Hit & Run: Why do you think they call it Soylent Green? cites an Interfax article, Media exposure forces government to respond to hair-into-soy sauce scandal, with a peculiar story to tell:
China Central Television (CCTV), the state television station, first raised public worries over the quality of domestic soy sauce by uncovering a substandard workshop in central China’s Hubei Province, where piles of waste human hair were found. The hairs were treated in special containers to distill amino acid, the most common substance contained in soybean sauce.
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By producing soy sauce from such raw materials, the producers were said able to cut costs by half. Workers employed at the plants, however, never bought soy sauce marked as ‘blended’ on the packaging, because that usually meant that human hair was the basic material in the sauce.