Painty flavor

Comparative studies by Forss and co-workers (1960A.C) on the fishy, tallowy, and painty flavors of butterfat tended to emphasize the importance of the relative and total carbonyl contents in dairy products with different off-flavors. These researchers showed that three factors distinguished painty and tallowy butterfat from fishy butterfat. First, there was a relative increase in the n-heptanal, re-octanal, n-non-... 

Forss, D.A., Dunstone, E.A., Stark, W. 1960c. The volatile compounds associated with tallowy and painty flavor in butterfat. J. Dairy Res. 27, 381-387. 

Scales reportedly used by the oil industry combine intensity and quality characteristics in one scale. For example, oil with a weak melon flavor is rated as a 5, whereas oil with a weak painty flavor is rated as a 4. These scales are not recommended because information cannot be accurately captured using scales of this nature. 

As indicated previously in this chapter, regular soybean salad oil, if processed and stored properly, has very good oxidative stability as a salad oil. In some instances, however, extra oxidative stability may be needed. In those cases, soybean oil with a modified fatty acid profile may be appropriate, such as one with reduced linolenic acid. Several studies on soybean oil modified to reduce the linolenate content showed that this approach improved the flavor quality and oxidative stability of the soybean salad oils (Mounts et d., 1988 Liu ite, 1992a Mounts et al., 1994a Su et al., 2003). Decreasing the linolenic acid helps to inhibit oxidation and the development of painty flavors derived from the oxidation of linolenic acid. 

Polyunsaturated fatty acids in vegetable oils, particularly finolenic esters in soybean oil, are especially sensitive to oxidation. Even a slight degree of oxidation, commonly referred to as flavor reversion, results in undesirable flavors, eg, beany, grassy, painty, or fishy. Oxidation is controlled by the exclusion of metal contaminants, eg, iron and copper addition of metal inactivators such as citric acid minimum exposure to air, protection from light, and selective hydrogenation to decrease the finolenate content to ca 3% (74). Careful quality control is essential for the production of acceptable edible soybean oil products (75). 

Standards and Controls. In all experiments, the 85 g standard patties were made from freshly ground top round steaks (excess fat trimmed) and immediately frozen in covered glass petri plates until the day of the assay. The fat content was routinely from 4-5%, determined by the method of Koniecko (57). The standards generally had relatively low values for hexanal, total volatiles (TV) and TEARS, and low intensity values for painty (PTY), cardboardy (CED), sour (SUR) and bitter (ETR). These results indicated the absence of lipid oxidation and no formation of off-flavors. As expected, the desirable flavor notes, cooked beef/brothy (CEE), beefy/meaty (EM), brothy (ERO), browned/caramel (ERC) and sweet (SWT) had high intensity values. 

The overwhelming consideration in regard to lipid deterioration is the resulting off-flavors. Aldehydes, both saturated and unsaturated, impart characteristic off-flavors in minute concentrations. Terms such as painty, nutty, melon-like, grassy, tallowy, oily, cardboard, fishy, cucumber, and others have been used to characterize the flavors imparted by individual saturated and unsaturated aldehydes, as well as by mixtures of these compounds. Moreover, the concentration necessary to impart off-flavors is so low that oxidative deterioration need not progress substantially before the off-flavors are detectable. For example, Patton et al (1959) reported that 2,4-decadienal, which imparts a deep-fried fat or oily flavor, is detectable in aqueous solution at levels approaching 0.5 ppb. 

WOF is characterized sensorially as being "old, stale, rancid, metallic and painty". These flavors are highly related to concentrations of pentanal, hexanal, 2,3-octanedione and total volatiles in chicken, turkey and beef (21) and to twenty-one different oxidative volatiles in pork (22). The compounds were quantitated by the GLC/MS method of Suzuki and Bailey (23) and appear to be excellent markers for WOF. 

Figure 3 plots intensity changes perceived by gd hoc descriptive sensory panelists in intensity analysis for character notes involved in meat flavor deterioration during storage of the grilled beef samples reported in Figure 2 and Table II (12, 13). The loss of intensity for certain descriptors in Figure 3 is in accord with sensory panel experience that the positive notes such as cooked-beef brothy diminish with formation of new off-flavor compounds represented as cardboard and painty. 

Positive cooked-beef flavor components as perceived by descriptive sensory panelists are reduced during free radical catalyzed meat flavor deterioration (MFD) while negative flavor notes with descriptor definitions of cardboard and painty intensify, as reviewed recently by Love (13). Although the cardboard and painty off-flavors correlate well with lipid oxidation products and can be measured easily by gas chromatography (1, 14, 18). much less is known about the fate of the positive cooked-beef flavors in this MFD process (13). 

Numerous substances have the same odor. Table 13-1 shows examples of the odor descriptions musty , painty and plastic which are used for a number of different substances. It is therefore obvious that for example the description musty of an off-flavor does not give any concrete reference to the kind of the off-odor substance involved. 

In addition to positive aspects, numerous flavor and textural defects may be associated with the fat phase of ice cream. Such flavor defects are usually related to either autoxidation of the fat, resulting in oxidized flavors (cardboardy, painty, metallic) or, especially in the case of milk-fat, lipolysis of free fatty acids from triglycerides by the action of lipases (referred to as hydrolytic rancidity). A significant content of free butyric acid gives rise to very undesirable rancid flavors. These defects tend to be present in the raw ingredients used in ice cream manufacture, rather than promoted by the ice cream manufacturing process itself. However, processing... 

Forss et al. (1960a,c) compared the qualitative and quantitative distribution of carbonyl compounds in dairy products with fishy, tallowy or painty off-flavor. Total content of volatile carbonyl compounds was approximately 10 times greater in the tallowy and 100 times greater in the painty butterfat than in fishy butterfat. Tallowy butterfat contained greater amounts of -heptanal, -octanal, -nonanal, 2-heptanone 2-heptenal and 2-nonenal, while painty butterfat contained greater amounts of K-pentanal and C5 to C10 alk-2-enals. 

Aldehydes and ketones, major secondary products of autoxidatlon are known to impart burnt, sweet, fatty, painty, metallic and rancid flavor notes to meats (,6). Many aldehydes also have low odor and flavor thresholds and can be perceived at low concentrations (29. 30). 

Some volatile aldehydes formed by autoxidation of unsaturated fatty acids are listed in Table 1. The aromas of aldehydes are generally described as green, painty, metallic, beany, and rancid, and they are often responsible for the undesirable flavors in fats and oils. Hexanal has long been used as an index of oxidative deterioration in foods. Some aldehydes, particularly the unsaturated aldehydes, are very potent flavor compounds. Table 2 fists aroma characteristics of some common aldehydes found in fats and oils (8). 

Flavor. One of the most important palatability parameters for edible fats and oils users is flavor. Generally, the flavor of an edible oil product should be completely bland, so that it can enhance the food product s flavor rather than contribute its own. Cottonseed oil is well known for its initial bland flavor and the nutty flavor it develops with oxidation. It has been used as the standard for comparison with other oils for both flavor and odor. The nutty flavor developed with oxidation is more pleasant than the oxidized flavor of some of the other oils in the oleic linoleic classifications for example, soybean oil reverts to a painty, green, watermelon type flavor with oxidation. Another major cause of off-flavors in food oils is hydrolysis. The free fatty acids liberated with hydrolysis have a distinct flavor and odor that are more disagreeable when the fatty acid chain length is shorter than 14 carbons. Cottonseed... 

The oil after heating shall be bland and free from beany, rancid, painty, musty, soapy, fishy, metallic, and other undesirable or foreign flavors and odors when tested by the method prescribed in footnote m within 7 days after packaging each lot. 

Flavors and aromas commonly associated with seafoods have been intensively investigated in the past forty years ( l-7), but the chemical basis of these flavors has proven elusive and difficult to establish. Oxidized fish oils can be described as painty, rancid or cod-liver-oil like (j ), and certain volatile carbonyls arising from the autoxidation of polyunsaturated fatty acids have emerged as the principal contributors to this type of fish-like aroma ( 3, 5, 9-10). Since oxidized butterfat (9, 11-12) and oxidized soybean and linseed oils (13) also can develop similar painty, fish-like aromas, confusion has arisen over the compounds and processes that lead to fish-like aromas. Some have believed that the aromas of fish simply result from the random autoxidation of the polyunsaturated fatty acids of fish lipids (14-17). This view has often been retained because no single compound appears to exhibit an unmistakable fish aroma. Still, evidence has been developed which indicates that a relatively complex mixture of autoxidatively-derived volatiles, including the 2,4-heptadienals, the 2,4-decadienals, and the 2,4,7-decatrienals together elicit unmistakable, oxidized fish-oil aromas (3, 9, 18). Additionally, reports also suggest that contributions from (Z -4-heptenal may add characteristic notes to the cold-store flavor of certain fish, especially cod (4-5). 

The U.S. Department of Agriculture (USDA) quality standards for soybean oil state that soybean oil shall be clear and brilliant when held at 70-85°F and shall be free from sediment, such as metal, wood, dirt, glass, paint, insects, insect parts, or any other foreign material (Anonymous, 2005). In addition, the oil shall have a bland odor and flavor and shall be free of beany, rancid, painty, musty, metallic, fishy, putrid, or any orher undesirable odor and/or flavor and have a light viscosity and no heavy oily mouthfeel. Table 15.4 lists the analytical requirements for a RBD and... 

Oxidized fish oils, rich in n-3 polyunsaturated fatty acids, produced volatile compounds more readily than oxidized vegetable oils, rich in linoleic acid. Activation energy for the formation of propanal from fish oils was lower than for the formation of hexanal from vegetable oils. A mixture of aldehydes contributed to the characteristic odors and flavors of oxidized fish, described as rancid, painty, fishy and cod liver oil-like (Table 11.21). Oxidation of unsaturated fatty acids in fish was related to the formation of 2-pentenal, 2-hexenal, 4-heptenal, 2,4-heptadienal and 2,4,7-decatrienal. The fishy or trainy characteristic of fish oil was attributed to 2,4,7-decatrienal. Studies of volatiles from boiled trout after storage showed significant increases in potent volatiles by aroma extraction dilution analysis (Table 11.22). Volatiles with the highest odor impact included l,5-octadien-3-one, 2,6-nonadienal, 3-hexenal, and 3,6-nonadienal. 3,6-Nonadienal and 3-hexenal were considered to contribute most to the fatty, fishy flavor in stored boiled fish. 

The aroma substances that comprise flavors are found in nature as complex mixtures of volatile compounds. A vast majority of volatile chemicals that have been isolated from natural flavor extracts do not provide aroma contributions that are reminiscent of the flavor substance. For instance, n-hexanal is a component of natural apple flavor (1) however, when smelled in isolation, its odor is reminiscent of green, painty, rancid oil. Similarly, ethyl butyrate has a nondescript fruity aroma although it is found in strawberries, raspberries, and pears, it does not uniquely describe the aroma quality of any of these individual fruits. It has long been the goal of flavor chemists to elucidate the identity of pure aroma chemicals that have the distinct character impact of the natural fruit, vegetable, meat, cheese, or spice that they were derived from. Often, these are referred to as character impact compounds (2). 

---