Type of milk feeding in infancy and taste acceptance

The development of taste begins even before the infant has taken his first solid food. During pregnancy food flavours from mother's diet enter the amniotic fluid, while during lactation they migrate into breast milk. The formula fed infant, while receiving a more constant flavour profile than the breast fed infant, still experiences different flavours, depending on the type of formula used, its ingredients and processing method. A recent study has looked at whether infants show a preference for the same taste profile found in their milk feeding ( sweet, sour, bitter, salty, savoury) when introduced to solid foods (1).

Breast milk has a predominantly sweet taste while the taste of cows milk infant formula varies from low sweet to sour. Hydrolyzed infant formulas are generally savoury, sour and bitter due to their high content of amino acids.  Glutamate, an amino acid found in all milks imparts a savoury taste. It is found in greatest quantities in hydrolyzed casein infant formulas. Breast milk contains more glutamate than cows milk based infant formulas.

Healthy, term infants aged 4-9 months, who had been eating infant cereal from a spoon for at least 2 weeks but who were not eating any other solid foods, were recruited for the study. Based on the type of milk they were receiving they were divided into 3 groups - breast milk ( BM), cows milk infant formula (IF) and hydrolyzed casein infant formula (HCF). Infants were given 40g of their usual  infant cereal prepared with either 160ml of distilled water (plain) or a sweet (lactose), salty (sodium chloride), savoury (monosodium glutamate), bitter (urea), or sour (citric acid) solution. Mothers fed their infant at the same time daily and at least 30-60 minutes before the next feed, so  intake and facial expressions ( indicating food acceptance) reflected the response to the food served. Feedings were videotaped and the duration of feeding, infants facial expressions, time of feeding and mothers perceptions of how the infant fed were noted.

The infants showed taste preferences which reflected the taste of the milk they were receiving. The HCF group ate more of the savoury, sour, bitter and plain cereals than BM or IF groups and at a faster rate. They also displayed fewer negative facial expressions for bitter and sour cereals than breast fed infants. IF and BM groups both showed a preference for the sweet cereals. However the IF group also displayed a liking for the salty and sour flavours while the BM group preferred the savoury, probably reflecting breast milks higher quantity of glutamate. In general, infants showed more facial expressions of distaste with the bitter cereal than with any of the other cereals. 

Another set of similar analyses was done using the same cereal feeding combinations but to BM, IF and HCF infants who were already eating a wide variety of solid foods. As numbers were limited for those being breast fed and fed solids, a general conclusion was that the more solids an infant was eating the less he showed distaste for the cereals offered. In formula fed infants, the liking for the various tastes reflected the overall types of food being eaten.

This research provides more information on how differences in taste develop and may also help to explain cultural taste differences.

Reference:

1. Menella JA, Forestell CA et al. Early feeding influences taste acceptance and liking during infancy. Am J Clin Nutr 2009;90(suppl):780S-8S