Application Of Optical Colorimetric Sensor Array In The Detection Of Volatile Compounds In Animal Food

Freshness is an important index to measure the quality of animal derived food. As traditional examinations, such as physico-chemical methods for freshness detection are so tedious and time-consuming, it is difficult to meet the demands in industry and our daily life.Development of fast online detection equipment is of great significance for our country’s food industry and meantime guaranteeing human health. In recent years, optical colorimetric sensor array, as a new type of rapid online detecting instrument, has been widely used in the environment, food and other fields due to its low price, simple method, rapid response, and anti-disturbance capability. The thesis was focus on the rapid detection of Spanish mackerel and pork volatile compounds by optical colorimetric sensor array, which provide a reference for the application of this technology in freshness evaluation of animal-source food.pH indicators were used as gas sensing materials, and all of them were immobilized by sol-gel systems. The sensitivity of the pH indicators is usually confined in weakly acidic silica solvents because of the large deviation from their color transition points. By regulating the pH of indicators using organic acid or base, the color transition points of indicators could be readily achieved and the relative sensitivity could be greatly enhanced. Bromophenol blue was selected as an example to interpret this improvement. And Hue, Saturation and Value(HSV) color model was applied to obtain digital color information of pH indicators. Results showed that when alkaline concentrations ranged from 0.96 mmol/L to 1.04 mmol/L, the detection sensitivity reached the highest value. Eight kinds of pH indicators were chosen and regulated to their color transition points. The resultant indicators together with the original ones were composed to a colorimetric sensor array which contained 16 sensing materials and utilized to determine Spanish mackerel with different storage periods. The results showed that pH indicators of cresol red and metanil yellow did reach a much higher sensitivity in the detection of Spanish mackere freshness than the original ones. The RGB values corresponding to the image of each indicator before and after reaction were extracted and subtracted to obtain the response of the sensor array towards analyte and statistics with hierarchical clustering analysis(HCA). The results showed that Spanish mackere maintaining for differentstorage time could be well distinguished. Volatile organic compounds, such as amine and hydrogen sulfide, would be produced during pork corruption. Nine gas sensing materials including the ones specific to hydrogen sulfide were built as an array and used to monitor and distinguish pork volatile compounds under 4 ℃. Results of HCA can basically distinguish the pork meat between fresh and corruption, but the freshness with accurate classification needs to be further improved.This study was based on the optical colorimetric sensor array. An effective method to improve pH indicator sensitivity by acid-base regulation has been proved, and the volatile compounds of Spanish mackerel and pork which storaged different periods have been distinguished successfully.