Behavior of Different Salmonella spp. Strains in Black Pepper (Piper nigrum), Oregano (Origanum vulgare) and White Pepper (Piper nigrum)

Introduction: It has been established that Salmonella spp. can survive for long periods of time in foods with low water activities such as peanut butter and spices. In fact, some studies have reported Salmonella spp. prevalence in spices as high as 40% and different Salmonella spp. outbreaks have been traced back to this kind of products.

Purpose: The objective of the study is to analyze some factors affecting the behavior of Salmonella spp. in black pepper, white pepper and oregano.

Methods: Samples were inoculated with low (2 log CFU/g) and high (9 log CFU/g) levels of a Salmonella spp. cocktail (5 strains) using a spray method and drying inside a biosafety cabinet (12 h). High population samples were stored at 25 and 35°C for 2 months to determine survivability; these samples were also used to evaluate the thermal resistance of Salmonella spp. at 65°C. Low population samples were incubated at 25°C to evaluate growth after increasing the water activity of the product (0.991) with peptone water. Salmonella spp. populations were recovered on tryptic soy agar.

Results: Salmonella spp. was able to survive up to 61 days (both temperatures) in black and white pepper although the population decreased during storage. A shorter survivability (41 days) was observed in oregano at 25°C. D_65°C values of 5.7 ± 0.8 and 4.28 ± 0.4 min were observed for white and black pepper, respectively. Under high water activity conditions, Salmonella spp. population increased more than 4.0 log CFU/g in white pepper stored at 25°C but shorter increases (1.1 log CFU/g) were observed for black pepper.

Significance: These data demonstrate that there is an increased risk for persistence of Salmonella spp. in some herbs and spices that are used as raw material for other types of food products.