D-LACTIC ACID IN PORK AS A FRESHNESS INDICATOR MONITORED BY IMMOBILIZED D-LACTATE DEHYDROGENASE USING SEQUENTIAL INJECTION-ANALYSIS

A sequential injection analysis system was set up to quantify D-lactic acid in pork. D-Lactic acid seems to be a useful indicator of metabol ism of spoilage organisms. The analytical system is fully computerized and is able to monitor the concentration of the acid in an assay cycl e of 160 s including 90 s incubation time when the flow is stopped. Th e enzyme used in the analysis is D-lactate dehydrogenase that is co-im mobilized with L-alanine aminotransferase on porous glass. The experim ental set-up gave good reproducibility down to 0.1 mM D-lactate and th e assay could be repeated at least 50() times with the response mainta ined.