Category Archives: Food Microbiology Research

Research – Cooked rice safety: A review of status and potential of radiative pasteurization

Wiley Online

Abstract

Microbial contamination in cooked rice-based foods poses a global concern due to rice’s widespread consumption. This review aims to consolidate information on harmful microorganisms associated with such foods from various countries and their adverse effects on consumers. Additionally, it explores the reported causes of microbial contamination in cooked rice-based dishes and proposes an intervention strategy for safer consumption. The findings highlight that ready-to-eat cooked rice-based foods may harbor unsafe levels of microorganisms like Bacillus cereus, Staphylococcus aureus, and Aspergillus spp. A recommended solution is the application of microwave pasteurization. This method involves cooking rice in pasteurized packaging, minimizing human contact, and effectively controlling harmful microorganisms. Microwave pasteurization emerges as a promising approach to ensure the safe consumption of cooked rice-based foods by reducing microbial contamination levels.

Research – Microbacterium represents an emerging microorganism of concern in microfiltered extended shelf-life milk products

Journal of Dairy Science

Growing interest in the manufacture of extended shelf-life (ESL) milk, which is typically achieved by a high temperature treatment called ultra-pasteurization (UP), is driven by distribution challenges, efforts to reduce food waste, and more. Even though high temperature, short time (HTST) pasteurized milk has a substantially shorter shelf-life than UP milk, HTST milk is preferred in the United States because consumers tend to perceive UP milk as less desirable due to the “cooked” flavor associated with high-temperature processing. While ESL beyond 21 d may be possible for HTST, the survival and outgrowth of psychrotolerant aerobic spore-forming bacteria can still be a limitation to extending shelf-life of HTST milk. Microfiltration (MF) is effective for reducing vegetative microorganisms and spores in raw milk, but it is unclear what the effects of membrane pore size, storage temperature, and milk type (i.e., skim vs whole) are on the microbial shelf-life of milk processed by both MF and HTST pasteurization. To investigate these factors, raw skim milk was MF using different pore sizes (0.8 μm or 1.2 μm), and then MF skim milk and standardized whole milk [MF skim with heat-treated (85°C for 20 s) cream] were HTST pasteurized at 75°C for 20 s. Subsequently, milk was stored at 3, 6.5, or 10°C and total bacteria counts were measured for up to 63 d. An ANOVA indicated that mean bacterial concentrations between storage temperatures were significantly different from each other, with mean maximum observed concentrations of 3.67, 5.33, and 8.08 log10 cfu/mL for storage temperatures 3, 6.5, and 10°C, respectively. Additionally, a smaller difference in mean maximum bacterial concentrations throughout shelf-life was identified between pore sizes (<1 log cfu/mL), but no significant difference was attributed to milk type. An unexpected outcome of this study was the identification of Microbacterium as a major contributor to the bacterial population in MF ESL milk. Microbacterium is a psychrotolerant, thermoduric gram-positive, non-spore forming rod with a small cell size (∼0.9 μm length and ∼0.3 μm width), which was able to permeate the membranes used in this study, survive HTST pasteurization, and then grow at refrigeration temperatures. While spores continue to be a key concern for the manufacture of MF, ESL milk, our study demonstrates the importance of other psychrotolerant, thermoduric bacteria such as Microbacterium to these products.

Research – Emergence of Novel Type C Botulism Strain in Household Outbreak, Japan

CDC

kswfoodworld

In 2021, an outbreak of food poisoning caused by Clostridium botulinum type C occurred in Kumamoto, Japan. Analysis of the isolated strain revealed that it possessed the bont/C gene and was slightly different from the reference bont/C gene. The risk for human infection with this new toxin type may be low

Research – Evaluation of low-energy x-rays as an alternative to chlorine washing to control internalized foodborne pathogens in lettuce

Wiley Online

Abstract

Low-energy X-rays can be used to reduce the number of pathogenic microorganisms in fresh produce, but the efficacy of this process against internalized bacteria in leafy greens has not yet been reported. The leaves of iceberg lettuce were cut into pieces and subjected to vacuum perfusion to force the foodborne pathogen cells into the intercellular spaces within the leaves. Sodium hypochlorite (200–400 ppm) washes were not effective in inactivating internalized bacterial cells from lettuce leaves. In contrast, treatment with 1.5 kGy low-energy X-rays reduced Escherichia coli O157: H7, Salmonella enterica Serovar Typhimurium, and Listeria monocytogenes levels by 6.89, 4.48, and 3.22 log CFU/g, respectively. Additionally, the maximum dose of X-rays did not adversely affect the color or texture of lettuce. These results suggest that low-energy X-ray treatment can be used to control internalized and surface-adhering pathogens in leafy vegetables without affecting product quality.

Research – Sporadic Shiga Toxin–Producing Escherichia coli–Associated Pediatric Hemolytic Uremic Syndrome, France, 2012–2021

CDC

Abstract

Shiga toxin–producing Escherichia coli–associated pediatric hemolytic uremic syndrome (STEC-HUS) remains an important public health risk in France. Cases are primarily sporadic, and geographic heterogeneity has been observed in crude incidence rates. We conducted a retrospective study of 1,255 sporadic pediatric STEC-HUS cases reported during 2012–2021 to describe spatiotemporal dynamics and geographic patterns of higher STEC-HUS risk. Annual case notifications ranged from 109 to 163. Most cases (n = 780 [62%]) were in children ❤ years of age. STEC serogroups O26, O80, and O157 accounted for 78% (559/717) of cases with serogroup data. We identified 13 significant space-time clusters and 3 major geographic zones of interest; areas of southeastern France were included in >5 annual space-time clusters. The results of this study have numerous implications for outbreak detection and investigation and research perspectives to improve knowledge of environmental risk factors associated with geographic disparities in STEC-HUS in France.

Research – Listeria monocytogenes: a surprisingly adaptive bacterium

ANSES

Listeria monocytogenes is a ubiquitous bacterium found in food, livestock and wild animals, soil, water and vegetation. The European ListAdapt project focused on the ability of strains of this bacterium to adapt to these different environments. It found that this ability is independent of the strains’ environments of origin or their belonging to a given sub-group.

Research -Two successive outbreaks of acute gastroenteritis due to Norovirus GII.6 in a holiday camp house

Nature

Food Borne Illness - Norovirus -CDC Photo

When two outbreaks occur in the same institution within a short period of time, an important health and social concern is generated. Two gastroenteritis outbreaks occurring a week apart in the same facility were reported in Lleida, Spain, in 2018. The objective of this study was to describe the clinical, epidemiological and microbiological investigation carried out and to determine the risk factors. Demographic data, food consumption and symptoms were collected. Health inspections of the facility were carried out. Risk ratio and their 95% confidence intervals were estimated for the implication of each food consumed. The attack rate was 89.7% in the first outbreak and 69.6% in the second outbreak. The most frequent symptoms in the first and second outbreak were abdominal pain (88.5% and 100%, respectively), vomiting (80.8% and 87.5%, respectively) and nausea (69.2% and 81.3%, respectively). The first outbreak was associated with the consumption of a salad and the second with a cheese omelet. Norovirus GII.6 was detected by RT-PCR and sequenced in both groups of students and in the food handlers who prepared the meals. These results highlight the importance of exclusion from work of food handlers with gastroenteritis, the adequate availability of mechanisms for correct hand washing and the correct cleaning of surfaces.

Research – Study shows outbreaks increasing in Switzerland

Food Safety News

Researchers have highlighted increased foodborne outbreaks in Switzerland in the past 15 years.

Foodborne outbreaks in the country are identified by cantonal authorities and reported to the Federal Food Safety and Veterinary Office (FSVO). Between 2007 and 2021, 200 outbreaks were recorded. The highest amount during the study period was in 2021, and the lowest was in 2012.

At least 4,668 people fell ill, 303 were hospitalized, and 18 died. The top pathogens detected were Salmonella, Campylobacter, norovirus, and coagulase-positive staphylococci. Other incidents were caused by Scombroid poisoning, Bacillus, Listeria, and Clostridium perfringens.

Outbreaks took place in restaurants, canteens and catering sites, private households, kindergartens and schools, and takeaway establishments, according to the study published in the Journal of Consumer Protection and Food Safety.

Food items reported concerning outbreaks included mixed products (such as composite meals), fish and fish products, milk and milk products, and meat and meat products.

Research – Detection and Control of Foodborne Pathogens

MDPI

The globalization of food trade and the emergence of disease outbreaks involving several foodborne pathogens and foods has focused the attention of both the research community and consumers on food safety. Microbial contamination can involve different stages of food processing and distribution, with a potentially dramatic impact on human health and food business. Several methods, involving culture-dependent and -independent techniques, were developed to detect foodborne pathogens in the food supply chain. In this respect, gold-standard reference methods are currently available for most pathogens, but some of them are time-consuming and expensive. Moreover, routine controls carried out by manufacturers and food safety authorities are normally focused on bacteria and not on viruses and fungi, which can have a significant impact on food safety. In the European Union, the number of human cases caused by Noroviruses and other Caliciviruses increased sharply in 2021 [1]. Therefore, based on the evidence given by an increasing amount of research, control strategies show a clear trend towards molecular techniques, such as polymerase chain reaction (PCR), multiplex PCR, real-time PCR (qPCR), reverse transcriptase PCR (RT-PCR), DNA microarrays, nucleic acid sequence-based amplification (NASBA), isothermal DNA amplification techniques, and next-generation sequencing (NGS) [2]. Moreover, to expand the knowledge on the behaviour of pathogens in food environments, proteome profiling and biosensors shed light on how these microorganisms interact and prevail in food systems [3].

Research – Natural Antimicrobial Agents Utilized in Food Preservation

MDPI

Since the initial transformation of food surpluses, improving food quality and safety are of principal importance to human health. Due to the mass production (eggs, poultry, meat, grains, and pulses) of huge quantities of food, as well as storage and transport, food technologists are faced with challenges of contamination, undesirable microbial growth, the production of toxins, or the deterioration of food (food spoilage). Different food preserving methods (drying, smoking, etc.) have been developed throughout human history to increase the storage time of perishable raw materials or improve diets. For a long time, chemical preservatives used in the prevention of food spoilage or foodborne diseases were considered convenient for consumer protection. Effective in small concentrations and maintaining the sensory properties of food, as well as exhibiting stability at different temperatures or pH values, made their application in the prevention of food spoilage highly applicable. Indeed, they reduce food losses, increase quality, extend shelf life, and enable the development of new formulations as well as food stabilization and standardization [1]. Although consumers still demand safe, fresh-like (minimally processed), nutritionally highly valuable, high-quality foods, attitudes towards chemical conservatives have changed in contemporary nutrition. The continuous intake of chemicals during our (increasingly long-lived) lifetime and the documented adverse activity have changed consumer perceptions and attitudes towards synthetic preservatives in food technology [2]. More natural food production or the application of natural compounds in maintaining food safety have become highly desirable for many consumers in developed countries. Bio-preservatives, naturally occurring compounds from plants, animals, or microorganisms, can be successfully used in extending the shelf life of food, the inhibition/elimination of spoilage and pathogenic microorganisms, and the enhancement of food’s functionality and quality. Natural antimicrobials can be used directly in product formulation, incorporated into packaging material, or surface-coated to prevent spoilage processes or pathogen growth [3].
The most important naturally occurring used compounds in the food industry are essential oils, enzymes, and edible coatings.
Essential oils are highly volatile compounds from herbs and spices such as basil, thyme, oregano, cinnamon, clove, and rosemary, and are used to reduce spoilage microorganisms, increase overall food quality, and to inhibit food-borne pathogens such as SalmonellaListeria monocytogenesEscherichia coliBacillus cereus, and Staphylococcus aureus [4]. Essential oils are effective in inhibiting fungal growth as well as mycotoxin synthesis, reducing fungal damage and health risks [5,6]. Although essential oils are mainly used in the food industry as flavorings, by increasing knowledge of their modes of action and interactions with food matrix components, they can be successfully used in reducing targeted microbes.
Enzymes from animal sources such as lyzozime, lactoferrin, and bacteriocins (natamycin, nisin, pediocin, and reuterin) from bacteria are used in small concentrations in a similar way to prolong shelf life and inhibit pathogen proliferation [7].
Edible coatings, thin layers of naturally occurring polymers, with or without the addition of essential oils or enzymes, used for food coating reduce moisture loss, reduce microbial contamination, and minimize the impact of packaging materials on the environment [8].
Many natural compounds are promising for replacing synthetic food additives while improving overall quality and safety. Through cooperation, food scientists and food technologists can help meet consumer needs for safe and nutritionally valuable food without the adverse effect of synthetic preservatives.
This Special Issue aims to publish quality articles on natural antimicrobials in food preservation, their activity towards pathogens and contaminants, and novel formulations or applications in the production of safe and healthy foods.

Author Contributions

Conceptualization, S.K.-T. and H.P.; writing—original draft preparation, H.P.; writing—review and editing, S.K.-T.; supervision, S.K.-T. All authors have read and agreed to the published version of the manuscript.