Effect of taste recall training using five sweet substances on sweet taste sensitivities

The mechanisms involved in the discrimination of basic tastes have been previously studied. However, the mechanisms that differentiate between various substances within the same taste quality remain largely unexplored. This study aimed to determine whether individuals can distinguish five different sweet substances and whether this ability can be improved through taste recall training, serving as an entry point for elucidating the underlying mechanism. Forty healthy individuals were divided into two groups: a training group (10 males and 10 females) and a control group (10 males and 10 females). The taste recall training involved five sweet substances: glucose, fructose, sucrose, maltose, and lactose. Using the filter paper disc method, participants recalled the taste of the five sweet substances at a concentration one level below their taste thresholds and then matched the five substances. This training was conducted for 3 consecutive days. There were no significant differences in the number of participants, sex, age, body mass index (BMI), oral moisture, or baseline taste sensitivity between the training and control groups. The training group showed a significant improvement in the taste thresholds for all five sweet substances compared to the control group (glucose: p<0.001, fructose: p<0.001, sucrose: p<0.001, maltose: p<0.005, lactose: p<0.001). These findings suggest that taste recall training enhances taste sensitivity for all five sweet substances and may improve both taste thresholds and discrimination performance within the same taste quality.