General Question

bw's avatar

What's going on behind the scenes with strawberry topping?

Asked by bw (71points) June 28th, 2007

All you need is a bit of sugar and fresh strawberries. Presto, magical delicious strawberry topping? What's the sugar doing to extract the juices to make the syrup? I've never understood it.

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9 Answers

figbash's avatar

I like how you make it sound sinister.

The juice is actually coming from inside the strawberries. It's osmosis!

Here's what I found:

The sugar begins to dissolve in whatever water is on or near the surface of the
strawberries. This concentrated sugar solution is then diluted by moisture diffusing
out of the strawberries and into the sugar solution. Gradually, the strawberry tissue
is depleted of water as the solution outside becomes more dilute. Depending on the
amount of sugar added and the water-content of the strawberries, the result is a very
sweet juice (syrup) surrounding the pieces of strawberry.

If you look closely at the strawberries after they have rested in the solution, you will
note that the pieces have become rather shriveled and soft because their internal
moisture has been depleted. This is most apparent in store-bought containers of
pre-sweetened frozen strawberries. Their residence time in the syrup is so long that
the strawberries are almost transformed into a formless mush.

bw's avatar

Cristi, so true, I think I've found too that fresh strawberries are much less mushy than frozen ones when making strawberry topping.

I still wonder though - why is it that sugar makes the water just ooze out of the strawberries?

figbash's avatar

Oh! This is the osmosis part! From the same source:

the passage of water across a semipermeable membrane to equalize the water on both sides. So if the water inside the strawberry and outside the strawberry are equal, there will be no net movement of water. But if there is more water on one side or the other, the water will moveto the side with the least water until there is equal water on both sides.

In the case of sugar (or salt), these molecules take up space. When sugar
molecules are present, there is not as much room for water. If you sprinkle
dry sugar on the outside of strawberries, there is no water on the outside.
The water inside the strawberry will begin to leave the cells until there is
equal water on both sides of the cell membrane. So the strawberry juice comes
out of the strawberry and mixes with the sugar and makes them "juicy".

andrew's avatar

What source is that, Cristi?

figbash's avatar

A: should I paste the link or cite the source in a specific format?

boomslang's avatar

Water follows a difference in a concentration gradient. Therefore, the water in the strawberries is moving out of the fruit to equalize the difference in sugar on the outside compared to the inside. To possibly complicate matters, Gatorade works the same way. With electrolytes and water, the electrolytes are absorbed first, thereby creating a concentration gradient. The water follows. This is a quicker way to hydrate then by water alone.

susanc's avatar

with regard to the Gatorade example, I heard that Gatorade has changed its formula,
leaving out whatever electrolytes are, which used to be in it, so that now all it is is
sugar water and some flavorings and dyes. Is this true? And whether it is or not,
how would drinking sugar/flavoring/dye water affect hydration?

bw's avatar

So it seams water is the key thing that makes the difference. It's not sugar alone. For instance, strawberries growing on the ground get dirt on them, it's not like voila we have a mushy dirt strawberry mess. But if you get strawberries wet, add some sugar then you have a concentration gradient right? It's not like just touching sugar to strawberries oozes out the water from the inside?

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