A novel quantified bitterness evaluation model for traditional Chinese herbs based on an animal ethology principle

Traditional Chinese herbs (TCH) are currently gaining attention in disease prevention and health care plans. However, their general bitter taste hinders their use. Despite the development of a variety of taste evaluation methods, it is still a major challenge to establish a quantitative detection technique that is objective, authentic and sensitive. Based on the two-bottle preference test (TBP), we proposed a novel quantitative strategy using a standardized animal test and a unified quantitative benchmark. To reduce the difference of results, the methodology of TBP was optimized. The relationship between the concentration of quinine and animal preference index (PI) was obtained. Then the PI of TCH was measured through TBP, and bitterness results were converted into a unified numerical system using the relationship of concentration and PI. To verify the authenticity and sensitivity of quantified results, human sensory testing and electronic tongue testing were applied. The quantified results showed a good discrimination ability. For example, the bitterness of Coptidis Rhizoma was equal to 0.0579 mg/mL quinine, and Nelumbinis Folium was equal to 0.0001 mg/mL. The validation results proved that the new assessment method for TCH was objective and reliable. In conclusion, this study provides an option for the quantification of bitterness and the evaluation of taste masking effects.

Quantification of astringency for traditional Chinese medicine based on animal preference index and electronic tongue / 中国中药杂志

Current evaluation method for astringency is mainly focused on human sensory evaluation. However, it is subjective, vague, and short of assessment indicators for objective quantification. In this paper, the quantification method for astringent intensity of traditional Chinese medicine was established based on the animal preference index and electronic tongue in vitro and in vivo. Firstly, the standard substance of astringency, tannic acid, was used for the methodology optimization and validation of two-bottle preference test. It was determined that the standard experimental animals were female rats of 140-180 g. The functional relationship between concentration of tannic acid and preference index was obtained Y= ln(1.682 6－0.441 66X), r=0.997 3. Then the typical astringent Chinese herbs Chebulae Fructus, Ardisiae Japonicae Herba, Canarii Fructus, Catechu, and Arecae Pericarpium were evaluated by the optimized method. Their corresponding concentration of tannic acid was converted by the concentration-preference index relationship through preference index. Their astringency was equivalent to 0.56, 0.29, 0.24, 0.34, 0.25 g•L⁻¹ tannic acid. Finally, the results were verified by electronic tongue. The correction analysis between Euclidean distance in PCA and preference index and concentration of tannic acid converted by samples showed a high correlation through pearson correlation analysis. The above results indicated that the method was objective, true and reliable. The method provided a reliable tool for the quantification of astringency and evaluation of taste masking effect for Chinese medicines, and also offered a new idea and model for the quantification of taste in the pharmaceutical and food fields.