Evaluating the Taste of Tomato Cultivated Under Salt-stress Conditions by Component Change, Sensory Evaluation, and Taste Sensor

Abstract

In general, food taste is a product of the 5 senses such as touch, taste, smell, sight, and sound of humans (Yamaguchi, 1995). Sensory evaluation is useful for digitizing taste, but there are individual differences in human senses and preferences, and variations in taste values tend to be large (Yamaguchi, 1995; 2008). Taste values differ depending on the evaluation method and panelist profile (e.g., sex, age, eating experiences), and the quality of vegetables used as samples also depends on the cultivation method and external factors (e.g., weather, temperature) (Horie, 2006; Yamaguchi, 2008). To evaluate taste with high reproducibility, it is necessary to use an objective taste evaluation method rather than sensory evaluation. Analysis of metabolic components (sugars, organic acids, amino acids, and other functional components) is frequently used to assess the quality of vegetables. It is a highly reproducible method such as high-performance liquid chromatography (HPLC) and capillary electrophoresis, but it is difficult to evaluate taste on the basis of the amounts of a food’s components (Cristina-Gancedo and Luh, 1986; Horie, 2006; Oikawa, 2013). Recently, taste sensors and electronic tongues have attracted attention as methods for evaluating objective and reproducible taste, and have been used to evaluate the tastes of various foods such as vegetables, juices, teas, alcoholic drinks, and oils (Ghasemi-Varnamkhasti et al., 2010; Kobayashi et al., 2010; Wajima et al., 2012; Tahara and Toko, 2013; Xu et al., 2018). Humans perceive each type of taste (sweetness, sourness, saltiness, umami, and bitterness) on taste buds, a sensory organ on the tongue (Ghasemi-Varnamkhasti et al., 2010; Tahara and Toko, 2013). Taste sensors mimic the mechanisms of taste perception in humans by using a lipid polymer membrane that responds to the taste of chemical substances, and can be used to quantify each of the 5 basic tastes (Kobayashi et al., 2010; Tahara and Toko, 2013). The taste of tomatoes is influenced by the contents of sugars, organic acids, and glutamic acid, and tomatoes with high contents of these are considered to taste good (Fuke and Konosu, 1991). Several studies reported that tomato cultivated under salt-stress conditions has higher contents of sugars, organic acids, and amino acids, tastes good, and is expensive (Cuartero and Fernández-Muñoz, 1999; Zushi, 2008; Zushi and Matsuzoe, 2015). Some studies have evaluated the tastes of tomatoes of different cultivars and harvest seasons using taste sensors or electronic tongues (Wajima et al., 2012; Xu et al., 2018). In our previous study, we developed a taste map of tomatoes that differ in cultivation method, production area and harvest time, by