Читать книгу Nurturing a Healthy Generation of Children: Research Gaps and Opportunities - Группа авторов - Страница 15

At birth, previous works revealed evidence of differential preferences across tastes, with a preference for sweet taste, a rejection of bitter taste [12], and very little evidence of inborn flavor preferences (but rather of avoidance of smell of rotten foods [13]), except when infants had been previously exposed to specific flavors from the maternal diet [10, 11]. Thus, inborn taste and flavor preferences are not numerous although marked food preferences exist in adults and even in young children. It is then much needed to understand the factors contributing to the building of food preferences. The evolution of taste and flavor preferences at later stages in early childhood has received little attention. Within the OPALINE cohort, we studied longitudinally in a group of 285 infants the evolution of taste preferences from 3 to 20 months [14, 15] and the evolution of flavor preferences from 8 to 22 months [16].

Acceptance of each taste (sweet, salty, bitter, sour, and umami) and of a fat emulsion relative to water was defined based on ingestion or liking at 3, 6, 12, and 20 months of age [14, 15]. For each taste, 4 bottles were presented (water, tastant, tastant, water). The acceptance of each taste relative to water was defined using proportional variables that are ratios of ingestion or liking evaluated by the experimenter. These data were analyzed with mixed models that accounted for age and subject effects. Taste acceptance trajectories for all primary tastes and for a fat emulsion were modeled. For saltiness, acceptance increased sharply between the ages of 3 and 12 months. The trajectories of acceptance were parallel for sweetness, sourness, and the umami taste between 3 and 20 months, with sweetness being preferred. Between 12 and 20 months, the acceptance of all tastes, except bitterness, decreased, and at 20 months, only sweetness was not rejected. The acceptance of bitterness remained stable. For the fat emulsion, acceptance evolved from indifference to rejection. Moreover, more rejections were reported based on the judgment of the experimenter than of the infant’s liking. Ingestion and liking ratios are rather complementary, and this result highlights that a grimace is not necessarily associated with reduced ingestion.

Similarly, acceptance of each food odor was defined using proportional variables based on behavioral analysis [16]. Four control stimuli and 8 odors (4 rated by adults as a priori pleasant and 4 as a priori unpleasant) were presented in bottles to infants at 8, 12, and 22 months of age. The infant’s exploratory behavior towards odorized and control bottles was measured in terms of mouthing defined as a direct contact with perioral and/or perinasal areas. For each odorized bottle, durations of mouthing were calculated relative to the control bottles. In this age range, shorter durations of mouthing were found for unpleasantly scented bottles (trimethylamine, dimethyl disulfide, and butyric acid) than pleasantly scented bottles. So, between 8 and 22 months, unpleasant food odors lead to avoidance behavior in infants, but pleasant food odors did not elicit specific behaviors.

In these studies, we noted that developmental changes were dependent on taste and odor. We will now examine to which extent these developmental changes also depend on the taste and flavor experiences the infant receives during this period.