Original article Effects of killing conditions of vanilla (Vanilla planifolia, Andrews) pods during the curing process on aroma composition of pod ethanol extract Violeta T. Pardio, 1 Maria D. Mariezcurrena, 2,3 Krzysztof N. Waliszewski, 2 * Victor Sa ´nchez 3 & Mariusz K. Janczur 3 1 Laboratorio de Toxicologı´a, Facultad de Medicina Veterinaria y Zootecnia, Universidad Veracruzana, 91710 Veracruz, Me´xico 2 Instituto Tecnolo´gico de Veracruz, Unidad de Investigacio´n y Desarrollo de Alimentos, A.P. 1380, 91700 Veracruz, Me´xico 3 Universidad Auto´noma del Estado de Me´xico, Toluca, 50040 Estado de Me´xico, Me´xico (Received 13 October 2008; Accepted in revised form 17 February 2009) Summary The effects on the aroma compositions of ethanol extracts obtained by traditional and enzyme-assisted methods from seven killing conditions used in vanilla pod curing were studied. Two procedures of vanilla pod killing consisted of either freezing pods at )10 °C for 24 h or immersing pods in 80 °C water for 10 s each of three times with 30 s intervals resulted in the highest vanillin values in terms percentage of dry weight of the bean (2.84 and 2.96), 4-hydroxybenzaldehyde (0.18 and 0.20), vanillyl alcohol (0.56 and 0.57) and vanillic acid (0.18 and 0.19 respectively) when traditional vanilla ethanol extraction was used. When this extract was aged for 3 months it showed improvement in flavour compounds. Enzyme-assisted vanilla ethanol extraction showed a higher content of flavour compounds than traditional extract, for example vanillin 4.38% and 2.96% respectively. Only vanillic acid levels were improved after ageing of the enzyme- assisted extracts. Keywords Curing methods, vanilla ethanol extract, Vanilla planifolia. Introduction During the curing process, mature vanilla pods develop vanilla flavour, as a result of naturally induced native enzymatic reactions. Developing a complex flavour requires a curing time of weeks that is also very laborious. Some vanilla cultivating countries developed their own curing protocols consisting of the following steps: killing, sweating and simultaneous drying and conditioning. Although all steps are important, killing step considered as the most important (Mariezcurrena et al., 2008). The objective of killing is to stop further vegetative development in the fresh pod and promote cell decompartmentalisation by disrupting the cell membrane to create better conditions for contact between substrates and their respective enzymes (Purse- glove et al., 1981). In this way, encapsulated glucosyl precursors of aromatic compounds and their hydrolytic enzymes catalyse the liberation of vanillin and other vanilla aromatic compounds (Dignum et al., 2001; Odoux et al., 2003). It is also very important that the best killing conditions limit native enzyme inactivation. The most common vanilla bean killing protocol is a heat treatment, including uncontrolled temperature in the sun, controlled time and temperature in oven or hot water treatment. In the past, considerable studies were devoted to determining the optimal conditions for vanilla curing (Jones & Vicente, 1948; Broderick, 1956; Theodose, 1973; Dignum et al., 2002), isolation of aroma gluco- sides responsible for vanilla flavour production (Odoux, 2000; Dignum et al., 2001) and assaying of enzymes activity involved in flavour development (Wild-Altamir- ano, 1969; Hanum, 1997; Jiang et al., 2000; Odoux et al. 2000; Dignum et al., 2001, 2002; Havkin-Frenkel et al., 2004; Ma´rquez & Waliszewski, 2008) and still more studies are needed. The major product derived from cured beans is an ethanolic extract which is submitted to an ageing process that is critical in furthering the development of flavour in the extract. High ethanol content in the vanilla extract accelerates the reaction of ethanolysis, hydrolysis of esters of high molecular weight alcohols into free alcohols, acids and esters of organic acids and *Correspondent: Fax: +522299345701 (ext. 201); e-mail: kw@itver.edu.mx International Journal of Food Science and Technology 2009, 44, 2417–2423 2417 doi:10.1111/j.1365-2621.2009.01944.x Ó 2009 The Authors. Journal compilation Ó 2009 Institute of Food Science and Technology