There’s Nothing Wrong With Raw Fish That Has Been Frozen

Whether you're eating sushi, poke, or ceviche, you’re safer if the seafood has been in a freezer first.

(Photo: Flickr)

Jul 29, 2015· 5 MIN READ
Jane Lear is a regular contributor to TakePart and the executive editor of CURED, a magazine devoted to the art and craft of food preservation. She was on staff at 'Gourmet' for almost 20 years.

“I’ve heard the raw fish in ceviche is safe to eat because it’s marinated, but what about things like sushi, sashimi, crudo, and salmon tartare?”

—Mia Babb

There’s something about the clean taste and supple, sensuous texture of raw fish that is greatly appealing, but there are some risks you should be aware of, especially if you or anyone you wish to feed is pregnant, elderly, very young, or has a compromised immune system. That holds true for ceviche—which starts out with fresh seafood marinated in lemon or lime juice and then gets tricked out with whatever takes a chef’s fancy—as well as more obvious raw-fish dishes. The acid in the juice turns translucent seafood white and almost opaque, but even though ceviche may look cooked, it’s not. (Far less fraught for the home cook is a ceviche composed of lightly cooked seafood.)

There is, of course, the ever-present risk of harmful bacteria, so easily transferred to food through unhygienic handling or kitchen practices. “Most recently, sushi was believed to have caused at least 50 illnesses in a nine-state Salmonella outbreak,” reported Food Safety News on July 14, 2015. “In 2012, raw tuna contaminated with Salmonella caused an outbreak that sickened more than 300 people in 26 states.”

And then there are the parasites that are present in certain kinds of fish. They’re a natural occurrence, not caused by contamination, and according to Seafood Health Facts—a joint project of Oregon State University, Cornell University, the universities of Delaware, Rhode Island, Florida, and California and the Community Seafood Initiative—two types of parasitic worms can infect humans: “Anisakiasis is caused by ingesting the larvae of several types of roundworm [aka nematodes] which are found in saltwater fish such as cod, plaice, halibut, rockfish, herring, pollock, sea bass and flounder. Tapeworm infections occur after ingesting the larvae of diphyllobothrium, which is found in freshwater fish such as pike, perch and anadromous (fresh-saltwater) fish such as salmon.”

Ick factor aside, parasites can cause mild to moderate illness, and occasionally the symptoms are severe. The good news? They’re easily killed by thorough cooking or freezing, according to FDA guidelines, to an ambient (surrounding) temperature of -4 degrees Fahrenheit or below for at least seven days; freezing at an ambient temperature of -31 degrees Fahrenheit or below until the fish is solid and storing at the same temperature for 15 hours; or freezing at an ambient temperature of -31 degrees Fahrenheit until the fish is solid and storing at -4 degrees Fahrenheit or below for 24 hours.

This fish-freezing business is making headlines in my neck of the woods. In March, the New York City Department of Health and Mental Hygiene brought local regulations in line with FDA recommendations—starting in August, fish served raw, undercooked, or marinated raw in restaurants must first be frozen to guard against parasites.

Before you go all Nanny State on me, you should be aware that many chefs in top restaurants in New York City and elsewhere in the world, including Japan, have long been deep-freezing fish as a health precaution. In fact, the vast majority of “fresh” fish is already flash frozen at some point in the supply chain to maintain freshness.

“If done well, as on at-sea freezer boats, this involves using impeccable-quality fish bled and frozen pre-rigor,” explained fish missionary Jon Rowley, whom you met in my column on salmon a few weeks ago. “A frozen fish can actually be better quality than 95 percent of fresh fish because of the time fresh fish is out of water and various handling and temperature conditions. That’s why even in the best sushi bars, much of the fish has been frozen. You couldn’t get fresh fish of the same quality, at least with any consistency.”

Rowley isn’t crazy about the New York law (“There are two issues here that aren’t connected: parasite infection prevention and quality”), but you won’t catch him eating salmon tartare or salmon sushi made from fish that hasn’t been frozen first. If you’re an in-for-a-penny-in-for-a-pound kind of reader, you may want to check out his 2008 Gourmet piece on tapeworms. Page two is particularly eye-opening.

By this point, you’re probably wondering why everyone in Japan doesn’t have a parasite problem. I know I was, which is why I sent off an email to Japanese food authority Elizabeth Andoh, who, by the way, will be teaching a “Fully Fish” cooking class in Tokyo on Aug. 8.

“Japanese sushi chefs are trained during their seven-year apprenticeship about which fish have which parasites and how to deal with them. Wild salmon is always frozen before being served raw, as one example,” she replied. “It requires knowledge of which (sea) creatures are most susceptible to which parasites.” As far as salmon goes, she quoted the Japanese “official” recommendation for “fresh” (intended to be eaten untreated by heat): “Freeze at -20C/-4F for at least 24 hours.”

The real issue, in Andoh’s opinion? “The quality of all fish is determined by how the fish is taken from the water (line-fished? gill-netted? other method?) and handled immediately thereafter,” she wrote. “Depending upon the variety of fish (salmon, tuna, mackerel, and snapper are all different from one another), the waters from which they are taken, and how far they need to travel to market, the way in which the fish is handled for optimal quality (safety and eating pleasure) is different. There is no one rule that applies. Some are best blood-let (similar to a ‘kosher kill’) and gutted and iced onboard ship; others fare better if kept in mini aquariums and brought to market whole. It is the knowledge and know-how of the fishing industry in Japan that makes the consumption here safe for most consumers.”

Andoh wasn’t done yet; in fact, she was just settling into her stride. “Before I finish my commentary, let me address the problems that can arise with middlemen (supermarkets, especially) and consumers. Once a product has been frozen, it must be defrosted, and that creates room for all sorts of really dangerous things to happen. Bacteria especially, but some parasites, too. At what temperature, and under what conditions, should frozen fish be brought back to room temperature? Again, the answer depends upon the type of fish and whether it has been previously broken down into fillets, or if it’s still on bone. The biggest problem is ‘drip’—the puddles of (often bloody-colored) liquid that seeps out as the flesh returns to a softened state.”

Part of being a responsible consumer is being an educated one. When it comes to eating fish, raw or cooked, sustainability is at the forefront of everyone’s mind—and rightfully so—but don’t check your brain at the door when it comes to basic food safety. Especially if you’re interested in preparing raw fish to eat at home, you should be aware that much of the advice floating around out there ranges from cavalier to just plain wrong.

You should know that, depending on the fish, when it’s fresh off the boat, it isn’t necessarily safer unless the boat has frozen the fish to the required temperature for the required amount of time. If you plan on freezing fish at home, check your freezer temp with an appliance thermometer (they’re readily available and inexpensive) first. Home freezers, which are usually between 0 degrees and 10 degrees Fahrenheit, often aren’t cold enough to kill parasites.

You’ll also see that many sources set great store by the terms “sushi grade” or, more correctly, “sashimi grade” (sashimi refers to sliced raw fish, while sushi involves rice). Those terms mean one thing to the highly trained experts at Tokyo’s Tsukiji fish market, say, but the typical American consumer should view them as nothing more than marketing buzzwords intended to imply impeccably fresh fish that is of such high quality it can be eaten raw. The terms aren’t defined, implemented, or regulated by any governmental agency or official organization.

So buy from a fishmonger you know and trust, and don’t be shy about asking questions about his or her handling practices. Is the fish frozen, and if so, how? How is it thawed? Do they store unwrapped sashimi-grade fish in the same refrigerator as the other fish? Do they cut sashimi-grade fish on the same cutting board used for non-sashimi-grade fish? If so, is it (and the knife) disinfected first, and are new gloves used?

Yes, it seems like a lot of work, but hey—the more you know, the more you know!