1. Why a Potato Chip Weighs So Much Less Than the Potato It Came From
Potatoes are about 80% water. When slices are fried, most of that water boils off as steam. The skin and any damaged parts are also removed before slicing. J-Net21, a business information site supported by the Japanese government, reports that only about 30% of a potato's weight ends up as potato chips at Calbee, Japan's largest potato chip maker. [1]
So 100 grams of potatoes become roughly 30 grams of chips. That 30% is a ratio of product weight to starting weight. It is not the water content of the finished chip, and not all of the missing 70% is water, because peels and bad spots are part of it. [1]
Where the water used to be, the slice is left with tiny air pockets separated by thin walls. A simple way to picture it is a honeycomb of fragile walls: when you bite down, the walls snap, and the snap is the crunch. This picture is our own way of explaining it, not a quotation from the sources.
Driving out water needs a lot of heat, though. What does that heat do to the color and the chemistry of the chip?
2. Why Chip Makers Have to Watch the Golden Color Closely
Heat that is hot enough to dry a slice quickly can also brown it too far. Japan's Ministry of Agriculture, Forestry and Fisheries (MAFF) explains that a substance called acrylamide can form when food is fried, baked, or stir-fried at 120°C (248°F) or higher, and that the more browned the food is, the more of it there is. [2]
For this reason a potato chip line has several safeguards stacked one after another. MAFF lists these steps: storing the potatoes at a suitable temperature, choosing potato varieties that suit chips, parboiling and washing the slices, adjusting the slice thickness, adjusting the frying temperature, cooling the chips with a blower, and using a color sorter to pick out burnt pieces. [2] Not every company necessarily uses every step.
One way to read this list (our interpretation) is that the chip maker is walking a narrow path: hot enough to remove water, but not so hot or so long that the chip burns. That is why slice thickness and frying temperature appear on the list.
Chips are not the only way to make a crunchy snack, and not all of them are fried. A shrimp-flavored snack from Japan shows a very different method.
3. How a Shrimp-Flavored Snack Is Made Crunchy Without Frying
In Japan, Calbee's Kappa Ebisen (roughly "shrimp snack") has been sold since 1964. It is a shrimp-flavored snack made from a wheat-flour dough. The founder, Takashi Matsuo, remembered catching small river shrimp as a child and eating the fritters his mother made from them, and he wanted to turn that taste into a snack. [3]
After trying boiled shrimp and shrimp powder without satisfying results, the company settled on mixing raw small shrimp, from head to tail and shell included, into a wheat dough as a mince, like fish paste. [3]
The cooking method is different from what you might expect. A J-Net21 interview article says the snack is not a fried snack. The company calls the step "roasting": the dough is stir-fried first and then lightly sprayed with vegetable oil. According to the same article, roasting makes the dough puff up moderately and gives it a fine, crisp texture. [3] That article dates from 2010, so today's factory process may differ.
The goal is still the same: dry the dough and leave air pockets. But a third family of snacks does it with pressure instead of a fryer.
4. How a Machine Makes a Dough Puff Up the Moment It Comes Out
Many puffed snacks are made in an extruder, a machine that pushes a dough or flour mixture continuously through a narrow opening called a die. Inside, the mixture is cooked under high temperature, pressure, and shear (a kind of stirring and squeezing force). A research review in PubMed Central describes extrusion as high-temperature, short-time cooking above 100°C (212°F), with the material forced through a small die at the end of the barrel. [4]
The same review explains that the expansion is linked to water that is superheated, meaning kept liquid above its usual boiling point while under pressure, and then turns into steam. A higher barrel temperature increases this effect, and so does lower moisture in the feed. [4] A simple way to picture the final moment is the pressure easing as the dough leaves the die, so the hot water inside rushes into steam and blows the dough up into a light, airy shape. That picture is ours; the review itself supports the main idea that steam drives the expansion.
More water is not always better. In one study the review describes, raising the feed moisture from 10% to 13% increased the expansion, but at 14% the expansion went down again. [4] That was one set of experiments with particular ingredients, not a rule for every snack.
So three snacks, three paths. How can you tell them apart at home?
5. How to Compare Snacks at Home by Breaking Them Open
Our grouping is a simple summary of the sources above: sliced and fried (potato chips), roasted dough (the shrimp-flavored snack), and extruded and puffed (many puffed snacks). Real products can mix these ideas, so treat it as a starting point and not a rule.
Break two or three different snacks in half and look closely at the broken edges. Are the air pockets large or small? Are they evenly spread? Are the walls thin or thick? Which one snaps most cleanly?
Then read the ingredient list on the back of each bag. Labeling rules differ from place to place, but the order of the ingredients can often give you a rough idea of which ones are used in larger amounts, such as potato, wheat flour, or corn. The list shows what is inside but not how the snack was made. If you have a food allergy, check the ingredient label before eating. Wheat, shellfish, and milk are among the ingredients that can cause allergies.
To find out how a particular snack is really made, look for a factory tour video or a manufacturing page from the company that makes it.