Summary: Children whose saliva produced high amounts of sulfur volatiles disliked raw Brassica vegetables the most. The levels of sulfur volatiles were similar in parents and children, suggesting a shared oral microbiome. However, the relationship between sulfur volatiles and the dislike of Brassica vegetables was not as high in adults, suggesting they may have learned to tolerate the taste of the vegetables over time.
Many children, as well as adults, dislike Brassica vegetables, such as broccoli, cauliflower, cabbage and Brussels sprouts. In the mouth, enzymes from these vegetables and from bacteria in saliva can produce unpleasant, sulfurous odors.
Now, researchers reporting in ACS’ Journal of Agricultural and Food Chemistry have found that levels of these volatile compounds are similar in parent-child pairs, suggesting shared oral microbiome.
They also found that high levels cause children to dislike the vegetables.
Brassica vegetables contain a compound called S-methyl-ʟ-cysteine sulfoxide that produces potent, sulfurous odors when acted upon by an enzyme in the plant’s tissues, as well as by the same enzyme produced by bacteria in some people’s oral microbiome.
Previous studies have shown that adults have different levels of this enzyme in their saliva, but whether children also have different levels, and whether this influences their food preferences, is unknown.
Damian Frank and colleagues, who conducted this research at CSIRO, Australia’s national science agency, wanted to investigate differences in sulfur volatile production in saliva from children and adults and analyze how they affect Brassica acceptance.
The researchers used gas chromatography-olfactometry-mass spectrometry to identify the main odor-active compounds in raw and steamed cauliflower and broccoli. Then, they asked 98 child/parent pairs, with children between 6 and 8 years of age, to rate the key odor compounds. Dimethyl trisulfide, which smells rotten, sulfurous and putrid, was the least liked odor by children and adults.
The team then mixed saliva samples with raw cauliflower powder and analyzed the volatile compounds produced over time. Large differences in sulfur volatile production were found between individuals, and children usually had similar levels as their parents, which is likely explained by similar microbiome.
Children whose saliva produced high amounts of sulfur volatiles disliked raw Brassica vegetables the most, but this relationship was not seen in adults, who might learn to tolerate the flavor over time.
These results provide a new potential explanation for why some people like Brassica vegetables and others (especially children) don’t, the researchers say.
About this microbiome research news
Original Research: Closed access.
“In-Mouth Volatile Production from Brassica Vegetables (Cauliflower) and Associations with Liking in an Adult/Child Cohort” by Damian Frank et al. Journal of Agricultural and Food Chemistry
In-Mouth Volatile Production from Brassica Vegetables (Cauliflower) and Associations with Liking in an Adult/Child Cohort
Interactions between Brassica vegetables and human saliva can affect in-mouth odor development, which in turn may be linked to individual perception and liking.
S-Methyl-l-cysteine sulfoxide is a unique substrate present in Brassicas that produces odor-active sulfur volatiles due to the activity of enzymes present in plant tissue and due to bacteria, which may be present to varying extents in an individual’s oral microbiome.
Proton transfer reaction mass spectrometry was applied to measure individual differences in sulfur volatile production in real time when fresh human saliva was incubated ex vivo with raw cauliflower for a cohort of child–adult pairs. Large differences in the rate of sulfur volatile production were measured between individuals, but not between age groups.
Significant positive relationships were found for volatile production between the adult–child pairs, suggesting a degree of commonality in saliva composition and oral microbiome activity.
Furthermore, significant negative relationships were measured between the amount of in-mouth sulfur volatile production and liking for raw cauliflower in children.