Have you ever wondered why sugar is added to jam? – While it is true that sugar contributes to the sweetness of the jam, it does much more than that. The sugar draws water out of the fruit and holds onto it. This makes the water unavailable for bacteria to grow and in this way, it acts as a preservative against spoilage. You will notice that sugar containing jam has a higher shelf life than the sugar free jams and this is because of the preservative properties of the sugar. Another great function of making water unavailable in jam-making is that it allows the jam to set. The secret to creating the perfect jam is using the correct amount of sugar. Use too little and the jam is runny, use too much and the jam gets too hard.