CHEMICAL ENGINEERING TRANSACTIONS VOL. 56, 2017 A publication of The Italian Association of Chemical Engineering Online at www.aidic.it/cet Guest Editors: Jiří Jaromír Klemeš, Peng Yen Liew, Wai Shin Ho, Jeng Shiun Lim Copyright © 2017, AIDIC Servizi S.r.l., ISBN978-88-95608-47-1; ISSN 2283-9216 Ascorbic Acid Content and Proteolytic Enzyme Activity of Microwave-Dried Pineapple Stem and Core Nurul Asyikin Md Zaki* ,a,b , Norazah Abd Rahman a,c , Norashikin Ahmad Zamanhuri a,c , Syafiza Abd Hashib a,c a Faculty of Chemical Engineering, Universiti Teknologi MARA, 40450 Shah Alam, Selangor, Malaysia. b Green Technology and Sustainable Development, Community of Research (CoRe), Universiti Teknologi MARA, 40450 Shah Alam, Selangor, Malaysia. c Frontier Materials and Industrial Application, Community of Research (CoRe), Universiti Teknologi MARA, 40450 Shah Alam, Selangor, Malaysia. asyikin6760@salam.uitm.edu.my Solid wastes generated from the industrial processing of pineapple are favourable raw materials for obtaining antioxidants and bioactive compounds because of their low cost and the possibility of reducing environmental problems caused by waste disposal. Hence this study aims to investigate the microwave drying characteristics of pineapple waste and its effect on the ascorbic acid content and proteolytic enzyme activity. Pineapple stem and core were subjected to microwave drying process at three different power intensities (380 W, 530 W and 680 W). Dried samples were then analysed for ascorbic acid concentration and proteolytic enzyme activity. Results show that ascorbic acid concentration in the stem sample dried at 530 W was the highest. The proteolytic enzyme activity was found to be the highest in pineapple core dried at 380 W. As the power level increased, more proteolytic enzyme denaturated and resulted in the reduction of enzyme activity. Microwave drying could remarkably preserve both pineapple stem and core while retaining the ascorbic acid content and proteolytic enzyme activity of dried pineapple wastes. 1. Introduction Pineapple is mainly exported into varieties of processed products such as canned fruits, fresh juices, concentrates and jams besides freshly consumed. The production of pineapple have increasingly generated substantial wastes consist of pineapple stem, core, leaves, peels, crown and also residual pulp. The generation of great waste by this tropical fruit is mainly due to assortment and removal of parts that are unfit for human consumption. In addition, Upadhyay et al. (2010) found that huge generation of pineapple wastes have incredibly increase the dump site area and cause serious environmental problem as these wastes interfere with BOD and COD of natural systems. Pineapple waste could be exploited more for its natural content such as antioxidants, vitamins, phenolic contains, enzymes and many others nutritional value. Ascorbic acid and proteolytic enzymes are among the important nutrients that can be preserved in pineapple stem and core using drying method. Drying is a technique employed to improve the stability of the product and decreasing the water activity thus slower the microbiological activity in order to reduce physical and chemical reactions that may occur prior to storage (Layla, 2013). Various drying methods are used in the drying of fruits and vegetables. Microwave drying is one of the methods that have gained interests among researchers as an alternative drying technique for many agricultural products due to increasing concerns about product quality and production costs (Gursoy et al., 2013). Microwave drying offers several advantages over others conventional drying including increase operation speed, lower energy usage, accurate process control and fast start-up and shut down of the equipment (Datta and Anantheswaran, 2001). Microwave drying may preserve and improve product quality such as aroma, taste, rehydration ability, microbial stability, nutritional value and overall appearance as the detrimental effects DOI: 10.3303/CET1756229 Please cite this article as: Zaki N.A.M., Rahman N.A., Zamanhuri N.A., Hashib S.A., 2017, Ascorbic acid content and proteolytic enzyme activity of microwave-dried pineapple stem and core, Chemical Engineering Transactions, 56, 1369-1374 DOI:10.3303/CET1756229 1369