In-Mouth Measurement of pH and Conductivity during Eating

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.