International Journal of Food Science and Nutrition Engineering 2014, 4(2): 27-35 DOI: 10.5923/j.food.20140402.01 Iron and Ascorbic Acid Content in Hibiscus sabdariffa Calyces in Tanzania: Modeling and Optimization of Extraction Conditions Emanuel Peter 1,* , Kijakazi O. Mashoto 1 , Susan F. Rumisha 2 , Hamisi M. Malebo 3 , Angela Shija 1 , Ndekya Oriyo 1 1 Health system and Policy Research, National Institute for Medical Research, 2448, Ocean Road, P.O.BOX 9653, Dar es Salaam, Tanzania 2 Disease Surveillance and GIS, National Institute for Medical Research, 2448, Ocean Road, P.O.BOX 9653, Dar es Salaam, Tanzania 3 Department of Traditional Medicine Research, National Institute for Medical Research, P.O. Box 9653, Dar es Salaam, Tanzania Abstract The main purpose of this study was to optimize extraction conditions for ferrous (iron II) and L-ascorbic acid from dried calyces of Hibiscus sabdariffa L grown in Dodoma in Tanzania by using Response Surface Methodology (RSM). Plant materials were taxonomically identified and authenticated by a plant taxonomist whereby a voucher specimen number 4992 was deposited at the herbarium in the Department of Botany at the University of Dar es Salaam. RSM with five level three-factor central composite rotatable design (CCRD) was employed to determine optimal combination of independent factors- soaking time, extraction temperature and solid-solvent ratio. Both single and multiple factor experiments were conducted. In single factor experiment (SFE) each independent factor was assessed to give experimental range. Ferrous was estimated by atomic absorption spectrophotometric method (AAS) while L-ascorbic acid was measured by iodometric titration technique. Data were analyzed using SPSS Version 16.0 and Design-Expert software Version 8.0.7.1. Mean and standard deviation of triplicates were calculated and assessed. One way analysis of variance (ANOVA) was also performed to find differences between the effect of the factors and their interaction. Significance was considered at 5% level of confidence (i.e. P<0.05). Finally, the obtained data was fitted using a cubic order polynomial model. The optimized extraction parameters were determined at soaking time 48 minutes, solid-solvent ratio 44% and extraction temperature 55 ° C. Under these extraction conditions, amount of L-ascorbic acid and ferrous extracted were 83.1 and 7.8 mg/100g respectively. The RSM helped to study interaction effect of extraction temperature, soaking time and solid-solvent ratio. Industries may adopt these optimal extraction conditions for production of Rosella beverages. Keywords Response surface methodology, Hibiscus sabdariffa L, Iron, Ascorbic acid, Extraction conditions 1. Introduction Hibiscus sabdariffa L. (Roselle) is an annual herbaceous shrub of the family Malvaceae. It has red calyces which are formed as the flowers fall off [1]. Originally from Angola, it is now cultivated throughout tropical and subtropical regions, especially in Sudan, Egypt, Thailand, Mexico, China, Tanzania, Senegal, Mali and Jamaica for both international market and domestic use [1,2]. Roselle is a drought tolerant, relatively easy to grow, and can be grown as part of multi-cropping system [1]. In Tanzania Roselle is cultivated mainly in the central and some of coastal regions. Analysis of aqueous extract of dried roselle calyces revealed many chemical constituents. Among the identified * Corresponding author: lordiswithus5@gmail.com (Emanuel Peter) Published online at http://journal.sapub.org/food Copyright © 2014 Scientific & Academic Publishing. All Rights Reserved constituents are alkaloids, L-ascorbic acid, citric acid, anisaldehyde, anthocyanin, β-carotene, β-sitosterol, cyanidin-3-rutinoside, delphinidin, galactose, gossypetin, hibiscetin, mucopolysaccharide, pectin, protocatechuic acid, polysaccharide, quercetin, stearic acid and wax [3–6]. It also rich in minerals such as calcium, magnesium, iron, potassium, sodium and zinc [7–9]. The chemical and mineral composition of dried roselle calyces could suggest its potential for both medicinal and nutritious value. The aqueous extract of dried calyces of H. sabdariffa, has been taken in many parts of the world for the treatment of various medical conditions. Previous clinical studies highlighted that, the extract has significant effect in controlling hypertension, liver diseases, fever, hyperlipidaemia and type-2 diabetes [8,10–14]. In Tanzania, the use of roselle calyces has taken importance for the variety of its nutritious and medicinal values. Individuals especially women, soak these calyces and drink the resulting juice. The practice may have been