Effect of salt concentrations and drying methods on the quality and formation of histamine in dried milkfish (Chanos chanos) Chiu-Chu Hwang a , Chia-Min Lin b , Hsien-Feng Kung c , Ya-Ling Huang b , Deng-Fwu Hwang a , Yi-Cheng Su d , Yung-Hsiang Tsai b,⇑ a Department of Food Science, National Taiwan Ocean University, Keelung, Taiwan, ROC b Department of Seafood Science, National Kaohsiung Marine University, Kaohsiung, Taiwan, ROC c Department of Biotechnology, Tajen University, Pingtung, Taiwan, ROC d Seafood Research and Education Center, Oregon State University, Astoria, OR 97103, USA article info Article history: Received 22 December 2011 Received in revised form 6 March 2012 Accepted 3 May 2012 Available online 12 May 2012 Keywords: Histamine Dried milkfish Sun drying Hot-air drying Quality abstract The effects of salt concentrations (0–15.0%) and drying methods on the quality of dried milkfish were studied. The results showed that the levels of aerobic plate counts, total coliform, water activity, moisture contents, total volatile basic nitrogen (TVBN) and thiobarbituric acid (TBA) of the dried milkfish samples prepared with the same drying method decreased with increased salt concentrations. The samples pre- pared with the cold-air drying method had better quality in term of lower TVBN and TBA values than those of samples prepared with other drying methods. The histamine contents in all samples, except two, prepared with various salt concentrations by different drying methods were less than 1.9 mg/ 100 g. Two unsalted samples prepared with hot-air drying at 35 °C and sun drying methods were found to contain histamine at levels of 249.7 and 67.4 mg/100 g, respectively, which were higher than the potential hazard level of 50 mg/100 g. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Histamine is the causative agent of scombroid poisoning and a foodborne chemical hazard. Although scombroid poisoning is usu- ally a mild illness with a variety of symptoms including rash, urti- caria, nausea, vomiting, diarrhoea, flushing and tingling and itching of the skin (Taylor, 1986), severity of the symptoms can vary con- siderably with amounts of histamine ingested and individual’s sen- sitivity to histamine. Scombroid fish such as tuna, mackerel, bonito and saury that contain high levels of free histidine in their muscle are often implicated in scombroid poisoning incidents (Taylor, 1986). However, several species of nonscombroid fish such as mahi-mahi, bluefish, herring and sardine can also be implicated in incidents of scombroid poisoning. In Taiwan, scombroid poison- ing occurs occasionally and has commonly been associated with tuna, mackerel and black marlin (Chen & Malison, 1987; Chen et al., 2008; Tsai et al., 2005). However, sailfish, swordfish and mar- lin have recently become the fish species most frequently impli- cated in scombroid outbreaks in Taiwan (Chang, Kung, Chen, Lin, & Tsai, 2008; Chen et al., 2010b; Chen, Lee, Lin, Hwang, & Tsai, 2010; Tsai et al., 2007a). Milkfish (Chanos chanos) is an important aquaculture species in the Indo-Pacific region, particularly the Philippines, Indonesia and Taiwan (Chen, 1990). The fish has a free amino acid (FAA) pattern similar to migratory fish, such as skipjack, mackerel and tuna, which possess high levels of histidine in their white muscle (Kono- su & Yamaguchi, 1982; Suzuki, Hirano, & Suyama, 1987). A study reported that histidine at approximately 441 mg/100 g was the most prominent FAA in the white muscle of milkfish and ac- counted for 80% of the total FAAs in the fish (Chiou, Shiau, & Chai, 1990). Tsai, Chang, Kung, Wei, & Hwang (2005) reported that milk- fish was a better substrate than sailfish for histamine formation by bacterial histidine decarboxylation at elevated temperatures (>15 °C). Recently, the first histamine intoxication linked to con- sumption of dried milkfish occurred in the February of 2006 in southern Taiwan and Raoultella ornithinolytica was identified as the major histamine-producing bacterium responsible for the high contents of histamine in the implicated milkfish samples (Tsai et al., 2007b). Our previous study demonstrated that most dried milkfish products sold at retail markets in Taiwan contained hista- mine at levels of higher than the 5 mg/100 g guideline value sug- gested by the United States Food and Drug Administration with 40.6% (13/32) of tested samples contained >100 mg/100 g of hista- mine (Hsu et al., 2009). 0308-8146/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.foodchem.2012.05.035 ⇑ Corresponding author. Address: Department of Seafood Science, National Kaohsiung Marine University, No. 142, Hai-Chuan Rd., Nan-Tzu, Kaohsiung City 811, Taiwan, ROC. Tel.: +886 7 3617141x3609; fax: +886 7 3640634. E-mail address: yhtsai01@seed.net.tw (Y.-H. Tsai). Food Chemistry 135 (2012) 839–844 Contents lists available at SciVerse ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem