Every now and then, we get an inquiry from our spring roll and crispy wonton loving customers wondering where in the world our microwave heating instructions are.
We don’t offer microwave instructions for these items and it is time to reveal why with a little help from science!
First off, let’s explain the phenomenon of frying. No matter if you are sautéeing (a little oil on the pan), shallow frying (when there is enough oil to come up half way up the side of food), or deep frying (where the food is completely submerged in the oil); cooking any food in hot fat is considered fried food. Hot oil, which when heated, gets much hotter than the boiling point of water, dehydrates the surface of the food when the two come into contact. A chemical reaction, called the Maillard Reactions, where the sugar and protein break down, will create the golden-brown colour and flavour we know. You can read more about the Maillard Reaction here.
When deep frying food, maintaining the correct oil temperature is super important. You often see recipes calling for a specific temperature required to properly cook the item. For example, if the temperature of the oil is too low, the crust is slow to form, and the food is allowed to absorb more fat; therefore, making the food greasy. If the oil is too hot, the food burns on the surface before it is cooked through.
Now let’s look at the creation of a crispy exterior (we will use our Crispy Vegetable Spring Rolls as an example). When food plunges into a bath of hot oil, the water in the food starts to boil. The water, as steam, will then want to escape through the surface of the food. In order to keep and protect the moisture in the food, a barrier is required to limit the amount of water (or steam) to escape. The best way to do this is with something starchy. This is why flour is often used to coat chicken before frying. In the case of the spring roll, the wrapper acts as this barrier. As the wrapper dries out, it turns into a crispy wrapper that protects the moisture inside and lets the filling steam cook itself.
Ever notice when you leave fried food sitting on the counter to cool for a period of time, it loses its crunch? Well, as the crust cools, it is, once again, absorbing both moisture from the stuffing inside the product as well as any water vapor in the atmosphere. This is why fried foods are best eaten as soon as possible after frying.
So what happens when you try to reheat our spring rolls in a microwave vs reheating it in an oven?
To become crispy again, the wrapper needs to be reheated at a high temperature to create that barrier to protect the moisture inside from escaping. Unfortunately, a microwave heats food by heating the whole product at the same time, reaching not much higher than the boiling point. Since the interior of the microwave oven never heats up, and it is only the food which heats, there is no reaction with a hot exterior to crisp the wrapper up. The steam from the moist filling inside the wrapper will build up and rise to the surface. When the steam from inside the spring roll meets the cool air inside the microwave oven, condensation is formed on the wrapper; therefore, softening it.
We recommend using a conventional or toaster oven to reheat our products because it uses hot air to reheat the product, cooking it from outside in, slowly. At our suggested heating temperature of 375° F, this allows the surface of the spring roll to crisp up first.
Next time when you are ready to put something in the microwave to be reheated, think about whether or not it is the appropriate heating method!