Salmonella and Petfood: The Reality and the Recalls

 

It seems that everywhere you look in the Petfood industry Salmonella-related illnesses and product recalls are making news. The reality, however, is that over an 18-month period (beginning January 2018), Petfood recalls due to Salmonella concerns have been just a fraction of the number of human food recall cases.

Why the laser focus on Salmonella in Petfood?

Salmonella in Petfoods can have serious impacts on the health and wellness of animals. Common symptoms of Salmonella-related illness in dogs include loss of appetite, decreased activity, fever, vomiting and diarrhea.

 

However, while Salmonella can lead to illness in pets, the related illnesses in humans are significantly more prevalent and potentially serious. Common symptoms include headache, diarrhea, intestinal cramps, blood in the stool, loss of appetite, and an infection that can reach the blood stream, potentially causing death.
In the last 17 years, Salmonella outbreaks have impacted nearly 67,000 humans and caused 87 deaths. Due to the impact of Salmonella on human health, the U.S. Food and Drug Administration (FDA) has instituted a zero-tolerance policy for Salmonella in pet food. The agency states that the risk of handling contaminated pet foods poses a significant risk to human health, especially to children, the elderly and those with compromised immune systems.

 

Dry Petfood and Salmonella

The pet food manufacturing process includes heat lethality steps (the pre-conditioner and extruder) that make the incidence of Salmonella relatively low. However, instances of contamination continue to occur, likely the result of recontamination after the extruder. This recontamination could potentially occur from growth of Salmonella inside the conveying system or possibly from airborne dust in air-handling systems. If either is the case, it is also likely the Salmonella detected are only on the surface of the kibble which could allow a surface-active compound to prove effective.

 

Using Acids for Salmonella Control

Acids have the potential to control Salmonella by lowering the pH. Acids that are in a physically dry state have an advantage for Salmonella control as they can be made into a powder that can be dusted onto the kibble without reacting with the surface. Liquid acids will react with the surface components, causing them to be neutralized by proteins and other buffering agents they come into contact with, thus rendering them less effective for Salmonella control.

It is also important to note that acid strength impacts its ability to control Salmonella. Acid strength is denoted by pKa value (Figure 1). The lower the pKa value the stronger the acid.

Figure 1
Acid Strength5
Acid pKa Value
Sodium Bisulfate 1.99
SAPP 2.10
Phosphoric Acid 2.16
Citric Acid 3.14
Acetic Acid 4.75
Propionic Acid 4.87
Pet - Sodium Bisulfate Logo SBS Pet™ has unique characteristics that make it effective against Salmonella contamination on the kibble surface, including acid strength and a dessicating physically dry state. For pH applications below 3.6, less SBS Pet™ is required to lower pH than most commonly used acids, including phosphoric acid, which reduces cost in pet food, treats, slurry or any low pH application. Sodium bisulfate has one of the lowest pKa’s, at 1.99, of the common acids used in food production.

 

Research conducted at independent laboratories indicates that sodium bisulfate, the main ingredient in SBS Pet™, has been shown to control Salmonella contamination on the surface of extruded dry pet food. (Aldrich, 2012).

The Power to Control Salmonella in Dry Petfood

In a study done at Kansas State University, ten different dry, extruded commercial cat and dog foods were inoculated with dry Salmonella enterica at day 0. SBS Pet™ was applied as a coating at a rate of 0.0, 0.6 and 0.8% to cat food, and 0.0, 0.2 and 0.4% to dog food. Salmonella was then tracked over the course of 14 days.

SBS Pet™ was shown to reduce Salmonella contamination by one to two logs when applied to dry, extruded pet food (Tables 1 and 2) without affecting palatability.

Table 1. Impact of SBS coating on Salmonella in commercial cat foods
Table 2. Impact of SBS coating on Salmonella in commercial dog foods

Learn more about the mode of action of SBS Pet

 

Reducing Salmonella in Rendered Fats

Another potential source of Salmonella contamination is the fat and flavors commonly coated on dry pet foods to increase energy density and enhance palatability. In a separate study done at Kansas State University, researchers found that SBS Pet™ reduced Salmonella in rendered chicken fat contaminated from the residual water encountered during storage and transport.

Alone SBS Pet™ was more effective than lactic acid at 0h with a >4 log reduction at 2h and a complete kill for both treatments at 6h (Table 3).

Table 3. Effective of SBS and LA on Salmonella in residual water

 

In the fat phase, only a >4 log reduction was detected regardless of treatment, and by 12h Salmonella were not detected in any treatments in the fat phase as it does not support Salmonella growth (Table 4).

 

Table 4. Effective of SBS and LA on Salmonella in fat

 

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