Why do cakes and bread go hard when stale, but biscuits go soft? (2024)

Why do cakes and bread go hard when stale, but biscuits go soft? T. Clarke

Think of a sponge cake. That beautiful light, bouncy texture is due to air bubbles trapped by the elastic strands of gluten created when the batter was made.

At the same time, the starch in the flour in the batter was soaking up water and going from a fine powder of tiny crystal-like forms into a thick gel (think Clag or wallpaper paste) that hardens up when baked.

Together with the elastic gluten they create the spongy matrix we love to slather with cream and jam and call a sponge. But as that cake cools, that soft starch begins to lose water and slowly return to its hard crystalline state.

The same with bread. You can reverse the state of stale bread by rehydrating it and heating it.

• Spray a stale bread roll with water and pop it in the oven at 180C fan-forced (200C conventional) for 5-10 minutes where it reabsorbs the water and goes from hard to soft.

A biscuit, on the other hand, is packed with loads of sugar and tends to have little gluten structure. As the biscuits sit around, even in a tin, the sugar absorbs moisture from the air.

Leave sugar in a bowl in the tropics, for example, and it will absorb so much water it will eventually turn into a liquid! As the sugar in the biscuit absorbs more moisture, it becomes softer and softer and less and less appetising.

• Soft biscuits can be hardened up by 10 minutes in an oven at 180C fan-forced (200C conventional).

I have become lactose intolerant. Can I still eat cheese? D. Hansen

The good news is that most cheese contains very little lactose. Lactose is milk sugar suspended in a liquid with fat, protein and minerals in milk. When milk is made into cheese, the protein coagulates into curds with the fat while the lactose remains with the whey.

This watery whey is drained from the rubbery curds. Some cheeses are made with a lactic acid bacteria starter that turns the lactose into lactic acid. So, most cheese contains very little lactose.

While people with mild lactose intolerance can eat some fresh and soft cheeses, those with severe intolerance may still need to avoid them. The best news is that as cheese ages, an enzyme called lactase breaks down almost all remaining lactose into lactic acid.

Cheeses aged longer than six months, such as cheddar, gruyere, manchego, emmental, comte, aged blue cheese and parmigiano reggiano, are considered safe for most with lactose intolerance. See a cheesemonger and tell them what you want.

Letters

Last week we did a deep dive into kelp. This inspired one reader, B. Morgan, to write: "I always put a piece of kombu in my pot when cooking lentils and other pulses. It softens the fibres and reduces the cooking time and makes them more digestible. The kombu also adds loads of flavour."

Send your culinary conundrums and ingredient suggestions to brainfood@richardcornish.com.au or Twitter and Insta @foodcornish.

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