Flavor lipid effects

Human perception of flavor occurs from the combined sensory responses elicited by the proteins, lipids, carbohydrates, and Maillard reaction products in the food. Proteins Chapters 6, 10, 11, 12) and their constituents and sugars Chapter 12) are the primary effects of taste, whereas the lipids Chapters 5, 9) and Maillard products Chapter 4) effect primarily the sense of smell (olfaction). Therefore, when studying a particular food or when designing a new food, it is important to understand the structure-activity relationship of all the variables in the food. To this end, several powerful multivariate statistical techniques have been developed such as factor analysis Chapter 6) and partial least squares regression analysis Chapter 7), to relate a set of independent or "causative" variables to a set of dependent or "effect" variables. Statistical results obtained via these methods are valuable, since they will permit the food... 

PG, TBHQ and the two Tenox formulations at the 25 or 50 ppm levels were found to be very effective in preventing MFD in the raw (stored overnight) and the 2-day cooked/stored samples. In the raw antioxidant-treated samples, the 0-day controls, the MFD and lipid oxidation markers were generally decreased and the on-flavor notes increased in comparison to those of the 0-day raw controls. These trends were particularly observed in the samples treated with 50 ppm. Of the four antioxidants examined, TBHQ was the most effective. 

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 ... 

EFFECT OF STORAGE ON THE GENERATION AND LOSS OF FLAVOR NOTES AND PRODUCTS OF LIPID OXIDATION IN COOKED MEATS ... 

Homstein and Crowe 18) and others (79-27) suggested that, while the fat portion of muscle foods from different species contributes to the unique flavor that characterizes the meat from these species, the lean portion of meat contributes to the basic meaty flavor thought to be identical in beef, pork, and lamb. The major differences in flavor between pork and lamb result from differences in a number of short chain unsaturated fatty acids that are not present in beef. Even though more than 600 volatile compounds have been identified from cooked beef, not one single compound has been identified to date that can be attributed to the aroma of "cooked beef." Therefore, a thorough understanding of the effect of storage on beef flavor and on lipid volatile production would be helpful to maintain or expand that portion of the beef market. 

Metal-catalyzed lipid oxidative reactions were recognized in dairy products as early as 1905 (Parks 1974). Investigations throughout the years have shown that copper and iron are the important metal catalysts in the development of oxidized flavors. Of these two metals, copper exerts the greater catalytic effect, while ferrous ion is more influential than feric ion. 

Edmondson et al (1971), who studied the enrichment of whole milk with iron, found that ferrous compounds normally caused a definite oxidized flavor when added before pasteurization. Aeration before addition of the iron reduced the off-flavor. The authors recommended the addition of ferric ammonium citrate followed by pasteurization at 81 °C. Kurtz et al. (1973) reported that iron salts can be added in amounts equivalent to 20 mg iron per liter of skim milk with no adverse flavor effects when iron-fortified dry milk is reconstituted to skim milk or used in the preparation of 2% milk. Hegenauer et al. (1979A) reported that emulsification of milk fat prior to fortification greatly reduced lipid peroxidation by all metal complexes. These researchers (Hegenauer et al. 1979B) concluded that chelated iron and copper should be added after homogenization but before pasteurization by a high-temperature-short-time process. 

Smith, L. M. and Dunkley, W. L. 1959. Effect of the development of oxidized flavor on the polyunsaturated fatty acids of milk lipids. J. Dairy Sci. 42, 896. 

For many years, in connection with certain food products, a barrier to freeze-drying has been the problems associated with the storage stability of foods that are susceptible to lipid oxidation. In order for such foods to have a reasonable shelf life and acceptable flavor characteristics, protective additives, which retard oxidation, are often added before dehydration. Such antioxidants must carry through the process and not be lost because of volatilization. For these applications, BHA, BHT, and tert-butylhydroquinone (TBI1Q) have been found quite effective. 

Lipids are important macromolecules in food. A food product s nutritional value as well as its flavor, texture, general palatability, and storage stability are affected by lipids. Therefore, both physical and chemical criteria are needed by the food processor to assess or monitor the quality of fats and oils. The basic characteristics of certain food items, such as edible oils, will be dependent upon their source. Variation from these norms can be ascertained before the oils are used in other foodstuffs. In effect, knowledge of the quality of the lipid before shipping the product to market, or use in fabricated foods, is of economic importance to the processor. 

Up until now, most of the published work on the SFE of natural products has been concerned primarily with nonpolar substances such as essential oils, lipids, flavor, and fragrance ingredients. However, recent reports have shown that some polar plant constituents (e.g. flavonoid glycosides, proteins, and steroidal glycosides) can be extracted by SFE as effectively as conventional organic solvent extraction. Examples of SFE applications for natural products are well reviewed in several literature sources [19-22]. 

From a dietary standpoint, the contribution of citrus lipids is insignificant and only between. 06 and. 09 percent has been found in oranges (37J. They are, however, of importance because of their effects on the development of off-flavors (12J, thus lowering the palatability of these products. The near absence of lipids in citrus makes it a desirable food for those on a limited fat diet. 

In addition to simple model systems, more complex systems which are closer to actual foodstuffs have been used to investigate the formation of flavor chemicals in the Maillard reaction. Sixty-three volatile chemicals were isolated and identified from starch heated with glycine (4). When beef fat was used as a carbonyl compound precursor in a Maillard model system with glycine, 143 volatile chemicals were identified (6). These included fifteen n-alkanes, twelve n-alkenes, thirteen n-aldehydes, thirteen 2-ketones, twelve n-alcohols, and eleven n-alkylcyclohexanes. Recently, the effect of lipids and carbohydrates on the thermal generation of volatiles from commercial zein was studied (7). 

In heated foods the main reactions by which flavors are formed are the Maillard reaction and the thermal degradation of lipids. These reactions follow complex pathways and produce reactive intermediates, both volatile and non-volatile. It has been demonstrated that lipids, in particular structural phospholipids, are essential for the characteristic flavor development in cooked meat and that the interaction of lipids with products of the Maillard reaction is an important route to flavor. When model systems containing amino acids and ribose were heated in aqueous buffer, the addition of phospholipids had a significant effect on the aroma and on the volatile products. In addition a number of heterocyclic compounds derived from lipid - Maillard interactions were found. The extent of the interaction depends on the lipid structure, with phospholipids reacting much more readily than triglycerides. 

Lipids in foods vary from traces as in cereals to 30-50% as in nuts. The physical state and distribution of lipids vary considerably among food items. In each item lipid distributions affect its flavor as it undergoes chemical reactions and act as a flavor components vehicle or partitioning medium. Furthermore, lipids have a pronounced effect upon the structure of food items. Fatty acids of neutral (triglycerides) and polar lipids of beef and pork are tabulated in Table III. 

Lipolysis, the enzymic hydrolysis of milk lipids to free fatty acids and partial glycerides, is a constant concern to the dairy industry because of the detrimental effects it can have on the flavor and other properties of milk and milk products. However, free fatty acids also contribute to the desirable flavor of milk and milk products when present at low concentrations and, in some cheeses, when present at high concentrations. 

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