The confusion is in having a complicated unnecessary step.
I will personally guarantee you will get no mould or bacterial growth in your syrup if you do the following.
Make a 2000X concentrated stock by dissolving 20g of Thymol Crystals in 100ml of Isopropyl alcohol (Iso-Propanol) or Surgical spirits.
Takes about 2 to 3 minutes to dissolve the crystals with a little shaking...No heating required.
Add at rate of 0.5 ml to every litre of your syrup (either thick or thin..... makes no odds)
Job done.
You syrup will now keep fresh for a very very very very long time....years if need be.
And as I say above I will guarantee if you follow these instructions you will not get any moulds etc.
It worked for Manley in 1946 and it still works today.
no lecithin then
