Survival of Salmonella during Drying of Fresh Ginger Root (Zingiber officinale) and Storage of Ground Ginger

Abstract

The survival of Salmonella on fresh ginger root (Zingiber officinale) during drying was examined using both a laboratory oven at 51 and 60°C with two different fan settings and a small commercially available food dehydrator. The survival of Salmonella in ground ginger stored at 25 and 37°C at 33% (low) and 97% (high) relative humidity (RH) was also examined. To inoculate ginger, a four-serovar cocktail of Salmonella was collected by harvesting agar lawn cells. For drying experiments, ginger slices (1 ± 0.5 mm thickness) were surface inoculated at a starting level of approximately 9 log CFU/g. Higher temperature (60°C) coupled with a slow fan speed (nonstringent condition) to promote a slower reduction in the water activity (aw) of the ginger resulted in a 3- to 4-log reduction in Salmonella populations in the first 4 to 6 h with an additional 2- to 3-log reduction by 24 h. Higher temperature with a higher fan speed (stringent condition) resulted in significantly less destruction of Salmonella throughout the 24-h period (P < 0.001). Survival appeared related to the rate of reduction in the aw. The aw also influenced Salmonella survival during storage of ground ginger. During storage at 97% RH, the maximum aw values were 0.85 at 25°C and 0.87 at 37°C; Salmonella was no longer detected after 25 and 5 days of storage, respectively, under these conditions. At 33% RH, the aw stabilized to approximately 0.35 at 25°C and 0.31 at 37°C. Salmonella levels remained relatively constant throughout the 365-day and 170-day storage periods for the respective temperatures. These results indicate a relationship between temperature and aw and the survival of Salmonella during both drying and storage of ginger.

Effect of water activity and storage of tahini on the viability of stressed Salmonella serovars

“…In contrast to the present work, some studies have shown that reduced a w protects against the decrease of Salmonella serovars in low moisture food products (Archer et al, 1998;Doyle & Mazzotta, 2000;Beuchat & Scouten, 2002;Keller et al, 2013;Gradl et al, 2015). Gradl et al (2015) and Keller et al (2013) reported that Salmonella viability decreased during 25 and 37 °C storage of ground ginger and black pepper when a w was about 0.86, however, viability remained relatively stable when the a w of samples was < 0.40. Similarly, Salmonella numbers decreased during 25 and 37 °C storage on alfalfa seeds with an a w of 0.21 to 0.60, but not when stored at 5 °C, as the a w in seeds was increased (Beuchat & Scouten, 2002).…”

Induction of a Viable but Nonculturable State, Thermal and Sanitizer Tolerance, and Gene Expression Correlation with Desiccation-Adapted Biofilm and Planktonic Salmonella in Powdered Infant Formula

“…Janning et al (17) also found a negligible decrease in culturable Salmonella cells in milk powder that was dried with anhydrous silica gel at 228C for at least 3 months. The findings of the present study are consistent with the a w inactivation kinetics of Salmonella reported previously (12,13).…”

Salmonella Inactivation During Extrusion of an Oat Flour Model Food

“…An average of a 0.68 log CFU/g drop was observed between the day of preparation of inoculated flour and the day of use. This initial drop and subsequent Salmonella survival is consistent with observations made in other low a w foods (Keller and others ; Blessington and others ; Gradl and others )…”