Detection of off-flavour in channel catfish (Ictalurus punctatus Rafinesque) fillets by trained dogs.

摘要

Four mixed-breed adult dogs (2 males and 2 females), which had been trained to detect geosmin (GSM) and 2-methylisoborneol (MIB) in purified water and pond water, were used to detect these off-flavour compounds in fillets of channel catfish (Ictalurus punctatus) obtained from commercial ponds in west-central Mississippi, USA, in 2002. The dogs were led past the boxes containing fillet samples with or without the off-flavour compounds, and correct responses were tabulated. The test began with fillet samples having the highest MIB and GSM levels until the lowest levels. The GSM and MIB levels in the fillets were considered typical for catfish obtained from west Mississippi commercial catfish ponds. The mean combined correct response rate for all dogs and all samples was 81%. The percentage of correct responses did not appear to decrease with decreasing levels of GSM or MIB. GSM and MIB were detected with equal accuracy regardless of which compound or level of the compound was present. The exception was when one on-flavour nontarget sample was placed with 4 different on-flavour nontarget samples. In this case, most dogs had difficulty in detecting the "different" sample. However, even for this sample, the total correct response was significantly greater than would be expected because of chance alone. In a sample in which both the target (off-flavour) and nontarget (on-flavour) fillets came from ponds which were determined to be on-flavour by SPME-GC-MS, all dogs were able to identify the single different sample with a mean accuracy of 53%. It is suggested that this approach would enable the catfish fillet producers to be aware of the development of off-flavour problems earlier, and take management actions to reduce and eliminate the accumulation of off-flavour compounds in the farm-raised catfish..