Early detection of fish and meat spoilage

Studies have recently been completed analysing the ability of the Syft Technologies Voice 200 instrument, which utilises the SIFT-MS platform, to detect early spoilage of meats and seafood. These studies examined samples of fresh fish (New Zealand groper and tarakihi), shellfish (New Zealand green-lipped mussel) and meat (New Zealand sirloin beef steak and minced beef) which were purchased from retailers in Christchurch, New Zealand.

Triplicate 25 g samples of each product were placed in 250 mL capped Schott bottles and were allowed to warm to room temperature before the initial analysis. This is represented as ‘time zero’ on the graphs due to uncertainties in the actual age and history of the samples. The bottles were then incubated at 37°C for the duration of the experiment with the headspace being sampled hourly for the mussels and two hourly for the fish and meats.

For the analysis, 13 compounds were targeted, including a variety of sulfur-containing species and amines. The graphs illustrate the concentration measurements for those compounds which showed a change in concentration over the duration of the experiment.

The results for the New Zealand groper and tarakihi both showed significant increases in the concentration of trimethylamine, a compound having the ‘fishy’ aroma characteristic of fish spoilage. Ammonia, various sulfur compounds and oxygenates were also detected in the early stages of spoilage and increased as the samples aged.

The New Zealand mussels showed a very different headspace composition as they decayed. The headspace is dominated by high levels of dimethyl sulfide even at the initial measurement. Again the concentration of trimethylamine, the ‘fishy’ aroma compound is seen to increase during decay.

The minced beef, having a higher surface area than steak, is more susceptible to spoilage so it is common for an inorganic preservative to be added to mince beef to prolong its shelf life. The preservative appeared to suppress the evolution of dimethyl sulfide as the concentration of this compound remained almost constant for the duration of the experiment and ethyl acetate production was at only moderate levels compared with the sirloin steak. Ammonia and trimethylamine continued to be produced however.

The versatility of SIFT-MS means it can be easily applied to other food, flavour and fragrance applications such as measuring volatile profiles for flavour and aroma perception.

Manufacturing processes and quality control can also benefit from this real-time technology for determining batch quality and food integrity. The instantaneous results allow critical decisions to be made as and when required and necessary action taken immediately.