Lipid oxidation beef flavor

The changes in the protein composition and flavor of "cooked" and "cooked- -stored" beef seemed to be related to degradation by free radical species induced during lipid oxidation 1-10, 16, 22, 23), Based on the information presented in the aforementioned publication, it seemed reasonable to suggest that the appearance of "bitter" and "sour" tastes and the disappearance of "meaty" and "beefy" flavors were a result of the activity of the free radicals derived from lipid oxidation on flavor proteins (2, 24-28),... 

Over the years, scientists have used many types of antioxidants in a variety of foods to retard or inhibit lipid oxidation and, thus, increase shelf-life and preserve quality. These antioxidants include free radical scavengers, chelators, and oxygen absorbers. While there are numerous antioxidants available to food scientists, the objective of this report was to discuss several of these antioxidants as they relate to meat flavor quality research and to show how they were used to retard lipid oxidation and prevent meat flavor deterioration in ground beef patties. 

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. 

When the antioxidants were used in the cooked/stored samples, data indicated that they were very effective in inhibiting lipid oxidation and MFD. The chemical and off-flavor indicators were reduced and the on-flavor notes were increased. Thus, phenolic-type primary antioxidants that function as free radical scavengers are very effective tools for preventing lipid oxidation and MFD in ground beef. It should also be noted that the intensity of the desirable flavor notes remained at very high levels, which meant that the patties retained their beefy tastes. Therefore, for an antioxidant to be highly effective, it should not only prevent lipid oxidation, but it should also retain the desirable flavor properties of the food commodity. 

Effect of Sodium Ascorbate on Stored Ground Beef. The effectiveness of sodium ascorbate (SA) as an antioxidant was determined on both raw and cooked stored ground beef. The experimental models, i.e., standards, controls and experimental samples were similar to those described in the section on primary antioxidants. Data from the use of 150 and 200 ppm and 250 and 500 ppm are reported in Tables 7 and 8, respectively. At a concentration of 500 ppm, SA was the most effective inhibitor of MFD and lipid oxidation in both raw and cooked/stored ground beef when compared to the other three concentrations. Tlie markers of MFD and lipid oxidation were suppressed to the greatest extent and the desirable beefy flavor markers were maintained at their highest intensities when SA was added to the beef samples. SA was effective as an inhibitor at all levels tested. 

When rosemary-W was added to the cooked patties, as the concentration was increased from 125 to 500 ppm, both hexanal and TBARS levels decreased. The desirable flavor note, CBB, showed improvement over that of the 2-day MFD sample when the rosemary-W concentration was less than 500 ppm. However, at a concentration of 500 ppm, CBB decreased to an unacceptable level of 3.95. The undesirable flavor notes, PTY and CBD, were less in the rosemary-W group at 2-days than in the 2-day MFD samples, but were higher than the 0-day control. With the 500 ppm treatment, rosemary-W seems to effect PTY more than CBD. The data showed that rosemary-O is more effective than the water-based formulation. Consequently, smaller quantities of the oil based rosemary formulation are required for use in retarding lipid oxidation and maintaining the desirable beefy taste. A similar use of rosemary as an inhibitor of MFD in restructured beef steaks was reported recently by Stoick et al 40 ... 

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). 

Our own work has shown a great decrease In the concentration of the volatiles In the cured, as compared to uncured, meats (Figure 5) (Ifi). The concentration of aldehydes originally present in cooked pork was reduced to < 12 of their original quantities (Table III, unpublished results). However, we did not Identify any new flavor active compound which could have been responsible for the cured flavor. Lipid oxidation, as measured by TBA number, was almost eliminated In cooked pork by adding nitrite at a level of 150 ppm (13.) Furthermore in preliminary evaluations, our untrained panelists were unable to differentiate amongst the flavor of nitrite-cured meats prepared from beef, chicken, mutton and pork (unpublished results). 

The oxidation products of lipids include volatile aldehydes and acids. Therefore, lipids are one of the major sources of flavors in foods. For example, much of the desirable flavors of vegetables such as tomatoes, cucumbers, mushrooms, and peas (Ho and Chen, 1994) fresh fish (Hsieh and Kinsella, 1989), fish oil (Hu and Pan, 2000) and cooked shrimp (Kuo and Pan, 1991 Kuo et al., 1994), as well as many deep-fat fried foods such as French-fried potatoes (Salinas et al., 1994) and fried chicken (Shi and Ho, 1994), are contributed by lipid oxidation. LOX-catalyzed lipid oxidation produces secondary derivatives, e.g., tetradecatrienone, which is a key compound of shrimp (Kuo and Pan, 1991). The major difference between the flavors of chicken broth and beef broth is the abundance of 2,4-decadienal and y-dodeca-lactone in chicken broth (Shi and Ho, 1994). Both compounds are well-known lipid oxidation products. A total of 193 compounds has been reported in the flavor of chicken. Forty-one of them are lipid-derived aldehydes. 

The structure of the food matrix is also known to affect the release of volatile compounds having an impact on flavors and aroma. Changes in flavor result from the interactions of lipid-derived carbonyl compounds by aldolization with the amino groups of proteins. Undesirable flavors are produced when beef or chicken are fried in oxidized fats by the interaction of secondary lipid oxidation... 

Boneless beef roasts Fresh dried plum juice concentrate, spray dried plum powder Reduce lipid oxidation warmed-over flavor Nunez de Gonzalez et al., 2008b... 

As previously discussed, lipid oxidation is generally related to the flavor deterioration in meat and meat products. However, boar taint, an intense urinelike off-odor, is attributed primarily to the flavor synergy between two compounds in boar fat, androstenone (5-a-androst-16-ene-3-one) from testes and the fecal-like skatole (3-methyl indole) from tryptophan breakdown (125). Generally, women tend to be more sensitive to the odor than men. Skatole has also been implicated in a medicinal off-odor in beef (126). 

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