Effects of Starch Type and Concentration on the Physicochemical, Antioxidant, Textural, and Sensory Properties of Tomato Juice–Incorporated Gwapyeon

Imagine a world where food isn't just about taste, but about the invisible dance between ingredients. This story lives in the kitchen of food science, a place where researchers act like culinary detectives, trying to figure out how different "glues" hold liquids together. In this case, the liquid is a fruit or vegetable juice, and the glue is starch. You know starch as the white powder in corn, potatoes, or beans that makes sauces thick and puddings jiggly. When you heat starch with water, the tiny granules swell up, burst, and link together to form a gel—a wobbly, semi-solid network that traps the liquid inside. But here's the tricky part: not all glues are created equal. Some hold water tightly, while others let it leak out (a process scientists call "syneresis," which is just a fancy word for a gel crying). The big question for this study was: Can we take a traditional Korean dessert and swap its classic ingredients for something new, like tomato juice, without the whole thing falling apart or tasting weird?

The dessert in question is called Gwapyeon. Think of it as a Korean fruit jello, but with a history lesson baked in. Traditionally, it's made by boiling fruit juice with starch (often from mung beans) and sugar, pouring it into a mold, letting it cool, and then slicing it into neat, bite-sized cubes. It's a treat that has been around for centuries, known for its tender, cuttable texture. The researchers wanted to see if they could modernize this ancient recipe by using tomato juice instead of the usual fruit juices. Tomatoes are a bit different; they are full of pulp, acids, and fibers, which might mess with the starch's ability to form a perfect gel. The team set out to test three different types of starch—corn, potato, and mung bean—at various concentrations to see which one could turn tomato juice into a stable, delicious, and cuttable Gwapyeon.

The Great Tomato-Starch Experiment

The scientists mixed commercial 100% tomato juice with water and sugar, then added their chosen starches. They cooked the mixture, poured it into square molds, and let it set. Then, they put the resulting tomato-gels through a gauntlet of tests to see how they held up. They checked the pH (how sour they were), the color, how much water leaked out over five days in the fridge, how "antioxidant-rich" they were, and most importantly, how they felt in the mouth and how much people liked them.

The Results: A Tale of Three Starches

First, the pH and sweetness. All the tomato Gwapyeons were mildly sour, with pH levels hovering between 4.46 and 4.62. This makes sense because the tomato juice was the main flavor driver, and the starch didn't really change the acidity. The sweetness and sugar content were also pretty much the same across the board, meaning the starch type didn't alter the basic taste profile.

The Color and the "Crying" Gel
When it came to looks, the potato starch gels were the dark horses (literally darker in color). They had a lower "lightness" score, making them look deeper red-brown compared to the others. But the real drama happened in the fridge. Over five days, the researchers watched to see how much liquid would leak out of the gels.

• Corn starch was the champion of water retention. The gels made with corn starch (especially at 10% and 11% concentrations) barely cried at all, leaking less than 8.5% of their weight in liquid.
• Mung bean starch, on the other hand, was a bit of a mess. Even though it made the firmest gels, it leaked the most water, with some samples losing up to 26.46% of their weight!
• Potato starch fell somewhere in the middle, but it wasn't as good at holding water as the corn.

The Texture: Hard vs. Soft
If you've ever tried to chew gum, you know the difference between a soft, squishy piece and a tough, rubbery one. The mung bean starch gels were the tough guys. The sample with 9% mung bean starch (called TM9) was incredibly hard, gummy, and chewy. It required a lot of effort to bite through.
In contrast, the corn starch and potato starch gels were much softer and easier to chew. The corn starch gels were particularly springy, bouncing back well when pressed. The potato starch gels were soft but had a bit of a weird reaction to concentration changes, sometimes getting springier and sometimes softer depending on how much starch was used.

The "Health" Check
The researchers also checked for antioxidants, which are compounds that help fight damage in the body. They measured total phenols (a type of antioxidant) and the ability to neutralize harmful free radicals (ABTS capacity).

• The corn starch sample with 9% concentration had the highest total phenol content.
• The mung bean starch sample with 7% concentration had the highest ability to neutralize free radicals.
• Interestingly, the amount of flavonoids (another type of antioxidant) didn't change much no matter which starch was used.
  However, the paper notes that these are just chemical tests done in a lab; they don't prove that eating the Gwapyeon will make you healthier, just that the chemical ingredients are there.

The Taste Test: What Did People Think?
Finally, 37 students tasted the nine different versions. The results were a bit of a letdown for the researchers.

• Overall Acceptance: Nobody loved the tomato Gwapyeon. The scores for "overall acceptance" and "would you buy this?" were low and statistically the same for all versions. It seems the tomato flavor, combined with the specific textures, just didn't click with the tasters.
• The One Exception: The only thing that made a difference was chewiness. The TM9 sample (9% mung bean starch) was the most liked for its chewiness. It was the toughest gel, and surprisingly, people liked that specific texture more than the softer ones. But even though they liked the chewiness, it didn't make them like the dessert overall or want to buy it.

The Bottom Line

This study shows that you can make a Gwapyeon with tomato juice, but it's not as simple as just swapping ingredients. The type of starch you choose changes everything:

• Corn starch is the best at keeping the gel from leaking water, making it the most stable for storage.
• Mung bean starch makes the hardest, chewiest gel, which some people liked, but it also leaks a lot of water.
• Potato starch makes a darker, softer gel that doesn't hold water as well as corn starch.

The researchers conclude that while the traditional Korean method of making Gwapyeon works with tomato juice, the current recipes need more work. The balance of sweet and sour needs tweaking, and the texture needs to be just right—not too hard, not too leaky. Until then, tomato Gwapyeon remains a promising but unfinished experiment in the world of Korean ethnic foods. The paper doesn't claim to have solved the problem, but it has mapped out exactly where the trouble spots are, giving future chefs a clear path to a better, tastier tomato treat.