Category Archives: Yeasts

RASFF Alert – Yeast Growth – Soy Dessert


Bulging packaging of soy dessert due to yeast growth in Germany and Denmark

Research – Microbial Load of Fresh Blueberries Harvested by Different Methods



Currently, more and more growers are transitioning to the use of over-the-row machine harvesters for harvesting fresh market blueberries. This study assessed the microbial load of fresh blueberries harvested by different methods. Samples (n = 336) of ‘Draper’ and ‘Liberty’ northern highbush blueberries, which were harvested using a conventional over-the-row machine harvester, a modified machine harvester prototype, ungloved but sanitized hands, and hands wearing sterile gloves were collected from a blueberry farm near Lynden, WA, in the Pacific Northwest at 9 am, 12 noon, and 3 pm on four different harvest days during the 2019 harvest season. Eight replicates of each sample were collected at each sampling point and evaluated for the populations of total aerobes (TA), total yeasts and molds (YM), and total coliforms (TC), as well as for the incidence of fecal coliforms and enterococci. The harvest method was a significant factor (p < 0.05) influencing the TA and TC counts, the harvest time was a significant factor influencing the YM counts, while the blueberry cultivar was an insignificant (p > 0.05) factor for all three indicator microorganisms. These results suggest that effective harvester cleaning methods should be developed to prevent fresh blueberry contamination by microorganisms. This research will likely benefit blueberry and other fresh fruit producers.

France – 4 waffles – Microbiological Contamination

Gov france

Identification information of the recalled product

  • Product category Feed
  • Product subcategory Cereals and baked goods
  • Product brand name Stephan Pastry
  • Model names or references723: Brussels waffles x 4,280 g in blister pack
  • Identification of products
    GTIN Lot Date
    3533950000617 03823A Date of minimum durability 07/02/2025
  • Packaging Brussels waffles x 4 – 280g in blister pack
  • Marketing start/end date From 02/11/2023 to 02/25/2023
  • Storage temperature Product to be stored at room temperature
  • Further information Break in the cold chain during transport
  • Geographic area of ​​sale Regions: Hauts-de-France
  • Distributors Carrefour – Montsoult logistics warehouse
  • List of points of sale Traceability_Frozen_waffle_Carrefour.pdf

Practical information regarding the recall

  • Reason for recall Break in the cold chain during transport
  • Risks incurred by the consumer Other biological contaminants
    Organoleptic changes
  • Additional description of the risk Bacteriological risk due to the breaking of the cold chain – yeasts, moulds

Research – Increasing the Safety and Storage of Pre-Packed Fresh-Cut Fruits and Vegetables by Supercritical CO2 Process



This work presents a feasibility lab-scale study for a new preservation method to inactivate microorganisms and increase the shelf life of pre-packed fresh-cut products. Experiments were conducted on coriander leaves and fresh-cut carrots and coconut.
The technology used the combination of hydrostatic pressure (<15 MPa), low temperature (≤45 °C), and CO2 modified atmosphere packaging (MAP). The inactivation was achieved for the naturally present microorganisms (total mesophilic bacteria, yeasts and molds, total coliforms) and inoculated E. coli. Yeasts and molds and coliform were under the detection limit in all the treated samples, while mesophiles were strongly reduced, but below the detection limit only in carrots.
Inoculated E. coli strains were completely inactivated (>6.0 log CFU/g) on coconut, while a reduction >4.0 log CFU/g was achieved for carrots and coriander. For all the treated products, the texture was similar to the fresh ones, while a small alteration of colour was detected. Microbiological stability was achieved for up to 14 days for both fresh-cut carrots and coconut.
Overall, the results are promising for the development of a new mild and innovative food preservation technique for fresh food.

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 

Journal of Food Protection

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

Journal of Food Protection

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.

Research – Selection of Microbial Targets for Treatments to Preserve Fresh Carrot Juice


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

Research – Microbial Diversity and Safety in Fermented Beverages


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

Wiley Online

Vegetable Bacteria Danger

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.