CHANGES IN ACID AND HEAT RESISTANCE OF SALMONELLA NEWPORT AND SALMONELLA SAINTPAUL STORED IN MANGO AND PINEAPPLE JUICES YISHAN YANG 1 , JIA HAN TEO 1 , WOO-SUK BANG 2 and HYUN-GYUN YUK 1,3 1 Food Science and Technology Programme, Department of Chemistry, National University of Singapore, Science Drive 2, Singapore 117543, Singapore 2 Department of Food and Nutrition, Yeungnam University, Gyeongsan-si, Gyeongsangbuk-do, South Korea 3 Corresponding author. TEL: +65 6516-1136; FAX: +65 6775-7895, EMAIL: chmyukhg@nus.edu.sg Received for Publication January 13, 2012 Accepted for Publication May 9, 2012 doi:10.1111/j.1745-4565.2012.00382.x ABSTRACT The aim of this study was to investigate survival of Salmonella Newport and Salmo- nella Saintpaul in simulated gastric fluid (SGF) at pH 1.9 or at 56C after storage in mango or pineapple juice at 4 or 24C for 24 h. In SGF, only Salmonella Saintpaul adapted to mango juice at 4C significantly (P < 0.05) enhanced its acid resistance with D value of 3.88 min, whereas both serovars stored in mango juice at 24C had significantly lower D values with 0.88 and 0.72 min, respectively. The D56C values of both serovars adapted to juices significantly decreased compared with nonadapted cells, except for Salmonella Newport stored in pineapple juice at 24C. Overall, two Salmonella serovars tested in this study did not show the enhanced acid or heat resis- tance after storage in these two tropical fruit juices, indicating that introduction of Salmonella Newport and Salmonella Saintpaul to mango and pineapple juices is unlikely to enhance their survival during gastric transit or thermal processing. PRACTICAL APPLICATIONS Salmonella spp., one of the leading causative agents of gastroenteritis, are a major public health concern in the world. It has been reported that Salmonella spp. can survive in unpasteurized orange juice or apple cider and become more resistant to subsequent exposure to acid or heat conditions.However,there is limited information in the literature on the effect of survival of Salmonella spp. in tropical fruit juices on their acid and heat resistance. This research was conducted to investigate the surviv- ability of Salmonella Newport and Salmonella Saintpaul in simulated gastric fluid at pH 1.9 or at 56C after adaptation in mango or pineapple juice. The results of this study would enrich our understanding on the stress response of Salmonella spp. in these juices,as well as provide guidance to developing intervention technology to eliminate Salmonella Newport and Salmonella Saintpaul in mango and pineapple juices. INTRODUCTION Salmonella spp., gram-negative, facultative anaerobic and nonspore-forming bacteria, are a major cause of foodborne infections worldwide (Soyer et al. 2009). Although Salmo- nella enterica serovars Enteritidis and Typhimurium are the most frequently isolated serotypes in most countries (Hen- driksen et al. 2011), S. enterica serovars Newport and Saint- paul have been increasingly identified as causative agents in several salmonellosis outbreaks related with unpasteurized orange juice (Jain et al. 2009), vegetables (CDC 2009; Mohle- Boetani et al. 2009) and fruits (Sivapalasingam et al. 2003; Munnoch et al. 2009). Recently, foodborne outbreaks related to fruit and veg- etable juices increased. Between 1995 and 2005 in the U.S.A., there were 21 juice-associated outbreaks; 10 were associated with apple juice or cider, eight were linked to orange juice and three were involved with other types of fruit juice. Moreover, five out of 13 outbreaks of known etiology were caused by Sal- monella spp. (Vojdani et al. 2008). As a result, the United Journal of Food Safety ISSN 1745-4565 1 Journal of Food Safety •• (2012) ••–•• © 2012 Wiley Periodicals, Inc.