Flavor irradiation temperature

IV. Smaller but possibly significant effects of warming rate and packaging environment are shown in Figure 6, complicated by interaction with the irradiation temperature. The effects of both packaging and warming rate variables were largest at — 196°C. The lowest irradiation flavor intensity... 

The cooling rate showed no appreciable effect on flavor scores and was eliminated as a variable in subsequent tests. Since there was some indication of a tendency toward texture deterioration on rapid cooling, a standard method of cooling to 4°C. followed by vapor phase cooling (essentially slow) to irradiation temperature was followed in subsequent studies designed to measure the effects of the other variables more accurately. 

The irradiation flavor scores in Table V show quantitatively the dependence of irradiation flavor intensity on irradiation temperature for both oxygen-packed and vacuum-packed steaks brought to 4°C. rapidly after irradiation. 

Table V. Effect of Irradiation Temperature on Irradiation Flavor Intensity of Steaks Irradiated at 6.0 Megarads...

Correlation of Chemical Yields in Model Systems with Irradiation Flavor Intensity. The observed effect of irradiation temperature on irradiation flavor intensity in beefsteak is shown in Figure 7. For 6-megarad irradiation the flavor intensity scores at —80°C. are roughly 75% of those at +20°C. and at — 196°C. are approximately 50% of +20°C. scores. Comparing these percentage decreases at each temperature with the corresponding decreases in chemical yields reported in Table III shows no obvious correlation beyond the fact that both irradiation flavor scores and chemical yields from the peptides decrease with decreasing irradiation temperature. 

Organoleptic studies on irradiated beefsteaks showed that irradiation flavor intensity is significantly lower at lower irradiation temperatures and depends on postirradiation warming rates. 

While the chemical and organoleptic results cannot be directly correlated, it should be remembered that only a small fraction of the known chemical products were included in this investigation. Investigation of irradiation temperature effects on yields of other chemical products may well produce better correlation with flavor scores. 

The industrial flavor producers offer a very broad selection of natural and synthetic flavors,mainly in the form of liquid concentrates.The majority of flavor constituents in such concentrates exhibit considerable sensitivity to air,light irradiation and elevated temperature. These flavor concentrates are moreover oily,greasy rather lipophilic materials,which are difficult to work with. The natural plant extracts also have microbiological contaminations that need to be removed. 

Table III. Stability of complexed and adsorbed flavors to UV/365nm/ irradiation in the solid state at room temperature...

A problem associated with beef sterilized by irradiation at approximately room temperature is the production of an unpleasant flavor and aroma. This paper summarizes knowledge of the volatile components of enzyme-inactivated irradiated and nonirradiated beef, reviews the effects of concurrent and nonconcurrent irradiation procedures and of storage on these components, and presents evidence that methional (3-methylmercaptopropion-aldehyde), 1-nonanal, and phenylacetaldehyde are of primary importance to irradiation off-odor in beef thus processed. 

Figure 1. Temperature-programmed separation of irradiation flavor isolates on a 20% Carbowax 20M column...

These four compounds were also selected because they were commercially available in pure form and reasonably soluble in unbuffered solutions at room temperature. In addition, the radiation chemistry of glycine, glycylglycine, and methionine has been studied at room temperature (4, 5, 6, 12, 36, 49, 50, 51). Also, sulfur-containing amino acids have been suggested by chemical-irradiation flavor correlation studies (4, 21, 38, 44f 49, 50, 53) as being related to irradiation flavor. 

The relationship between irradiation flavor intensity and temperature is essentially linear for both packaging methods, except for the temperature of — 140°C. where in both cases the irradiation flavor intensity observed was too high. This suggests that the temperature control system may have failed during the irradiations at this temperature. The flavor scores shown in Table V for a second set of samples (from a different animal) irradiated at —140° and — 196°C. in a subsequent experiment support this suggestion. 

Radiation Biochemistry of Flavor and Odor. Some 17 carbonyl compounds have been isolated in irradiated fish, and 12 have been identified. Nonirradiated clams show an increase in carbonyls during storage. Following irradiation at 450 krads the concentration of carbonyls increases sharply. The use of cryogenic temperatures significantly lowers the production of carbonyls. (2). 

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