Tuna bones find new life as high-value feed ingredient through mealworm research

Tuna byproducts that the fishing industry has long paid to dispose of are finding new life as a high-value resource.

A research team led by Dr. Heo Seong-yeong at the Korea Institute of Ocean Science and Technology (KIOST) announced Wednesday that it had successfully used tuna byproducts as feed for mealworms, in a joint study with a team led by professor Kwon Jun-pyo at Ajou University.

Mealworms — the larvae of the darkling beetle — are protein-rich insects widely used in animal feed and increasingly sought as an ingredient in health supplements such as protein powders. The research team focused on a key trait of mealworms: their body composition changes depending on what they eat. That characteristic, the researchers reasoned, means mealworms can effectively be "designed" to carry specific nutritional profiles by controlling their diet.

Tuna generates far more byproduct during processing than most other fish species, saddling processors with considerable disposal costs. Tuna bones are already valued for their use as bone-graft material in dental implant procedures and as an industrial material owing to their heat resistance. Their composition closely resembles that of natural bone, and their high osteoconductivity and biocompatibility make them widely used in orthopedics and dentistry. They also carry no risk of zoonotic infection, giving them a safety advantage over bones from land animals.

Yet the preprocessing required to strip flesh and marrow from the bones has relied on chemical methods, bringing environmental concerns and high costs. Those burdens have forced the fishing industry to discard large quantities of tuna bones despite knowing their value.

The research team replaced chemicals with mealworms, feeding the insects tuna bones directly. As the mealworms consumed the remaining flesh and marrow, the preprocessing was handled in an eco-friendly way — and the mealworms themselves emerged as a high-value resource enriched with tuna's nutritional components.

The team divided mealworms into two groups, feeding one group conventional feed and the other tuna spine byproducts, then compared the results. The conventional feed was wheat bran, a byproduct of flour milling. Mealworms fed tuna byproducts maintained a protein content of 45 percent while their fat content rose from 26.9 percent to 32.5 percent. Unsaturated fatty acids — including oleic acid found in olive oil and linoleic acid found in nuts, both known to help improve blood cholesterol levels and boost immunity — increased by 84 percent.

The team also confirmed functional and safety benefits. The mealworms' ability to neutralize free radicals, which are linked to aging and skin damage, grew stronger. Their antioxidant capacity was roughly twice that of the wheat-bran group. Cell tests showed no toxicity, establishing a basic safety profile for potential use in food products.

"We plan to expand the scope to various other marine byproducts and continue research toward commercializing eco-friendly biomaterials in pursuit of zero waste," said Dr. Heo.

The findings were published in the international food science journal Food Chemistry: X.