J. Agric. Food Chem. 2002, 50, 806−812
Generation of Maillard Compounds from Inulin during the Thermal Processing of Agave tequilana Weber Var. azul
NORMA A. MANCILLA-MARGALLI
MERCEDES G. LOPEZ* Ä
Unidad de Biotecnologıa e Ingenierıa Genetica de Plantas, Centro de Investigacion y Estudios ´ ´ ´ ´ Avanzados del IPN, Apartado Postal 629, 36500 Irapuato, Gto., Mexico
Duringthe cooking process of Agave tequilana Weber var. azul to produce tequila, besides the hydrolysis of inulin to generate fermentable sugars, many volatiles, mainly Maillard compounds, are produced, most of which may have a significant impact on the overall flavor of tequila. Exudates (agave juice) from a tequila company were collected periodically, and color, °Brix, fructose concentration, andreducing sugars were determined as inulin breakdown took place. Maillard compounds were obtained by extraction with CH2Cl2, and the extracts were analyzed by GC-MS. Increments in color, °Brix, and reducing sugars were observed as a function of time, but a decrease in fructose concentration was found. Many Maillard compounds were identified in the exudates, including furans, pyrans, aldehydes, andnitrogen and sulfur compounds. The most abundant Maillard compounds were methyl-2-furoate, 2,3-dihydroxy-3,5-dihydro-6-methyl-4(H)-pyran-4-one, and 5-(hydroxymethyl)furfural. In addition, a series of short- and long-chain fatty acids was also found. A large number of the volatiles in A. tequilana Weber var. azul were also detected in tequila extracts, and most of these have been reported as a powerfulodorants, responsible for the unique tequila flavor.
KEYWORDS: Agave tequilana; inulin; Maillard compounds; tequila; GC-MS
The well-known Maillard reaction results from an interaction between amino compounds, usually amino acids or proteins, and reducing carbohydrates (1). This reaction leads to the formation of compounds that, because their volatility, influence the overallflavor of a product (2, 3). Since Ruckdeschel in 1914 reported aroma generation by Maillard pathways, the food industry has patented flavor formation processes from the heated aqueous mixtures of amino acids and reducing sugars. In the same way, thermal treatments of foods as well as their basicity are favorable conditions for the generation of these compounds (4). Tequila is one of the mostconsumed Mexican liquors worldwide and is made from AgaVe tequilana Weber var. azul, a native plant of Mexico (5), the only raw material appropriate to produce this beverage (6). During tequila production, stems of A. tequilana are submitted to a cooking process for at least 32 h at ∼100 °C. The exudates (agave juice or cooking honey) obtained are then fermented and double-distilled to generate tequilablanco (white). This product can be matured from 3 to 12 months in oak casks to produce tequila reposado (rested) or from 1 to 5 years to produce tequila anejo (aged) (7). ˜ The main reason for the cooking process during tequila production is to hydrolyze the inulin, the principal polysaccharide in the core of the agave pine plants. Inulin is thus converted
* Corresponding author (telephone52-462-623-9632, fax 52-462-6245996; e-maill email@example.com).
into free sugars, mainly fructose (6), for their subsequent fermentation. Shu (8) in 1998 showed that inulin heated with asparagine, even under mild conditions, produced Maillard molecules in an analogous way to fructose. The cooking conditions of the agave pines such as high temperature, low pH (4.5), time, and humidity arehighly favorable to the Maillard reaction (9). Therefore, the main objective of this study was to determine the Maillard compounds generated in the thermal processing of A. tequilana Weber var. azul during tequila production.
MATERIALS AND METHODS Materials. The sweet liquid generated during the cooking of A. tequilana Weber var. azul pines, known as exudates or cooking honey, was collected from an...