D-Lactic acid in pork as a freshness indicator monitored by immobilized d-lactate dehydrogenase using sequential injection analysis

Abstract

A sequential injection analysis system was set up to quantify d-lactic acid seems to be a useful indicator of metabolism of spoilage organisms. The analytical system is fully computerized and is able to monitor the concentration of the acid in an assay cycle of 160 s including 90 s incubation time when the flow is stopped. The enzyme used in the analysis is d-lactate dehydrogenase that is co-immobilized with l-alanine aminotransferase on porour glass. The experimental set-up gave good reproducibility down to 0.1 mM d-lactate and the assay could be repeated at least 500 times with the response maintained.