When you come across a recipe that calls
for red or yellow onions, you probably think that you can use whatever
onions you have handy, but this is actually not the case. When a recipe
calls for a particular kind of onion to be used, they actually mean that
kind of onion!
Red, yellow, and white onions are all
slightly different when it comes to their flavor and texture. Before
delving into these differences, how do you know which onions to buy at
the store?
Well, when purchasing onions, go for those that feel heavy and firm in
your hand. Avoid soft onions or ones that have a sharp odor before
peeling; these are clear signs that the onion is old. Except for sweet
onions, since these onions can be stored for a number of weeks in a
cool, dark pantry or cupboard.
Why are sweet onions stored differently? Well, read on to find out why,
and what the crucial differences are between common onion varieties.
Yellow Onions
More often than not, yellow onions are our
go-to onions - kind of like an all-purpose onion. They tend to have a
nice balance of astringency and sweetness, becoming sweeter the longer
that they are cooked.
They are usually fist-sized and have a fairly tough outer skin and meaty
layers that can be tricky to cut. The only variety of yellow onion that
we are most likely to find in the store are Spanish ones. This type is
slightly sweeter and more delicate in flavor.
White Onions 
These onions have a sharper and more
pungent flavor than yellow ones, and they also have a thinner and more
paper-like skin. They can be cooked exactly like yellow onions, but
they're best minced and added to chutneys and raw slaws.
Red Onions
With their deep purple outer skin and
reddish flesh, these are the black sheep of the onion family. Despite
the fact that they look so different, red onions are similar to yellow
ones in flavor, though their layers are less tender and meatier. They
tend to lean more towards the sour end of the flavor spectrum. Red
onions are great for salsas, salads, and other raw preparations for
their lovely color and mild flavor.
Sweet Onions
These onions are trickier because they look
very similar to your average yellow onion. However, while they might
look similar, they taste very different. They lack the sharp astringent
taste of other onions, and taste really sweet.
These are usually what you'll find on top of sandwiches. They can range
in color from white to yellow and often have a flattened or squashed
appearance. These tend to be more perishable than other varieties, and
so should be stored in the fridge.