Life & Style

All pulp, no fiction: Swetha Sivakumar on the history and science of jams

“Forty times I’ve said if you didn’t let that jam alone I’d skin you. Hand me that switch.” With these lines, we’re introduced to Tom Sawyer, the adventurous hero of Mark Twain’s 1876 classic. Tom has been caught by his aunt red-handed, jam all over his lips and fingers. As kids, we all rooted for his escape from this predicament, while fully sharing in his enthusiasm for sweet, delicious jam.

For children around the world, there is something enchanting about these concoctions. Perhaps it’s the fruity fragrances and bright colours, or the tender, translucent gel consistency. Bun-butter-jam was one of my favourite foods as a child. Most adults grow out of this sandwich preference, and switch to savoury options such as the grilled cheese variant, but I still love a good snack of bread, butter and jam.

The history of sweetened, preserved fruit, be it jams, jellies, preserves or murabbas, traverses a path similar to that of many foods we now take for granted. They started out as the exclusive preserve of the royals and the elite, only becoming mass-manufactured and affordable in recent centuries.

Preserving seasonal fruit through the addition of sugar is an ancient technique. As far back as 50 CE, in his work De Materia Medica (Greek for On Medical Material), the Greek physician Pedanius Dioscorides wrote of quince preserved in honey. As sugarcane cultivation spread in Asia, royal kitchens from those of King Khosrow II of Persia (7th century CE) to those of France’s Louis XIV (17th century CE) served fruit preserves with pride, from quince murabba to cherry jam.

Sugar was expensive; records indicate that in 14th-century England, a pound of it cost the equivalent of a skilled workman’s weekly wages. So it wasn’t used in large quantities in regular kitchens until the 18th century.

What changed at this time was that the abomination of slavery became widespread. Slaves were taken from Africa to work on sugar plantations in the Portuguese, British and Dutch colonies of South America and the Caribbean. By the late 1700s and early 1800s, thousands of tonnes of sugar, produced using slave labour, were being exported to Europe annually. There was a sugar boom; prices fell. Jams began to be made in the average home.

In 1810, a French chef named Nicolas Appert invented canning. He discovered that if foods in glass bottles or cans were submerged in boiling water, then hermetically sealed, the heat killed microorganisms that would otherwise have caused the food to spoil, thereby extending the shelf-life of the product by years. This method would eventually be used to manufacture jams commercially.

Making jam at home takes time; temperatures and pectin levels must be monitored carefully. But a good jam only needs four ingredients: Fruit, sugar, pectin and acid. Jams start off with 55% sugar to 45% fruit. Accounting for water evaporation, sugar levels end up closer to 65%.

The high levels of sugar bind the water molecules, inhibiting microbial growth. The sugar also draws water away from the pectin molecules, so that they can form a delicate sponge-like network that holds the jam together.

Whether homemade or commercial, the sugar in jams, along with the low pH of the fruit and the sterilisation of jars, is enough to produce a shelf-stable product. So avoid buying jams that list preservatives such as potassium sorbate (E 202) or sodium metabisulfite (E 233); and ingredients such as artificial flavours and artificial colours. They are unnecessary in a jam.

A sugar-free jam will have a longer list of ingredients such as maltodextrin or polydextrose, and preservatives such as potassium sorbate. Since the sugar performed the multiple functions of providing sweetness and body as well as preserving the jam, multiple additives are needed in its place.

Because when it comes to jam, sugar and fruit are like the lead couple in a Bollywood dance number. If you take one out, you must distract the audience with a lot of ancillary talent. Even so, it’ll never be quite the same.

KNOW YOUR FRUIT SPREADS

There are roughly four types of fruit spreads: preserves, jams, jellies and marmalades. All involve fruit, sugar and boiling. The difference lies in the way the fruit is processed.

* If the fruit is used wholeor in large chunks, it is called a preserve

* If the fruit is crushed and the texture is left coarse, it’s a jam.

* If the fruit is strained, and just the juice used to make a sparkling, clear product with no fruit solids, then it’s a jelly.

* Add cooked pieces of fruit and rind (usually citrus) back into the jelly, and it’s a marmalade.

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