Changes in volatiles with the application of progressive freeze-concentration to Andes berry (Rubus glaucus Benth) F.A. Ramos a , J.L. Delgado a , E. Bautista b , A.L. Morales a, * , C. Duque a a Departamento de Quı ´mica, Universidad Nacional de Colombia, A.A. 14490, Bogota ´, Colombia b Departamento de Fı ´sica, Universidad Nacional de Colombia, A.A. 14490, Bogota ´, Colombia Received 23 May 2002; revised 3 February 2004; accepted 14 July 2004 Abstract Progressive freeze-concentration was applied to Andes berry (Rubus glaucus Benth) pulp to observe changes in the volatile com- position. The effective partition constant K, the water removed and a yield parameter defined as water removed per unit of time was used to adjust the performance of the apparatus. For freeze-concentration effectiveness, an enzymatic treatment of the pulp was found to be necessary. This treatment does not change the flavor and improves the volatile quantity, without producing changes in physicochemical properties of the final product. Freeze-concentration process preserves the flavor, with a total volatiles loss near 20%. Sensorial analyses show that progressive freeze-concentration process does not change the sensorial properties of Andes berry pulp. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: Freeze-concentration; Volatiles; Rubus glaucus Benth; Enzymatic treatment 1. Introduction Colombia has a great variety of tropical and sub- tropical fruits which are characterized by their fine and exquisite flavor. Andes berry (Rubus glaucus Benth) is a native fruit from the north of the Andes highly ac- cepted for its properties such as taste (sweety-acid), beautiful color (dark-red) and its pleasant aroma. How- ever, this fruit is very perishable and presents difficulties in post-harvest conservation. The search for improved concentration methods of thermolabile pulps or juices obtained from this kind of fruits to avoid unacceptable flavor changes led to the use of freeze-concentration methods. In freeze-concentration the water is removed as ice crystals after freezing the pulp or juice. Apart from preserving the flavor, freeze-concentration keeps the chemical and biochemical properties. In spite of the high initial equipment investment, this method has considerably less energy costs when compared with con- centration by evaporation methods. Therefore, freeze- concentration has been applied to produce concentrated liquid food such as fruit juices (Deshpande, Bolin, & Salunkhe, 1982; Liu, Miyawaki, & Hayakawa, 1999) and products like coffee, tea and diary products (Desh- pande et al., 1982; Van Pelt, 1975). Due to its easy scale up, the majority of industrial applications to liquid foods make use of the suspension crystallization method. This method is characterized by the generation of a size distribution of crystals growing isothermically in the mother liquor. The small ice crystals formed are transferred to a ripening vessel to be enlarged, then transferred to a washing column and separated from the mother solution after washing with water. This steps: 0260-8774/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.jfoodeng.2004.07.022 * Corresponding author. Tel.: +57 1 3165000x14472; fax: +57 1 3165220. E-mail address: almoralesp@unal.edu.co (A.L. Morales). www.elsevier.com/locate/jfoodeng Journal of Food Engineering 69 (2005) 291–297