Short Communication: Influence of Serving Temperature on the Retronasal Thresholds of Two Kokumi Peptides: γ-Glu-Phe and γ-Glu-Val-Gly

Kokumi, prospectively the sixth basic taste, provides mouthfulness, thickness, continuity, and a rich and long-lasting taste, attributed to several peptides, two of which were previously preliminarily identified as key compounds responsible for kokumi perception in fermented doenjang. The sensory perception is reportedly influenced by the serving temperature of food. Herein, the influence of the serving temperature (4°C, 25°C, and 60°C) on the retronasal thresholds of two kokumi peptides, γ-Glu-Phe and γ-Glu-Val-Gly, was evaluated. Seven series of three ascending forced choices (7–3 AFC) were selected for the independently conducted retronasal threshold tests (n = 20). The best estimate thresholds (BETs) depended on the serving temperature, differing for γ-Glu-Phe (p < 0.05), but were temperature-insensitive for γ-Glu-Val-Gly. For γ-Glu-Phe, the BET at 4°C was significantly lower than that at 25°C, suggesting that kokumi perception derived from γ-Glu-Phe is better recognized at 4°C than at other temperatures.