Changes in S-allyl cysteine contents and physicochemical properties of black garlic during heat treatment Sang Eun Bae a , Seung Yong Cho b, ** ,1 , Yong Duk Won c , Seon Ha Lee d , Hyun Jin Park a, e, * , 1 a School of Life Science and Biotechnology, Korea University, Seoul, Republic of Korea b Institute of Life Sciences and Biotechnology, Korea University, Seoul, Republic of Korea c Uiseong Black Garlic Farming Association, Gyeongsangbuk-do, Republic of Korea d College of Health and Welfare, Kyungwoon University, Gyeongsangbuk-do, Republic of Korea e Department of Packaging Science, Clemson University, Clemson, SC 29634-0370, USA article info Article history: Received 14 September 2011 Received in revised form 25 March 2013 Accepted 4 May 2013 Keywords: Black garlic Heat-treated garlic S-Allyl cysteine Antioxidant activity abstract This study aimed to investigate the effects of temperature on the black garlic manufacturing process. The moisture content, pH, browning intensity, S-allyl cysteine (SAC) content and antioxidant activity, including DPPH radical scavenging activity and reducing power, were determined. The moisture content of garlic gradually decreased throughout the heating process. The rate of moisture removal was higher at high temperatures compared with low temperatures. The pH also decreased more significantly in garlic heated at high temperatures. The browning intensity increased with increasing temperature. The SAC contents of black garlic were significantly different according to heating temperature; the garlic samples heated at a low temperature had a higher SAC contents. Antioxidant activity, as determined by the DPPH radical scavenging activity and reducing power, increased when the garlic was exposed to higher temperatures. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Garlic (Allium sativum L.) is widely used as a seasoning for food and has long been used as a medicinal agent for the treatment of multiple human diseases and disorders. Recently, garlic has attracted much research interest due to its beneficial health effects, which include antioxidant activity (Gorinstein et al., 2006), anti- microbial activity (Rees, Minney, Plummer, Slater, & Skyrme,1993) and anticancer activity (Durak, Yilmaz, Devrim, Perk, & Kaçmaz, 2003). Accordingly, garlic has become one of the most wide- spread disease-preventing foods (Block, 1992). Although garlic has many active components that contribute to its health benefits, including allicin and its derivatives, consumption of unprocessed raw garlic is limited due to its characteristic odor, taste and tendency to cause stomach upset. Therefore, in recent years, various processing methods such as heat treatment, aging and fermentation have been used to eliminate the offensive odor and improve the palatability of garlic. Heat treatment is the most widely used processing method for removing the unpleasant taste and odor of garlic. When garlic undergoes heat treatment, various physicochemical changes occur, including changes in flavor, color and nutrient content. Particularly, heat treatment leads to non-enzymatic browning reactions such as the Maillard reaction, caramelization and the chemical oxidation of phenols. A number of non-enzymatic browning reactions are associated with the formation of compounds with strong antioxi- dant properties (Legault, Hendel, & Talburt, 1954; Manzocco, Calligaris, Mastrocola, Nicoli, & Lerici, 2000; Osada & Shibamoto, 2006; Peleg, Mannheim, & Berk, 1970; Yanagimoto, Lee, Ochi, & Shibamoto, 2002; Yilmaz & Toledo, 2005). Black garlic is a type of heat-treated garlic that is generally produced by heating whole bulbs of raw garlic at high temperature under controlled humidity for more than 1 month. Many studies have demonstrated the health benefits of black garlic. It was re- ported that black garlic has stronger antioxidant activity compared with raw garlic and may have greater efficacy for preventing metabolic diseases and alcoholic hepatotoxicity (Ide & Lau, 1999; Ide, Matsuura, & Itakura, 1996). * Corresponding author. School of Life Sciences and Biotechnology, Korea Uni- versity, 1,5-Ka, Anam-Dong, Sungbuk-gu, Seoul 136-701, Republic of Korea. Tel.: þ82 2 3290 3450; fax: þ82 2 953 5892. ** Corresponding author. Institute of Life Sciences and Biotechnology, School of Life Sciences and Biotechnology, Korea University,1,5-Ka, Anam-Dong, Sungbuk-gu, Seoul 136-701, Republic of Korea. Tel.: þ82 2 3290 4282; fax: þ82 2 953 5892. E-mail addresses: sycho@korea.ac.kr (S.Y. Cho), hjpark@korea.ac.kr (H.J. Park). 1 Hyun Jin Park and Seung Yong Cho contributed equally to this research as co- corresponding authors. Contents lists available at ScienceDirect LWT - Food Science and Technology journal homepage: www.elsevier.com/locate/lwt 0023-6438/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.lwt.2013.05.006 LWT - Food Science and Technology 55 (2014) 397e402