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SAFETY OF COLD SMOKED SALMON
By: Janice Brown, CSU Food Science Graduate Student - Fall 2008
Approximately 50% of farm reared Atlantic salmon reaches the consumer as a cold-smoked product. Many of us love the taste of smoked salmon and consider it a delicacy. However, not many of us have thought about the delicacy of the processing methods used to produce this product.
In the cold smoking process, fish are held at temperatures ranging from 20 to 30°C/68 to 90°F for less than 24 hours (AFDO, 1991). The "less than" inference can mean anywhere from less than 6 hours to less than 24 hours depending on the temperature of the smoker and the desired product. Under the Hazard Analysis and Critical Control Point (HACCP) program, a critical control point is a point or process at which the organism of concern is eliminated, or a combination of preserving factors can guarantee that growth of the organism does not occur. To insure the safety of cold-smoked salmon, these critical control points have been identified:
- Receiving raw materials: salmon can be fresh caught or frozen. To reduce the risk of potential parasite contamination, frozen is recommended, along with correct procedures for thawing.
- Brining: a liquid brine solution must be used to produce a final salt content of between 3.5 to 5%. This critical step has specific procedures that must be followed, including the use of fresh brining solutions to avoid contamination of the fish with salt tolerant microorganisms like Listeria monocytogenes. An injection procedure or bath procedure for brining can be used.
- Draining: this step is critical due to potential cross-contamination if drying hooks or draining areas are not kept clean.
- Cold smoking: fish must be of uniform size and shape and arranged to allow for uniform smoke absorption, heat exposure, and dehydration. Smoke can be generated, or a liquid smoke used or a combination of both. Temperatures of smoking should not exceed 90°F (32°C) for more than 20 hours, not exceed 50°F (10°C) for more than 24 hours, or not exceed 120°F (49°C) for more than 6 hours.
- Cooling: cooling to 50°F (10°C) within 3 hours and to 37-38°F (3.0-3.3°C) within 12 hours.
- Packaging: either air packaged or vacuum packaged. Air packaging must contain 2.5% WPS (water phase salt content).
- Storage and shipping: temperatures of 37-38°F (3.0-3.3°C) must be adhered to as any deviation will compromise both the safety and quality of the smoked product.
Like other ready-to-eat meats, the organism of concern for cold smoked salmon is Listeria monocytogenes. Listeriosis is a severe but uncommon infection caused by Listeria monocytogenes and has been a nationally notifiable disease since 2000. Listeriosis is primarily foodborne and occurs most frequently among persons who are older, pregnant, or immunocompromised. The reduction of L. monocytogenes to the lowest possible levels must rely on prerequisite programs adhering strictly to Good Hygienic Practices (GHPs) and Good Manufacturing Practices (GMPs). Focus must be on education of staff, cleaning and sanitation, redesign of equipment, and proper flow and separation in the processing plant. The prevalence of L. monocytogenes can be dramatically reduced in a smoke house by strictly adhering to GMPs and targeting spots where the organism had been found to reside with appropriate cleaning and disinfection procedures. Special attention to brining, injection needles and slicing equipment must be a priority. Other methods of preservation that have been found to inhibit L. monocytogenes include the following: 1) Extended frozen storage; 2) Carbon dioxide; 3) Nitrite; 4) Lactate; 5) Sorbate; 6) Bacteriocins; 7) Background microflora; and 8) High Pressure Processing.
Cold smoked salmon is considered safe for healthy, non-immune compromised persons; however, as with other raw or semi-raw meat products, it is risky for pregnant women, the frail elderly and others with compromised immune systems due to disease or medical therapy. Many countries, including the U.S., recommend these groups avoid cold smoked fish. The shelf life of smoked salmon is very short, one to two weeks in the refrigerator and about one month in the freezer. Storage time is another critical factor in the proliferation of L. monocytogenes.
- CDC. 2004. MMWR. Summary of notifiable diseases. Available at: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5353a1.htm.
- FDA/CFSAN. Processing parameters needed to control pathogens in cold smoked fish: Potential hazards in cold-smoked fish Listeria monocytogenes. Available at: http://www.cfsan.fda.gov/seafood1.html.
- US FDA. FDA Extends Nationwide Health Alert on Mama's and King Salmon Brands of Smoked Salmon Products - 2005.
- US FDA. Enforcement Report - 2002, 2003, 2004, 2005. http://www.fda.gov/bbs/topics/enforce/2002/ENF00728.html.
- AFDO, Association of Food and Drug Officials. 1991 June. Cured, salted and smoked fish establishments good manufacturing practices [model code]. [York (PA)]: Association of Food and Drug Officials. 7p.
- Lakshmanan R, Piggott JR, Paterson A. 2003. Potential applications of high pressure for improvement in salmon quality. Trends in Food Science & Technology. 14:354-363.
- CDC. National Ag Safety Database. Food Storage for Food Safety and Quality. http://www.cdc.gov/nasd/docs/d000001-d000100/d000066/d000066.html.
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