The effect of the pungent sensation elicited by Sichuan pepper oleoresin on the sensory perception of saltiness throughout younger and older age groups

https://doi.org/10.1016/j.foodqual.2020.103987Get rights and content

Highlights

  • RT of saltiness is decreased in the sub-threshold pungent carrier.

  • The enhancement effect of slight pungency carrier on salty intensity differs among age groups.

  • The perception of saltiness is influenced by the individual sensitivity and psychological traits.

Abstract

Excessive salt in the diet can pose significant health risks and, therefore, the reduction of salt derived from food is an important issue relating to human nutrition and health. Furthermore, the perception of saltiness will be different among people when considering their innate sensitivity, gender, age, psychological traits and dietary habits. In this study, 31 younger participants and 29 older participants were used as research subjects. A web-based questionnaire survey was used to collect information regarding of socio-demographics, consumption frequency and liking for salty and pungent food, as well as personality traits throughout the younger and the older participants. In addition, the 6-n-propylthiouracil (PROP) ratings were tested by the generalized Labeled Magnitude Scale (gLMS) in the laboratory conditions. The rated difference from control method was used to test the sensitivity differences in the saltiness of NaCl and the pungent sensation elicited by Sichuan pepper oleoresin between the younger and older groups. The results showed that the thresholds were significantly lower in the younger group than in the older group, except for the detection threshold of saltiness. Furthermore, the recognition threshold of saltiness  decreased in the presence of the sub-threshold pungency solution, while, the salty intensity was enhanced in both the younger and older groups when exposed to the slightly pungent solution (0.106 g Sichuan pepper oleoresin/L water solutions) compared to the control (spring water). For the younger group, the enhancement percentage of the salty intensity was between 9.3% and 12.5%, while, at the concentration of 4.05 g/L, the salty-enhancement percentage increased by 6.4% in the older group. In addition, the reduction percentage of NaCl reached a level of up to 34.4% in the younger group and was 4.4% in the older group. The Partial Least Squares Regression (PLSR) results indicated that the percentage change in salty intensity increased when the detection threshold of saltiness, the sensation seeking ratings, and PROP ratings increased. On the contrary, the change decreased when the age, life satisfaction ratings, detection threshold of pungency, and consumption frequency of salty food increased. These findings not only provide new information for the flavor design of salt-reduced food and dishes, but also be valuable to public health as well as economic benefits.

Introduction

Excessive salt in the diet can pose significant health risks, such as cardiovascular disease (Li et al., 2017), stroke (Strazzullo, D’Elia, Kandala, & Cappuccio, 2009) and neurodegenerative pathologies (Faraco et al., 2019). The World Health Organization (WHO) recommended dietary allowance of salt for adults is less than 5 g, however, the daily intake of salt regularly exceeds this standard worldwide (US: 8.2–9.4 g, UK: 9.4 g, Asia: 12 g) (Liem et al., 2011). The especially high-salt diet of Chinese elderly is well-known. In recent years, internet survey data has found the prevalence of hypertension in Chinese elderly to be about 53.24% (approximately 94.5 million people) (Li et al., 2019). Therefore, food salt reduction and consumer acceptance are important issues in relation to human nutrition and health.

At present, there are three main types of salt reduction strategies (Hsueh, Tsai, & Liu, 2017): adjusting cognitive mechanisms (dietary salt limit method, or salt reduction method), changing product structures, and finding substitutes for salt. Due to factors such as consumer dietary habits, sensory pursuits, cognitive mechanisms and the poor flavors of saltiness substitutes, the above mentioned salt reduction strategies have not been sufficiently effective (Liem et al., 2011) and it is essential that dietary salt reduction and consumer acceptance should be further researched. Sensory interaction can be used to enhance saltiness intensity, that is, the sensory enhancement or synergistic interaction effect generated by the presence of another stimulus in order to achieve the goal of constant stimulus and enhanced perception. Researches have reported that adding herbs, spices or other flavorful substances in food formula can enhance the perception of saltiness (Doyle and Glass, 2010, Kremer et al., 2009, Manabe, 2008). Naturally brewed soy sauce, for example, can reduce the NaCl content in salad sauce, stir-fried pork and vegetable soup by 50%, 17% and 29%, respectively, while maintaining a constant salty intensity. The addition of capsaicin near the detection threshold (0.5 mM or 1 mM) to a certain amount of salt also significantly enhance the perception of saltiness (Narukawa, Sasaki, & Watanabe, 2011). Nilius and Appendino (2013) reported that Sichuan pepper can enhance saltiness while reducing salt intake and is, therefore, a great salt substitute for French fries based on the chef’s experience.

Sichuan pepper is a spice characteristic of China and offers several significant physiological benefits, such as being anti-inflammatory, analgesic and anti-wrinkle properties (Artaria, Maramaldi, Bonfigli, Rigano, & Appendino, 2011). Therefore, this study hypothesizes that the perception of saltiness can be enhanced by the pungent sensation elicited by Sichuan pepper oleoresin. Several factors must be considered before this hypothesis can be verified. First, the perception of saltiness will be different among participants due to their innate sensitivity, gender, age, psychological features, and dietary habits, etc. Barragán et al. (2018) reported that sensitivity to sourness, sweetness, bitterness, saltiness, and umami decreases with age, with bitterness and sourness showing the most significant decline. Sensitivity to reward has been found to significantly affect on sweetness ratings (Monteleone, Spinelli, & Dinnella, 2017). Spinelli et al. (2018) indicated that supertasters report significantly higher sensations of burning, sourness, sweetness, and overall flavor than do medium and non-tasters, while also establishing a positive relationship between the heat intensity levels of capsaicin and sensitivity to disgust in both men and women. Therefore, when studying the effect of the pungent sensation on the perception of saltiness, the socio-demographics, anthropometrics and physical health factors of participants should be considered. Second, the human taste system can convey three aspects of sensory information, namely sensory intensity, attributes, and dynamic changes (Kawasaki, Sekizaki, Hirota, Sekine-Hayakawa, & Nonaka, 2016). Therefore, it is necessary to consider whether the detection threshold and recognition threshold of saltiness can be reduced via pungency carriers and whether the response to saltiness can be intensified, as well as various other considerations. Third, the perception of saltiness and pungency occur via different psychophysical functions. This effect may be enhanced by low concentrations of NaCl and suppressed by high concentrations. Therefore, the salty and pungent compounds, in a concentration range of low to high should be considered when investigating the impact of the pungent sensation on the saltiness. As such, it is necessary to definitively determine the effect of sub-threshold, slight, moderate, and strong pungency on different levels of saltiness in experimental research.

Consequently, the study concentrated on four main aspects. First, a web-based questionnaire is used to collect information regarding of socio-demographics, anthropometrics, physical health, liking, consumption frequency, and psychological scales. Second, the gLMS is used to obtain the PROP ratings while the 2-AFC method is employed to determine the DT and RT. Third, the 2-AFC and the 15 cm linear scale methods are used to establish whether the pungent sensation can enhance the saltiness threshold and intensity. Finally, the PLSR model is used to gain insight into the impact of age, sex, PROP ratings, consumption frequency of salty and pungent food, as well as personality factors, on the percentage change in salty intensity in the presence of a slightly pungent carrier.

Section snippets

Stimuli

The Sichuan pepper oleoresin (the content of total alkymide was 0.55 g/kg) was purchased from the Zhongjing Super Kitchen Co., Ltd. The Capsicum oleoresin (the purity of capsaicin was 99%) was acquired from the Chengdu Gui Yi Food Development Co., Ltd. The NaCl was obtained from the Zhongyan Shanghai salt industry Co., Ltd. The Sucrose was purchased from the Beijing Ershang Group Co., Ltd. The PROP test paper contained 20 µg per strip was obtained from the Amazon Seller-Bartovation. The Ethanol

Questionnaire results and PROP ratings

The results of liking for pungency and saltiness, consumption frequency of pungent and salty food, PROP ratings, LSS, PAS and PNS, AISS and FN ratings are shown in Fig. 1 and the results were also analyzed using the two-way ANOVA model (age and gender). Age * gender effects were significant for liking for saltiness and consumption frequency of pungent food (p < 0.05). Age effects were found to be highly significant in liking for pungency (p < 0.01), PROP ratings and NAS ratings. There were

Possible mechanisms of the enhancement effect

According to Fig. 3, the sub-threshold and slightly pungent solution enhanced the perception of saltiness among the younger participants. Furthermore, the salty intensity was enhanced in both the younger and older groups when exposed slightly pungent solution (0.106 g Sichuan pepper oleoresin/L water solutions) (Table 4). PLSR, was used to analysis the relationship between the socio-demographics, anthropometrics, physical health, consumption frequency and liking for salty and pungent food, PROP

Conclusions

This study ascertained that the recognition threshold of saltiness decreased within the presence of the sub-threshold pungency solution, while, the enhancement effect of slight pungency on the perception of salty intensity differs among the age groups. For the younger group, the percentage enhancement of the salty intensity was between 9.3% and 12.5%, while the percentage increased by 6.4% in the older group. Additionally, the reduction percentage of NaCl reached a level of up to 34.4% in the

CRediT authorship contribution statement

Lu-Lu Zhang: Writing - original draft, Writing - review & editing. Lei Zhao: Funding acquisition. Qing-Bin Zhang: Formal analysis. Bo-Lin Shi: Methodology. Kui Zhong: Software. Hou-Yin Wang: Methodology. Ran Xie: Visualization. Long-Yun Liu: Software.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (China, item number: 31801622), the General Program Fund for China National Institute of Standardization (China, item number: 562020Y-7484), the Special Fundamental Research Fund for the Central Public Scientific Research (China, item number: 562018Y-5983) and the Science and Technology Program of China State Administration for Market Regulation (China, item number: 2019MK117).

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