This may just be my cold speaking, but I’d like to hear more about sugar as part of an alternative preservative system. I always thought sugar was food for microbes. Anyhow, I remain very, very, very loyal to my conventional preservatives.
Sugar (and many other substances) may be used as part of an alternative preservation system. Whilst sugar is certainly “food for microbes”, the vast majority of organic substances are also biodegradable (which is another way of saying “food for microbes”) and can be broken down – including “non-alternative” preservatives.
The “conventional” preservatives mostly work by causing the metabolism of the microbial cell to fail in some way, either by directly interfering with the metabolic process, or by causing a breach of the microbial cell wall – everything then spills out, and the cell dies. Sugar, and other, similarly-acting substances can be effective at high concentrations by binding much/most/all of the available water (depending upon the concentration used). This is known as reducing the water activity (note – not reducing the concentration of water; just its availability), and there comes a point where there is just not enough water left available for the microbial cells to survive and grow.
The main issue with the use of sugar, espcially on its own, is the high concentration required to have the desired effect. It is very sticky to the touch, and is usually an undesirable component, although it may be possible, as suggested, as PART of an alternative preservation system, to add enough to compliment the rest of the system without making the product too sticky. It is a delicate balancing act. Other substances that behave similarly include glycerine (40%), propylene glycol (25%), butylene glycol (15%). The figures in brackets are the approximate concentrations you would need to properly preserve using each component on its own.
My advice is to stay loyal to your conventional preservatives – life is far more simple that way, and your products will still be safe!