The quest for historic sweeteners continues…
Pear juice is made thus
(marginalia: to make pear juice)
Take juicy pears such as Speckbirn (lit: bacon pears) or Muscatellerpirn (muscatel pears) and other pears that have much juice. You must not peel them but just stamp them in a vat or grate them on a grater quite small, put them in a sack and press it out. Boil the juice in a brass cauldron close to seven hours and always skim it, and put the foam into a separate container because it can be used. You must not stir the juice because juice does not burn. Let it boil until it is bronwish or yellowish and is drawn with the ladle like honey. Then it has enough. It must be given a gentle fire so that it always boils steadily because if you boil it too much, it does not turn out well. In the end, you pour it into new pots rinsed with boiling water (außgebrühete). It is a deliciously sweet thing that is used in food in place of sugar when you cook black dishes (i.e. dishes cooked with blood) of hares, fish, and birds.
(Oeconomia, p. 209)
There is frequent speculation about the use of concentrated fruit juices as sweeteners in pre-modern Europe, but this is the first actual recipe I have come across from north of the Alps. Germans trying to avoid industrial sugar still often turn to Birnendicksaft, concentrated pear juice, though the description here suggests a thicker consistency, something more like the Birnenhonig still traditionally made in Switzerland.
It is interesting that Coler suggests using this specifically as an ingredient in blood-thickened dishes. That is what the words schwarz eingemacht refer to at the time. The combination of sweetness, tartness and blood is still popular in German cuisine, where many blood sausages are slightly sweetened. I look forward to finding out how this works, though it will likely take a comsiderable time before I can assemble all the ingredients.
Johann Coler’s Oeconomia ruralis et domestica was a popular book on the topic of managing a wealthy household. It is based largely on previous writings by Coler and first appeared between 1596 and 1601. Repeatedly reprinted for decades, it became one of the most influential early works of Hausväterliteratur. I am working from a 1645 edition.