Collection of saliva samples

The subjects were seated comfortably on a chair with their heads bent forward, and were asked to spit into a sterile cup. Saliva was collected twice: before the consumption of the test date fruit and 5 min after eating the grapefruit. The salivary pH was directly estimated using a digital pH meter (HORIBA B-713 LAQUAtwin Compact pH Meter, Kyoto, Japan) and calibrated with buffers (pH 4 and 7). The use of this technique for measuring salivary pH has been reported previously.12, 13 The electrode was cleaned with a stream of distilled water and placed in a standard solution (pH 7) in between readings to ensure that the readings were stable. The readings were obtained by a well-calibrated recorder who was blinded to the study subjects; the saliva containers were coded to eliminate the possibility of observer's bias.