Detection of Microbial Contamination Utilizing an Infrared CO2Analyzer

Infrared (IR) analysis of headspace gas for the presence of CO2 was evaluated as a method of nondestructively sampling and segregating microbiologically contaminated products. Approximately 1.8 million 7-oz bottles containing citrus juices and fruit drinks were inspected and segregated based on IR CO2 analysis. Comparison of IR analysis with conventional plating methods indicated 89% of the samples determined to be positive by conventional methods were also detected by IR analysis. False negatives were found to be the result of nonfermentative microorganisms in over 80% of the contaminated samples not detected by IR analysis. Nonfermentative organisms were identified and effects on product were evaluated. The expected contamination rate was 5.3% compared to 6.3% contamination detected by IR analysis. SUMMARY IN SUMMARY, an IR CO2 analyzer was utilized successfully to inspect 100% of product suspected of microbial contamination. When proper procedures were followed, contaminated product was detected and removed for destruction while good product was recovered for subsequent shipment to consumers. This system is advantageous because it allows for a 100% nondestructive inspection, is comparable to conventional plating methods in determining the presence of microbial contamination, and can be automated to a high degree. It is probable that automated container handling would have resulted in fewer false positives due to tilting of bottles as well as elimination of false negatives containing CO2 which were the result of insufficient time of analysis. Disadvantages include the requirement of an IR detectable microbial product, a container or package adaptable to an IR transmission or reflection type analysis, and a considerable cost for equipment. Any product contaminated by fermentative microorganisms and packaged in glass containers having a headspace of approximately 0.5 inch could be inspected by the methods described here. Justification for the cost of equipment would depend on the amount of contaminated product and the expected recovery rate. It is quite possible that future application of IR analysis could include monitoring food process streams for indicators of microbial contamination.