Seward’s Stomacher® Laboratory Blenders Help Investigate the Effectiveness of Preservation

Seward Ltd’s Stomacher® laboratory paddle blender range has recently been used in a research project to investigate the effectiveness of fish and chip vinegar in preserving fresh catfish fillets using concentrations of vinegar that are effective, but do not over power the flavour1. Stomacher® is often used in preservative evaluations, as it is essential to use an effective benchmark blending process to detect the changes in microorganism recovery that indicate the efficacy of the preservative processes evaluated.

The antimicrobial activity of vinegar has long been known as a cost effective way of preserving foods of various kinds. The pickling of food adds a flavour dimension that is not only acceptable to the consumer but in the case of certain products, such as roll mop herring, is essential. However, for many food types, a flavour as strong as fish and chip vinegar is not desirable, despite the preservative effect it achieves.

The research project1 utilised Seward’s Stomacher® 400 Circulator to prepare the preserved samples and bacterial inocula, as well as to evaluate the recovery of the microorganisms after exposure of catfish to fish and chip vinegar in a simple challenge test.

The results showed that vinegar diluted to 0.5% acetic acid on catfish fillets would be suitable for prolonging shelf life and did not make the product unappealing to consumers. This presents a simple opportunity at an affordable price to reduce economic loss due to spoilage in food products, even where the flavour of vinegar is not desirable.

The Stomacher has also been used recently in the evaluation of red wine as a food preservative2. The exact mechanisms responsible for the antimicrobial activity of wine are not fully understood, but different components of wine have been proposed to contribute to its antimicrobial activity. Some authors give emphasis to the role of wine phenolics and others suggest the role of non-phenolic constituents of wine, such us organic acids, ethanol.

The aim of the study2 was to investigate the antibacterial efficiency of three phenolic compound combinations and total phenolic compounds at concentrations of 100-200mg/l of three Argentinean red wine varieties on E. coli and L. monocytogenes viability in a fish-meat model system, at 4 °C and 20 °C.

The results of this investigation suggest phenolic compounds found in wine could be used to extend the shelf life of fish. The results also indicate the use of rutin–quercetin in combination as a preservative during the transport and conservation of fish meat to the fish market. This is an effective antibacterial agent even when there is an interruption in the refrigeration of the product.

1. Antimicrobial Activity of Vinegar on Bacterial Species Isolated from Retail and Local Channel Catfish. Talaysha Lingham, Samuel Besong, Gulnihal Ozbay and Jung-Lim Lee (September 2012). J Food Process Technol S11-001

2. Phenolic Compounds from Wine as Natural Preservatives of Fish Meat. María José Rodríguez Vaquero, Pedro Aredes Aredes Fernández and María Cristina Manca de Nadra (April 2012).