Effects of Different Drying Methods on Proximate Composition of Three Accessions of Roselle (Hibiscus sabdariffa) Calyces

Abstract

Seeds of three roselle accessions (HS11, HS89 and HS41) were obtained from the Department of Horticulture, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana and grown to obtain the calyces. The calyces were dried by sun (34.9°C), solar (56.5°C) and oven (60.0°C) methods. Most people consume the roselle calyces due to their nutritional and medicinal benefits. The study sought to, therefore, determine the effect of the different drying methods (oven, sun and solar) on the proximate composition of roselle accessions. The experiment was set up in a 3×3 factorial arrangement in a Completely Randomized Design (CRD) with three replications. The roselle accessions were harvested 12 weeks after sowing. From the results, HS89 had significantly (P ≤ 0.01) least moisture content of 8.43% and highest carbohydrate content (65.30%). Ash and protein contents were highest (P ≤ 0.01) in HS41 being 6.40% and 6.91%, respectively. As regards crude fat and crude fibre contents, HS11 had the highest being 2.49% and 17.92%, respectively. Concerning the methods of drying, oven-drying resulted in calyces with significantly (P ≤ 0.01) lower moisture content (6.97%), but higher fat (2.88%), ash (5.80%) and carbohydrate (62.46%) contents. solar-dried calyces had significantly higher (P ≤ 0.01) protein content (5.86%) while sun-dried calyces had significantly higher (P ≤ 0.01) crude fibre content (17.60%). Interactively, oven-dried HS89 had significantly (p≤ 0.01) lowest moisture (6.50%) and highest fat (3.23%) while solar-dried HS41 had highest protein (8.17%) and ash (7.25%) contents. The study concluded that oven drying was more efficient than solar and sun in reducing the moisture, maintaining fat, ash and carbohydrate contents of roselle calyces. Solar drying resulted in higher protein content while sun-dried calyces produced higher fibre content in all the three accessions.