Food Protection Trends - May/June 2024 - 187

A similar study showed that wood ear mushroom that was
contaminated with S. enterica and L. monocytogenes (ca. 6.22
log CFU/g) showed 2.26 and 2.49 log CFU/g reductions,
respectively, after 24-h dehydration at 60°C and 1-h drying
at ambient temperature, whereas enoki mushrooms showed
no reduction in the initial population of bacteria. This
highlights the intrinsic variability of different mushroom
types, such as the presence of antimicrobial compounds (e.g.,
polysaccharides, melanins, and polyphenols) in wood ear
mushrooms (7). In another study, ganodermadiol, a sterol in
mushrooms, has been supported to have antiviral properties
(6). During 180-day storage at 25°C, the populations of S.
enterica and L. monocytogenes reduced by approximately 1 to
2 log CFU/g to 1.79 and 1.78 log CFU/g, respectively. Once
a pathogen survives in the food product, rehydrating the
product at room temperature for a few hours before cooking
introduces the risk of pathogens regrowing to unsafe levels
(13). Powdered wood ear mushrooms were used in this
study to explore the growing trend of a blended mushroom
beverage as a coffee alternative. Although mushroom " coffee "
blends typically consist of other types of mushrooms (i.e.,
lion's mane, Cordyceps, reishi), we believe that the results
found in this study would still provide beneficial data in
determining the safety considerations of low-moisture
mushroom powders.
The results of this study showed that grinding sliced
mushroom to powdered form did not significantly impact
the thermal inactivation kinetics of Salmonella Stanley (P
> 0.05). In this study, mushroom powder was prepared by
inoculating dried mushroom with Salmonella and grinding
to fine powder by using a spice grinder. A study has indicated
that the inoculation method used to prepare powdered foods
might affect the survivability of Salmonella when challenged
at high temperature. Specifically, the inoculation of almond
meal and date paste prior to grinding of the samples
increased the heat sensitivity of Salmonella as compared
with the inoculation occurring post-grinding; however, the
opposite was true for wheat flour (16). This shows that the
inoculation method might affect the survival of Salmonella
differently in various low-moisture products. It was unknown
how grinding would impact Salmonella heat resistance on
mushrooms, but inoculating the sliced mushrooms prior
to grinding allowed consistency with the other, nonground
samples. Furthermore, particle size has been shown to impact
REFERENCES
1. Ajis, A. H., L. J. Chong, Y. S. Tan, and L. C.,
Chai. 2017. Microbial food safety assessment
of dried edible mushrooms. J. Verbrauch.
Lebensm. 12:265-269.
2. Bourdoux, S., Li, D., A. Rajkovic, F.
Devlieghere, and M. Uyttendaele. 2016.
Performance of drying technologies to
ensure microbial safety of dried fruits and
vegetables. Compr. Rev. Food Sci. Food Saf.
15:1056-1066.
3. U.S. Centers for Disease Control and
Prevention. 2020. Outbreak of Salmonella
Stanley infections linked to wood ear
mushrooms. Available at: https://www.cdc.
gov/salmonella/stanley-09-20/index.html.
Accessed 7 December 2023.
the heating rate and inactivation of pathogens in dried food
products, such as red pepper powder (32). This study does
not quantitatively measure the particle size of mushroom
powder, but powder size was consistent by using the same
amount of mushroom per batch and maintaining the duration
of grinding. In addition, the results showed that steeping 3 g
of inoculated powdered mushroom in 230 ml of 80°C water
(a common powder to water ratio used for coffee and tea
brewing) (20) and leaving them for 10 min to cool naturally
did not result in a 5-log reduction of Salmonella, meaning
these parameters could be insufficient in reducing Salmonella
to safe levels. However, the differences in Salmonella
reductions on powdered and sliced mushrooms after steeping
in 80°water were not significantly different due to large
standard deviations, though they were significantly less than
sliced mushrooms held at 100°C after soaking in ambient
water for 30 min. Hence, it is imperative to ensure that
contamination risk is minimized early on during cultivation
and processing of mushroom powders and to provide clear
directions for heat treatments, so outbreaks related to these
health foods do not occur in the future.
CONCLUSIONS
According to the data analysis, treating dried mushrooms
in water at 100°C for several minutes (after presoaking
the mushrooms for 30 min in ambient water) proves to be
highly effective in reducing Salmonella. However, it was
observed that in various cooking scenarios, the reduction of
Salmonella was inconsistent when using temperatures lower
than 100°C and not holding for specific time periods. Our
findings shed light on the diverse effectiveness of thermal
interventions in different dried wood ear mushrooms
products. Properly implementing thermal treatments during
mushroom processing can serve as a valuable strategy to
mitigate pathogens and enhance food safety measures. These
insights hold significance for retailers and consumers who
may be using dried mushrooms in recipes, emphasizing the
importance of adopting appropriate practices to safeguard
consumer health and prevent potential foodborne illnesses.
ACKNOWLEDGMENT
This project was funded by the U.S. Department of Agriculture
research program (Future of Food: Opportunities and
Careers for Undergraduate Students, 2022-68018-36612).
May/June Food Protection Trends 187
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