When teaching jam making, the one ingredient that usually captures most people’s interest is sugar and its relatively high content. One of the questions always asked is, “Why all this sugar?” Many have a very negative perception of sugar, especially when it is a part of their food. However, stay with us and learn why this ingredient is essential in jam-making.
Too much sugar?
The one thing to remember is that to make jam successfully, you must have sugar. Reducing or eliminating it altogether is just asking for trouble, which is a failed or runny jam. As much as contributing to sweetening the jam, it does much more.
A typical batch of any fruit jam requires sugar in the ratio of 1 part sugar and 1 part fruit, i.e 1:1. So that if you have 3 cups mango puree, you will need 3 cups sugar and a few tablespoons of lemon juice to successfully make jam.
Once these have been brought to a boil, the hot fruit mix is cooked down to a “jammy” consistency before filling and sealing into sterile glass jars.
The Science in Jam Making
To properly understand the science of jam-making, let’s examine each ingredient in our homemade mango jam, apart from the fruit that is.
Fresh mangoes, like all living plant tissue contain a very high percentage of water (90%). Adding sugar and mixing it with the crushed fruit then cooking makes a sufficiently high sugar concentration. This is when interesting reaction begins to occur between the sugar and the water inside the fruit.
Preservation against spoilage by making water unavailable for microorganisms
The sugar “sucks” out water from the fruit and form chemical bonds which bind the water molecules to the sugar molecules. The bound water is held so tightly that it is no longer available to support the growth of spoilage microorganisms. In this way, sugar acts as a means of preservation against future microbial growth problems.
The other qualities that sugar is important for is in developing flavour and texture. I find that I especially enjoy the taste of homemade mango jam paired with peanut butter on freshly baked brown bread.
Pectin is a natural compound found in most fruits. The riper the fruit the lower it is and vice versa. Citrus fruits contain the most. Since lemons have it in abundance, having its juice is a sure way of ensuring that your jam will have this important ingredient.
Pectin is a large molecular compound that is capable of forming bonds with other pectin molecules to form a gel. Because the sugar is holding onto much of the water in the fruit, the pectin can form a gel creating the desired jammy texture.
Adding lemon juice lowers the fruit’s pH hence making it acidic. This acidic environment helps the pectin into forming a gel that is so beneficial in jam-making. It is also important to note that the tangy flavour in the lemon juice balances the sugar taste, producing a nice round flavour of jam.