with a hard fat. In this experiment it would be worth comparing the shelf life of the control and the sample. 

The selection of the most suitable antioxidant depends on the character of food and the targets which should be attained. Naturally occuring fats and oils contain indigenous antioxidants that protect the unsaturated lipids from free-radical destruction in their native vegetable and animal sources. On the other hand, fats and oils exist in a commingled fashion with reactive substances which cause their rapid decomposition. Intensity of oxidative alterations is also influenced by the shelf-life of products and storage conditions. All these facts should be considered when deciding whether any and if so what antioxidant will be used. 

Fig. 2.137. Left electrophoregram of chlorophyll pigments in fresh extra virgin olive oil, added with copper chlorophyllin (1) chlorophyllin B (2) pheophytin B (3) pheophytin B(4) chlorophyllin A (5) pheophytin A (6) pheophytin A (7) copper chlorophyllin. Right electrophoregram of chlorophyll pigments in extra virgin olive oil, with a long shelf-life, added with copper chlorophyllin (1) chlorophyllin B (2) chlorophyllin derivatives (3) chlorophyllin A (4) copper chlorophyllin. Reprinted with permission from L. Del Giovine et al. [308].

Ointments and Creams Ointments are applied to the skin for topical treatment or to be absorbed into the blood system for delivery to target areas. They are semisofid preparations obtained by mixing the API with selected ointment bases depending on intended use. These bases include petrolatum, paraffin, mineral oil, lanolin, and glycols. Preservatives are often added to ensure the ointments will maintain the recommended shelf life. 

The use of enantiomers as additional markers for taxonomic characterization of aromatic plants may be very helpful. The differences in the enantiomeric distribution of trans- and cis- sabinene hydrates in two Origanum species enable the species to be distinguished in spite of their similar essential oil compositions. A further study on the natural variation of the enantiomeric composition within a wild population may be carried out in order to examine the stability in a taxon (including the possible presence of chemotypes). The enantiomeric ratio of essential oil components is a reliable parameter for assessing quality because it may be indicative of adulteration, contamination, aging, shelf life, technological process and the botanical source of a specific chiral compound. ... 

Over thousands of years for writing, the ancient people used naturally occurring colloidal fine material from ash (mostly charcoal) dispersed in oil (olive oil). Modem inkjet printers employing color are based on much more sophisticated components. Inkjet printers have a number of nozzles that inject ink droplets on the surface of paper. Simultaneously, different colors are mixed to obtain the desired color shade (more than hundreds of thousands). In a typical printer, there may be 30,000 injections per second, and there may be more than 500 nozzles (each with a size less than a human hair (pm =10 6 m). (The ink has a shelf life of more than a year.) In this process, the surface and colloidal principles most obvious are... 

Microencapsulation using extrusion is mainly described for glassy carbohydrate matrices [14-16, 28-29]. The glassy carbohydrates, such as starch and maltodextrins, are melted at elevated temperature and low water contents and are intensively mixed with the active in the extrusion barrel. Extrusion has been used for volatile and unstable flavours. The shelf life of flavour oils could be extended from several months to 5 years, compared with 1 year for spray-dried materials. The main drawbacks of the technology are the high investments costs and the formation of rather large particles (500-1,000 pm). 

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