Sulfur Volatiles Influence People's Dislike of Cauliflower and Broccoli

Many children and some adults dislike Brassica vegetables, such as broccoli, cauliflower, cabbage, and Brussels sprouts. Brassica vegetables contain a compound called S-methyl-ʟ-cysteine sulfoxide (SMCSO) that produces potent, sulfurous odors when acted upon by enzymes in the plant’s tissues or enzymes produced by bacteria in some people’s oral microbiomes. Previous studies have shown that individuals can have different levels of this enzyme in their saliva.

Damian Frank, Commonwealth Scientific and Industry Research Organisation (CSIRO), North Ryde, NSW, Australia, and colleagues have investigated differences in sulfur-volatile production in saliva from children and adults and analyzed how they affect Brassica acceptance. They found that levels of these volatile compounds are similar in parent-child pairs, suggesting shared oral microbiomes. They also found that high levels of some volatiles cause children to dislike the vegetables.

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 six and eight 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 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. Children usually had similar levels as their parents, which could likely be explained by similar microbiomes. Children whose saliva produced high amounts of sulfur volatiles disliked raw Brassica vegetables the most, but this relationship was not seen to s significant degree in adults, who might learn to tolerate the flavor over time. These results could provide a new explanation for why some people like Brassica vegetables and others, especially among children, do not.