Microwave processing of avocado: Volatile flavor profiling and olfactometry Rosa I. Guzmán-Gerónimo a, ⁎, Mercedes G. López b , Lidia Dorantes-Alvarez c a Instituto de Agroindustrias, Universidad Tecnológica de la Mixteca, Km. 2.5 Carretera a Acatlima, C.P. 69000, Huajuapan de León, Oaxaca, Mexico b Unidad de Biotecnología e Ingeniería Genética de Plantas, Centro de Investigación y de Estudios Avanzados del IPN, Km. 9.6 Libramiento Norte Carretera Irapuato-León, C.P. 629, 36500 Irapuato, Guanajuato, Mexico c Departamento de Graduados e Investigación en Alimentos de la Escuela Nacional de Ciencias Biológicas del IPN, Carpio y Plan de Ayala S/N, Casco de Santo Tomás, Mexico ABSTRACT ARTICLE INFO Article history: Received 19 December 2007 Accepted 18 May 2008 Keywords: Avocado Microwave treatment Response surface Volatiles Olfactometry The aim of this research was to evaluate the effect of microwave time, pH and avocado leaves on the volatile profile of avocado using response surface methodology, and aroma extract dilution analysis (AEDA) was employed to evaluate changes in the odorant composition. Response surface analyses showed maximum values for volatiles derived from lipid oxidation at high levels of microwave time and low values of pH. The presence of terpenoids, estragole, hexanal and 2-hexenal [E] was enhanced with the addition of avocado leaves. The optimum condition to prepare avocado puree was 30 s heating time, pH 5.5 and 1% of leaves. Comparative AEDA analysis for microwaved avocado puree added with and without avocado leaves showed changes in the FD of compounds derived from lipids. In addition, AEDA suggests that the addition of avocado leaves to microwaved avocado is related to the presence of important odorants such α-pinene, estragole and 2-hexenal [E]. Industrial relevance: Several attempts have been made to process avocados as purée or “guacamole”. Microwave treatment offers an alternative for the blanching of fruits and vegetables, since the application of high temperatures for short times often results in minimum damage. Furthermore, previous studies have shown that better retention of color and lightness is obtained when avocado purée is processed in a microwave oven. However, a great loss of flavor takes place when this commodity is treated by heat. The application of a combined treatment consisting of microwaves, pH and the addition of avocado leaves to the purée minimizes flavor loss and results in a product with the characteristic flavor of avocado. © 2008 Elsevier Ltd. All rights reserved. 1. Introduction The avocado fruit is greatly appreciated for delicate and sweet flavor. This fruit is usually consumed fresh, but can be also used as ingredient in salads or as the well known guacamole. On the other hand, avocado leaves are often used in the preparation of many ethnic dishes in Mexico to add a delightful avocado taste. Microwave processing offers an alter- native way to blanch fruits and vegetables, since the application of high temperature in a very short time often results in minimum damage. Previous studies have shown that better retention of color and lightness is obtained when avocado puree microwaved for 30 s with copper or zinc chloride addition at pH 5.5 (Guzmán et al., 2002). However a great loss of flavor takes place when this commodity is microwaved. Additionally, it is known that the presence or absence of some aroma compounds play a definitive role in food quality. So, increasing the knowledge on avocado odorants is important to understand the development of flavor during avocado heating. Gas chromatography-olfactometry (GC-O) is a useful technique for estimating the contribution of most odor-active com- pounds in an overall odor, and has been successfully used to characterize key aroma compounds in foods (Acree, 1997). Among the different GC-O techniques, AEDA is a screening method to determine the relative odor potency of compounds in different products and to estimate the changes or the entire set of aroma-active volatiles of a given food induced by, for instead, processing (Kilic, Hafizoglu, Kollmannsberger, & Nitz, 2004; Kumazawa & Masuda, 2001). SPME is a rapid, solvent-less, inexpensive and sensitive extraction method that allows the concentration of aroma compounds, as well as their analysis by GC-MS and olfactometry (Lecanu, Ducruet, Jouquand, Gratadoux, & Feigenbaum, 2002; Marti, Mestres, Sala, Busto, & Guasch, 2003). On the other hand, there are a few reports (Nagalingam, 1993; Siyinda & Gramshaw, 1998) on the volatile composi- tion of avocado fruit but none on the effect of microwave treatment on its sensory properties using olfactometric techniques. Therefore, the aim of this work was to study the effect of microwave treatment, pH and avo- cado leaves addition on volatile compounds by response surface me- thodology and to evaluate odorant changes by SPME-GC-O. 2. Materials and methods 2.1. Sample preparation Hass avocado was obtained from a local market and selected for uniformity on size, appearance, ripeness and absence of physical defects. Avocado puree was prepared by mixing and homogenizing three parts of Innovative Food Science and Emerging Technologies 9 (2008) 501–506 ⁎ Corresponding author. Tel.: +52 953 532 0399x400. E-mail address: riguzman@mixteco.utm.mx (R.I. Guzmán-Gerónimo). 1466-8564/$ – see front matter © 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.ifset.2008.05.003 Contents lists available at ScienceDirect Innovative Food Science and Emerging Technologies journal homepage: www.elsevier.com/locate/ifset