Instrumental and Sensory Characterization of Heat-Induced Odorants in Aseptically Packaged Soy Milk PATRICIO R. LOZANO, † MARYANNE DRAKE, § DANIEL BENITEZ, # AND KEITH R. CADWALLADER* ,† Department of Food Science and Human Nutrition, University of Illinois, 1302 West Pennsylvania Avenue, Urbana, Illinois 61801; Department of Food Science, North Carolina State University, Raleigh, North Carolina 27695; and Cargill, Inc., 2525 Ponce de Leon Boulevard, Suite 800, Coral Gables, Florida 33134 Predominant heat-induced odorants generated in soy milk by ultrahigh-temperature (UHT) processing were evaluated by sensory and instrumental techniques. Soy milks processed by UHT (143 °C/14 s, 143 °C/59 s, 154 °C/29 s) were compared to a control soy milk (90 °C/10 min) after 0, 1, and 7 days of storage (4.4 ( 1 °C). Dynamic headspace dilution analysis (DHDA) and solvent-assisted flavor evaporation (SAFE) in conjunction with GC-olfactometry (GCO)/aroma extract dilution techniques and GC-MS were used to identify and quantify major aroma-active compounds. Sensory results revealed that intensities of overall aroma and sulfur and sweet aromatic flavors were affected by the processing conditions. Odorants mainly responsible for the changes in sulfur perception were methional, methanethiol, and dimethyl sulfide. Increases in 2-acetyl-1-pyrroline, 2-acetyl-thiazole, and 2-acetyl-2-thiazoline intensities were associated with roasted aromas. A marginal increase in intensity of sweet aromatic flavor could be explained by increases in 2,3-butanedione, 3-hydroxy-2-butanone, -damascenone, and 2- and 3-methylbutanal. Predominant lipid-derived odorants, including (E,E)- 2,4-nonadienal, (E,E)-2,4-decadienal, (E,Z)-2,4-decadienal, (E)-2-nonenal, (E)-2-octenal, 1-octen-3- one, 1-octen-3-ol, and (E,Z)-2,6-nonadienal, were affected by processing conditions. Intensities of overall aroma and sulfur notes in soy milk decreased during storage, whereas other sensory attributes did not change. Color changes, evaluated by using a Chroma-meter, indicated all UHT heating conditions used in this study generated a more yellow and saturated color in soy milk in comparison to the control soy milk. KEYWORDS: Thermal processing; cooked off-flavors; soy milk; UHT; storage effect; color INTRODUCTION Soy milk, a water extract of soybeans, is an excellent source of protein and essential fatty acids. It is cholesterol-free and relatively cheap in comparison with other sources of protein. Despite the beneficial attributes of soy milk, its consumption in the Western world has been limited due to its unacceptable beany flavor (1). A considerable number of studies have been conducted to determine the volatile compounds responsible for the beany off-flavor in soy milk. As a result, in the past decade novel processing technologies have been developed to reduce beany off-flavors, obtain better yields, eliminate antinutritional factors, and extend the shelf life of soy milk. High temperature- short time (HTST) and ultrahigh-temperature (UHT) processing methods have been a crucial part of this development (1, 2). The use of high-temperature processing combined with aseptic packaging has opened new markets and avenues for the distribution of soy milk (2). Unfortunately, color changes, loss of nutrients, and creation of “cooked off-flavors” have been encountered in soy milks produced under these conditions. A viable solution to this problem has been difficult to address because little information exists about the chemical reactions that occur at these temperatures and also due to the uncertainty of the effect of storage on these heat-induced aroma compounds. The aim of this project was to characterize the major aroma- active components generated under UHT conditions, to assess their impact on the overall soy milk aroma and flavor, and to determine the effect of short-term storage on key heat-induced aroma compounds. MATERIALS AND METHODS Chemicals. Analytical grade authentic compounds were obtained from Aldrich Chemical Co. (St. Louis, MO) except for 2-acetyl-1- pyrroline, which was a gift from Dr. R. Buttery (USDA, ARS, WRRC, Albany, CA); -damascenone, which was provided by Firmenich Co. (Princeton, NJ); and δ-octalactone and γ-nonalactone, which were * Corresponding author [telephone (217) 333-5803; fax (217) 333-1875; e-mail cadwlldr@uiuc.edu]. † University of Illinois. § North Carolina State University. # Cargill, Inc. 3018 J. Agric. Food Chem. 2007, 55, 3018-3026 10.1021/jf0631225 CCC: $37.00 © 2007 American Chemical Society Published on Web 03/21/2007