Travel to the southern mountain ranges, the Monchique which border the Algarve of Portugal and you are sure to encounter the potent sausage, Morcela de Arroz. (MA). It is a ready-to-eat and cooked sausage, up to 400g in weight and prepared from ground pork meat, blood and rice, minced fresh onion, ground spices notably cumin, clove, allspice, pepper and spearmint. It also contains salt, all of which is then stuffed into a natural casing of pork stomach, or pork and cattle intestine. It is then boiled in seasoned broth.

The sausage is an important delicacy and keeps a number of food industries going. It is not preserved with antimicrobials and does not present a significant number of hurdles or barriers to microbial growth. It has an average pH of 6 and a water activity of 0.97 so must rely on heating. It is not packed either and is usually eaten as a snack.

The heating process generally kills all micro-organisms. It is generally taken to above 90 °C for 30 minutes at its core temperature. This should mean it complies with recommendations for the safe production of low acid refrigerated processed foods with extended durability (REPFEDs). The recommendation states there should be a cook time at the core of 2 minutes at 70 °C allowing a reduction of a particularly nasty microorganism Listeria monocytogenes. (ICMSF, 2002). It is generally treated as a very short shelf-life food.

Improving its shelf-life and reducing its susceptibility to microbial contamination is important if the sausage is to enjoy progressive commercial growth. One way to improve its acceptability is to produce it in thick slices like haggis or try other novel approaches to packaging and presentation. However, modifying the traditional appearance or applying new product development approaches is not without risk – it could jeopardise the what microbial stability there is.

Methods to understand the heating processes  in such an inhomogeneous product had started back in 2008 (Pereira et al., 2008) in various research departments of the Portuguese capital, Lisbon. Now, further studies on the sausage and its behaviour with different types of packing have been examined (Perreira et al., 2015) by investigating how L. monocytogenes behaves in such a food system.

A consumer panel tested the sensory performance of the Morcela, especially the storage temperatures needed. A  shelf life was based on sensory rejection by the consumers, long before the product was considered hazardous due to the possible growth any Listeria. based on the types of packaging used, the shelf-life was set at 4, 8, and 10 days in either aerobic, vacuum, and Modified Atmospheric Packaging (MAP).

References

ICMSF. (2002) Microorganisms in foods 7: microbiological testing in food safety management. New York: Kluwer Academic/Plenum Publishers.

Pereira, J.A., Ferreira-Dias, S., Matos, T.J.S. (2008) Application of unsteady-state heat transfer equations to Portuguese traditional meat products from Monchique region. 54th International Congress of Meat Science and Technology; Cape Town, South Africa 10–15 August. Helsinki, Finland: ICoMST2008.

Pereira, J. A., Silva, P., Matos, T. J. S. and Patarata, L. (2015), Shelf Life Determination of Sliced Portuguese Traditional Blood Sausage—Morcela de Arroz de Monchique through Microbiological Challenge and Consumer Test. Journal of Food Science. doi: 10.1111/1750-3841.12782