Holy Smoke! Evidence that the controversial fourth ingredient in sacred incense comes from a sea snail

Published 12 December 2017
Incense and sea snail

Since biblical times incense has been used in religious ceremonies and purification rituals, with its fragrant smoke evoking reverence and reflection. For much of that time this holy incense has also been shrouded in secrecy and controversy because of uncertainty over the identity of its major ingredients, onycha. Scientific evidence now supports the identification of onycha as the opercula, or trapdoor, from the sea snail Muricidae (murex whelks). In biblical times these sea snails were also used to produce purple and blue dyes of religious significance.

Southern Cross University researchers made the discovery after analysing the smoke of opercula from predatory sea snails to provide chemical support that aligns with the biblical descriptions of onycha.

And the Lord said unto Moses, Take unto thee sweet spices, stacte, and onycha, and galbanum; these sweet spices with pure frankincense: of each shall there be a like weight: And thou shalt make it a perfume, a confection after the art of the apothecary, tempered together, pure and holy. Exodus 30:34-36.

Published in the Nature journal Scientific Reports, the study investigates the volatile, fragrant and biologically active compounds found in the opercula, after range of preparations based on historical and contemporary methods for preparing incense and traditional medicines.

The findings are of significant interest to historians, theologians, anthropologists, fragrance and ethnomedical researchers.

The research was undertaken by PhD candidate Bijayalakshmi Devi Nongmaithem under the supervision of Associate Professor Kirsten Benkendorff from the University’s Marine Ecology Research Centre, co-supervised by Professor Caroline Sullivan from the School of Environment, Science and Engineering, and in collaboration with researchers from Southern Cross Plant Science Analytical Research Laboratory.

Using a purpose-built ‘smoke collector’, the team captured some simple phenols, which are extensively used in commercial fragrances as anti-oxidants, and consistent with the use of onchya to stabilise and contribute to the long-lasting perfume of incense. They also detected chlorinated phenols, which have an odour quality described as ‘medicinal’, which is compatible with use in ceremonial incense employed for spiritual cleansing.

Shows the samples in bowls of Opercula processing steps: from sea snail to smoke extract in vial Opercula processing steps: from sea snail to smoke extract in vial

Professor Benkendorff explained: “The most universally-accepted definition for onycha is the operculum, which is a structure like a trapdoor attached to the foot of gastropod molluscs. The opercula from certain types of marine whelks are referred to as unguis odoratus or ‘sweet hoof’ in ancient texts. However, controversy still surrounds the identification of opercula as ingredient for use in holy incense, because molluscs, like all shellfish, are included amongst the ‘unclean’ animals of biblical times.”

However, one particular family of predatory sea snails, the Muricidae or murex whelks, were highly revered for the production of Tyrian purple and were the only source of an insoluble purple dye in ancient times. In the Holy Bible, Exodus outlines the use of purple thread in the Tabernacle and garments for the high priesthood. Furthermore, murex snails have been recently been confirmed as the source of the biblical blue dye Tekhelet (Sterman, 2012 “The Rarest Blue”), which is incorporated into tassels of the Jewish prayer shawl (Numbers).

“So far from being considered ‘unclean animals’, murex snails represented wealth, status and sanctity,” said Professor Benkendorff.

The ancient dye industry from Muricidae whelks peaked around the 13th century BC in the Mediterranean region and there is good evidence for a large-scale industry with ancient dye vats and mounds of broken shells in Lebanon. The opercula from these snails would have been a by-product generated from this dye industry. The cargo from an ancient Uluburun shipwreck, dated to 1300BC, provides further evidence that the operculum were extensively traded during this time.

The only other argument against murex opercula as an ingredient in holy incense was the lack of evidence for ‘bearing any powerful and agreeable odour’.

“Our study provides the last piece in the puzzle, by providing evidence that when prepared using traditional methods, the opercula does contain agreeable fragrances,” Professor Benkendorff said.

“Soaking in wine or vinegar effectively removes the ‘fishy’ smell, as well as the potentially toxic compound pyridine, and when burnt the smoke releases stabilising phenols and chlorinated phenols with a medicinal smell that can be detected at low concentrations.”

Professor Benkendorff said that due to the high value and religious significance of the ancient Muricidae industries, the processes of preparing opercula for holy incense were probably deliberately kept secret.

“The tradition of dying with Muricidae Shellfish purple and Tekhelet blue were both lost from history with the fall of the Byzantine court in Constantinople and the destruction of the Hebrew Second Temple in Jerusalem, respectively, only to be ‘rediscovered’ centuries later by careful chemical research. It seems feasible that simultaneous to the loss of these mollusc dye industries, the identity of onycha, the fourth ingredient in ‘holy incense’, was also lost.”

“Whilst we cannot conclusively identify muricid opercula as the original source of onycha retrospectively, our chemical analyses do confirm fixative properties and medicinal scent qualities consistent with this type of ceremonial use."

Media contact: Sharlene King, media officer, Southern Cross University. 02 6620 3508 or 0429 661 349.