Color development and acrylamide content of pre-dried potato chips Franco Pedreschi a, * , Jorge Leo ´n a , Domingo Mery b , Pedro Moyano c , Romina Pedreschi d , Karl Kaack e , Kit Granby f a Departamento de Ciencia y Tecnologı ´a de Alimentos, Facultad Tecnolo ´ gica, Universidad de Santiago de Chile (USACH) Av. Ecuador 3769, Santiago, Chile b Departamento de Ciencia de la Computacio ´ n, Pontiﬁcia Universidad Cato ´ lica de Chile, Vicun ˜a Mackenna 4860, Santiago, Chile c Departamento de Ingenierı ´a Quı ´mica, Universidad de Santiago de Chile (USACH), P.O. Box 10233, Santiago, Chile d Departament Biosystems—Division MeBioS, Katholiek Universiteit Leuven, Willem de Croylaan 42, B-3001 Leuven, Belgium e Department of Horticulture, Danish Institute of Agricultural Sciences, Kirstinebjergvej 10, 5792 Aarslev, Denmark f Department of Food Chemistry, Danish Institute for Food and Veterinary Research, Moerkhoej Bygade 19, 2860 Soeborg, Denmark Received 5 February 2006; received in revised form 2 March 2006; accepted 2 March 2006 Available online 18 April 2006 Abstract The objective of this work was to study the development of color formation in pre-dried potato slices during frying and acrylamide formation in the ﬁnal potato chips. Color measurement was done by using an inexpensive computer vision technique which allowed quantifying representatively and precisely the color of complex surfaces such as those of potato chips in L * a * b * units from RGB images. Prior to frying, potato slices (Desire ´e variety, diameter: 37 mm, width: 2.2 mm) were blanched in hot water at 85 °C for 3.5 min. Unblanched slices were considered as the control. Slices of the same dimensions were blanched as in the previous step, and then air-dried until reaching a moisture content of 60% (wet basis). These samples were called pre-dried potato slices. Potato slices were fried at 120 °C, 140 °C, 160 °C and 180 °C until reaching moisture contents of 1.8% (total basis) for color quantiﬁcation. Acrylamide concentration was determined only in ﬁnal chips fried at 120 °C, 150 °C and 180 °C and compared with that of two brands of commercial chips pro- duced in Chile (Moms and Frito Lay). Color values in L * a * b * units were recorded at diﬀerent sampling times during frying at the four mentioned temperatures using the total color diﬀerence parameter (DE). Pre-drying did not aﬀect the color of potato chips considerably when compared against blanched chips; however when fried at 180 °C, pre-dried potato chips present 44%, 22%, 44% lower acrylamide content than that of the control, Moms and Frito Lay chips, respectively. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Potato chips; Frying; Color; Pre-drying; Blanching; Acrylamide 1. Introduction Potato chips have been a popular salty snack for 150 years whose consumption yearly in US is around 1.2 billion of pounds (Clark, 2003). Potato chips are thin potato slices that are dehydrated by deep fat frying to a moisture con- tent of 0.02 kg/kg or less (Baumann & Escher, 1995). Potato chips have an oil content that ranges from 35% to 45% (wet basis) and gives the product a unique texture–ﬂa- vor combination that makes them so desirable (Garayo & Moreira, 2002; Mellema, 2003). Dehydration in hot oil at temperatures between 160 °C and 180 °C is characterized by high drying rates that are critical for ensuring favorable structural and textural properties of the ﬁnal product (Baumann & Escher, 1995). Color development only begins when suﬃcient amount of drying has occurred in potato slices and depends also on the drying rate and the heat transfer coeﬃcient during the diﬀerent stages of frying. Color is visually considered one of the most important parameters in the deﬁnition of 0260-8774/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.jfoodeng.2006.03.001 * Corresponding author. Tel.: +56 9359 1679; fax: +562 682 3536. E-mail addresses: fpedresc@lauca.usach.cl, fpedresc@usach.cl (F. Pedreschi). www.elsevier.com/locate/jfoodeng Journal of Food Engineering 79 (2007) 786–793