Almost everyone loves crispy food, but only a few attempt to understand crunchy food texture science. Imagine the agreeable texture of popcorn, French fries, potato chips, salted peanuts, or even fresh carrots. These are foods that make mastication a pleasurable experience, as they often have a satisfying crunch.
The crispiness of certain food products is either a structural or chemical phenomenon. Also, it is sometimes a product of the two phenomena. Consequently, food properties like process temperature, starch and moisture content or even sound contribute to texture perception science.
Almost every culture around the globe has a couple of crunchy foods to which locals seldom say ‘no.’ So, this piece will break down the science behind a food texture that cuts across all cultures.
The Role of Water Activity: Crispiness Begins With Low Moisture
Fun tip: To make your food crispy, reduce its water activity. For the uninitiated, water activity (aw) is the percentage of water molecules that are available for biological processes and chemical reactions. So, foods with low aw either contain only a small amount of water or contain a substantial amount of water, but the molecules are not available for activities like microbial growth or replication. Water activity ranges between a value of 0 and 1.
It is possible to reduce water activity in foods by baking, frying or even drying. These water-activity-reducing processes, beyond improving the shelf stability of the product concerned, can also improve its crispiness. For instance, it is possible to make a tender and juicy chicken drumstick crunchy by deep-frying them. So, low water activity, between 0.35 – 0.45, is one of the reasons why food crunches.
In addition, crunchy food texture science also helps establish the difference between crispy vs. soggy food. As explained earlier, crispy food chemistry usually involves low aw. Meanwhile, soggy foods are often the product of moisture migration, from, say, the environment or other wet foods close by, to previously low-moisture food.
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Starch, Proteins, and the Structure of Crunch
The chemical profile of food items and how the molecules are arranged also influence crunchy texture science. Take food items that are very rich in starch as an example. When such foods are cooked or dried, they gelatinize and subsequently become rigid. An easy way to explain gelatinization is the pasty gruel-like transformation that occurs during the cooking of oatmeal. Indeed, crunchy food texture science reveals that starch-rich foods like potatoes, peas, corn, or even energy bars, become crispy after heat or moisture-removing processing.
The presence of proteins in food also affects crispy food chemistry. Protein molecules tend to break into smaller units during food processing. They also become rigid when exposed to heat or moisture removal.
Another interesting attribute of crunchy foods is how their structure contributes to their characteristic crispiness. When moisture is removed from fresh food items either during frying, baking or drying, it leaves hollow pores in the resulting product. This porous and brittle network also contributes to food structure crispiness. It also explains why food crunches and the sound that accompanies the chewing of crispy food.
Typical examples of foods that will help you better understand sensory science crunch are fried chicken crust, tempura and chips.
The Maillard Reaction and Its Crunch Contribution
The Maillard reaction is a chemical process that occurs in foods or food mixes containing amino acids (building blocks of proteins) and reducing sugars. This reaction is often responsible for the characteristic aroma, color, and flavor of some cooked food. For instance, the crusty brown color on most baked, fried, and roasted foods is due to Maillard reactions.
Beyond browning and flavor development, Maillard reactions also contribute to crunchy texture science. This is evident in the hard and crackly surface of food products that have undergone the Maillard reaction.
So, next time you eat some fresh and crispy French fries, the Maillard reaction crunch is one of the phenomena that makes it possible.
The Sound of Crunch: Why Crispy Foods “Talk” to Us
Studies in crunchy food texture science have revealed that food structure and sound are closely related. A quick scenario: “You decided to spoil yourself a little during a Christmas grocery run, and added a couple of chocolate bars to your cart. However, you reach for one of the chocolates while preparing dinner, unwrapped it, and broke off a piece.” Now, in this scenario, it is very likely that you’ll second-guess the quality of the chocolate if it doesn’t ‘snap’ during biting or breaking.
Crispiness is a multi-sensory food attribute, one that combines the texture and sound of the food item. Some chocolate brands pay particular attention to the crunchy sound of their product, as some consumers use it as a measure of quality. In most cases, food product development teams consider sound frequencies between 2-6 kHz as appropriate for a ‘satisfying crunch.’ Wondering how the sensory science crunch of products is determined? Scientists often use sensitive microphones to measure crispiness.
Why Foods Lose Crispiness (and How to Slow It Down)
Have you ever wondered why potato chips become soggy when you leave the package open? Crunchy food texture science suggests that it boils down to two phenomena. One is moisture reabsorption, particularly in starch-rich crispy products. Also, oil oxidation in fried or baked foods often softens the crust.
However, if you want to keep your crispy food that way for as long as practicable, here are a few tips to follow:
- After cooking, cool crisp food properly before storage.
- Don’t add sauce before storage. Instead, add some whenever you’re ready to eat.
- If you need to transport crispy food that is still hot, for example, in take outs, use ventilated containers.
- Avoid refrigeration where possible, as it has the potential of making crispy food soggy.
- When reheating crispy food that has been stored for a while, you may want to use dry-heat methods to restore crispiness. Reheating in an oven or air fryer should serve the purpose.
ALSO READ: Homemade Energy Bars: How to Perfect Texture and Maximize Shelf Life
Innovations in Keeping Food Crispy
Some food brands are aware of how much the crispiness of their products influences consumer perception of quality, and by extension, sales. So, food companies are trying out multiple innovative methods of improving food structure and crispiness.
Crispy Coatings Made from Modified Starch Blends
Manufacturers are now complementing native starches with modified starch blends during food formulation. This is largely because modified starches hold their own under high heat. This high-temperature durability enhances the film-forming properties of food starch. By extension, moisture reabsorption in crispy foods is better controlled. Similarly, it reduces the absorption of oil during frying.
Freeze-Drying to Preserve Crunch
Some processors opt for freeze drying to maintain food structure crispiness during processing. The technology behind the freeze-drying process aids moisture removal without compromising cell structure.
Micro-Layer Batters in Fast Food R&D
Protein concentrates and hydrocolloids are making it possible for fast food chains to incorporate micro-layer barriers into their products. It’s more like a microfilm that prevents mass transfer during frying, thus enhancing the texture profile.
Packaging Innovations (Anti-Humidity Films)
Some food companies find the make-up of their product too classic or unique to tamper with. So, they revert to protecting such products with innovative packaging materials. Often, this involves using high-barrier, multilayer materials that prevent the ingress of moisture.
In most commercial food products, crispiness is seldom ever an accident. Instead, it is often a careful interplay between molecular structure, food chemistry and product sound. When crunchy food texture science is on its A-game, the crispy product may leave you asking for more.
Behind every satisfying crunch is a tiny symphony of physics and chemistry working together.
