Enrichment of the African catfish Clarias gariepinus (Burchell) with functional selenium originating from garlic: effect of enrichment period and depuration on total selenium level and sensory properties Edward Schram 1 , Rian A A M Schelvis-Smit 1 , Jan W van der Heul 1 & Joop B Luten 1,2 1 IMARES,Wageningen UR, IJmuiden,The Netherlands 2 No¢ma Marine,TromsÖ, Norway Correspondence: E Schram, IMARES, Wageningen UR, PO box 68,1970 AB, IJmuiden,The Netherlands. E-mail: edward.schram@wur.nl Abstract We wanted to optimize the procedure for the sele- nium enrichment of farmed African cat¢sh, using garlic as dietary selenium source. In the ¢rst experi- ment we established the relation between the length of the selenium enrichment period and the resulting total selenium level in the ¢llet of the ¢sh. It was found that at a dietary level of 11.7 mg kg  1 Se, a total selenium level in the ¢llet of 0.7 mg kg  1 was reached in a relatively short enrichment period of 10 days before harvest. In the second experiment we stu- died the e¡ect of depuration on the selenium level in the ¢llet and the sensory properties of selenium- enriched African cat¢sh. It was found that total sele- nium levels in the ¢llet were not a¡ected during a 7-day depuration period, while garlic odours and £a- vours in the raw and cooked ¢llets were signi¢cantly reduced after 2 days of depuration.We concluded that selenium enrichment of farmed African cat¢sh can be obtained by selenium-enriched ¢nishing diets, while garlic odours and £avours resulting from diet- ary garlic can be e¡ectively reduced in the ¢llet dur- ing a short depuration period without negatively a¡ecting ¢llet levels of total selenium. Keywords: African cat¢sh, functional food, sele- nium, garlic, depuration, sensory properties Introduction Dietary selenium is essential for human health (Ray- man 2000; Birringer, Pilawa & Flohe 2002) and at concentrations above dietary requirement, selenium is reported in several studies as having anti-carcino- genic e¡ects in humans (Ip 1998). However in some European countries the average daily intake is lower than the recommended daily intake (Rayman 2005). The need for selenium has resulted in an increase in selenium-rich functional foods (Dumont,Vanhaecke & Cornelis 2006), including the development of sele- nium-enriched farmed ¢sh. Functional food has been de¢ned in a European consensus document as ‘a food can be regarded as functional if it is satisfactorily demonstrated to a¡ect bene¢cially one or more target functions in the body, beyond adequate nutritional e¡ects, in a way that is relevant to either improved stage of health and well- being and/or reduction of risk of disease. A functional food must remain food and it must demonstrate its e¡ects in amounts that can normally be expected to be consumed in the diet: it is not a pill or a capsule, but part of the normal food pattern’ (Diplock, Aggett, Ashwell, Bornet, Fern & Roberfroid 1999). Aquacul- ture provides an excellent opportunity for the pro- duction of functional seafood products as many factors that determine the composition of the edible portion of ¢sh can be controlled under farming con- ditions. A number of studies have demonstrated the en- hancement of the selenium concentration in the muscle tissue of ¢sh as a result of elevated levels of dietary selenium (see Schram, Pedrero, Ca Ł mara, Van der Heul & Luten 2008 for an overview). None of these trials used garlic as source of functional sele- nium species while Ip and Lisk (1996) showed that Aquaculture Research, 2010, 41 , 793^803 doi: 10.1111/j.1365-2109.2009.02356.x r 2009 The Authors Journal Compilation r 2009 Blackwell Publishing Ltd 793