Flavor and oxidation

Goering, H.K., Gordon, C.H., Wrenn, T.R., Bitman, J, King, R.L., Douglas, F.W.. 1976. Effect of feeding protected safflower oil on yield, composition, flavor and oxidative stability of milk. J. Dairy Sci. 59, 416-425. 

In our search for nitrite alternatives, as far as flavor and oxidative stability Is concerned, we examined the effect of commonly used adjuncts In meat curing, as well as a large ntimber of antloxldant/sequesterant systems (40-42). In particular, the effect of sodium ascorbate (SA) and sodium tripolyphosphate (STFF) on the oxidative state of cooked meats was studied. These additives lowered the TEA numbers by a factor of about 2 and 4, respectively (Table IV). When used In combination, a strong synergism was observed. Furthermore, an Increase In the concentration of SA and/or STFF resulted In a decrease In the TEA values as depicted In Figure 6 (43). Addition of 30 ppm of butylated hydroxyanlsole (EHA) or tert-butylhydroqulnone (TEHQ) further reduced the TEA numbers and In fact the latter values were even lower than those obtained for meats treated with sodium nitrite (Table IV) (41). 

The stability of canola oil is limited mostly by the presence of linolenic acid, chlorophyll, and its decomposition products and other minor components with high chemical reactivity, such as trace amounts of fatty acids with more than three double bonds. These highly unsaturated fatty acids can possibly be formed during refining and bleaching (52). The presence of 7% to 11% of linolenic acid in the acylglyce-rols of canola oil places it in a similar category with soybean oil with respect to flavor and oxidative stability. The deterioration of flavor as the result of auto -and photo-oxidation of unsaturated fatty acids in oils and fats is referred to as oxidative rancidity. 

Although sesame seeds are higher in oil contents than most other oilseeds and sesame oil has good flavor and oxidation stability, sesame seeds have never been a major oil source. The low yield (400-500 kg/ha) of sesame seeds and the labor-intensive harvesting procedure are the limiting factors. When sesame capsules... 

Decomposition and condensation of hydroperoxides also produces a multitude of nonvolatile monomeric products, including di- and tri-oxygenated esters, and dimeric and polymeric materials, especially at elevated temperature. Many of these dimers and polymers are known to be rich sources of volatile carbonyl compounds and to decrease the flavor and oxidative stability of soybean oil (316). These high-molecular-weight materials also can produce a series of physical and chemical changes to the oil and food products, including increased viscosity, polarity, free acid content, development of dark color, and an increased tendency of the oil to foam (233). 

Oils from field-, frost-, moisture-, and storage-damaged beans usually have higher levels of free fatty acids and iron, lower levels of phosphorous, darker colors, and poorer flavor and oxidative stability in the finished products than do oils from undamaged beans. Such beans are difficult to process, and standard processing methods usually do not produce finished oUs that can meet soybean oil specifications for trading or domestic consumption. 

To produce an edible fat (an oil having the desired color, flavor and oxidative stability, and functional properties), naturally occurring and undesired compounds must be removed as efficiently as possible, with maximally preventing damage to the naturally occurring antioxidants and neutral oil fraction. Formation of new compounds, precipitated processing adjuncts, and contaminants are all undesirable. 

Prime concerns in storage of crude and once-refined soybean oils include increases in moisture and volatile matter, color after refining or bleaching, peroxide value, free fatty acids, and refining losses. Aside from possible effects on flavor and oxidative stability, many of these quality factors also affect the commercial value of oil in trading channels. With the exception of peroxide values and refined color, the other quality factors above are written into specifications for oils sold under trading rules of the National Soybean Processors Association (NSPA) (67). 

Phospholipids, if not removed from oils before deodorization, can lead to dark-colored oils and serve as off-flavor precursors (53, 54). Chlorophyll (55), pheophytins and pyropheophytins (56), and metal ions (57, 58) are prooxidants that decrease oil stability. Iron and copper at levels as low as 0.01 and 0.1 ppm, respectively, are capable of lowering flavor and oxidative stabihty (59). Free fatty acids, besides representing a refining loss, have also been shown to act as prooxidants (60) and to lower smoke points (61) of oils during frying. Uinolenic acid has... 

Warner, K. Effects on the flavor and oxidative stability of stripped soybean and sunflower oils with added pure tocopherols./. Agric. Food Chem. 2005, 53, 9906-9910. 

Edible oils are not bleached chemically because the color reduction occurs because of oxidizing reactions that have an undesirable effect on the flavor and oxidative stability of the oil (Sipos Szuhaj, 1996). The effective agents for edible-oil bleaching are natural clays, activated earths, carbon, and synthetic silicates (see detailed descriptions... 

The deodorized product, if properly pretreated and bleached, will be as stable and as high in quality as an alkali refined product. In some cases, a physically refined oil will show more flavor and oxidative stability than the alkali refined product. Physical refining has reduced processing losses by as much as 2%. As a result of eliminating alkali refining, many effluent problems are solved. Effluent is cleaner as a result of the elimination of soapstock production, acidulation, and reduced oil losses. The acidulation process accounts for the majority of the effluent from a refinery and is the most difficult to clean up. 

Table 3.5. Effect of j8-carotene on flavor and oxidative stability of light-exposed soybean oil...

Warner, K., Frankel, E.N. and Mounts, T.L. Flavor and oxidative stability of soybean, sunflower and low-emcic acid rapeseed oils. J. Am. Oil Chem. Soc. 66,558-564 (1989). 

Any oxidation during processing is injurious to the flavor and oxidative stability of processed oils, either directly by the formation and accumulation of oxidation products, or indirectly by the loss of protective naturally occurring tocopherol antioxidants. Optimum oxidative stability can be achieved therefore by proper handling of oilseeds and crude oils to minimize exposure to air. 

The production of oxidative dimers and triglyceride oligopolymers by oxidation prior to deodorization decreases the stability of oils. Flavor and oxidative stability of soybean oil correlates with the concentration of oxidative dimers determined chromatographicaUy. The oxidative stabihty of vegetable oils can therefore be markedly improved, if any oxidation products present in partially processed oils can either be removed or chemically reduced to stable hydroxides before deodorization. 

The flavor and oxidative stability of linolenate-containing oils can be improved substantially by blending them with different levels of high-oleic oils to lower the linolenate content. High-oleic sunflower and safflower oils are relatively... 

One obvious use of MFCs for improved packaging is for the storage of milk. This is because light transmission and oxygen permeability are considered to be two of the main problems associated with all-plastic milk packaging, as they allow light-induced off flavors and oxidative reactions to occur [28]. It is anticipated that MFCs could significantly... 

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