Effects of starch type and concentration on the physicochemical, antioxidant, textural, and sensory properties of tomato juice-incorporated Gwapyeon
Gwapyeon is a molded Korean starch confection traditionally prepared by heating a fruit-derived liquid with starch and cooling the paste to form a cuttable gel. The present study examined whether a contemporary tomato juice formulation could retain the inherited processing identity of Gwapyeon while accommodating formulation-dependent differences in product quality. Commercial 100% tomato juice was diluted 1:1 with distilled water and formulated with corn or potato starch at 9–11% (w/v) or mung bean starch at 7–9% (w/v). Physicochemical characteristics, color, refrigerated-storage syneresis, total phenolic and flavonoid contents, ABTS radical-scavenging capacity, texture profile, and consumer liking among 37 untrained participants were evaluated. The pH of the samples ranged from 4.46 ± 0.03 to 4.62 ± 0.06, with TP10 exhibiting a significantly higher value than TC9 (p < 0.05). The °Brix values varied from 1.83 ± 0.06 to 2.13 ± 0.15, with no significant differences observed. The L* values, ranging from 33.65 ± 2.36 to 39.42 ± 1.81, showed significant variation among formulations (p < 0.05), whereas a* values remained consistent across samples. Differences in b* values were noted only between TM8 and TP9 (p < 0.05). Over the 5-day storage, syneresis ranged from 0.42 ± 0.40% in TC11 to 26.46 ± 1.92% in TM7, with TM7 demonstrating the highest syneresis (p < 0.05). Total phenolic content, measured between 50.93 and 53.89 μg GAE/mL, and ABTS radical-scavenging capacity, ranging from 3.90 to 6.74 mg TE/mL, varied significantly among formulations (p < 0.05), whereas total flavonoid content, ranging from 99.74 to 118.57 μg QE/mL, did not show significant differences. TM9 exhibited the highest values for hardness (433.00 ± 58.25 g), gumminess (109.50 ± 7.37), and chewiness (82.03 ± 15.64) (p < 0.05). In the consumer test, significant differences were found only in the liking of chewiness, with TM9 receiving a score of 4.81 ± 2.61, surpassing TC9 and the three potato-starch formulations (p < 0.05); however, overall acceptance and purchase intention did not differ significantly. These findings indicate that tomato juice-incorporated Gwapyeon represents a contemporary application of a Korean ethnic-food processing framework, but requires formulation-specific optimization of flavor, texture, and refrigerated stability.