Key Factor in Tuna: How Moist Is It?
Aside from the few truly detested samples, one factor stood out as making the biggest difference to our tasters: dryness. Tasters described higher-rated products as moist, finding them “tender,” “silky,” and “juicy.” Even when tasters enjoyed the flavor of a sample, it lost points if it was dry. Tasters found these tunas “cottony” or “sawdust-y,” mealy, and tough. “This turns to dust as I chew,” one taster complained. “Breaks into splinters rather than flakes,” another wrote. So if moistness is a key factor, why were some products drier than others? It helps to understand a little about how tuna goes from ocean to can.
Here’s a quick overview: Freshly caught fish are frozen on the ship. At the plant, they’re inspected and thawed and then steam-cooked and cut up to remove the meat. The meat is then put in cans or jars with oil, salt, and any other ingredients; sealed; and finally pressure-cooked again inside the can to seal the jar and sterilize the contents.
According to tuna processing experts, things can go wrong at several stages. First, the fish has to be frozen fast and kept that way, or quality suffers. If not, ice crystals form in the meat and puncture cell walls, letting moisture leak out when the tuna thaws, just as you see with “freezer-burned” food at home. Proper freezing also halts the enzymes that will naturally start to break down the fish, helping to preserve flavor and texture. Second, the tuna goes through what one food scientist called the “critical thermal processing steps” at the plant that can make or break its flavor and texture. As we described, the fish is heated and cooled a few times, so timing and temperatures matter. Worst case? It gets overprocessed and/or overcooked. Similar to what happens when a beef steak is cooked to well-done, the tuna’s proteins lose their ability to hold moisture, and the texture becomes tough, dense, and dry. While packing tuna in oil offsets some of the sensation of dryness, it can only do so much, as our tasters noted. We aren’t privy to the precise processing conditions of each product, but it’s probable that products rated highly by the tasting panel are taking more care to retain the moist texture we preferred. As for one tuna that is sold in a glass jar, this is a likely indicator of moist, tender tuna, since glass can't withstand the high-heat treatment that be used for cans, so the contents are given a lower-temperature pasteurization which results in fish that is more moist.
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