November 14, 2008

Mouth Bacteria Responsible For Added Taste

Food chemists have shown how certain bacteria in our mouths can amplify the taste of certain foods.

The late Emile Peynaud, considered the father of modern winemaking, remarked that the Sauvignon blanc grape had only a weak taste when one bit into it, but that 20 to 30 seconds later, "you suddenly experience a powerful aromatic rush at the back of the mouth as the Sauvignon fragrance returns."

Dr. Christian Starkenmann, researcher at Firmenich, which develops flavors and fragrances for various companies, assembled a team of researchers who sought to discover the root cause of the flavor rush caused by some foods.

Previous researchers have found that retroaromatic foods contain odorless sulfur compounds called cysteine-S-conjugates, and that volatile sulfur compounds released from these precursors called thiols gave such foods their scent.

Starkenmann's team assembled 30 professional panelists to sample the sulfur thiol and corresponding cysteine-S-conjugate precursor for grapes, onions, and bell peppers. The panelists spit out each sample after five seconds and then reported their perceptions.

It took panelists 20-30 seconds to smell the cysteine-S-conjugate precursors. What's more the smell of the precursors lasted up to three minutes, compared to only a few seconds with the thiols.

Researchers studied the phenomenon by incubating the precursors with saliva that contained normal bacteria and with sterile saliva.

They noted 80 percent of the compound had been broken down within 24 hours of being in the normal saliva. But in the sterile saliva, the breakdown was much slower; after four days, less than 15 percent of the compound had disappeared.

Starkenmann's team concluded that mouth bacteria are responsible for releasing thiols from their precursor compounds contained in retroaromatic food and drink. Free thiols' shorter taste duration appears to occur because they are quickly absorbed by saliva, they add.

The findings should be useful in helping to develop food products with more complex, longer-lasting tastes, Starkenmann said.


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