pharmacy

Understanding jelly as a preservation method: a small-scale reconstruction report

/ mariekehendriksen / Leave a comment

Understanding jelly as a preservation method: a small-scale reconstruction report

Within the PRESERVARE research project, we use performative methods such as reconstructions to gain a better understanding of our sources and of the past in general. The aim of such reconstructions is not to replicate the past – that is impossible. The goal is to better understand the practices and processes underlying textual descriptions.[1]

For example, I am currently preparing a paper exploring how cane sugar became a widely used product in food conservation technology in the eighteenth century. Previously an expensive commodity mostly used in pharmaceutics and upper-class foods, cane sugar became so widely available in eighteenth-century Europe that it could be used to preserve perishable foods like fruits on a large scale.[2] This also meant that preparations previously only sold by apothecaries, such as jellies, were made by other entrepreneurs, became more widely available, and were used for hedonistic rather than medicinal purposes.

A fascinating example of this process is ‘conserf van vlier,’ elderberry jelly, which, judging by newspaper adverts, became very popular during the last quarter of the eighteenth century in the Northern Netherlands. One such advertisement, put up by an Amsterdam guild barkeeper in 1774, advertises three hundred pounds of elderberry jelly for sale. It mentions that the elderberry jelly has been made after The Amsterdam Apothecary pharmacopeia and has been put into jars in layers, so it can easily be taken out.[3] Large amounts of layered elderberry jelly are advertised by others too in this period, mostly by apothecaries. The layered elderberry jelly was more expensive than the unlayered variety.[4] Yet the 1751 edition of the Amsterdam Apothecary does not mention a ‘conserf van vlier’ (or rob sambuci, in Latin), nor does it offer instructions on how to layer jelly in jars. The only relevant information it contains is a general recipe for rob or jelly that indicates to mix fruit juice with half its weight in powdered sugar, boil until it becomes a gel, and pour the result into jars.[5]

Would it be possible for someone with an entrepreneurial mind and access to The Amsterdam Apothecary to create a layered elderberry jelly in jars at a scale that allows wholesale production? I attempted a small-scale reconstruction in my kitchen. As it was not elder season, I used bottled pure, organic elderberry juice without added sugar. For sugar, I chose organic powdered cane sugar, as this is closest to what would have been used in the eighteenth century. I was skeptical that this would work, as elderberries are relatively low in pectin.[6] Elder juice is however very acidic and astringent, which will help in forming a jelly– I did not test acidity with a pH meter as that is historically irrelevant, but I found the taste mouth-twistingly sour and bitter.

As I used a very small hand-turned, glazed earthenware jar (about 150 ml), I decided to start with 100 ml/101 g of elderberry juice and 50 g of powdered sugar. I first warmed the juice in a stainless-steel saucepan on medium heat (induction cooker). The sugar dissolved instantly, but initially little seemed to happen. After about 5 minutes, the mixture started to bubble violently, and I soon smelled caramel. I turned down the heat and boiled the mixture for another five minutes, constantly stirring with a stainless-steel spoon. When the mixture began to drip off the spoon in threads, I poured it into the jar. The mixture that remained stiffened instantly on the spoon and in the pan. The texture seemed more akin to taffy than jelly to me, but I let it cool and decided to add a second layer another day.

The first layer of jelly (or taffy?) in the jar

I returned to the rob two days later and created another layer in the same way as the first. I  turned down the heat a bit sooner, though, as I did not want the sugar to caramelize. I poured the second layer on top of the first one and cover the jar with a plate. I then left it on the countertop at room temperature for four days.

After four days, I assessed the result. The top layer had not solidified entirely; it was more like very thick syrup, slowly moving to one side when I tilted the jar. Unsurprisingly, I could not lift out the top layer as a whole: I had to spoon it into a dish. It was very sweet but not unpleasant, because the elderberries are so acidic that the jelly still had a tang. Once I had scraped off the top layer, I tried to retrieve the bottom layer from the jar. This was easier said than done: it was rock hard and stuck to the bottom and sides of the jar. Neither a spoon nor a knife allowed me to get it out. I resorted to warming the jar au bain-maire, scooping out most of the jelly, and washing out the jar with boiling water.

Elderberry jelly layered in jars – it sounds so simple. But this small reconstruction shows that it is anything but simple: someone with access to The Amsterdam Apothecary would need experiential and embodied knowledge to produce layered elderberry jelly in jars. It seems likely that the barkeeper advertising this jelly was not the manufacturer of this elderberry jelly, but merely a middleman, running a side business from his bar.

If you want to know more about the rise of sugar as a food preservation technology, see Marieke M.A. Hendriksen, “Luxurious thrift? Sugar as a preservation agent in early modern Dutch food and medicine,” Early Modern Low Countries, forthcoming 2026 (a link will be added once the article has been published).

[1] For a more detailed discussion of the use of performative methods in historical research, see e.g. Hendriksen, Marieke M.A. “Rethinking Performative Methods in the History of Science.” Berichte Zur Wissenschaftsgeschichte 43, no. 3 (2020): 313–22. https://doi.org/10.1002/bewi.202000017.

[2] For the economic, social and political implications of sugar see e.g. Mintz, Sidney W., Sweetness and Power: The Place of Sugar in Modern History. Penguin Books, 1986, and Bosma, Ulbe, The World of Sugar. How the Sweet Stuff Transformed Our Politics, Health, and Environment over 2,000 Years (Cambridge 2023).

[3] Advertentie. “Oprechte Haerlemsche courant”. Haarlem, 27-09-1774, p. 2. Geraadpleegd op Delpher op 12-02-2025, https://resolver.kb.nl/resolve?urn=ddd:010800395:mpeg21:p002

[4] Advertentie. “Oprechte Haerlemsche courant,” Haarlem, 10-09-1789, p. 2. Geraadpleegd op Delpher op 08-01-2026, https://resolver.kb.nl/resolve?urn=ddd:010801531:mpeg21:a0008

[5] Pharmacopoea Amstelredamensis, of Amsteldammer Apotheek, Amsterdam: Gerrit de Groot, 1756, p. 93.

[6] McGee, On Food and Cooking, 296-297.

A gemstone for every ailment?

/ mariekehendriksen / Leave a comment

Last week, I wrote about Boerhaave’s admiration for the stained glass windows in the St. John church in Gouda, and how his appreciation can be understood in the context of his life and times. Yet of course, the learned man did not write about stained glass windows in his chemistry book just because he thought they were beautiful. Always the scholar, Boerhaave had another reason to be interested in coloured glass, rooted in the medical and chemical theory of the day. In the Elements of Chemistry, Boerhaave described a number of ways to make coloured glass, but warns that this tends to result in artificial gems that, however lustrous, are more brittle than the real thing.[1]

Brooch, 1740-1750, Silver set with pastes (glass). Courtesy of the V&A (object nr. M.198-2007)

Brooch, 1740-1750, Silver set with pastes (glass). Courtesy of the V&A (object nr. M.198-2007)

Fake gemstones were used frequently in jewellery and fashion in the eighteenth century, but Boerhaave’s interest in them may still seem a bit curious. However, it is quite understandable in the light of a 1672 treatise by Robert Boyle, one of the alchemists Boerhaave admired. Boyle’s An essay, about the origine and virtue of gems argues that gem stones are infused with mineral and metal juices or particles when they are formed in the earth, either through great pressure, cold, or heat.[2]

These minerals and metals have medicinal qualities, and by grinding gemstones to powder, the medicinal qualities can be used in curative potions, creams, et cetera. But gemstones were rare, so it was beneficial for the early modern physician/chemist/natural philosopher to be able to create artificial gemstones with the same properties as real ones. As artificial gemstones are made mimicking the natural process, by infusing crystal with metals, it made perfect sense for Boyle, Boerhaave, and their contemporaries to use both natural and artificial gemstones as materia medica, basic medical materials.

Title page of Robert Boyle's 1673 'An essay, about the origine and virtue of gems.'

Title page of Robert Boyle’s 1672 ‘An essay, about the origine and virtue of gems.’

Artificial gemstones are an interesting case, as they shows that in the early modern period, the same artisanal and chemical knowledge and practices were relevant for experts in a number of fields, such as glassmaking, jewellery making, chemistry, pharmacy, and medicine. Often, these fields overlapped in more than one respect of course, and as I mentioned last week, studying the use of materials in the early modern period is a route into understanding the work of hybrid experts, people who combined artisanal and scholarly theories and practices.[3]

In the future, I hope to make the creation and use of gemstones in eighteenth-century chemistry and medicine one of the case studies in my research project. These initial findings raise questions about how involved university-trained chemists actually were in the making of materials such as artificial gemstones. Did they make them themselves in their laboratories? Or did they obtain them from glassmakers or apothecaries? And exactly how were the gemstones used in medicine and pharmacy? What were the various theories about their curative properties, and how were they transferred to the patient? Was the alchemical understanding of gemstones significantly different from the chemical understanding, or were alchemical theories and practices transferred into the chemistry and medicine of the late eighteenth century?

But first, summer, and on my program are a research trip to London, to look into a massive manuscript containing lecture notes taken by a student of the Leiden chemistry professor Hieronymus Gaub (1705-1780), presenting a paper at the huge and hugely exciting ICHSTM conference in Manchester, and delving into the work of Abraham Kaau Boerhaave (1715-1758), Boerhaave’s deaf nephew. I aim to keep the Medicine Chest filled with updates!

[1] Boerhaave, Herman. A new method of chemistry, 2 Vols, Vol. I, tranl. by Peter Shaw, London, 1741, p. 182-187.

[2] Boyle, Robert. An essay, about the origine and virtue of gems, London, 1673.

[3] Klein, Ursula, en Emma C. Spary. “Introduction: Why Materials?” In Materials and Expertise in Early Modern Europe. Between Market and Laboratory., Ursula Klein and Emma C. Spary (eds.), 1–23. Chicago and London: University of California Press, 2010, 1, 6.