Spoilage of vacuum-packed beef by the yeast Kazachstania psychrophila

The Emergence of N. sativa L. as a Green Antifungal Agent

BACKGROUND

Nigella sativa L. has been widely used in the Unani, Ayurveda, Chinese, and Arabic medicine systems and has a long history of medicinal and folk uses. Several phytoconstituents of the plant are reported to have excellent therapeutic properties. In-vitro and in-vivo studies have revealed that seed oil and thymoquinone have excellent inhibitory efficacy on a wide range of both pathogenic and non-pathogenic fungi.

OBJECTIVE

The present review aims to undertake a comprehensive and systematic evaluation of the antifungal effects of different phytochemical constituents of black cumin.

METHOD

An exhaustive database retrieval was conducted on PubMed, Scopus, ISI Web of Science, SciFinder, Google Scholar, and CABI to collect scientific information about the antifungal activity of N. sativa L. with 1990 to 2023 as a reference range using 'Nigella sativa,' 'Nigella oil,' 'antifungal uses,' 'dermatophytic fungi,' 'candidiasis,' 'anti-aflatoxin,' 'anti-biofilm' and 'biological activity' as the keywords.

RESULTS

Black cumin seeds, as well as the extract of aerial parts, were found to exhibit strong antifungal activity against a wide range of fungi. Among the active compounds, thymoquinone exhibited the most potent antifungal effect. Several recent studies proved that black cumin inhibits biofilm formation and growth.

CONCLUSION

The review provides an in-depth analysis of the antifungal activity of black cumin. This work emphasizes the need to expand studies on this plant to exploit its antifungal properties for biomedical applications.

Storage and Packaging Effects on the Protein Oxidative Stability, Functional and Digestion Characteristics of Yak Rumen Smooth Muscle

The objective of this study was to investigate the effects on protein oxidative stability, functional and digestion characteristics of yak rumen smooth muscle with overwrap packaging using oxygen-permeable film (OWP) and vacuum packaging bag (VP) during storage (0, 7, 14, 28, 42, 56, 84, 168 and 364 days) at −18 °C. The results show that yak rumen smooth muscle was oxidized with frozen storage through the formation of protein carbonyls and disulfide bonds, the loss of total sulfhydryl. The emulsifying activity of yak rumen smooth muscle protein (SMP) under VP began to perform a higher level than that under OWP after 14 days, and the foaming capacity under VP showed the highest level on the 28th day of 111.23%. The turbidity under VP reached the minimum 0.356 on the 28th day as well, followed by significantly increasing on the 56th day compared with OWP. The digestibility of yak rumen SMP under both OWP and VP reached the maximum on the 28th day of frozen storage. Moreover, yak rumen under VP at 28–56 days of frozen storage had good functional properties and high digestibility of SMP, which showed better edible value.

Rapid and multiplexed quantification of Salmonella, Escherichia coli O157:H7, and Shigella flexneri in ground beef using flow cytometry

Salmonella, Escherichia coli O157:H7 (E. coli O157:H7) and Shigella flexneri (S. flexneri) might contaminate similar types of meat products and cause deadly diseases in humans. In reality, ground beef samples may carry more than one pathogen and a rapid and accurate detection method for the simultaneous identification of multiple specific pathogenic strains in ground beef is crucial. In this study, a sample pretreatment protocol and a flow cytometry method were developed for rapid and multiplexed quantification of the three pathogens without cultural enrichment in ground beef. The whole process of sample pretreatment, staining, and instrument analysis can be accomplished within 1 h. The three bacteria upon sample pretreatment were demonstrated good recoveries (93.8%-101.2%). The quantitative detection range of the mothed was 10³ to 10⁸ cells/g for all three pathogens, and the detection limit for Salmonella, E. coli O157:H7 and S. flexneri in ground beef were 3.1 × 10³ cells/g, 2.1 × 10³ cells/g and 2.3 × 10³ cells/g, respectively. Therefore, the as-developed approach is a rapid and quantitative method for multiplexed detection of Salmonella, E. coli O157:H7, and S. flexneri in ground beef.

OUP accepted manuscript

Recent studies have suggested that species of the Kazachstania genus may be interesting models of yeast domestication. Among these, Kazachstania barnettii has been isolated from various microbially transformed foodstuffs such as sourdough bread and kefir. In the present work, we sequence, assemble, and annotate the complete genomes of two K. barnettii strains: CLIB 433, being one of the two reference strains for K. barnettii that was isolated as a spoilage organism in soft drink, and CLIB 1767, recently isolated from artisan bread-making sourdough. Both assemblies are of high quality with N50 statistics greater than 1.3 Mb and BUSCO score greater than 99%. An extensive comparison of the two obtained genomes revealed very few differences between the two K. barnettii strains, considering both genome structure and gene content. The proposed genome assemblies will constitute valuable references for future comparative genomic, population genomic, or transcriptomic studies of the K. barnettii species.

Dynamics of microbiota in Japanese Black beef stored for a long time under chilled conditions

In this study, changes in the microbiota of Japanese Black beef carcasses, which are expected to be transported for a long time in chilled temperatures, were investigated. Three Japanese Black beef samples (carcasses A, B, and C) immediately after slaughter were stored at 0 °C for 15 weeks under aerobic and vacuum conditions. The initial bacterial counts were 50 CFU/g for carcass A and less than the reliable quantitative detection limit for carcasses B and C. Under aerobic storage conditions, the bacterial count increased to 8.0 log CFU/g or higher, which is a measure of putrefaction, at 6-9 weeks. Under anaerobic storage conditions, the bacterial counts of carcasses A and C reached 3.5-6.5 log CFU/g, but carcass B showed no bacterial growth during the 15-week storage period. The predominant group was Pseudomonas spp. under aerobic conditions and Serratia spp. under anaerobic conditions. To the best of our knowledge, there is no previous study investigating the transition of microbiota when Japanese Black beef is stored at low temperatures for a long period of time, and the results of this study are considered very important findings for the expansion of international trade of Japanese Beef in the future.

Understanding spoilage microbial community and spoilage mechanisms in foods of animal origin

The increasing global population has resulted in increased demand for food. Goods quality and safe food is required for healthy living. However, food spoilage has resulted in food insecurity in different regions of the world. Spoilage of food occurs when the quality of food deteriorates from its original organoleptic properties observed at the time of processing. Food spoilage results in huge economic losses to both producers (farmers) and consumers. Factors such as storage temperature, pH, water availability, presence of spoilage microorganisms including bacteria and fungi, initial microbial load (total viable count-TVC), and processing influence the rate of food spoilage. This article reviews the spoilage microbiota and spoilage mechanisms in meat and dairy products and seafood. Understanding food spoilage mechanisms will assist in the development of robust technologies for the prevention of food spoilage and waste.

Mrakia fibulata sp. nov., a psychrotolerant yeast from temperate and cold habitats

Tree fluxes are sugar-rich, sometimes ephemeral, substrates occurring on sites where tree sap (xylem or phloem) is leaking through damages of tree bark. Tree sap infested with microorganisms has been the source of isolation of many species, including the biotechnologically relevant carotenoid yeast Phaffia rhodozyma. Tree fluxes recently sampled in Germany yielded 19 species, including several psychrophilic yeasts of the genus Mrakia. Four strains from tree fluxes represented a potential novel Mrakia species previously known from two isolates from superficial glacial melting water of Calderone Glacier (Italy). The Italian isolates, originally identified as Mrakia aquatica, and two strains from Germany did not show any sexual structures. But another culture collected in Germany produced clamped hyphae with teliospores. A detailed examination of the five isolates (three from Germany and two from Italy) proved them to be a novel yeast species, which is described in this manuscript as Mrakia fibulata sp. nov. (MB 830398), holotype DSM 103931 and isotype DBVPG 8059. In contrast to other sexually reproducing Mrakia species, M. fibulata produces true hyphae with clamp connections. Also, this is the first psychrotolerant Mrakia species which grows above 20 °C. Spring tree fluxes are widespread and can be recognized and sampled by amateurs in a Citizen Science project. This substrate is a prominent source of yeasts, and may harbor unknown species, as demonstrated in the present work. The description of Mrakia fibulata is dedicated to our volunteer helpers and amateurs, like Anna Yurkova (9-years-old daughter of Andrey Yurkov), who collected the sample which yielded the type strain of this species.

Spoilage yeasts: What are the sources of contamination of foods and beverages?

Foods and beverages are nutrient-rich ecosystems in which most microorganisms are able to grow. Moreover, several factors, such as physicochemical characteristics, storage temperature, culinary practices, and application of technologies for storage, also define the microbial population of foods and beverages. The yeast population has been well-characterised in fresh and processed fruit and vegetables, dairy products, dry-cured meat products, and beverages, among others. Some species are agents of alteration in different foods and beverages. Since the most comprehensive studies of spoilage yeasts have been performed in the winemaking process, hence, these studies form the thread of the discussion in this review. The natural yeast populations in raw ingredients and environmental contamination in the manufacturing facilities are the main modes by which food contamination occurs. After contamination, yeasts play a significant role in food and beverage spoilage, particularly in the alteration of fermented foods. Several mechanisms contribute to spoilage by yeasts, such as the production of lytic enzymes (lipases, proteases, and cellulases) and gas, utilisation of organic acids, discolouration, and off-flavours. This review addresses the role of yeasts in foods and beverages degradation by considering the modes of contamination and colonisation by yeasts, the yeast population diversity, mechanisms involved, and the analytical techniques for their identification, primarily molecular methods.

Antifungal Microbial Agents for Food Biopreservation-A Review

Food spoilage is a major issue for the food industry, leading to food waste, substantial economic losses for manufacturers and consumers, and a negative impact on brand names. Among causes, fungal contamination can be encountered at various stages of the food chain (e.g., post-harvest, during processing or storage). Fungal development leads to food sensory defects varying from visual deterioration to noticeable odor, flavor, or texture changes but can also have negative health impacts via mycotoxin production by some molds. In order to avoid microbial spoilage and thus extend product shelf life, different treatments—including fungicides and chemical preservatives—are used. In parallel, public authorities encourage the food industry to limit the use of these chemical compounds and develop natural methods for food preservation. This is accompanied by a strong societal demand for ‘clean label’ food products, as consumers are looking for more natural, less severely processed and safer products. In this context, microbial agents corresponding to bioprotective cultures, fermentates, culture-free supernatant or purified molecules, exhibiting antifungal activities represent a growing interest as an alternative to chemical preservation. This review presents the main fungal spoilers encountered in food products, the antifungal microorganisms tested for food bioprotection, and their mechanisms of action. A focus is made in particular on the recent in situ studies and the constraints associated with the use of antifungal microbial agents for food biopreservation.