Growth Of Spoilage Fungi Research Articles

A novel approach for accelerating smear development on bacterial smear-ripened cheeses reduces ripening time and inhibits the growth of Listeria and other unwanted microorganisms on the rind

Bacterial smear-ripened cheeses are commonly contaminated with fungi and the potentially dangerous pathogen Listeria monocytogenes, which compromises food safety and quality. Here, we present new approach for accelerating smear development on these cheeses, while reducing growth of unwanted microorganisms. We grew the smear microorganism Brevibacterium linens in acid whey (AW) supplemented with a by-product of whey protein hydrolysate production (FCH). B. linens grew to a high cell density (10.27 log 10 CFU/mL), and alkalized the AW-FCH medium. We found that the fermented AW-FCH, with its high pH, rapidly killed L. monocytogenes and yeasts. When culture medium was smeared on the cheese surface, the surface pH was rapidly neutralized, and in just 7 days, the cheeses developed a dense orange color and growth of spoilage fungi was inhibited. Summing up, by growing B. linens to high cell density on low-value dairy byproducts, and applying dense suspensions onto cheeses, we can reduce the time needed for establishing the smear. Added benefits are increased food safety and less spoilage, as quick smear development inhibits growth of unwanted microorganisms on the rind. Preliminary tests at a dairy show that flavor development is comparable to traditional bacterial surface-ripened cheeses with far more complex surface microflora.

Technological, functional and safety properties of lactobacilli isolates from soft wheat sourdough and their potential use as antimould cultures

Bakery products are a common medium for fungal growth due to their high-water activity and nutrients availability. The application of lactic acid bacteria (LAB) isolated from wheat bran or other cereals has shown great potential in controlling the growth of spoilage fungi, guarantee quality and prolong the shelf life of bakery products. This study outlines the antifungal, technological, functional and safety properties of autochthonous LAB microbiota isolated from type 0 soft wheat sourdough fermentation. Antifungal activity of 77 LAB belonging to Lactiplantibacillus plantarum and Lacticaseibacillus casei species isolated from spontaneous sourdough fermentation was tested in vitro against 16 spoilage fungi. Our findings demonstrated that the antifungal activity, enzymatic and safety properties of LAB isolates vary strain-dependently. Four LAB isolates (Lp. plantarum A16, A25, B11, and B15) showed the best traits, in particular strong antifungal activity and good capabilities to produce exopolysaccharides from different carbon sources in vitro. Care should be taken when using Lp. plantarum A310 and B18 and Lc. casei A23, as starter cultures, since these isolates exhibited a multiple antibiotic-resistance. Here we showed the promising potential of different LAB isolates as bio-preservative agents and to provide new insights regarding their prospective use as starter cultures to guarantee safety and palatability.Graphic abstract

Effect of controlled atmosphere, vacuum packaging and different temperatures on the growth of spoilage fungi in shelled pecan nuts during storage

Fungal spoilage significantly affects the quality of pecan nuts in post-harvest. Although several alternatives have been used to avoid this type of food spoilage, studies correlating controlled atmosphere (CA) and its effects on preserving pecan nuts are still scarce in the literature. Therefore, this study aimed to evaluate the use of vacuum and static controlled atmosphere with low oxygen partial pressure (pO2) and high carbon dioxide (pCO2) at different temperatures (1, 10, and 20 °C), for up to 6 months of storage, on the fungal contamination of shelled ‘Barton’ pecan nuts. The samples were mycologically analyzed at the beginning of storage and again at the second, fourth, and sixth month of storage by the direct plating method using dichloran 18% glycerol agar (DG18) with incubation for 7 days at 25 °C. Xerophilic Aspergillus was the leading spoilage agent under conventional storage (20 °C and normal atmosphere) with nuts becoming moldy in up to four months, while the CA ensured the absence and/or low contamination of Aspergillus sp. and Penicillium sp. after 2 months of storage, and Cladosporium sp. up to 4 months of storage at 10 °C. At 20 °C, high pCO2 presented lower contamination than the low pO2 condition. Vacuum packaging ensured that nuts stored at 20 °C maintained lower contamination levels by Aspergillus in all periods analyzed. Potential aflatoxin-producing species were not detected in any of the evaluated conditions.

INHIBITORY EFFECT OF ESSENTIAL OILS FROM SOME LAMIACEAE SPECIES ON GROWTH OF EUROTIUM SPP. ISOLATED FROM BREAD

Bread is considered an intermediate - moisture food product that is prone to mould spoilage. Growth of spoilage fungi is currently controlled with the addition of chemical preservatives. Consumers demand more natural products and there is a need to reduce the amount of chemical preservatives added to foods. Essential oils (EOs) and their constituents emerged as promising and effective compounds to protect foods from lipid peroxidation and provide microbiological food safety. So the aim of our study was to determinate microscopic fungi involved in contamination of bread target the genus Eurotium and to evaluate the antifungal activity of 5 EOs by vapor contact against the fungal species of this genus. In all samples after three days of cultivation fungi created colonies on the surface of the crust and the pieces of the bread samples stored on DRBC were after three days of cultivation covered with fungi colonies. Altogether 195 isolates were recovered from 8 bread samples and assigned to 10 fungal genera. The most frequently genus of fungi was Penicillium, Aspergillus, Cladosporium, Epicoccum and Eurotium. Based on phylogenetic and morphological studies, five different Eurotium species were identified: E. amstelodami, E. chevalieri, E. herbariorum, E. rubrum and E. repens. In this study, we explored the potential of five essential oils retrieved from some Lamiaceae species, concretely: basil (Ocinum basilicum L.), lavender (Lavandula angustifolia Mill.), oregano (Origanum vulgare L.), mint (Metha piperita L.) and sage (Salvia officinalis L.). Gas chromatography–mass spectrometry (GC-MS) analysis allowed for the identification of 28 compounds as main constituents. Inhibitory activity of EOs was assessed against 5 species of genus Eurotium (2 isolates for each specie). In all studied strains, the essential oils caused significant differences (Pbasil (with the best Mycelial growth Inhibition (MGI) 93.65% to E. herbariorum) and the low effect had sage essential oil (with the best MGI 68.62% to E. repens). The present study demonstrated the potential food preservative ability of essential oils from some Lamiaceae species.

Incidence, populations and diversity of fungi from raw materials, final products and air of processing environment of multigrain whole meal bread

This study aimed to assess the incidence, to quantify and to assess the diversity of fungi in a multigrain whole meal bread processing plant. Two hundred and eight one (n=281) samples were analyzed, including raw materials (n=120), air samples (n=136) and multigrain breads (n=25). Among the raw materials, the whole corn flour showed the highest counts of fungi (4.8logCFU/g), followed by whole-wheat flour (3.1logCFU/g). The counts of fungi in the air of processing environment were higher in post-baking steps (oven output, cooling, slicing, packaging) than in pre-baking steps (weighing and mixer) (p<0.05). Species of fungi isolated from spoiled bread samples stored at 5, 20, 25 and 30, and 40°C corresponded mostly to Penicillium paneum and Penicillium polonicum isolated from 20 and 24% of samples, respectively. These species were also isolated from raw materials (P. paneum and P. polonicum) and air collected at different processing sampling points (P. polonicum). The high counts of filamentous fungi in raw materials and air samples in processing steps such as cooling, slicing, and packaging, suggest that contamination that may occur in these steps can be critical for the shelf life of breads. The results of this study highlight that the prevention of contamination of breads by fungal spores is still a challenge for bakery industries and that other strategies such as control of germination and growth of spoilage fungi through the development of more stable formulations have to be developed.

Screening of Lactic Acid Bacteria for Antifungal Activity against Fungi

Many chemical preservatives that target fungi growth in food have been approved and used for many years. Recently the consumers are looking and demanding for products without chemical preservatives and still maintain good shelf life and safe. The growth of spoilage fungi have been a global concern because of the economy loses and the health hazard of the mycotoxins produced by the spoilage fungi. A total of 22 lactic acid bacteria isolated from Tarhana and Lactic acid bacteria were screened for antifungal activity using dual agar overlay method and well method against Alternaria alternata, Aspergillus parasiticus, Aspergillus oryzae Penicillium griseofulvum, Penicillium chrysogenum, Penicillium notatu, Penicillium citrinum, Penicillium roquefort, Aspergillus fumigatus. Ten isolates showed inhibition activity after 72 h incubation at 30°C. Supernatant of 10 isolates with strong antifungal activity was evaluated by well method and they inhibited the growth of the fungi at 30°C for 72 h. F2,1 supernatant reduced the mass growth of Penicillium griseofulvum, Penicillium chrysogenum Aspergillus fumigatus and Aspergillus parasiticus when incubated for 6 days at 30°C. The isolates were identified using rapid ID 32 Strep as Enterococcus durans F2.1. F2.1 isolates studied inhibited the growth of the mycelia and conidia germination of the fungi which indicate the possibility of using LAB isolates as biopreservative.

Screening of Lactic Acid Bacteria for Antifungal Activity against &lt;i&gt;Aspergillus oryzae&lt;/i&gt;

Problem statement: The growth of spoilage fungi have been a global concern because of the economy loses and the health hazard of the mycotoxins produced by the spoilage fungi. Approach: A total of 137 lactic acid bacteria isolated from Malaysian fruits and fermented foods were screened for antifungal activity using dual agar overlay method and well method against A. oryzae. Results: 23 isolates showed inhibition activity after 72 h incubation at 30°C. Supernatant of three isolates with strong antifungal activity was evaluated by well method and they inhibited the growth of the fungi at 30°C for 72 h. LAB supernatant reduced the mass growth of Aspergillus oryzae when incubated for 7 days at 30°C. The isolates were identified using API 50CH as Lactobacillus brevis G004, Lactobacillus fermentum Te007 and Pediococcus pentosaceus Te010. Conclusion: The three isolates studied inhibited the growth of the mycelia and conidia germination of the fungi which indicate the possibility of using LAB isolates as biopreservative.