Cooling sensation detection of menthol toothpaste

Cooling sensation detection of menthol toothpaste

Cooling sensation detection of menthol toothpaste：The cooling sensation of menthol toothpaste claims to require a scientifically rigorous testing system to support it. Professional testing requires three-dimensional verification of component quantification, sensory evaluation, and objective indicators to ensure the reliability of product claims. A third-party testing agency tested 15 toothpaste products claiming to be 'refreshing' and found that only 7 of them could simultaneously meet the standards of a menthol content of ≥ 0.1% and a decrease in oral temperature of ≥ 1.5 ℃ after 5 minutes of use, revealing a significant gap between the claimed coolness of market products and their actual performance.

Testing standards and technical basis

Perform basic component analysis in accordance with GB/T 35832-2018 "Determination of Friction Agent Content in Toothpaste", ensuring that the amount of menthol added is within the effective range of 0.1% -0.3%; Sensory evaluation is based on ISO 4120:2021 "General Principles for Sensory Analysis Methodology" and uses the nine point pleasure scale method; Objective efficacy verification refers to GB/T 35913-2018 "Evaluation of the Efficacy of Oral Cleaning and Nursing Products", and establishes a correlation model between temperature changes and neural response.

In terms of international standards, ISO 11035:1994 "Methodological Ranking for Sensory Analysis" provides a standardized process for sensory evaluation, while ASTM E1958-15 "Guidelines for Evaluating Skin Coolness" provides technical reference for temperature change detection. It is worth noting that the EU cosmetics regulation EC 1223/2009 requires cooling sensation claims to provide human trial data (n ≥ 30) and evidence of ingredient efficacy, which puts higher demands on exported products.

Core detection methods and experimental design

Accurate determination of menthol content

Quantitative analysis was performed using gas chromatography-mass spectrometry (GC-MS) technology: HP-5 capillary column (30m × 0.25mm × 0.25 μ m) was selected as the chromatographic column, and the column temperature program was maintained at 40 ℃ for 3 minutes, rising to 150 ℃ at a rate of 5 ℃/min; The injection port temperature is 200 ℃, the EI ion source is 70eV, and the ion monitoring mode (m/z 95, 123, 156) is selected. The detection limit of the method is 0.001%, the recovery rate is 85% -115%, and the relative standard deviation is ≤ 3%. A certain brand of toothpaste was forced to modify its product label due to its failure to pass the test, resulting in an actual menthol content of only 62% of the claimed value.

Construction of sensory evaluation system

Double blind controlled trial design: 30 healthy subjects (half male and half female) were randomly divided into an experimental group and a placebo group. After using the product, evaluations were conducted at four time points: 5 minutes, 30 minutes, 60 minutes, and 120 minutes. Using the Cool Visual Analog Scale (C-VAS), a score of 0 indicates' no coolness' and 10 indicates' extreme coolness', while recording the time of appearance and disappearance of coolness. The result judgment requires that the C-VAS score of the experimental group should still be ≥ 4 points at 120 minutes, and the difference between the experimental group and the placebo group should be statistically significant (P<0.05).

Objective indicator detection technology

Infrared thermal imaging monitoring: Use FLIR T650sc infrared thermal imaging camera (resolution 640 × 512 pixels, temperature measurement range -20 ℃ -150 ℃, accuracy ± 0.05 ℃) to record the temperature changes of oral mucosa before and after using toothpaste. Qualified products require a temperature reduction of ≥ 1.5 ℃ in the red part of the lips, and a cooling duration of ≥ 60 minutes. Experimental data shows that toothpaste containing 0.2% menthol has an average cooling range of 2.3 ℃, significantly higher than the 0.1% group (1.2 ℃).

TRPV1 receptor activity assay: The HEK293 cell model transfected with the human TRPV1 gene was used to detect receptor activation rate using fluorescence calcium imaging (excitation wavelength 488nm, emission wavelength 525nm). After treating cells with toothpaste extract (mass concentration 1%), a fluorescence intensity change rate of ≥ 30% is considered effective activation. This method can objectively quantify the stimulation intensity of menthol on cold receptors, avoiding the limitations of relying solely on subjective evaluation.

Professional instrument configuration and quality control

The laboratory needs to be equipped with a modular detection system: gas chromatography-mass spectrometry (such as Agilent 7890B-5977A) for menthol quantification; Infrared thermal imager (FLIR T650sc) monitors temperature dynamic changes; Fluorescence microscopy (Olympus IX83) was used to detect TRPV1 activity; The fully automated sample pre-processing platform (GERSTEL MPS) enables unmanned analysis. Key instruments need to be calibrated through CNAS, such as gas chromatography, which verifies retention time deviation of ≤ 0.02min with n-hexadecane standard every month.

Quality control measures include: conducting 3 parallel experiments on each batch of samples, with a relative standard deviation of ≤ 5%; Set up a positive control (standard toothpaste containing 0.2% menthol) and a negative control (basic toothpaste without cooling ingredients); Sensory evaluators must be certified according to ISO 8586-1:2012 "Selection, Training, and Management of Sensory Analysis", with a taste recognition accuracy rate of ≥ 90%. A certain laboratory was suspended from testing due to a deviation of 12% in the results of menthol testing caused by the failure to strictly implement quality control.

Stability and safety assessment

Accelerated stability test: Place the toothpaste sample at 45 ℃± 2 ℃ and relative humidity of 75% ± 5% for 3 months, and measure the changes in menthol content every month. The retention rate of active ingredients is required to be ≥ 90%, and the area under the cooling curve (AUCC) attenuation should be ≤ 15%. A certain natural mint toothpaste failed the test due to insufficient stability, resulting in a 42% decrease in cooling intensity after 3 months.

Mucosal irritation test: Rabbit eye irritation test (Draize method) and HET-CAM chicken embryo membrane test are used, with an average irritation index (ISI) of ≤ 3.5 and no bleeding or coagulation phenomenon. At the same time, the skin sensitization of menthol was detected, and the irritation index (SI) was calculated by local lymph node test (LLNA). If SI<3, it was judged as non sensitization. These security data are necessary information before the product is launched.

Comprehensive judgment of test results

The cooling sensation of menthol toothpaste needs to be comprehensively judged through three-dimensional indicators: menthol content of 0.1% -0.3% (GC-MS method), 120 minute C-VAS score ≥ 4 points (sensory evaluation), oral temperature reduction ≥ 1.5 ℃ (infrared thermography), TRPV1 receptor activation rate ≥ 30% (fluorescence method). Only when all four meet the standards can the 'cooling sensation' effect be claimed. A multinational brand toothpaste was deemed ineffective due to its TRPV1 activation rate of only 22%, despite meeting the standard for menthol content.

The testing report should include a complete uncertainty assessment, such as an extended uncertainty (k=2) of ± 0.015% for the determination of menthol and an uncertainty of ± 0.1 ℃ for temperature measurement. These data provide scientific basis for product quality disputes. It is recommended that enterprises establish full chain control of raw materials and finished products, choose raw materials with a content of ≥ 95% of L-menthol, and extend the duration of coolness through microcapsule embedding technology.

Through standardized testing processes and multidimensional indicator verification, precise data support can be provided for product development. With the increasing demand of consumers for oral care experience, detection technology will develop towards individual difference analysis (such as the impact of genetic polymorphism on cooling perception) and dynamic monitoring (real-time cooling sensation tracking), promoting the industry to progress towards more refined direction.