The story of salt will be in multiple parts, due to the importance of the topic, and the complexity. Salt, a.k.a sodium chloride, a.k.a. NaCl, a.k.a. sodium, is an essential element in the chefs or cooks toolbox to make things taste good. I read somewhere that Heston Blumenthal (one of the high priests of cooking, TV personality) stated salt is the most important ingredient in his kitchen. Why would that be the case? Below I begin the discussion on the many functions that salt has in foods, hopefully giving a clue to why such statements are made. Part 1 does not address the health issues and controversies around salt, just why we, as consumers and cooks, love salt. Also an explanation on terminology, I will use the term salty when referring to the taste we perceive, and NaCl when discussing salt (opps NaCl).
Taste perception is very complex, with highly sophisticated biological systems at work, but it can also be quite simple, put something in your mouth and you experience the taste/flavor of the food. Salt taste is experienced when the concentration of NaCl in the oral cavity reaches a level that not only activates a taste receptor, but the signal sent from the receptor is strong enough to elicit a salty perception, meaning low concentrations of NaCl may be present in the oral cavity yet not elicit a salty taste. There are multiple perceptual phases associated with salt taste perception and as the concentration of NaCl increases the detection threshold will be reached, the level at which NaCl in solution may be discriminated from water. As the concentration of NaCl increases further the recognition threshold is reached, the point at which the quality (e.g., salty) can be identified. As the concentration of NaCl increases still further, the intensity of saltiness mutually increases to a strongest salty intensity we can experience. It then starts to activate another sensory system (not taste) and becomes painful.
Two factors dictate the level of perceived saltiness for a given concentration of NaCl: 1/ an individual’s sensitivity to NaCl (which is highly variable for all tastes), and 2/ the food matrix being consumed. To further explain: 1/ just because you find something too salty does not mean I will, as we have variation in the biology or physiology relating to taste processing. And 2/, the food matrix will be important, potato chips are a salty food, they have NaCl at the surface of the chip, bread is not a salty food, yet it contains about the same amount of NaCl. The reason for the difference is that the NaCl in bread is trapped in the bread matrix and unavailable for taste activation. Therefore a salty food such as potato chips are not necessarily a food high in NaCl.
NaCl adds saltiness to foods, depending on the amount you add, the food matrix and individual taste will depend on the level of saltiness you experience, e.g., 50 mM NaCl in liquid is saltier than 50 mM NaCl in solid food. This doesn’t adequately explain why NaCl is the most important ingredient in Blumenthal’s toolbox. That can wait till Part 2.
Figure 1: (Keast et al. 2004)
It is not only perceived saltiness and concentration of NaCl we investigate in this study, but also an individual’s hedonic response to NaCl in foods. Hedonic responses to NaCl in foods will follow and inverted U shape in response to increasing intensity (and concentration) with an initial increase in liking as the perceived intensity increases until an optimum liking or “bliss point” is reached (Figure 1) (McBride 1990).
Environmental factors are believed to play a major role influencing an individual’s sensitivity, liking and consumption of salty foods (Keskitalo et al. 2008; Mattes 1997; Wise et al. 2007). Sodium reduced diets have been shown to increase an individual’s NaCl taste sensitivity in foods and subsequently decrease liking of higher concentrations of NaCl in various foods (Bertino et al. 1982; Blais et al. 1986). However, no association was found between usual dietary sodium intake and NaCl taste sensitivity (Pangborn and Pecore 1982) bringing into question the relevance of NaCl taste sensitivity to dietary intake. Actual sodium intake may have little relation with perceived saltiness due to various taste interactions or structural effects in foods that modify the perceived salty taste elicited by NaCl.
Bertino, M., Beauchamp, G., Engelman, K. (1982). Long-term reduction in dietary sodium alters the taste of salt. The American Journal of Clinical Nutrition, 36, 1134-1144.
Blais, C., Pangborn, R., Borhani, N., Ferrell, F., Prineas, R., Laing, B. (1986). Effect of dietary sodium restriction on taste responses to sodium chloride: A longitudinal study. The American Journal of Clinical Nutrition, 44, 232-243.
Keast, R. S. J., Dalton, P., & Breslin, P. A. S. (2004). Flavour interactions at the sensory level. In A. Taylor (Ed.), Flavour Perception (pp. 228-255): Blackwell Publishing
Keskitalo, K. (2008). A matter of taste: Genetic and environmental influences on responses to sweetness. National Public Health Institute, Finland, Academic Dissertation.
Mattes, R. (1997). The taste for salt in humans. The American Journal of Clinical Nutrition, 65(2), 6925-6975.
McBride, R. L., & Finlay, D. (1990). Perceptual integration of tertiary taste mixtures. Perception and Psychophysics, 48, 326-330
Pangborn, R., Pecore, S. (1982). Taste perception of sodium chloride in relation to dietary intake of salt. The American Journal of Clinical Nutrition, 35(3), 510-520.
Wise, P., Hansen, J., Reed, D., Breslin, P. (2007). Twin study of the heritability of recognition thresholds for sour and salty taste. Chemical Senses, 32(8)
Also seen on Russell Keast’s blog http://russellkeast.blogspot.com.au/