Roasting aroma formation

W. Baltes and G. Bochmann, Model reactions on roast aroma formation. IV. Mass spec-trometric identification of pyrazines from the reaction of serine and threonine with... 

Baltes W. (1990) Roast aroma formation. The role of amino acids during the Maillard reaction. 4th Int Symp. Maillard React., Lausanne, Switzerland, Sept. 1989, Finot et at. Eds, Birkhauser Verlag (1990), 43-61. 

Baltes W. and Bochmann G. (1986a) Model reactions on roast aroma formation—The reaction of serine and threonine with sucrose. 3rd Int. Symp. MaiUard React., Tokyo, Japan, July 1985, Fujimaki et al. Eds, Kodansha Ltd and Elsevier (1986), 245-55. 

Bohnenstengel C. and Baltes W. (1992) Model reactions on roast aroma formation. XII. Reaction of glucose with aspartic acid or asparagine at three different remperatures. Z. Lebensm. Unters. Forsch. 194, 366-71. 

Baggenstoss J, Poisson L, Kaegi R, Perren R and Escher F. 2008. Coffee roasting and aroma formation application of different time-temperature conditions. J Agric Food Chem 56(14) 5836-5846. 

Of the different types of lipids in foods, the phospholipids, being more unsaturated, are particularly important in relation to aroma formation in meat.151 The aroma of cooked meat was not affected by the prior extraction of triglycerides with hexane, but the use of a more polar solvent (chloroform-methanol), which extracts all lipids, including phospholipids, resulted, after cooking, in the replacement of the meaty aroma by a roast or biscuit-like one. This was reflected in the volatiles, the dominant aliphatic aldehydes and alcohols being replaced by alkylpyrazines. This implies that the participation of the lipids in the Maillard reactions inhibited the formation of heterocyclic compounds. 

One of the first researchers to study the aroma formation during the Maillard reaction was Ruckdeschel [21] in 1914. He described the reaction product of glucose with phenylalanine as rose-like, with leucine as bread-like, with valine as fine roasted and with alanine as similar to coloured malt. 

Silwar R. and Lullmann C. (1993a) The aroma composition of the coffee beverage. Quantitative determination of steam-volatile aroma constituents. 15th Int. Colloq Chem. Coffee (Montpellier, 6-11.6.1993) (ASIC, 1993), 2,873-7. Silwar R. and Lullmann C. (1993b) Investigation of aroma formation in robusta coffee during roasting. Cafe, Cacao, The 37, 145-51. 

A more complex flavor development occurs in the production of chocolate. The chocolate beans are first fermented to develop fewer complex flavor precursors upon roasting, these give the chocolate aroma. The beans from unfermented cocoa do not develop the chocolate notes (84—88) (see Chocolate and cocoa). The flavor development process with vanilla beans also allows for the formation of flavor precursors. The green vanilla beans, which have Htfle aroma or flavor, are scalded, removed, and allowed to perspire, which lowers the moisture content and retards the enzymatic activity. This process results in the formation of the vanilla aroma and flavor, and the dark-colored beans that after drying are the product of commerce. 

Several of the lower molecular weight aliphatic compounds, in a mixture, are part of the roasted coffee aroma. A nine-compound mixture with roasted coffee aroma contained isopentane, n-hexane, acetaldehyde, dimethyl sulfide, propanal, isobutanal, isopentanal, methanol, and 2-methylfuran.20 In addition, the freshness of aroma and taste has been correlated with 2-methylpropanal and diacetyl. When the concentration of these falls off, so does the taste.21 Other aliphatic compounds that are steadily lost from ground roasted coffee, unless it is vacuum packaged, include methyl formate, methyl acetate, methyl thioacetate, and acetone.22 The concentrations in roast coffee for four compounds whose contribution to the fresh flavor have long been known are dimethyl sulfide (4 ppm), methyl formate (12 ppm), isobutanal (20 ppm), and diacetyl (40 ppm). The taste thresholds are 0.1, 0.5, 0.5, and 1.0 ppm, respectively, in the brew made with 5 g coffee per 100 ml water.15... 

Holscher, W., Steinhart, H., Formation pathways for primary roasted coffee aroma compounds, in ACS Symposium Series 543, Thermally Generated Flavors, 1994, 206. (CA120 105189t)... 

Tressl, R., Gruenewald. K. G., Kamperschroer, H., Silwar, R., Formation of pyrroles and aroma contributing sulfur components in malt and roasted coffee, Prog. Food Nutr. Sci., 5, 71, 1981. 

Since it is precisely at the surface of roasting meat that water concentrations are lowest and temperatures are highest, it is at the meat surface that the flavor and color generating activity during roasting is most prominent. This situation is analogous to the formation of crust and aroma in bread and other baked cereal products. The same facts also account for the significant difference between roasted and boiled meats. 

By heating the mixture in a buffer solution at greater than 100° C in an autoclave the question about the influence of the reaction medium on number and kind of volatiles should be answered. The answer, indeed, is very simple most compounds formed in the autoclave have been identical to the volatiles after roasting the mixture. Consequently, the reaction temperature is the most decisive factor for the formation of thermal aroma compounds. 

C, no esters and furanones are found, but thiazoles, cyclopen-tenones and other heterocyclic compounds dominate. These data imply that esters and furanones are stable at mild temperatures while the formation of thiazoles, cyclopentenones and other heterocyclic compounds require a higher temperature. Also at 160°C, trithiolanes, thiophenones and 2,4-hexanedione predominate, indicating that formation of such compounds is favored by a medium temperature. Bread, crusty and caramel aromas were found in the 100°C sample, pot-roasted, roasted, meaty and clean aromas were found at 160°C, and roasted, roasted-meat, chemical and off-notes were produced at 200°C. 

Frying temperature was found to be the crlterial parameter that determined the flavor quality in Chinese pork bundle. Cooked meat aroma increased as the heating temperature varied from 134°C to 172°C., as shown in Figure 3. Below 130°C neither cooked meat aroma nor brown color developed. Slightly higher temperatures have been reported for the optimum flavor formation in fried potato chips at 180°C (2), and roasted beans at 200°C (3). 

Kahweofuran (Structure 32) is also a sulfur derivative of furan and occurs in coffee, together with its dimethyl and ethyl homologues. It provides a roasted, smoky aroma at high dilution. Its formation in coffee has not been elucidated.248 Kahweofuran and its dimethyl and ethyl homologues have also been found in bread volatiles.249... 

Isobutyl-3,5-diisopropylpyridine was identified in fried chicken and has a roasted cocoa-like aroma (21). Figure 3 shows the mechanism for the formation of this compound as proposed by Shu et... 

The extremely elusive nature of the chemical basis of Cheddar-like flavors supports the hypothesis that an unstable aroma compound is involved in the flavor of Cheddar cheese, and this view deserves thorough investigation. The circumstantial evidence in favor of the existence of a Cheddar-like aroma also includes considerations relating to the sensitivity of Cheddar flavor to heat and oxygen, and the fact that the redox of cheese is quite low. Additionally, sulfury or sulfide-like defects as well as brothy flavor-like defects are often encountered in Cheddar cheeses of various compositions and origin. These flavors could reflect either production of excessive amounts of certain sulfur compounds or the absence of certain essential compounds that are initially required to allow formation of a Cheddar compound. While attempts to date have not resulted in the isolation of such a compound, this could reflect the very unstable nature of the proposed compound. Other similar circumstances appear to occur in freshly roasted coffee and nuts where transient... 

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