Eect of dierent soluble solids in the water on the ascorbic acid losses during water blanching of potato tissue C. Arroqui a, * , T.R. Rumsey b , A. Lopez c , P. Virseda a a Food Technology Area, Applied Chemical Dept., Public Univ. of Navarra, Campus de Arrosadıa s/n 31006 Pamplona, Spain b Food Engineering Area, Biological & Agricultural Engineering Dept., UC Davis, California, USA c Food Engineering Area, Technical University of Cartagena, Cartagena, Spain Received 21 April 2000; accepted 19 June 2000 Abstract The aim of this work is to compare ascorbic acid losses by diusion in potato cylinders during water blanching with dierent soluble solids. Dierences between samples blanched in recycled water (2.6 kg/m 3 soluble solids from potato blanching process) and water with 0.5 kg/m 3 of glucose were observed. The apparent diusivities of ascorbic acid during blanching of potato in distilled, recycled and water with 0.5 kg/m 3 of glucose at 80°C were compared, being 17:39  10 10 , 16:09  10 10 and 17:78  10 10 m 2 /s, respectively. Ó 2000 Elsevier Science Ltd. All rights reserved. Keywords: Potato; Losses by diusion; Water blanching; Recycled water 1. Introduction Blanching is a treatment that takes place during preparation of the raw vegetables before preservation processes like canning and freezing. Its main objective is the inactivation of the enzymes responsible for deterio- ration reactions, as undesirable color, flavor or texture changes in the product. However, this operation also has some inconvenient eects on product quality. Excessive texture losses, un- desirable color changes, nutritional losses, environmen- tal impact and energetic cost are the most important ones. In potatoes, blanching causes important losses of ascorbic acid, one of its principal nutrients. The ascorbic acid losses are used as an indicator of the intensity of the thermal treatment applied. Although the ascorbic acid losses could be caused by enzymatic oxidation, thermic degradation and diusion, the main mechanism of ascorbic acid losses during po- tato blanching is by diusion (Garrote, Silva, & Bertone, 1986). Some studies have been done to obtain the experi- mental values of the apparent coecient of ascorbic acid diusivity in potato during blanching. Garrote et al. (1986) found that the values of the apparent coecient of ascorbic acid diusivity in potato blanching were the following: 0.93, 1.40 y 2:50  10 9 m 2 /s at 65°C, 80°C and 100°C, respectively and 1:326  10 9 m 2 /s at 77°C. In another study, Gekas,  Oste, and Lamberg (1993) showed a range of values of the apparent coecient of ascorbic acid diusivity in water blanching of potatoes from 0.1 to 3  10 10 m 2 /s at 25°C after dierent blanching treatments in the range of 50–90°C and dur- ing times intervals from 2 to 20 min. The diusion processes in a multicomponent solution from or to a polyphase medium like the potato tissue, could aect the Dapp coecient. These eects could appear when these components have dierent molecular weights, if there is no dilute solution or if the gradient of one of the solutes is bigger than that of the other one (Gekas, 1992). Some studies about the mass transfer in water con- taining soluble solids have been done. Selman, Rice and Abdul-Rezzak (1983) studied the eect of dierent su- crose concentration in the exterior water on the coe- cients of sucrose diusion during carrot blanching. Lombardi, Giannuzzi, and Zarizky (1996) observed that the ascorbic and citric acids concentrations in water Journal of Food Engineering 47 (2001) 123–126 www.elsevier.com/locate/jfoodeng * Corresponding author. Tel.: +34-948-169-091; fax: +34-948-169- 893. E-mail address: cristina.arroki@unavarra.es (C. Arroqui). 0260-8774/00/$ - see front matter Ó 2000 Elsevier Science Ltd. All rights reserved. PII: S 0 2 6 0 - 8 7 7 4 ( 0 0 ) 0 0 1 0 7 - 2