Survival of Salmonella during Production of Partially Sprouted Pumpkin, Sunflower, and Chia Seeds Dried for Direct Consumption

Abstract

Ready-to-eat foods based on dried partially sprouted seeds have been associated with foodborne salmonellosis. Whereas research has focused on the potential for Salmonella initially present in or on seeds to grow and survive during fresh sprout production, little is known about the potential for growth and survival of Salmonella associated with seeds that have been partially sprouted and dried. The goal of this study was to determine the growth of Salmonella during soaking for partial germination of pumpkin, sunflower, and chia seeds and subsequent survival during drying and storage. Pumpkin, sunflower, and chia seeds were inoculated with a four-serotype Salmonella cocktail by the dry transfer method and were soaked in sterile water at 25 or 37°C for 24 h. During the soaking period, Salmonella exhibited growth rates of 0.37 ± 0.26, 0.27 ± 0.12, and 0.45 ± 0.19 log CFU/h at 25°C and 0.94 ± 0.44, 1.04 ± 0.84, and 0.73 ± 0.36 log CFU/h at 37°C for chia, pumpkin, and sunflower seeds, respectively. Soaked seeds were drained and dried at 25, 51, and 60°C. Drying resulted in >5 log CFU/g loss at both 51 and 60°C and ∼3 log CFU/g loss at 25°C on partially sprouted pumpkin and sunflower seeds. There was no decrease in Salmonella during drying of chia seeds at 25°C, and only drying at 60°C provided losses >5 log CFU/g. Dried seeds were stored at 37 and 45°C at 15 and 76% relative humidity (RH) levels. The combination of temperature and RH exerted a stronger effect than either factor alone, such that rates at which Salmonella decreased generally followed this order: 37°C at 15% RH < 45°C at 15% RH < 37°C at 76% RH < 45°C at 76% RH for all seeds tested. Rates differed based on seed type, with chia seeds and chia seed powder having the smallest rate of Salmonella decrease, followed by sunflower and pumpkin seeds. Drying at higher temperatures (50 and 61°C) or storing at elevated temperature and humidity (45°C and 76% RH) resulted in significantly different rates of Salmonella decrease.

Salmonella Growth during the Soaking Step of ‘Sprouted’ Grain, Nut, and Seed Production

“…1C). Final cell densities were comparable to those previously reported for soaked pumpkin, sunflower, and chia seeds (14).…”

“…), will influence the lag time and the growth rate of Salmonella. Keller et al (14) reported average lag times of 3.45 h (sunflower) to 6.68 h (chia) during soaking at 25°C; however, these times were highly variable between replicates (standard deviations averaging 2 h). Shortening the soaking time to < 3 h to mitigate the potential growth of Salmonella is not a viable option because many of these commodities would not be fully hydrated in this time frame.…”

“…Grains, nuts, and seeds do not have sufficient moisture to support the growth of foodborne pathogens; however, the soaking stage of "sprouting" may create an environment that could support the growth of various microorganisms, including Salmonella. A single study conducted by Keller et al (2018) demonstrated significant growth (>3 log CFU/g) of Salmonella during the 24-h soaking period of pumpkin, sunflower, and chia seeds at 25°C (14). These results indicated that growth of Salmonella during the soaking period may have been a significant factor in the chia seed powder outbreak.…”

Complete Genome Sequences of Five Salmonella enterica Strains Used in Inoculation Cocktails in Low-Moisture Food Storage Studies

“…to survive on these foods (nuts, black pepper, and spices) in a low-moisture environment. Numerous studies on the survival of Salmonella enterica in dried foods have previously been published (1–3) using a cocktail of different strains. Here, we report the complete closed genome sequences of 5 strains commonly used in these studies, S.…”

Microbial quality of edible seeds commercially available in southern Portugal

“…However, higher values of Salmonella prevail in sesame (12%) and chia (31%) were detected by Arana et al [14] . In 2014, a chia seed meal was associated with an outbreak of Salmonella , which involved 63 cases recorded in Canada and 31 in the United States [15] . In addition, in the United States, several edible seeds, such as chia, sunflower and pumpkin seeds, have been subjected to multiple recalls from the market due to the presence of Salmonella [15] .…”