This bronze jar on display at the Ashmolean Museum contained a mysterious substance (shown in the foreground) that is very likely ancient honey. Credit: Adapted from the Journal of the American Chemical Society 2025, DOI: 10.1021/jacs.5c04888
Scientists have finally determined the composition of mysterious sticky residues inside 2,500-year-old bronze jars discovered more than 70 years ago.
The findings, published in a study in the Journal of the American Chemical Society, provide the first direct molecular evidence to support the presence of honey, likely honeycombs.
“Ancient residues aren’t just traces of what people ate or offered to the gods – they are complex chemical ecosystems,” says study lead Dr Luciana da Costa Carvalho from the UK’s Ashmolean Museum.
“Studying them reveals how those substances changed over time, opening the door to future work on ancient microbial activity and its possible applications.”
The remains of the ancient city of Paestum are located to the south of Naples in southern Italy. The inhabitants placed the jars in an underground shrine to an unknown deity where they remained undisturbed until they were unearthed in 1954.
The contents were initially described as a “paste-like residue with a strong wax aroma” by the archaeologists who discovered them.
“Archaeologists reported the residue to have been originally a liquid or viscous liquid, as traces of it were found on the exterior of the vessels, which were originally sealed with cork discs,” write the authors of the study.
They assumed it was honey, a substance which held significant religious and symbolic importance in ancient Greek and Roman cultures. But over the next 30 years, subsequent analysis by 3 separate teams cast a cloud of doubt over this hypothesis.
The teams concluded the jars did not contain sugary or starchy substances or proteins but instead some sort of animal or vegetable fat contaminated with pollen and insect parts.
In 2019, the jars arrived at the Ashmolean Museum for an exhibition. The researchers reanalysed the residues with the help of new advanced biomolecular techniques.
They compared the results to samples of modern honey and honeycomb, both fresh and artificially aged with heat, from Greece and Italy.
This is likely what 2,500-year-old honey looks like, according to new tests using modern techniques. Credit: Luciana da Costa Carvalho
“Climate, temperature and floral sources all affect protein expression in bees and their products,” write the authors.
“Fresh honey is composed of 79% hexose sugars (of which fructose is the most abundant at 39%), 18% water, 1.1% proteins, 0.17−1.17% acids (formic, citric and gluconic being the most abundant) and traces of vitamins, enzymes, flavonoids, and phenolic compounds.
“Over time, honey constituents undergo degradation … changing in appearance and chemical composition … During long-term storage (particularly at temperatures above 20°C), honey acquires a darker hue, sugars degrade into furans, and its acid content increases.
“The first analysis of the Paestum residue suggested that it was a wax. In antiquity, beeswax was almost invariably the one used. Beeswax has a very different composition to honey.
“Our analyses of the residue … suggested a composition much more complex than that of degraded beeswax.”
The results indicated the presence of intact hexose sugars at higher concentrations than in modern beeswax, as well as increased acidity levels consistent with long-term degradation of honey and beeswax. Degraded sugars also survived the test of time by mixing with copper ions, which kill bacteria, where the substance had touched the bronze jar.
Ultimately, it was the major royal jelly proteins (MRJP) found in samples from the core of the residue which provided definitive evidence it contained bee products.
“MRJPs are a series of 9 homologous proteins detected in insects of the order Hymenoptera, which includes thousands of species of sawflies, ants, wasps, and bees,” the authors write.
“Representing the main proteins found in honey, they are secreted by the nurse bees’ cephalic glands and mixed with honey and pollen to feed the larvae in the hive.”
The team says their findings “significantly expand the analytical toolkit available for investigating chemically complex archaeological residues”.
“The research highlights the value of reinvestigating archaeological residues in museums with advanced biomolecular techniques and offers a more specific method for detecting bee products in ancient contexts,” they write.