A raisin biscuit is a classic in most recipe books. But what the raisins actually do in those recipes goes beyond sweetness.
What is the sugar profile of raisins?
A hundred grams of raisins contains around 59 grams of sugar.
Most of that is glucose and fructose.
Sucrose — table sugar — is present at a very low level.
That difference matters.
Fructose is around 1.7 times sweeter than sucrose.
The sugar in raisins therefore gives a stronger sweetness than the same quantity of table sugar.
Glucose and fructose are also hygroscopic; they draw moisture from the air and from the dough.
That keeps the product soft.
A handful of raisins — thirty grams — brings around 18 grams of sugar, a clear share of the sugar in a biscuit recipe.
How does moisture retention work?
Raisins contain 15 to 18 percent moisture.
That moisture keeps them soft.
Added to a dough, a two-way exchange begins.
The raisins first draw water from the dough.
They then release it back during baking.
That creates moist regions around them.
The result is a variable rather than uniform texture, with some parts of the biscuit softer.
That is a preferred property.
The hygroscopic sugars in raisins also continue holding moisture after baking.
That lengthens shelf life; a raisin biscuit stays soft a day or two longer than a plain one.
| Contribution | Effect | Measure |
|---|---|---|
| Natural sugar | Sweetness | 59 g per 100 g |
| Moisture | Softness | 15-18% |
| Fibre | Texture, satiety | 3.7 g per 100 g |
| Potassium | Nutrition | 749 mg per 100 g |
| Phenolic compounds | Antioxidant | High in dark varieties |
| Acid | Balance of taste | pH 3.8-4.2 |
How much added sugar can be reduced?
That requires a practical calculation.
Sugar in a standard biscuit recipe runs 50 to 70 percent of the flour weight.
Fifty to seventy grams per hundred grams of flour.
Adding fifty grams of raisins to that recipe adds around 29 grams of sugar.
Allowing for the sweetness of fructose, that corresponds to around 35 grams of table sugar.
Added sugar can therefore fall by 20 to 25 grams.
But sugar does not only provide sweetness; it gives structure, rise and colour too.
The reduction should therefore be limited; no more than 30 percent of the total should come out.
Beyond that the biscuit hardens and its colour stays pale.
Using brown sugar compensates for the reduction; molasses provides both colour and moisture.
Why is hydration necessary?
Raisins added straight to a dough draw water from it.
That dries the dough and hardens the biscuit.
The raisins can also stay hard and dry after baking.
The solution is hydrating them first.
They sit in warm water for fifteen minutes.
They then get drained and dried thoroughly.
Wet raisins add too much moisture to the dough.
Fruit juice, tea or rum can be used instead of water, which provides extra aroma.
Orange juice is a classic choice; citrus aroma goes well with raisins.
Hydrated raisins are softer and plumper.
Where that step is skipped the raisins end up as hard as the biscuit and the textural difference disappears.
How is the distribution problem solved?
Raisins are heavy and can sink through a dough.
That is a problem particularly in fluid batters.
Three methods work.
The first is flouring. The raisins get mixed with a spoonful of the recipe's flour.
The flour keeps the surface dry and slows sinking.
The second is adding them last. They go in at the final stage and get folded by hand.
Raisins mixed in a machine break up.
The third is dough consistency. A firmer dough holds them better.
Resting the dough in a fridge increases the consistency and improves distribution.
The quantity should not be overdone; 30 to 40 percent of the flour weight is the upper limit.
How do raisins behave in gluten-free recipes?
The biggest problems in gluten-free biscuits are dryness and crumbling.
Raisins reduce both at once.
Their moisture retention addresses the dryness.
Their physical presence limits crumbling; the pieces form points of connection within the dough.
But gluten-free doughs are more fluid; the risk of sinking is higher.
The flouring step matters more in those recipes.
Raisins work very well in almond flour recipes; almond and raisin are a natural pairing.
It is a classic combination in oat-based gluten-free biscuits too.
In recipes based on rice flour, raisins reduce the gritty sensation.
The quantity of binder can fall slightly; the sugars in the raisins provide some binding.
Which variety is chosen?
Different varieties give different results.
Sultanas — seedless and pale — are the most widely used.
Sweet and neutral, they suit every recipe.
Dark raisins are more intensely flavoured and more acidic.
Their phenolic compounds are higher; they are richer in antioxidants.
But their colour passes into the dough and darkens pale biscuits.
Currants are small and intensely flavoured; they distribute better and register in every bite.
Golden raisins — treated with sulphur — stay pale and soft.
Sulphur dioxide is on the allergen list and has to be declared on the label.
Unsulphured varieties are darker but carry no additives.
The choice follows from the biscuit's colour and the intensity of aroma wanted.
How are raisins stored?
Raisins are low in moisture but storage conditions still matter.
They keep six to twelve months at room temperature in a closed container.
That extends to a year in a fridge.
Two years in a freezer.
Heat and humidity bring the sugars to the surface.
That forms a white, crystalline layer; not a problem, but it spoils the appearance.
Mould can begin in raisins that have taken up moisture; that product should not be used.
An airtight container should be used; product left in an open bag both dries and takes on odours.
Hardened raisins can be softened again by standing fifteen minutes in warm water and used in recipes without problems.
Where they are bought in bulk, dividing them into two containers and opening only one at a time keeps the rest at its original condition for months.
