Staphylococcus aureus and Zygosaccharomyces bailii as primary microbial contaminants of a spoiled herbal food supplement and evaluation of their survival during shelf life

Sea hedgehog-inspired surface-enhanced Raman scattering biosensor probe for ultrasensitive determination of Staphylococcus aureus in food supplements

Staphylococcus aureus contamination in food supplements poses substantial challenges to public health and large-scale production but the sensitive detection in a timely manner remains a bottleneck. Drawing inspiration from the sea hedgehog, gold nanostars (AuNSs) were leveraged to design an ultrasensitive surface-enhanced Raman scattering (SERS) biosensor for the determination of Staphylococcus aureus in food supplements. Besides the surface enhancement furnished by the AuNSs, Raman reporter molecules and specific aptamers sequentially self-assembled onto these AuNSs to construct the "three-in-one" SERS biosensor probe for label-based quantitation of Staphylococcus aureus. Following incubation with contaminated health product samples, the gold nanostars@Raman reporter-aptamer specifically recognize and assemble around Staphylococcus aureus cells, forming a distinctive sea hedgehog structure. This unique configuration results in an amplified Raman signal at 1338 cm-1 and an enhancement factor of up to 6.71 × 107. The entire quantitative detection process can be completed within 30 min, boasting an exceptional limit of detection as low as 1.0 CFU mL-1. The method exhibits a broad working range for the determination of Staphylococcus aureus, with concentrations spanning 2.15 CFU mL-1 to 2.15 × 105 CFU mL-1. Furthermore, it demonstrates outstanding precision, with relative standard deviation values consistently below 5.0%. As a showcase to validate the practicality of the SERS method, we conducted tests on determining Staphylococcus aureus in a herbal food supplement, i.e., Ginkgo Biloba extract (GBE); the results align closely with those obtained through the conventional lysogeny broth agar plate method, pointing to the potential applicability in real-world scenarios.

Zygosaccharomyces rouxii is the predominant species responsible for the spoilage of the mix base for ice cream and ethanol is the best inhibitor tested

A mix base for ice cream (MBIC) is used to produce artisanal or industrial ice creams and desserts and consists of a mixture of different ingredients, including sugar, egg yolk, natural flavors, starch and milk proteins. MBICs, which have chemical-physical characteristics that include a pH of 5.61 and an activity water (A_w) less than or equal to 0.822, are packaged in tin boxes and stored at ambient temperature. Despite the low A_w, MBIC can support osmotolerant and osmophilic yeast growth. The aim of our work was to study the behavior of Zygosaccharomyces rouxii, the main microorganisms responsible of MBIC spoilage, either in the vivo or in a model system in order to inhibit its growth by the selection of antimicrobial agents. Different osmotolerant yeasts belonging to the genus Zygosaccharomyces were isolated and identified from spoiled and unspoiled lots of MBICs. In particular, Z. rouxii was the predominant species responsible for the spoilage, which depended on the high temperature of storage (>20 °C) and was highlighted by the presence of alcohol, esters, acids and gas (CO₂), which blew open the tin boxes. To stop spoilage, different antimicrobial compounds were tested: sulfur dioxide, sorbic and benzoic acids and ethanol. However, only 2% v/v ethanol was required to achieve the total inhibition of the Z. rouxii cocktails tested in this work. The use of other antimicrobials cannot be recommended because they were not able to stop yeast spoilage and changed the color and flavor of the products. Conversely, the use of ethanol is suggested because of its extreme effectiveness against osmotolerant yeasts, and the added amount was less than or equal to the taste threshold limit. The MBICs, treated with ethanol, were stable till the end of their shelf-life (6 months).

Detection of microbiota in the vineyards of the Tokaj wine region

Tokaj is an important Central European wine-growing area with controlled planting and authorized varieties of white vines. This area has a specific microflora composition which changes based on its climate dependence, as well as during the fermentation process of wine production. Therefore, the aim of this study was, by culture examination of the samples, to detect the microbiota of soil, leaves, berries and fermentation must from two vineyards from the Slovak part of Tokaj. The highest total viable count (5.60 ±0.01 log cfu.g-1) and the highest total yeast and mould count (4.32 ±0.01 log cfu.g-1) in soil samples were recorded in vineyard Berecký. The highest total viable count in soil samples (6.71 ±0.01 log cfu.g-1) was confirmed by examination of samples originating from the vineyard of Čierna Hora. When determining the total yeast and mould count, the highest numbers were recorded in the must samples (4.15 ±0.01 log cfu.mL-1). Lactic acid bacteria were collected in samples from both vineyards, only in very low numbers. Overall, statistically significant differences (p <0.001) were detected by comparing the microbiota of the samples taken from the Berecký and Čierna Hora vineyards. The specific characterisation and identification of yeast was carried out using ITS-PCR-RFLP methods. The analysis confirmed the presence of yeasts of Saccharomyces cerevisiae, Zygosaccharomyces bailii, Zygosaccharomyces rouxii, Candida parapsilosis and Candida tenuis and their subsequent transfer to the must at varying percentages.

Public health risks related to food safety issues in the food market: a systematic literature review

BACKGROUND

Food safety in the food market is one of the key areas of focus in public health, because it affects people of every age, race, gender, and income level around the world. The local and international food marketing continues to have significant impacts on food safety and health of the public. Food supply chains now cross multiple national borders which increase the internationalization of health risks. This systematic review of literature was, therefore, conducted to identify common public health risks related to food safety issues in the food market.

METHODS

All published and unpublished quantitative, qualitative, and mixed method studies were searched from electronic databases using a three step searching. Analytical framework was developed using the PICo (population, phenomena of interest, and context) method. The methodological quality of the included studies was assessed using mixed methods appraisal tool (MMAT) version 2018. The included full-text articles were qualitatively analyzed using emergent thematic analysis approach to identify key concepts and coded them into related non-mutually exclusive themes. We then synthesized each theme by comparing the discussion and conclusion of the included articles. Emergent themes were identified based on meticulous and systematic reading. Coding and interpreting the data were refined during analysis.

RESULTS

The analysis of 81 full-text articles resulted in seven common public health risks related with food safety in the food market. Microbial contamination of foods, chemical contamination of foods, food adulteration, misuse of food additives, mislabeling, genetically modified foods (GM foods), and outdated foods or foods past their use-by dates were the identified food safety-related public health risks in the food market.

CONCLUSION

This systematic literature review identified common food safety-related public health risks in the food market. The results imply that the local and international food marketing continues to have significant impacts on health of the public. The food market increases internationalization of health risks as the food supply chains cross multiple national borders. Therefore, effective national risk-based food control systems are essential to protect the health and safety of the public. Countries need also assure the safety and quality of their foods entering international trade and ensure that imported foods conform to national requirements.

Diversity of Streptococcus thermophilus in bacteriocin production; inhibitory spectrum and occurrence of thermophilin genes

The bacteriocin-producing Streptococcus thermophilus strains that can dominate in natural dairy ecosystems, may also enhance safety in products obtained from natural cultures. In this study, we sought to identify bacteriocin production and bacteriocin genes in 75 strains of dairy and plant origin. The strains were tested for antimicrobial activity against pathogens or pathogen models, spoiling bacteria, and lactic acid bacteria associated with dairy products. All strains moderately inhibited Staphylococcus aureus P310, none inhibited Listeria innocua LMG 11387(T) or Clostridium tyrobutyricum LMG 1285(T). In addition, 14 were active against one or more indicators in addition to S. aureus P310. Inhibition of other starter bacteria was more common than the inhibition of unwanted microorganisms. The involvement of a proteinaceous compound was ascertained in all cases. Results suggested that the selection of bacteriocinogenic S. thermophilus strains for use in biopreservation must take into account the effects exerted on other lactic acid bacteria. PCR detection of thermophilin genes proved unreliable in predicting antimicrobial activity. For S. thermophilus PRI36 and PRI45, with relevant inhibitory features, the identity of the bacteriocin genes present in the thermophilin 9 cluster was defined, thus revealing novel variants for this genome region.

Advances in the control of wine spoilage by Zygosaccharomyces and Dekkera/Brettanomyces

Understanding the characteristics of yeast spoilage, as well as the available control technologies, is vital to producing consistent, high-quality wine. Zygosaccharomyces bailii contamination may result in refermentation and CO2 production in sweet wines or grape juice concentrate, whereas Brettanomyces bruxellensis spoilage often contributes off-odors and flavors to red wines. Early detection of these yeasts by selective/differential media or genetic methods is important to minimize potential spoilage. More established methods of microbial control include sulfur dioxide, dimethyl dicarbonate, and filtration. Current research is focused on the use of chitosan, pulsed electric fields, low electric current, and ultrasonics as means to protect wine quality.

Quality control of plant food supplements

It is essential to guarantee the safety of unprocessed plants and food supplements if consumers' health is to be protected. Although botanicals and their preparations are regulated at EU level, at least in part, there is still considerable discretion at national level, and Member States may choose to classify a product either as a food supplement or as a drug. Accurate data concerning the finished products and the plant used as the starting point are of major importance if risks and safety are to be properly assessed, but in addition standardized criteria for herbal preparation must be laid down and respected by researchers and manufacturers. Physiologically active as well as potentially toxic constituents need to be identified, and suitable analytical methods for their measurement specified, particularly in view of the increasing incidence of economically motivated adulteration of herbal raw materials and extracts. It remains the duty of food operators to keep up with the scientific literature and to provide sufficient information to enable the adaptation of specifications, sampling schemes and analytical methods to a fast-changing environment.