Food Protection Connection: Fish Should Not Smell Fishy

(reprinted from Dietary Manager, September 2011)

Has sushi made an appearance in your town? How about the raw oyster bar? Sushi (raw fish with rice) and sashimi (raw fish) are a popular and growing trend in the food industry. Where once you would only have found sushi in fine dining restaurants (or in Japan), now most large supermarket chains carry sushi or have a sushi chef on staff.

You can now find raw oyster bars in your local high-end grocery stores. Nutritional diets include lots of fish as a good alternative to higher calorie, higher fat meats. With all this promotion of fish and shellfish consumption, do you know how to choose fish or shellfish when you are standing at the market? Fish come with a variety of concerns for harvesters, producers, distributors and customers alike, that every consumer of fish and shellfish should know about. Fish is a great source of nutrition, so dont' stop eating it, just be educated about how to choose, handle, and consume fish wisely.

According to the National Oceanic and Atmospheric Administration's National Marine Fisheries Service, Americans consume 15.8 lbs of fish per person/year (2009). In 2009, US consumers spent $75.5 billion on fish. Fish is a huge part of the US diet. Imported fish made up 84 percent of the seafood eaten in the US in 2009. As such, the Hazards Guide now includes information on species of fish harvested and processed in non-US waters and facilities.

The Food and Drug Administration (FDA) publishes the "Fish and Fishery Products Hazards Guide," aka, "Hazards Guide." This resource is intended for harvesters (fishermen) and processors of fish and shellfish. This guide helps the industry (including regulator) ensure that consumers don't become sick from the consumption of fish parasites, pathogens (including bacteria, virus, and fungi) and toxins (chemicals produced by the fish themselves). A processor will find information in this guide on what contaminants might be present and what controls should be used to eliminate them.

Providing the latest scientific research to harvesters and producers of fish, the Hazards guide helps assure that our fish supply is safe. But once the fish has moved from the processors to the retailers, does it remain safe? The FDA Model Food Code sets the standard for retail storage, processing, and sale of fish. If a retailer follows the requirements within the Code, they will be providing safe fish to their consumers.

The last link in the food chain is the consumer. What can a consumer do to protect themselves from illness caused by fish or fishery products? First, you must understand some basics about fish and associated illness.

Parasites in Fish

Fish are animals that live in water. Some fish are bottom feeders. Big fish eat small fish. Parasites also live in water. Parasites, mostly worm-like, are commonly found in fish flesh. Some you cannot even see with the naked eye. If you eat fish with live parasites, you too will have the parasite grow in your body. One of the biggest concerns with eating raw or undercooked fish is parasite infections. Freezing kills parasites; therefore, it is required that all fish intended to be consumed raw or undercooked, with the exception of some tuna species, be frozen prior to consumption. This is true for sushi, sashimi, and other raw or undercooked fish preparations. The FDA requires that fish be frozen at -20°F or below for a minimum of 7 days or at -35°F or below for a minimum of 15 hours.

Freezing will not kill other pathogens; therefore, good sanitation is very important to control contamination or growth of other pathogens. Unless served within 4 hours, sushi or other similar fish preparations should be refrigerated to control the growth of microorganisms.

Toxins and Other Bacteria in Fish

There’s another important food safety concern with fish…scombrotoxism. Scombroid poisoning is a food-related illness associated with fish. It resembles an allergic reaction. A histamine (scombrotoxin) is produced which poisons the food and leads to the reaction. If exposed to elevated temperatures at any point from harvest to consumption, fish can produce this very dangerous toxin which will cause human illness. This bacteria, which naturally exists on the gills and inside live saltwater fish, can continue to grow even on dead fish, especially if the fish are not kept chilled properly. Scombroid is caused by bacterial spoilage of certain finfish such as tuna, mackerel, bonito, and, rarely, other fish, therefore temperature control of fish is very important. The Hazards guide addresses Scombroid from harvest (control measures at sea) through distribution.

Other marine toxins such as Ciguatera poisoning, Paralytic shellfish poisoning, and Neurotoxic shellfish poisoning, all caused by marine dinoflagellates, are of concern in marine fish. Dinoflagellates are the creatures that cause “red tides.’ Harvesting waters are monitored very closely by regulatory agencies. Buying fish from reputable suppliers is very important.

Vibrio is a naturally-occurring organism commonly found in waters where oysters are cultivated. When the appropriate conditions occur with regard to salt content and temperature, Vibrio thrives. Vibrio is a bacterium. Harvesting areas are monitored for conditions that may increase the chance of Vibrio growth and could be closed until such time as conditions return to normal; as such, purchasing shellstock from reputable dealers who harvest only from approved waters is most important. Of course, if you choose to eat shellstock raw, you are still eating a raw, unprocessed animal and are still taking a chance with your health. Pasteurized shellstock are a great alternative!

Mercury in Fish

Some fish are known to be high in mercury. Pregnant women, women trying to get pregnant, and young children are at highest risk for mercury poisoning due to elevated mercury levels in certain species of fish. Fish is a good healthy food, so don’t stop eating fish. Simply be aware of the amount of fish you consume.

To reduce exposure to mercury, FDA recommends the following:

• If you are a susceptible population, do not eat shark, swordfish, king mackerel, or tilefish. They are very high in mercury.
• Continue to eat up to 12 oz. a week of a variety of fish and shellfish with low mercury levels, such as shrimp, canned light tuna, salmon, pollock, and catfish.
• Albacore has high levels of mercury compared to canned light tuna. eat only 6 oz. of albacore per week.
• If you are fishing in local waters, be aware of any elevated mercury information from those waters. If no information is available, eat up to 6 oz. of local water fish and don’t consume other fish that week.

Consumers of Fish

Fish and shellfish are an important part of a healthy diet. They are low calorie, rich in high quality protein and other essential nutrients, low in saturated fat, and contain omega-3 fatty acids. So keep them in your diet, but be cautious and understand what you are buying.

Hopefully with a better understanding of fish and shellfish safety, your next trip to the grocery store or market will end in a great piece of safe fish in your cart for your evening meal.

Safety tips for Purchasing and Consuming Fish and Other Fishery Products

• When buying fish or shellstock, always buy from a reputable dealer.
• If fishing, make sure you are fishing in waters that have not been designated as waters of concern for algal blooms, dinoflagellate growth or “red tide” conditions.
• Watch your seafood counter personnel. Are they practicing good personal hygiene and proper food handling practices? Does the area look and smell clean? Is it free of flies? If not, walk away.
• When selecting fish at your local store, choose fish that do not smell fishy. The only fish that smell fishy are those that are beginning to decompose. The flesh should be springy, eyes clear but bulging just a small bit (if buying whole, except Walleye pike which have naturally cloudy eyes), firm flesh with a nice shine. The skin and flesh of the fish should not look dry or show darkening at the edges. Note: fish that have been previously frozen may have lost some of their shine but are still fine to eat.
• Do not buy or consume shellstock that are cracked, broken, or dead.
• Buy only fish or shellstock that is refrigerated or packed in ice to 38 degrees F or below to control histamine production or those fish listed above that are natural histamine producers. Toxins are not destroyed with cooking. Once they are formed, they are there for good.
• Once at home, consume fish within two days. If not used, wrap tightly and freeze.
• Thaw frozen fish/shellfish in the refrigerator, never out at room temperature. You can also immerse packaged fish in cool running water for a short time to thaw your product faster just prior to preparation or cooking.
• Wash your hands thoroughly before and after handling raw or partially cooked fish/shellfish.
• Be careful not to cross-contaminate your kitchen. Wash all surfaces thoroughly before and after fish preparation. Be aware of items that may have come in contact with the raw product and clean those areas thoroughly. You can even sanitize the area with bleach water (1 tablespoon of bleach to 1 gallon of water but DON’T mix with soap unless you desire a trip to the hospital).
• Highly susceptible populations (those who may be immune compromised) should not consume raw fish or shellstock.
• Consume only pasteurized raw shellstock if at all possible. Raw oysters are still raw and can still have pathogens. Hot sauce and alcohol will not kill the pathogen.
• When eating sushi or sashimi, be sure that the fish, except tuna, has been frozen as reqired to eliminate parasites. Note: freezing does not kill other harmful pathogens.
• Have a working and accurate food thermometer and cook all seafood to 145 degrees F.
• Relax and enjoy your fish and shellfish dinner!

by Melissa Vaccaro, MS, CHO
Melissa Vaccaro, MS, CHO is a Food Program Specialist for the PA Department of Agriculture and an Executive Board Member for the Central Atlantic States Association of Food Drug Officials (CASA). Contact her at mvaccaro@state.pa.us.