Research Article Drying Rate and Product Quality Evaluation of Roselle (Hibiscus sabdariffa L.) Calyces Extract Dried with Foaming Agent under Different Temperatures Mohamad Djaeni , Andri Cahyo Kumoro, Setia Budi Sasongko, and Febiani Dwi Utari Department of Chemical Engineering, Faculty of Engineering, Diponegoro University, Jl. Prof. H. Soedarto, SH, Tembalang, Semarang 50275, Indonesia Correspondence should be addressed to Mohamad Djaeni; moh.djaeni@live.undip.ac.id Received 4 September 2017; Accepted 10 February 2018; Published 20 March 2018 Academic Editor: Marie Walsh Copyright © 2018 Mohamad Djaeni et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Te utilisation of roselle (Hibiscus sabdarifa L.) calyx as a source of anthocyanins has been explored through intensive investigations. Due to its perishable property, the transformation of roselle calyces into dried extract without reducing their quality is highly challenging. Te aim of this work was to study the efect of air temperatures and relative humidity on the kinetics and product quality during drying of roselle extract foamed with ovalbumin and glycerol monostearate (GMS). Te results showed that foam mat drying increased the drying rate signifcantly and retained the antioxidant activity and colour of roselle calyces extract. Shorter drying time was achieved when higher air temperature and/or lower relative humidity was used. Foam mat drying produced dried brilliant red roselle calyces extract with better antioxidant activity and colour qualities when compared with nonfoam mat drying. Te results showed the potential for retaining the roselle calyces extract quality under suggested drying conditions. 1. Introduction Roselle (Hibiscus sabdarifa L.) is commercially cultivated in some countries like India, Indonesia, Malaysia, Sudan, Egypt, and Mexico [1]. Te roselle calyx is brilliant red in colour due to the existence of anthocyanins, such as cyanidin- 3-sambubioside, cyanidin-3-glucoside, and delphinidin-3- glucoside [2]. Te calyx is usually used to prepare jam, jelly, cakes, ice cream, preserves, and herbal beverage [3]. Te consumption of roselle calyx tea has been reported to promote health benefts, which mainly functions as an antiox- idant [4]. Te relationship between antioxidant activity and anthocyanin of roselle calyx has been reported in the litera- tures [5, 6]. Te total anthocyanin content of roselle calyces is 2.52 g/100 g expressed as delphinidin-3-glucoside [7]. Besides, the roselle extracts also contain ascorbic acid. Wang et al. observed that anthocyanins have many times more antioxidant activity than ascorbic acid [8]. Terefore, the antioxidant activity of roselle extract is predominantly con- tributed by anthocyanins. However, the use of anthocyanins in food products experienced problems related to their instability during processing and storage caused by direct exposure to heat, oxygen, and light [9]. Mazza and Miniati observed that thermal degradation of anthocyanin of roselle extract was fast at temperatures above 100 ∘ C [10]. Microencapsulation technique is one of the methods to maintain anthocyanins stability by entrapping them inside a coating material to reduce direct interactions with external factors, such as temperature, light, moisture, and oxygen. Although spray drying and freeze drying are the most common microencapsulation methods applied in the food and pharmaceutical industries, freeze drying is 30 to 50 times more costly than that of spray drying [11]. However, extreme moisture loss during spray drying may trigger shrinking and deformation of dried particles [12]. Foam mat drying is carried out by transforming liquid and semisolid materials into stable foam by incorporation of air and a foaming agent. It is a good option to shorten drying time and to retain product quality [13]. Ovalbumin is usually chosen as a foaming agent due to the ability of its proteins Hindawi International Journal of Food Science Volume 2018, Article ID 9243549, 8 pages https://doi.org/10.1155/2018/9243549