When looking for a traditional British dish, you can’t get much better than fish and chips; a huge slab of deep-fried white fish accompanied by a heap of hot, thick potatoes smothered with salt and malt vinegar. It’s enough to get my mouth watering. I especially love those crispy bits of extra batter that hide at the bottom of the basket.
But I bet you’ve never considered the science behind achieving that perfectly crisp texture and avoiding the pitfalls of a flabby or chewy crust. Now thanks to a team of food chemists in Japan, we might have come up with a recipe to ensure perfect crunch every time – maybe even with less fat.
The key, according to lead author Pariya Thanatuksorn at the Tokyo University of Technology, is moisture content of the batter. The wetness of the batter affects the rigid microstructure of pores that form during the deep-frying process – essentially the holes left behind as the water vapor bubbles and escapes. The size and distribution of these pores determines the texture of the food, as well as influences how much oil is absorbed during the frying. Though more overall pores means more space for fat to move in, if those pore are few and large, as opposed to many and small, fat moves less readily through the dough by capillary action. Large pore size also means good crispiness, as measured by the force required to break the fried batter.
Using test batters at 40% and 60% water and frying times of 1, 3, 5 and 7 minutes, the Japanese team developed a scale for predicting the pore number, size and crunchiness for all sorts of battered, deep-fried foods. For example, they found that at 60% water, a fry time of 5 minutes gave the best batter crunch – maximum pore size without overcooking to crumbliness. This moisture content and fry time also yielded a lower fat content (now, I don’t think anyone is going to be fooled into thinking that fried foods can be positively healthy thanks to this research, but every little bit helps, right?). They published their results in this week’s Journal of the Science of Food and Agriculture.
So there you have it, who would have thought the humble fish supper could be so complex!