ANALYSIS OF VOLATILE COMPOUNDS IN THE CITRUS PEELS USING 6 SEMICONDUCTOR GAS SENSORS

Mixtures of two compounds and volatiles in the Citrus peels were analyzed by six semiconductor gas sensors. From the result of mixed compounds, responses of semiconductor gas sensors were affected by vapor pressures of individual compounds. It was found that sensor responses as well as vapor pressures changed by the solubility and the ratio of the concentration of compounds dissolved in the solutions. On the other hand, Citrus sudachi, Citrus limone, Citrus iyo, two Citrus sinensis, and two Pummelos were used for the sensor analysis as the samples. Factor analysis of the response patterns of six gas sensors was conducted and then factor 1 and factor 2 scores were plotted on a two dimensional diagram. The factor scores of Citrus sudachi and Citrus limone were located in the similar area and formed individual groups. However, the other orange families except one Pummelo were dispersed on the close area of the diagram. One Pummelo was dispersed widely on the diagram. The discriminant analysis of response data of semiconductor gas sensors for Citrus peels distinguished more than 70% of probability as the response of the correct fruit. We tried to explain the distribution of the factor scores of Citrus fruits by sensor responses to model mixtures of 5 compounds (limonene, beta-pinene, gamma-terpinene, myrcene, and linalool) found in individual fruits as the main components. However, it could not be explained by the small number of compounds well because of the high similarity of sensor responses among limonene, gamma-terpinene and myrcene.