Understanding the Origin of Flavor Preferences

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Food traditions mirror a people’s beliefs and values and are among the last characteristic of a culture that is lost during the immigration of an individual or group into a new culture (Rozin, 1996). However, the origins of preferences and aversions for flavors and food in humans have elicited much speculation but, until recently, remarkably little experimental investigation (Ganchrow and Mennella, 2003). We now know that initial experiences with flavors occur prior to birth when the flavor of amniotic fluid changes as a function of the mothers’ dietary choices (Mennella et al., 1995). Some of these same flavors continue to be experienced in mother’s milk (Mennella and Beauchamp, 1991). Because early flavor experiences have been shown to enhance acceptance and enjoyment of foods during weaning and childhood (Mennella et al., 2001), culturally determined flavor preferences, one of the most enduring characteristic of an ethnic group, can be understood in the context of early flavor exposure. The major factor that has inhibited even greater progress in understanding the origin of flavor preference is the absence of a robust paradigm to investigate the role of infant experience. Practically, it is difficult experimentally to vary the flavor experiences of infants and children over long time periods and so few studies investigating consequences of major differences in feeding experience have been conducted (Mennella et al., 2001). What is needed is a naturally occurring flavor variation that can be exploited to investigate the effects on subsequent acceptance. During the past decade, we have identified a convenient and powerful model system to study the origin of flavor preferences—infants’ acceptance of formulas containing protein hydrolysates, the feeding regimen of choice for formula-fed infants who cannot tolerate cows’ milk and other intact proteins (American Academy of Pediatrics, Committee on Nutrition, 1989). It is perhaps one of the most striking examples of a developmental change in chemical sensory perception. Although this type of formulas is extremely unpalatable to older children and adults because of its offensive flavor, infants 4 months of age or younger accept it without difficulty (Mennella and Beauchamp, 1991, 1996). However, if infants receive exposure by the third month of life, they continue to accept these formulas for a considerable period of time thereafter (Mennella et al., 2003). From these data, we hypothesized that there is an early sensitive period during which the hedonic value of this formula—and likely the flavors of other foods and beverages—is established. The overall goal of the present study was to explore the specificity of the flavor experience during this sensitive period. Although all brands of protein hydrolysate formula share common flavor attributes and are judged unpleasant by adults, they differ in their flavor profiles. Here we exploit the inherent flavor variation of different brands of formulas to determine whether experience with one brand of protein hydrolysate formula influences acceptance of another brand that differs in flavor. In other words, is the acceptance pattern that develops specific to the flavor profile experienced? Or does the infant, regardless of the brand of formula currently being fed, prefer the one that tastes sweeter or the one that tastes less bitter? To this aim, we studied infants’ acceptance of two commercial brands of hydrolysate formulas widely used in the Philadelphia area of the United States: Alimentum™and Nutramigen™.