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Category Archives: Yeasts
Research – Insights into the Bacterial Diversity and Detection of Opportunistic Pathogens in Mexican Chili Powder
Chili powder is the most frequently consumed spice in Mexican diets. Thus, the dissemination of microorganisms associated with chili powder derived from Capsicum annuum L. is significant during microbial quality analysis, with special attention on detection of potential pathogens. The results presented here describe the initial characterization of bacterial community structure in commercial chili powder samples. Our results demonstrate that, within the domain Bacteria, the most abundant family was Bacillaceae, with a relative abundance of 99% in 71.4% of chili powder samples, while 28.6% of samples showed an average relative abundance of 60% for the Enterobacteriaceae family. Bacterial load for aerobic mesophilic bacteria (AMB) ranged from 104 to 106 cfu/g, while for sporulated mesophilic bacteria (SMB), the count ranged from 102 to 105 cfu/g. Bacillus cereus sensu lato (s.l.) was observed at ca. ˂600 cfu/g, while the count for Enterobacteriaceae ranged from 103 to 106 cfu/g, Escherichia coli and Salmonella were not detected. Fungal and yeast counts ranged from 102 to 105 cfu/g. Further analysis of the opportunistic pathogens isolated, such as B. cereus s.l. and Kosakonia cowanii, using antibiotic-resistance profiles and toxinogenic characteristics, revealed the presence of extended-spectrum β-lactamases (ESBLs) and Metallo-β-lactamases (MBLs) in these organisms. These results extend our knowledge of bacterial diversity and the presence of opportunistic pathogens associated with Mexican chili powder and highlight the potential health risks posed by its use through the spread of antibiotic-resistance and the production of various toxins. Our findings may be useful in developing procedures for microbial control during chili powder production. View Full-Text
Research – Microbiological Profile, Prevalence and Characterization of Salmonella enterica in Peanuts, Pecans, Raisins, Sun-dried Tomatoes, and Chocolate Sprinkles Sold in Bulk in Markets of Queretaro, Mexico ￼
In Mexico, the prevalence of Salmonella enterica in low water activity foods and their link to outbreaks is unknown. The aim of this study was to determine the microbiological profile and the prevalence of S. enterica in low water activity foods (peanuts, pecans, raisins, sun-dried tomatoes, and chocolate sprinkles) purchased in retail establishments in Queretaro, Mexico. Seventy samples of each food item sold in bulk were purchased. Aerobic plate count (APC), molds, yeasts, total coliforms, Escherichia coli, and Staphylococcus aureus were quantified in 10-g samples. The prevalence of S. enterica in 25 g samples was determined. From positive samples, S. enterica isolates (60) were characterized based on their antimicrobial susceptibility to 14 antibiotics, the presence/absence of 13 virulence genes and serotype. The concentration of APC, molds, yeast, total coliforms, and E. coli ranged from 3.1-5.2 Log CFU g-1, 2.0-2.4 Log CFU g-1, 2.0-3.0 Log CFU g-1, 0.6-1.1 Log MPN g -1, and 0.5-0.9 Log MPN g -1, respectively. S. aureus was not detected in any sample (<10 CFU g -1). The prevalence of S. enterica in chocolate sprinkles, raisins, peanuts, pecans, and sun-dried tomatoes was 26%, 29%, 31%, 40%, and 52%, respectively. Most isolates (68.3%) were resistant to at least one antibiotic. The chromosome-associated virulence genes were found in all isolates and only one strain had sopE, and 98.3% of the isolates were grouped in the same virulotype. Among the isolates, the most frequent serotype was Tennessee (51/60). According to the characteristics evaluated, the isolates were grouped in 24 clusters. The elevated prevalence of S. enterica highlight the role of low water activity food items sold in bulk at markets as a potential vehicle for pathogens transmission. Regardless of the low variability among S. enterica isolates, their characterization could be helpful to elucidate which strains are circulating in these foods for improving epidemiological surveillance.
Research – Impact of chlorinated water on pathogen inactivation during wheat tempering and resulting flour quality
Outbreaks of enteric pathogens linked to wheat flour have led the wheat milling industry to seek solutions addressing this food safety concern. Chlorinated water at 400-700ppm has been used in the flour milling industry as a tempering aid to control growth of yeast and mold in tempering bins. However, the effectiveness of chlorinated water for inactivating enteric pathogens on wheat kernels remained unknown. Five strains of Shiga-toxin producing Escherichia coli (STEC) and two strains of Salmonella were inoculated onto hard red spring wheat at 7 log CFU/g and stored at room temperature for 1-month. Inoculated wheat was tempered with four concentrations (0, 400, 800, 1200ppm) of chlorinated water (pH 6.5). The reduction due to chlorine was determined by calculating change in cell density at each chlorine level using the response at 0ppm as a reference. Uninoculated wheat tempered with chlorinated water was used to measure flour quality parameters. Changes in pathogen density over 18 hours ranged from -2.35 to -0.30 log CFU/g with 800ppm chlorinated water and were not significantly different from changes at 400ppm and 1200ppm. Significant (p< 0.05) differences in the extent of reduction were observed among strains. However, the effect of chlorinated water at reducing native microbes on wheat kernels was minimal, with an average reduction of 0.39 log CFU/g for all concentrations. No significant (p>0.05) changes occurred in flour quality and gluten functionality, or during breadmaking for grains tempered at 400 and 800ppm chlorinated water. There were small but significant (p<0.05) changes in flour protein content, final viscosity, and water absorption when tempered with 1200ppm chlorinated water. The data showed that the level of chlorinated water currently used in industry for tempering could reduce enteric pathogen numbers by 1.22 log CFU/g for STEC and 2.29 log CFU/g for Salmonella, with no significant effects on flour quality and gluten functionality.
Fresh carrot juice presents nutritional and organoleptic qualities which have to be preserved. However, it is a fast perishable beverage, and its low-acidic pH promotes the development of foodborne pathogens and spoilage microorganisms. This study aims to assess the modification and variability of physicochemical and microbial indicators during storage of carrot juice, and to isolate and select microorganisms to be used as promoters of spoilage to quantify the effect of preservation treatments. To achieve that, 10 batches of carrot Daucus carota cv. Maestro juice were prepared independently, stored up to 14 days at 4 °C and analyzed. Volatile compound composition differed mainly according to the analyzed batch. During storage, an increase of the content of ethanol, ethyl acetate or 2-methoxyphenol, which are produced by different microorganisms, was noticed. Isolation of bacteria revealed Pseudomonas, lactic acid bacteria, and enterobacteria, some of them provoking odor modification of carrot juice at 4 °C. Assays in carrot juice with isolated yeasts and molds showed the ability of Meyerozyma guillermondii to induce texture modification and some isolates, e.g., Pichia guillermondii, resulted in gas production. Selected isolates able to induce spoilage are useful to test preservative treatments of fresh carrot juice under controlled conditions. View Full-Text
For thousands of years, humans have exploited the natural process of fermentation of various foods to preserve them, and to enjoy the changes in the sensory characteristics that could be produced. Recently, the world of fermented beverages has gone through a rapid transformation linked to deep changes in consumer preferences, consumption habits, climate, new regulations and entry of emerging countries, accompanied by safety concerns and an important reduction in economic resources available to people. As with all food handling and preparation, we need to be sure the fermented food produced is safe. Fermentation is a complex biological process where microbial diversity takes place and the environment created inside of the fermented food provides the conditions to reduce the risk of pathogenic bacteria growth, thus providing safe food. In addition, food manufacturers fermenting food carefully control their processing and must comply with the National Food Standards Codes. Although these products have a generally good food safety record, sometimes inadequate manufacturing practices or the presence of acidophilic pathogens could compromise food safety. In fact, fermented beverages may adversely become contaminated with pathogens or microbial toxins and thereby transform into vehicles that can transmit diseases to the consumers. Moreover, many microorganisms can deteriorate the physical-chemical and sensory properties as well as the flavor of the final products. In this editorial, we present an overview of a review and six original research papers published in the Special Issue “Fermentation Process and Microbial Safety of Beverages” of the Beverages journal.
Research – Comparing the effectiveness of Cinnamomum zeylanicum essential oil and two common household sanitizers to reduce lettuce microbiota and prevent Salmonella enterica recontamination
The washing step is necessary to remove biological and physical hazards from minimally processed vegetables. Nevertheless, the risk of foodborne diseases could persist even after washing due to postsanitizing contamination, and little is known about the antimicrobial effect of residual sanitizers. This study was conducted to compare the effectiveness of sodium hypochlorite (SH), sodium bicarbonate, and Cinnamomum zeylanicum essential oil (CEO) as sanitizers on lettuce (8°C, 48 h). First, the effect of sanitizers in reducing total aerobic mesophilic and psychrotrophic bacteria, yeast and molds, lactic acid bacteria, and Enterobacteriaceae on lettuce was evaluated with some insights on lettuce quality attributes (pH, color, and sensory analysis). Then, the capability of the treatments in preventing postwashing Salmonella adhesion on lettuce surface was investigated. Commercial SH disinfectant (solution at 2%) and CEO (0.5%) reduced microbial contamination in lettuce, without affecting the overall acceptability after 48 h at 8°C. SH reduced postsanitizing Salmonella adhesion of about 2.7 Log colony forming unit (CFU)/g. The microbial reduction was confirmed by confocal laser scanning microscopy, which also evidenced Salmonella internalization within stomata. Interestingly, CEO as well reduced Salmonella adhesion but with lower efficacy (0.44–1.00 Log CFU/g reduction), while sodium bicarbonate (15 mg/ml) was not effective. In conclusion, SH and CEO seem to be effective sanitizing agents, capable of improving the microbiological profile of fresh produce. In addition, the residual sanitizers, that remain on lettuce after washing, play a role in reducing Salmonella adhesion.
Microbiology is important to food safety, production, processing, preservation, and storage. Microbes such as bacteria, molds, and yeasts are employed for the foods production and food ingredients such as production of wine, beer, bakery, and dairy products. On the other hand, the growth and contamination of spoilage and pathogenic microorganisms is considered as one of the main causes to loss of foodstuff nowadays. Although technology, hygienic strategies, and traceability are important factors to prevent and delay microbial growth and contamination, food remains susceptible to spoilage and activity of pathogen microorganisms. Food loss by either spoilage or contaminated food affects food industry and consumers leading to economic losses and increased hospitalization costs. This chapter focuses on general aspects, characteristics, and importance of main microorganisms (bacteria, yeasts, molds, virus, and parasites) involved in food spoilage or contamination: known and recently discovered species; defects and alterations in foodstuff; most common food associated with each foodborne disease; resistance to thermal processing; occurrence in different countries; outbreaks; and associated symptoms.
Research – Gaseous chlorine dioxide inactivation of microbial contamination on whole black peppercorns
Black peppercorn is a common ingredient imported and used in uncooked or ready-to-eat foods in the United States. They might be exposed to fecal coliforms and other microbial contamination due to a lack of good agricultural and manufacturing practices in some developing countries under which they were grown and harvested, thus causing economic losses to the peppercorn industry in the United States. We investigated the effect of gaseous chlorine dioxide (ClO2) on reducing the microbial population levels of coliforms, aerobic bacteria, yeasts, and molds on unprocessed black peppercorns. Treatments on peppercorns were conducted in a 30-L airtight chamber, and equal amounts of dry media precursors were used to generate gaseous ClO2. Whole peppercorns (200 g) were exposed to 20, 30, and 40 g of precursor dose for up to 60 min at 21 ± 0.4°C and in combination with mild heat at 40 ± 2°C. Aerobic bacteria, coliforms, yeasts, and molds on peppercorns were enumerated before (7.4, 7.2, and 7.1 log CFU/g, respectively) and after treatments. Results after treatment demonstrated 0.8–1 log10 (90%) reduction for all the microbes post-treatment at 21 ± 0.4°C. The treatments conducted with a 30 g precursor dose for 60 min at 21 ± 0.4°C reduced statistically higher (p < .05) microorganisms than those at 40 ± 2°C. Our work demonstrated that gaseous ClO2 could be used as a part of an overall hurdle technology to reduce the coliforms, aerobes, yeasts, and molds on black peppercorns without affecting the visual quality.
Germany – Various delicatessen salads from the HOMANN, Gut & Favorable and K-Classic brands – Yeasts
Warning type: Food
Date of first publication: 11/09/2021
Various delicatessen salads from the HOMANN, Gut & Favorable and K-Classic brands Please refer to the attached press release for the products concerned with the best-before dates (best before date) and the batch codes.
Homann Feinkost GmbH
Homann Feinkost GmbH
EDEKA ZENTRALE AG & Co. KG
EDEKA ZENTRALE AG & Co. KG
Hamker Vertriebsgesellschaft mbH
Manufacturer for all products: HOMANN Feinkost GmbH Bahnhofstr. 4 49201 Dissen Distributor: HOMANN Feinkost GmbH, Bahnhofstr. 4, 49201 Dissen Hamker Vertriebsgesellschaft mbH, Bahnhofstr. 4, 49201 Dissen Sales by EDEKA ZENTRALE AG & Co. KG, New-York-Ring 6 in 222917 Hamburg
Reason for warning:
Occasional occurrence of yeasts, which can lead to premature spoilage and deviations in odor
Production date: 10/13/2021 to 10/19/2021
Only the above-mentioned products from HOMANN, K-Classic and Gut & Favorable with the specified best-before dates (best before dates) and the specified batch identification are affected.
As a preventive consumer protection measure, the Homann Feinkost GmbH reacts with the immediate recall of the affected products. As a precaution, do not consume the products listed above with the specified best-before dates and the specified batch. Reference is made to the company’s customer information sheet attached.
Homepage of the manufacturer:
Germany – Berg Quellen Apfelschorle returnable glass bottle 0.7 l “with the best before date 06/23/22, Berg Quellen Iso Sport Pink Grape returnable glass bottle 0.7 l with the best before 06/18/22 and Berg Quellen Iso Sport Grape lemon returnable glass bottle 0.7 l” with the best before 06/18/22 -Secondary Fermentation
Warning type: Food
Date of first publication: 10/27/2021
Berg Quellen Apfelschorle returnable glass bottle 0.7 l “with the best before date 06/23/22, Berg Quellen Iso Sport Pink Grape returnable glass bottle 0.7 l with the best before 06/18/22 and Berg Quellen Iso Sport Grape lemon returnable glass bottle 0.7 l” with the best before 06/18/22
Branded drinks Schwollen GmbH
Reason for warning:
As part of quality assurance, it was found that individual bottles undergo fermentation, which can lead to alcohol formation and the bottles to burst.