A comparison was made between the amounts of volatiles in the headspace above a solution and the breath volatile content (exhaled from the nose or mouth) after consumption of the same solution. The amounts of volatiles in the breath were lower than those in the headspace, with breath exhaled via the mouth containing, on average, 8-fold more volatiles than breath exhaled via the nose. Dilution of the sample by saliva in-mouth did not appear to be a major factor affecting volatile delivery. Instead, the rate of in vivo equilibration (mass transfer) appeared to be the most significant factor, principally affecting volatile delivery from the solution to the gas phase. Thereafter, gas-phase dilution of the volatile as it passed through the upper airway resulted in a further decrease in volatile concentration. The final factor affecting the volatile concentration exhaled from the nose was absorption of volatiles to the nasal epithelia, which was greatest for those compounds with the lowest air/water partition coefficients.
A dental brace containing two sensors was constructed to allow the in-mouth monitoring of
conductivity and pH during eating. The salt release from peanuts, salt and vinegar crisps, cheese,
and mashed potato was measured during eating. There was a lag of 22 s after placing the crisps in
the mouth before there was a significant increase in conductivity. This highlighted the problems of
measuring salt release from dry foodstuffs. The conductivity electrodes were not ion specific, and
consequently, when testing processed cheese, the high ion content (salt cations and anions)
contributed to the signal, producing a complex release curve. The acid release from a blackcurrant
gelatine gel and an orange was successfully measured. The average minimum pH reached was 3.8
with the gel, and 4.5 with the orange. It was found that the buffering capacity of saliva affected the
pH of successive replicates.
Keywords: Nonvolatile, in-mouth; pH; conductivity; salt
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