Refined cane and beet sugars are both suitable as preserving sugar — there is no difference in the keeping quality. Any type of sugar can be used granulated, caster cubed or brown but granulated sugar is probably the most widely used preserving sugar; and the cheapest. True preserving sugar is specially made sugar, with large crystals but is more expensive than ordinary sugar. Its main advantage is that it produces less scum and therefore less wastage; it also tends to give a clearer and brighter result. Special jam sugar contains pectin and acid, which helps the preserve to set better than one made with ordinary sugar but preserves made with special jam sugar tend to have a more limited shelf life than those made with ordinary preserving sugar. Store for no more than six months and, once opened, keep them in the fridge and eat within 3—4 weeks.
Demerara sugar has a crunchy texture and a distinctive, crystalline appearance; it is available in both refined and unrefined versions. Muscovado sugars are raw cane sugars which are softer in texture than demerara and are available in varying shades of brown, usually light or dark. Their pronounced flavour may override those of other ingredients, so this needs to be considered when choosing which kind of preserving sugar to use.
Organic and unrefined preserving sugar are now widely available. Unrefined sugars are very simply processed and retain the natural colour and flavour of the molasses in the sugar. Organic sugar is produced without the use of chemicals and will be certified by the Soil Association. These sugars also tend to have a pronounced flavour and this may be detectable in the finished preserve: whether this is desirable or not is a matter for the individual cook to decide. Recipes usually give guidance on which preserving sugar gives the best result.