A family-owned karaage restaurant in Mishima, Shizuoka Prefecture, has sparked heated debate online after revealing that its signature flavor comes partly from frying oil that dates back to its founding in 1960.
Wakadori, which just took home the top prize at this year’s Japan Karaage Grand Prix, uses what its third-generation owner calls “matured oil.” Rather than discarding the oil and starting fresh, the restaurant filters it daily, removes debris, and regularly tops it up with new oil — keeping a portion of the old oil as a flavor base.
The revelation quickly went viral on Japanese social media, with many users expressing unease. Many said the description alone was enough to put them off, while others said they would steer clear of anything fried in oil that dark.
Defenders argue the “66-year-old oil” description is misleading. The oil isn’t the exact same batch from 1960 — it’s constantly refreshed and diluted, more like a perpetual sourdough starter or a long-running restaurant sauce than a static vat of ancient grease.
Food commentator Wayne Wei weighed in, explaining: “Fresh oil is continually added. The older oil only serves as a flavor foundation.”
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This approach isn’t entirely uncommon in Japan. Some traditional eel restaurants maintain sauces that have been replenished for decades or even centuries. Similar practices exist in ramen shops and fermentation kitchens, where flavor is believed to improve with age.
The concept also has an American parallel: Dyer’s Burgers in Memphis has been frying its patties in the same continuously maintained beef grease since 1912. The shop has attracted its share of celebrity visitors over the years, including Tom Hanks and Michael Jordan. Its most devoted regulars go a step further, ordering what the staff call a “double dip” — the entire assembled burger submerged in the old grease before wrapping.
Still, food safety experts caution that repeatedly heating oil can lead to oxidation and the buildup of potentially harmful compounds, including trans fatty acids and acrylamide, a probable carcinogen. While properly filtered and replenished oil can remain safe for long periods, the risks increase if maintenance slips.
