September 25, 2019

Interpretive Summary: Salmonella survival in poultry fat

Interpretive Summary: Effects of different moisture and temperature levels on Salmonella survival in poultry fat.

By: Dr. Caitlin Vonderohe 

The rendering industry collects and safely processes an estimated 25 million tons of animal by-products into livestock feed, fertilizer, pet food, and pharmaceuticals, among many other products. In the rendering process, heat is applied to the products, and fat is separated for further processing. The rendering industry has done a great deal to minimize food safety risk by applying long cook times and high temperatures, however, there is still a risk post-processing contamination with pathogens such as Salmonella spp.

Recent research has now shown Salmonella can successfully contaminate fat products. This contamination represents a significant food safety issue because rendered animal fat is often directly applied to pet food as one of the final steps in processing. A recent paper published in Translational Animal Science by Trinetta et al., “Effects of different moisture and temperature levels on Salmonella survival in poultry fat,” explored how different storage temperatures and moisture levels affect the survival of Salmonella in poultry fat.

Samples of poultry fat were obtained from a local supplier and divided into four different beakers, where sterile water was added to achieve moisture levels of 0%, 0.5%, 1%, and 3%. These samples were subsequently wet, or dry inoculated with Salmonella enterica and stored at 48° or 76° for seven days where Salmonella populations were evaluated daily. After seven days, samples were enriched, serial diluted, and plated for final enumeration.

Wet inoculation was used to simulate cross-contamination from excess moisture during storage. In this case, there was a significant reduction in salmonella population from the 1% and 3% moisture poultry fat samples from the point of inoculation to the end of the seven day storage period at 48°C. There was no overall difference in pathogen count. Salmonella population decreased to undetectable levels by day 4 of storage at 48°C. When samples, both wet and dry inoculated were stored at 76°C, Salmonella populations were below detectable levels after 24 hours.

Salmonella populations in poultry fat decreased when temperature increased. Salmonella levels were undetectable after 24 hours when fat was stored at 76°C. When samples were inoculated with high levels of Salmonella, and stored at 48°C, higher moisture resulted in greater reductions in bacterial load. Therefore, if a sample is contaminated with a high level of Salmonella from moisture during transport, and subsequently held at 48°C, this may help reduce bacterial load over time.

To view the full article, visit Translational Animal Science