Influences of product pH and salinity on the retronasal threshold values of capsaicin

The aim of this study was to determine the retronasal threshold values of capsaicin with regard to changes in product pH and salinity. Retronasal threshold testing was conducted using five series of the ascending three-alternative forced-choice method on water-based matrices with varying pH and salinity levels. Overall, retronasal BET values of capsaicin tended to decrease with increases of pH in a water-based model system, and the retronasal BET value of capsaicin at a pH of 6 was significantly lower than the BET values at other pH levels (p <.05). This result suggests lower capsaicin concentration is required for human to detect capsaicin-related spiciness at pH 6 than the capsaicin concentration at pH 4.0–5.5. No significant differences in BET values of capsaicin were detected at salinity levels of 1.0–2.0% with 0.18 mg/L (p >.05). No significant differences were observed in BET values of capsaicin at salinity levels of 2.5–3.5%, which corresponded to capsaicin concentrations of 0.42 (2.5%), 0.40 (3.0%), and 0.30 mg/L (3.5%). Retronasal BET values for capsaicin at 2.5–3.5% salinity were significantly higher than those at 1.0–2.0%, suggesting that capsaicin-related spiciness of low capsaicin concentrations may be better recognized at salinity ranges of 1.0–2.0% than at higher salinity values (2.5–3.5%). Practical Applications: Capsaicin is well known for its spicy perception in kimchi. Analysis of the spiciness of kimchi has been heavily dependent on instrumental analysis of capsaicin content. However, a gap exists between the instrumental analysis results and the perceived spiciness intensity of kimchi products by humans. This study investigated different pH and salinity ranges similar to those found in commercially available kimchi in Korea and determined the retronasal thresholds of capsaicin. Results suggest a difference in retronasal threshold values of capsaicin according to product pH and salinity, and this finding may explain the disparity between the instrumental analysis of capsaicin and the perceived spiciness intensity in kimchi by humans.