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. 2023 Jul 29;33(5):1261–1268. doi: 10.1007/s10068-023-01385-z

Microbiological quality and safety of fresh mushroom products at retail level in Korea

Boyang Meng 1, A-Ra Jang 1, Hyunji Song 1, Sun-Young Lee 1,✉
PMCID: PMC10909044  PMID: 38440672

Abstract

Several investigations and recalls have demonstrated that Listeria monocytogenes can occur on mushrooms. This study aimed to assess the microbiological quality and safety of four types of edible mushrooms (Flammulina velutipes, Pleurotus ostreatus, Pleurotus eryngii, and Agaricus bisporus) available in the Korean market, and to evaluate the prevalence of Listeria spp., including L. monocytogenes. Results revealed that out of 100 samples tested, 16% (32/200) were positive for Listeria spp. Of the Listeria-positive samples, five strains of Listeria innocua were detected. The total microbial counts ranged from 0.79 to 5.84 log CFU/g, with F. velutipes exhibiting the highest microbial load (mean 5.03 log CFU/g). These findings provide significant data for risk assessment and emphasize the need for continued monitoring of the microbiological safety of edible mushrooms.

Keywords: Mushroom, Microbiological quality, Listeria monocytogenes, Contamination

Introduction

Listeria monocytogenes is a significant foodborne pathogen responsible for listeriosis, which can occur in various foods, including dairy products, meat products, seafood, fresh vegetables, and ready-to-eat foods. This bacterium can survive and proliferate in low temperatures, increasing the risk of cross-contamination during food processing and storage (Churklam et al., 2020). Edible mushrooms are a popular food globally, providing essential nutrients and bioactive components such as carbohydrates, proteins, vitamins, minerals, unsaturated fatty acids, and fiber (Chang, 1996; Mattila et al., 2001). Several beneficial functions have been reported, including immunomodulatory, hypoglycemic, hypotensive, hypocholesterolemic, hypolipidemic, antioxidant, and anti-obesity effects (Cheng et al., 2002; Kabir et al., 1987; Manohar et al., 2002; Sia and Candlish, 1999). The global consumption of mushrooms was approximately 40 million tons in 2018, with an anticipated annual growth rate of 9.2% between 2016 and 2021 (Chen et al., 2018).

Fresh foods undergo several processes from the farm to the retail store and to the consumer, such as harvesting, washing, cutting, packaging, storage, and transportation, which can affect their quality and shelf life (Schill et al., 2021). In Korea, there are few cases of food poisoning related to mushrooms because they are typically consumed after being cooked. However, it has been confirmed that there is a higher risk of food poisoning in countries where mushrooms are eaten raw, such as in salads. In fact, over the past three years, there has been an increasing number of foods recalls due to microbiological contamination of mushrooms, which has led to severe infections, hospitalizations, and deaths (Dygico et al., 2020). For instance, in March 2020, L. monocytogenes-contaminated Flammulina velutipes caused 36 hospitalizations and 4 deaths in the USA (Byun et al., 2022). In the same year, dried Lentinus edodes were recalled in the USA due to Salmonella contamination that infected 55 people in 12 states and hospitalized six (Pennone et al., 2018). Following these incidents, countries such as the USA have developed standards and policies to minimize the potential risk of foodborne illness, but there are no specific regulations and standards for mushrooms in Korea.

At retail, extrinsic factors such as changes in the storage environment, such as exceeding the refrigeration temperature, moisture level, and packaging defects, can affect the shelf life of food products. Moreover, intrinsic factors in the product itself, such as spoilage bacteria, microbial contamination, pH, moisture, and redox potential, can also contribute to the spoilage of mushrooms. Mushrooms contain approximately 80% to 90% water, have an average pH of 6.9 (6.6 to 7.0) and a high CO2 respiration rate and are highly perishable in nature (Jiang et al., 2018; Reis et al., 2012; Valerie and David, 2007). Recent studies of the microbiological quality of fresh cultivated mushrooms at the retail level have found high levels of aerobic bacteria and the presence of L. monocytogenes (Chen et al., 2018; Venturini et al., 2011; Zhang et al., 2020). However, the research on the prevalence of Listeria spp. and other microbial contaminants in mushrooms distributed in Korea is limited. As such, this study aims to investigate the degree of microbial contamination and Listeria spp. contamination in four major types of mushrooms commonly distributed in Korea. This study provides valuable information on the current status of microbial and Listeria spp. contamination in commercially available mushrooms in Korea, which can be used to inform the development of effective food safety guidelines and measures for the production, distribution, and consumption of mushrooms.

Materials and methods

Sampling of mushroom

In this study, a total of 100 mushroom samples, consisting of 25 samples each of four mushroom species (F. velutipes, Pleurotus ostreatus, Pleurotus eryngii, and Agaricus bisporus) were collected in duplicate from 2022 to 2023. The samples were obtained from various commercial sources, including hypermarkets, small supermarkets, open-air markets, and farm supply, and were selected based on their origin. To maintain the samples' quality, they were placed in insulated shipping coolers with frozen gel packs surrounding and between the samples to keep them at a temperature below 4 °C during transportation. Testing was conducted within 4 h of receipt to ensure the samples' freshness (Fig. 1).

Fig. 1.

Fig. 1

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The number of Four different mushroom samples obtained from different region in Korea. Flammulina velutipes (A); Pleurotus ostreatus (B); Pleurotus eryngii (C); Agaricus bisporus (D). Samples were purchased from hypermarkets, small supermarkets, open-air markets and farm supplies from 2022 to 2023. Twenty-five samples of each mushroom species were purchased, and the experiment was repeated twice

Microbiological analysis

To assess the prevalence of microbial contamination in mushroom products, 25 g of each mushroom sample was homogenized in sterile filter stomacher bags (Difco Laboratories, Detroit, MI, USA) containing 100 mL of 0.85% salt (99.0% NaCl, Samchum, Seoul, Korea), and each sample bag was stomached using a BagMixer 400 (Interscience, Breteche, France) for 90 s. Total mesophilic aerobic bacteria (TMAB), total psychrophilic aerobic bacteria (TPAB), E. coli/coliforms (EC), and yeast/molds (YM) were analyzed using Petrifilm™ Aerobic Count Plate, Petrifilm™ EC Count Plate, and Petrifilm™ YM Count Plate (3 M, St. Paul, MN, USA), respectively. Sample suspensions were diluted with 0.2% sterile peptone (PW, Difco), and 1.0 mL aliquots were placed on four different Petrifilms™. The Petrifilms™ were then incubated at specific temperatures for different durations depending on the microorganism type. TMAB and EC were incubated at 37 °C for 24 h, TPAB was incubated at 25 °C for 24 h, and YM was incubated at 30 °C for 120 h. Microbial loads were expressed as colony forming units per gram (CFU/g) and log10 transformed.

Isolation of L. monocytogenes

The prevalence of L. monocytogenes was determined using the methods outlined in the Korean Food Code with some modifications (MFDS, 2021). In brief, 25 g of mushroom product samples were homogenized in sterile filter stomacher bags (Difco Laboratories, Detroit, MI, USA) containing 100 μL of Listeria Enrichment Broth (LEB, Difco Laboratories), and each sample bag was stomached (BagMixer 400, Interscience, Breteche, France) for 90 s. The homogenates were incubated at 30 °C for 48 h, and then 1 μL of the aliquots were plated on Oxford Listeria Agar Base (OAB, Difco Laboratories) and incubated at 37 °C for 24 h. Colonies developed on the medium were identified as positive results and confirmed by PCR electrophoresis and 16S rRNA sequencing (SolGent Co., Daejeon, Korea).

Confirmation of L. monocytogenes

The presence of L. monocytogenes was determined by a PCR method with some modifications of the foodborne illness outbreak investigation test act of 2022 (MFDA, 2022). First, positive strain for selective agar were incubated in Tryptic Soy Broth with Yeast Extract (TSB-YE) for 24 h. and DNA was extracted using the QIAamp AccuPrep® Genomic DNA Extraction Kit (Bioneer, Daejeon, Korea) according to the manufacturer's instructions. The extracted DNA was used as a template for PCR, and three positive L. monocytogenes DNA controls (ATCC 19111, 19117, and 19114) were used for comparison. The PCR reaction mixture was prepared by combining 5 μL of 10 × reaction buffer without MgCl2, 5 μL of MgCl2, 4 μL of dNTPS, 2 μL of forward primer (1 μL of hly and inl (F)), 2 μL of reverse primer (1 μL of hly and inl (R)), 5 μL of template DNA, 0.2 μL of Taq, and 26.8 μL of distilled water. The primer sequences were hly (F): 5′-GACCRRCCAGATTTTTCGGC-3′, hly (R): 5′-CACAAGTGGTAAGTTCCTG-3′, inl (F): 5′-AGTAACATCAGTCCCCTAGC-3′, and inl (R): 5′-GGTTCTGCGTAACTACCGCC-3′. The PCR reaction was performed in a GeneMate Thermal Cycler (GeneMate, Beijing, China) with the following conditions: an initial denaturation at 95 °C for 5 min, followed by 35 cycles of denaturation (94 °C for 1 min), primer annealing (56 °C for 1 min), and elongation (72 °C for 1 min), and a final elongation at 72 °C for 10 min. The PCR products were separated by electrophoresis in a 2% agarose gel containing 1 × Tris–acetate-EDTA (TAE) buffer at 100 V for 25 min (Mupid-exU, Advance, Japan), and the DNA standard Thermo Scientific™ GeneRuler™ 100 bp (Thermo Fisher Scientific Inc. Waltham, MA, USA) was used for fragment length comparison.

Statistical analysis

The experiment was performed in duplicate of one sample (n = 2) and the data were analyzed using the Statistical Analysis System (SAS) Version 9.1 (SAS Institute, Cary, NC, USA) or Microsoft Excel 2010 (Microsoft Office XP; Microsoft, Redmond, WA, USA). The significant differences (p ≤ 0.05) of means of microbial contamination levels among samples collected from different regions were determined by performing an analysis of variance (ANOVA) and using Duncan’s multiple range test.

Results and discussion

Quantitative microbial risk assessments

Table 1 shows the microbial counts of mesophilic aerobes, psychrophilic aerobes, coliforms, yeasts, and molds found in the four mushroom species. Among the 100 samples collected in Korea, F. velutipes and A. bisporus exhibited the highest mesophilic aerobic loads at 4.12 ± 0.82 and 3.88 ± 0.90, respectively, and these levels were significantly higher than those of the other samples (p ≤ 0.05). Levels of mesophilic aerobic loads in P. ostreatus and P. eryngii were 3.20 ± 0.95 and 2.96 ± 0.71, respectively. In F. velutipes, levels of psychrophilic aerobes and coliforms were found to be 5.03 ± 0.74 and 2.55 ± 1.22, respectively, which were significantly higher than those in other mushroom varieties (p ≤ 0.05). In addition, contamination by psychrophilic aerobic bacteria was higher than that by mesophilic aerobic bacteria in all four mushroom species. This may be due to preservation at low temperatures during storage and transportation. And Simón et al. (2005) found that the growth of cryophilic bacteria was about log10 CFU/g when mushrooms were stored at a low temperature of 4 °C. P. eryngi had the lowest microbial load due to its smooth surface and the fact that it was sold after treatment of most of the rhizomes, with mean counts ranging from 1.09 to 3.46 log10 CFU/g. The highest mean yeast/molds (3.35 log10 CFU/g) was detected in A. bisporus. Meanwhile, levels of yeasts/molds were significantly higher in P. ostreatus and A. bisporus than in the other samples (p ≤ 0.05), measuring 3.16 ± 0.53 and 3.16 ± 0.53, respectively. According to our results, the levels of microbial contamination varied by mushroom type. Different cultivation and process methods for mushrooms may influence their levels of microbial contamination however the sample size in this study was insufficient to determine significant differences among the types of mushrooms. Additionally, microbial contamination levels varied among mushrooms in this study, but other studies have not found significant differences (Schill et al., 2021). Therefore, additional research is required to confirm the levels of microbial contamination according to the type of mushroom.

Table 1.

Averages (log10 CFU/g)1 of bacteria isolated from four different mushrooms in different geographical regions of Korea

Mushrooms Region Type of microorganism
Total mesophilic aerobes Total psychrophilic aerobes Coliform Yeast/mold
Flammulina velutipes Chungcheongbuk-do 3.77 ± 0.34b,2 4.96 ± 0.20a 2.59 ± 0.84a 2.82 ± 0.48b
Gyeongsangbuk-do 4.12 ± 0.62ab 5.13 ± 0.80a 2.62 ± 1.13a 2.74 ± 0.46b
Jeollabuk-do 4.80 ± 0.22ab 5.47 ± 0.03a 3.65 ± 0.24a 2.50 ± 0.14b
Jeollanam-do 3.80 ± 0.93b 4.83 ± 0.85a 2.16 ± 1.23a 2.98 ± 0.53b
Other4 4.93 ± 0.96a 5.07 ± 0.56a 2.95 ± 1.75a 3.78 ± 0.40a
Total 4.12 ± 0.82A,3 5.03 ± 0.74A 2.55 ± 1.22A 2.94 ± 0.57B
Pleurotus ostreatus Chungcheongbuk-do 2.00 ± 0.85c 2.45 ± 0.78b 0.79 ± 0.28b 2.99 ± 0.77ab
Chungcheongnam-do 2.87 ± 0.47bc 2.31 ± 0.23b 0.69 ± 0.00b 2.62 ± 0.11b
Gangwon-do 4.55 ± 1.24a 4.97 ± 0.72a 2.16 ± 1.04a 3.63 ± 0.35a
Gyeonggi-do 3.34 ± 0.66b 4.30 ± 0.79a 2.62 ± 0.89a 3.17 ± 0.49ab
Gyeongsangbuk-do 2.87 ± 0.04bc 4.17 ± 0.06a 2.26 ± 0.20a 3.72 ± 0.09a
Gyeongsangnam-do 2.59 ± 0.08bc 2.57 ± 0.50b 0.69 ± 0.00b 3.70 ± 0.04a
Jeollanam-do 3.80 ± 0.65ab 4.33 ± 0.19a 2.22 ± 0.84a 2.96 ± 0.41ab
Other 3.20 ± 0.16bc 4.38 ± 0.27a 2.66 ± 0.35a 3.02 ± 0.19ab
Total 3.20 ± 0.95B 3.92 ± 1.06BC 2.07 ± 1.04B 3.16 ± 0.53AB
Pleurotus eryngii Chungcheongbuk-do 3.12 ± 0.51a 3.54 ± 0.92b 1.62 ± 0.92b 2.88 ± 0.43a
Chungcheongnam-do 2.35 ± 1.60a 3.01 ± 0.85b 1.86 ± 1.39b 2.55 ± 0.68a
Gyeonggi-do 3.45 ± 0.13a 4.36 ± 0.08ab 0.69 ± 0.00ab 2.93 ± 0.21a
Gyeongsangbuk-do 2.86 ± 0.62a 3.26 ± 1.08b 0.80 ± 0.37b 2.60 ± 0.69a
Incheon Gwangyeoksi 3.25 ± 0.58a 5.54 ± 0.12a 0.69 ± 0.00a 2.44 ± 0.06a
Jeollanam-do 3.12 ± 0.69a 3.37 ± 1.07b 0.69 ± 0.00b 2.42 ± 0.32a
Total 2.96 ± 0.71B 3.46 ± 1.06C 1.09 ± 0.77C 2.66 ± 0.57C
Agaricus bisporus Busan Gwangyeoksi 4.75 ± 0.60a 5.25 ± 0.69a 1.66 ± 1.05a 3.28 ± 0.98a
Chungcheongnam-do 4.16 ± 0.81ab 4.58 ± 1.73a 1.38 ± 0.88a 3.56 ± 0.90a
Daegu Gwangyeoksi 3.35 ± 1.13b 4.24 ± 0.05a 1.35 ± 0.93a 3.79 ± 0.00a
Gwangju Gwangyeoksi 4.54 ± 0.37ab 5.84 ± 0.09a 0.93 ± 0.34a 3.71 ± 0.03a
Gyeonggi-do 3.43 ± 0.77b 3.63 ± 1.14a 1.88 ± 0.96a 3.88 ± 0.43a
Gyeongsangbuk-do 3.57 ± 0.23ab 5.02 ± 0.52a 1.97 ± 0.52a 2.79 ± 1.04a
Other 3.67 ± 1.03ab 3.49 ± 1.89a 1.19 ± 0.68a 3.18 ± 0.80a
Total 3.88 ± 0.90A 4.25 ± 1.60B 1.46 ± 0.81C 3.35 ± 0.84A
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1Data represent means ± standard deviations of two measurements

2Means with the same letter within a column in the same mushroom are not significant different (p > 0.05)

3Means with the same letter within a column in the mushroom type are not significant different (p > 0.05)

4Sample whose production area cannot be identified

In the F. velutipes samples, 56% (14/25) of the samples had a lower-than-average contamination load of other mesophilic aerobic bacteria. The average count range of all samples was 2.33–4.06 log10 CFU/g (data not shown). The sources of origin were mainly distributed in Gyeongsangbuk-do (6) and Jeollanam-do (5) and were purchased from small supermarkets (8). Sixteen samples (Gyeongsangbuk-do, 8; Jeollanam-do, 5; Other, 2; Chungcheongbuk-do, 1) had levels of psychrophilic aerobic bacteria exceeding 5 logs, with a mean of 5.03 log10 CFU/g. Of these, 43.7% were purchased from small supermarkets (7/16). Compared to mesophilic aerobic bacteria, the counts of coliforms and yeasts/molds were very similar, with mean counts of 2.55 and 2.94 log10 CFU/g, respectively, and no significant differences were detected (p > 0.05). Among the 25 samples analyzed, 5 (20%) had no detectable coliform bacteria, and the level of yeast/molds was below the mean (2.94 log10 CFU/g) in 16 (64%) samples. The mean values of mesophilic aerobes and yeast/molds in P. ostreatus were similar, with mean values of 3.2 and 3.16 log10 CFU/g, respectively. Approximately 52% (13/25) of the samples were below the mean (3.2 log10 CFU/g). The majority of the samples were obtained from Gyeonggi-do and Chungcheongbuk-do and were purchased from farm suppliers and small supermarkets. For the total psychrophilic aerobic bacteria counts, most of the species (20 out of 25) were in the range of 3 to 6 log10 CFU/g. This microbial group was the most prevalent and was present in all sources of origin, except for Chungcheongbuk-do (3), Chungcheongnam-do (1), and Gyeongsangnam-do (1). Similar to P. eryngii, coliform bacteria were not detected in 5 of the 25 samples analyzed. Most of these samples originated from Chungcheongbuk-do and farm suppliers. More interestingly, P. eryngii had the lowest total microbial load of all mushroom samples. In particular, coliform bacteria were not detected in 72% (18/25) of the samples. The average microbial load was 1.09 log, with the highest values reaching 3.03 log. Most of them originated from Chungcheongbuk-do. This is consistent with the finding of Schill et al. (2021) that P. eryngii is at a low level of contamination. Among the mushrooms studied, A. bisporus had the highest average microbial load (3.35 log10 CFU/g). Yeasts/molds had the highest contamination level (4.41 log10 CFU/g, Gyeonggi-do, open-air market) of all mushrooms, while the average microbial load of coliform bacteria was higher than that of P. eryngii (1.46 log10 CFU/g), but the highest contamination level was the lowest among the four mushrooms (2.95 log10 CFU/g, Busan Gwangyeoksi, farm supply). Eight samples showed no detectable coliform bacteria. Mesophilic (3.88 log10 CFU/g) and psychrophilic (4.25 log10 CFU/g) bacteria were the second highest in terms of average contamination level, and the majority of these samples originated from farm supply deliveries. Eight out of 25 samples had microbial loads below 4 log10 CFU/g.

Qualitative microbial risk assessments

Studies on the presence of potentially pathogenic bacteria are summarized in Table 2. 32 samples were positive for Listeria spp. in selective agar, a bacterium found in F. velutipes (50%) and P. ostreatus (14%). Finally, similar electrophoretic results for Listeria spp. were detected in only five samples from the F. velutipes (Fig. 2), with a low incidence. The distribution was Gyeongsangbuk-do, 2; Jeollanam-do, 3. Derived from all sales channels except hypermarkets. The five strains isolated from F. velutipes were subjected to a DNA homogeneity test using 16S rRNA sequencing. All PCR-positive samples showed high homogeneity with L. inocua strain ATCC 33090, ranging from 97 to 98%. Consequently, all samples tested negative for L. monocytogenes (Table 2).

Table 2.

Numbers of positive samples for Listeria monocytogenes contamination of raw mushrooms

Mushrooms No. of positive samples
SAa PCRa 16Sa
Flammulina velutipes 25/50 5/25 0/5
Pleurotus ostreatus 7/50 0/7 –/–
Pleurotus eryngii 0/50 –/–b –/–
Agaricus bisporus 0/50 –/– –/–
Total 32/200 5/32 0/5
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aSA, isolation methods using selective agar; PCR, identification methods using conventional PCR method; 16S, identification methods using 16S rRNA sequencing method. Numbers of positive sample in conventional PCR method among positive samples in selective agar

bNot tested

Fig. 2.

Fig. 2

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Agarose gel electrophoresis results for the conventional PCR assay of Listeria spp serotypes. Lane S: Ladder, 100 bp; N1–N3: Positive control group (L. monocytogenes ATCC 19111, 19117, and 19114); lane A-FF: Positive isolates and sample numbers; FV: F.velutipes; PO: P.ostreatus; Amplification product size is 719 bp for the hly gene and 446 bp for the inl gene

The objective of this study was to evaluate the microbiological quality of fresh cultivated mushrooms in the Korean retail market. Information on the microbial quality of commercial samples was very limited, and the available information was mainly focused on F. velutipes strains. Mushroom quality is defined by a combination of parameters including whiteness, texture, and microbial counts (Gormley, 1975). Beelman et al. (1989) found that the presence of high bacterial populations in fresh mushrooms is a major factor that significantly reduces quality by causing a brown, spotted appearance, and that the rate of postharvest deterioration of fresh mushrooms is directly related to the initial microbial load. These authors also reported that deterioration of mushroom quality, as indicated by maturity and color measurements, appeared to be associated with increases in bacterial counts (Soler-Rivas et al., 1999; Wong et al., 1982). The microbial load of the mushroom species examined in this study was characterized by aerobic genera. Psychrophilic aerobic bacteria were present in all samples. Those exceeding 5 log counts accounted for 33% of all samples. Coliform were also present in all mushrooms, but the prevalence was low, and the average microbial load was low (~ 2 log10 CFU/g). The highest microbial load was detected in F. velutipes (~ 4 log10 CFU/g) and was not detected in 72% of the P. eryngii samples.

The qualitative analysis of F. velutipes samples revealed that 50% of them were positive for Listeria spp., but none of them had L. monocytogenes. Similarly, a Spanish study failed to isolate L. monocytogenes and Salmonella spp. in cultivated mushrooms (Venturini et al., 2011). However, in P. ostreatus, P. eryngii, and Lentinus edodes sold in Chinese markets, L. monocytogenes was found in 6.7%, 4.4%, and 2.9% of the samples, respectively. The contamination rate of L. monocytogenes was higher in F. velutipes samples (55.50%) than in other edible mushroom types, and 36.21% of the positive F. velutipes samples had contamination levels above 110 MPN/g. Therefore, F. velutipes should be considered a potential source of L. monocytogenes transmission (Chen et al., 2018). Recent studies reported incidences of L. monocytogenes in processed mushrooms of 0.8% and 50.0% (Willis et al., 2020; Zhang et al., 2020). Chen et al. (2014) found that mycelium scraping machines' surfaces may be the primary source of L. monocytogenes contamination in F. velutipes plants. Besides, the harvesting room of F. velutipes products was also contaminated with L. monocytogenes (Murugesan et al., 2015). Increasing evidence suggests that L. monocytogenes results from contamination during processing. Some studies have suggested that contamination of mushrooms with L. monocytogenes may occur during production and processing. Chen et al. (2014) sampled four F. velutipes factories and found that the rate of L. monocytogenes contamination in 295 samples was approximately 18.6%. The contamination appeared to originate from mycelium scraping machines. The survey of four P. eryngii factories found a 14.3% rate of positive L. monocytogenes contamination in 203 samples. The main stages of contamination were identified as composting, harvesting, and processing, according to Xu et al. (2023). Therefore, it is crucial to formulate a thorough standard operating protocol for the sanitation of production machinery and associated environments to ensure the microbiological safety of mushroom products. Additionally, Chen et al. (2018) reported that the pathogen has multiple stress adaptations and that 53.89% of the isolates were multi-drug resistant, although more than 90% of them were susceptible to 16 antibiotics. These findings emphasize the need to continuously monitor Listeria spp. contamination in edible mushroom. Therefore, it is crucial to develop a comprehensive standard operating procedure for sanitizing production machinery and related environments to guarantee the microbiological safety of mushroom products. For example, using high-temperature steam to disinfect and clean the floors in mushroom growing rooms can effectively reduce the risk of cross-contamination with L. monocytogenes (Pennone et al., 2020). Measures should be taken in the processing room to prevent cross-contamination by Listeria spp. Sanitizing footbaths should also be installed at entrance doors. Floors should be cleaned regularly to remove any spilled substrate and casing debris (Prema et al., 2013). Currently, the most common methods for controlling microorganisms during sterilization and cold circulation are traditional high-temperature disinfection, disinfectant cleaning protocols, and innovative protocols. Chemical and physical methods can effectively reduce microorganisms and maintain bacteriostatic effects during storage. However, excessive usage can also impact the characteristics and nutritional value of food. Therefore, future research should focus on optimizing the duration and concentration of the treatment. On the other hand, mushrooms have the potential to host a diverse range of microbial communities that can effectively inhibit the growth of foodborne pathogens through competition (Tajalipour et al., 2014). Therefore, it is possible to utilize beneficial microorganisms isolated from mushrooms as bio-controls. However, this idea requires further discussion. Furthermore, it is believed that implementing systematic safety regulations will be necessary to establish specific standards for mushroom production in Korea.

The study focused on the quality of fresh mushrooms at the retail level, and it found that most mushrooms tested on the day of purchase had high microbiological quality, especially F. velutipes and A. bisporus. However, in order to ensure the microbiological safety of mushrooms, it is necessary to continuously monitor the level of Listeria spp. contamination in edible mushrooms and investigate effective control methods. This includes evaluating the effectiveness of different steps in the processing chain and packaging systems to prevent microbial growth. These measures are important to ensure the microbiological safety of edible mushrooms.

Acknowledgements

This research was supported by grants (22192MFDS024) from the Ministry of Food and Drug Safety, South Korea, and the Chung-Ang University Graduate Research Scholarship in 2023.

Declarations

Conflict of interest

The authors declare no conflicts of interest.

Footnotes

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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