Predicting sodium chloride content in commercial king (Oncorhynchus tshawytscha)andchum(O. keta)hotsmoked salmon fillet portions by short-wavelength near-infrared (SW-NIR) spectroscopy Mengshi Lin a , Anna G. Cavinato b , Yiqun Huang a , Barbara A. Rasco a, * a Department of Food Science and Human Nutrition, Box 646376, Washington State University, Pullman, WA 99164-6373, USA b Chemistry Program, Eastern Oregon University, One University Blvd., La Grande, OR 97850, USA Received 15 February 2003; received in revised form 29 April 2003; accepted 1 May 2003 Abstract Partial least square (PLS) based short-wavelength near-infrared (SW-NIR) prediction models for salt content in commercial hot smoked fillet portions of king or Chinook (Oncorhynchus tshawytscha)(N=140; 212–468 g) and chum (O. keta) salmon (N=120; 137–356 g) were developed. Spectra were collected in the diffuse reflectance mode (600–1100 nm). The total salt content ranged from1.66to5.95%w/wforkingand2.15to5.69%w/wforchumsalmon.Themoisturerangedfrom50.7to71.6%w/wforking and55.5to69.7%w/wforchumsalmon.AnoptimalPLSmodelforsaltrequiredeightlatentvariablesforkingsalmon(R 2 =0.83, SEP=0.32% w/w) and eight latent variables for chum salmon (R 2 =0.82, SEP=0.25% w/w). # 2003 Elsevier Ltd. All rights reserved. Keywords: King salmon; Chum salmon; Moisture; Smoked fish; Sodium chloride; Short-wavelength near-infrared spectroscopy; SW-NIR 1. Introduction Ready-to-eat smoked aquatic food products such as hotsmokedsalmonincontrolledatmospherepackaging are important commercial products with an increasing domestic and international market. On a per pound basis, the wholesale value of salted salmon roe is higher than cured salmon, but on a volume basis, the value of the cured and/or smoked muscle is greater. The inter- national harvest of salmon (including aquaculture) exceeds 4000 million pounds with an estimated whole- sale market value of over 10,000 million dollars (John- son,2001).Approximately15%oftheharvestedsalmon is cured and/or smoked with a value at first sale of between 2000 and 3000 million dollars (Huang, Cavi- nato, Mayes, Bledsoe, & Rasco, 2002; Johnson, 2001). Two procedures are commonly used to produce smokedfish:coldsmokingandhotsmoking.Hotsmok- ing applies both heat and smoke to cook the product. CurrentFDAguidelinespasteurizehotsmokedproducts by subjecting them to a thermal process equivalent to 145  F(62.8  C)foratleast30min(FDA,2001). Mostsmokedaquaticfoodproductsaredistributedat refrigeration temperatures, but may not be held at tem- peratureslowenoughtoinhibitthegrowthofmicrobial pathogens. These products pose food safety risks if not properly processed and stored and are currently under heightened scrutiny by the FDA (Huang et al., 2002; Busta,Bledsoe,Flick,Gram,Herman,Jancke,&Ward, 2001; Herman, 1999). Akeyhazardanalysiscriticalcontrolpoint(HACCP) preventive measure for smoked fish is adequate salt content. The FDA requires a level of water phase salt (WPS) sufficient to inhibit the germination of Clos- tridium botulinum spores with the current regulatory criteria of: 53.5% WPS for vacuum packaged product; 53.0%WPSforproductwith 5100ppmnitriteheldin vacuum or modified atmosphere packaging; or 52.5% WPS for products packaged in an air atmosphere (FDA,2001).Thelevelofsaltaddedduringbrining,the 0963-9969/03/$ - see front matter # 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0963-9969(03)00070-X Food Research International 36 (2003) 761–766 www.elsevier.com/locate/foodres * Corresponding author. Tel.: +1-509-335-1858; fax: +1-509-335- 4815. E-mail address: rasco@wsu.edu (B.A. Rasco).