Vapor-Phase Essential Oils as Antifungal Agents against Penicillium olsonii Causing Postharvest Cherry Tomato Rot

Recent reports of P. olsonii causing postharvest rot of cherry tomatoes emphasize the need for effective strategies to prolong fruit shelf life. This study is the first to explore the use of essential oils (EOs), recognized for their antimicrobial properties, as a potential method to prevent postharvest losses from P. olsonii. Antifungal activity was tested for ten EOs at a concentration of 625 μL/L using the vapor diffusion method. Thyme, wild thyme, savory, oregano, and marjoram completely inhibited fungal growth over 14 days. Thyme EO, at a minimum inhibitory concentration (MIC) of 250 μL/L, fully inhibited all strains, while oregano, wild thyme, and savory were effective at 500 μL/L. Marjoram EO showed weaker activity. The lowest IC90 values, ranging from 35.72 to 162.72 μL/L, were estimated for thyme and oregano. In cherry tomatoes, oregano EO completely halted P. olsonii growth at 250 μL/L; thyme was effective for seven days; wild thyme and savory for two days. Thyme EO prevented P. olsonii spore germination at 500 μL/L for seven days, though germination occurred at half that concentration. The IC90 values varied between 256.2 and 138.7 μL/L depending on the strain. The vapor phase of EOs at 125 μL/L influenced the sensory characteristics of cherry tomatoes; however, for thyme and oregano, this effect was not negative due to their culinary association with tomato flavor. The selected EOs could be used to control and prevent postharvest fruit losses, but further research is needed to optimize their application.

A novel PGPF Penicillium olsonii isolated from the rhizosphere of Aeluropus littoralis promotes plant growth, enhances salt stress tolerance, and reduces chemical fertilizers inputs in hydroponic system

The hydroponic farming significantly enhances the yield and enables multiple cropping per year. These advantages can be improved by using plant growth-promoting fungi (PGPF) either under normal or stress conditions. In this study, the fungal strain (A3) isolated from the rhizosphere of the halophyte plant Aeluropus littoralis was identified as Penicillium olsonii based on sequence homology of its ITS region. The A3 fungus was shown to be halotolerant (up to 1 M NaCl) and its optimal growth was at 27°C, but inhibited at 40°C. In liquid culture medium, the A3 produced indole acetic acid (IAA) especially in the presence of L-tryptophan. Tobacco plants grown under hydroponic farming system were used to evaluate the promoting activity of the direct effect of A3 mycelium (DE) and the indirect effect (IDE) of its cell-free culture filtrate (A3CFF). The results showed that for the two conditions (DE or IDE) the tobacco seedlings exhibited significant increase in their height, leaf area, dry weight, and total chlorophyll content. Interestingly, the A3CFF (added to the MS liquid medium or to nutrient solution (NS), prepared from commercial fertilizers) induced significantly the growth parameters, the proline concentration, the catalase (CAT) and the superoxide dismutase (SOD) activities of tobacco plants. The A3CFF maintained its activity even after extended storage at 4°C for 1 year. Since the A3 is a halotolerant fungus, we tested its ability to alleviate salt stress effects. Indeed, when added at 1:50 dilution factor to NS in the presence of 250 mM NaCl, the A3CFF enhanced the plant salt tolerance by increasing the levels of total chlorophyll, proline, CAT, and SOD activities. In addition, the treated plants accumulated less Na⁺ in their roots but more K⁺ in their leaves. The A3CFF was also found to induce the expression of five salt stress related genes (NtSOS1, NtNHX1, NtHKT1, NtSOD, and NtCAT1). Finally, we proved that the A3CFF can reduce by half the chemical fertilizers inputs. Indeed, the tobacco plants grown in a hydroponic system using 0.5xNS supplemented with A3CFF (1:50) exhibited significantly higher growth than those grown in 0.5xNS or 1xNS. In an attempt to explain this mechanism, the expression profile of some growth related genes (nitrogen metabolism (NR1, NRT1), auxin (TRYP1, YUCCA6-like), and brassinosteroid (DET2, DWF4) biosynthesis) was performed. The results showed that all these genes were up-regulated following plant treatment with A3CFF. In summary the results revealed that the halotolerant fungus P. olsonii can stimulates tobacco plant growth, enhances its salt tolerance, and reduces by half the required chemical fertilizer inputs in a hydroponic farming system.

Autochthonous fungi are central components in microbial community structure in raw fermented sausages

Raw meat sausage represents a unique ecological niche rich in nutrients for microbial consumption, making it particularly vulnerable to microbial spoilage. Starter cultures are applied to improve product stability and safety as well as flavour characteristics. However, the influence of starter cultures on microbial community assembly and succession throughout the fermentation process is largely unknown. In particular the effect on the fungal community has not yet been explored. We evaluate the microbiological status of four different raw meat sausages using high‐throughput 16S rRNA gene and ITS2 gene sequencing. The objective was to study temporal changes of microbial composition during the fermentation process and to identify potential keystone species that play an important role within the microbial community. Our results suggest that fungi assigned to the species Debaryomyces hansenii and Alternaria alternata play a key role in microbial community dynamics during fermentation. In addition, bacteria related to the starter culture Lactobacillus sakei and the spoilage‐associated genera Acinetobacter, Pseudomonas and Psychrobacter are central components of the microbial ecosystem in raw fermented sausages. Elucidating the exact role and interactions of these microorganisms has the potential to have direct impacts on the quality and safety of fermented foods.

A comprehensive review of the role of microorganisms on texture change, flavor and biogenic amines formation in fermented meat with their action mechanisms and safety

Meat fermentation ensures its preservation, improved safety and quality. This prominently used traditional process has survived for ages, creating physical, biochemical, and microbial changes, and to significantly affect the functionality, organoleptic property, and nutrition of the fermented products. In some process, the growth of various pathogenic and spoilage microorganisms is inhibited. The production of fermented meat relies on naturally occurring enzymes (in the muscle or the intestinal tract) as well as microbial metabolic activities. In this review, fermented meat types and their health benefits were firstly introduced. This was followed by a description of fermentation conditions vis-à-vis starters, bacterial, yeast and mold cultures, and their role in meat. The review focuses on how microorganisms affect texture change, flavor formation, and biogenic amines (BA) accumulation in fermented meat. In addition, the production conditions and the major biochemical changes in fermented meat products were also introduced to present the best factors influencing the quality of fermented meat. Microorganisms and microbial enzymes in fermented meats were discussed as they could affect organoleptic characteristics of fermented meats. Moreover, safety concerns and prospects for further research of fermented meat were also discussed with emphasis on novel probiotic and starter cultures development; bioinformatics, omics technologies and data modeling to maximize the benefit from fermentation process in meat production.

Effect of clove bud and curry leaf essential oils on the anti-oxidative and anti-microbial activity of burfi, a milk-based confection

With scientific advancement in the field of food science and technology, there has been an increased availability of innovative ingredients that can be utilized towards value addition, quality enhancement, natural preservation, shelf life enhancement and adding novelty to traditional Indian dairy products. Here a scientific attempt has been made to increase the anti-oxidative and anti-microbial potential of burfi, a popular confection of Indian sub-continent with low shelf life using herbal essential oils (EOs) (natural preservative, antioxidant and antimicrobial) such as curry leaf (CRYF) (0.05-0.15 ppm) and clove bud (CLVB) (0.15-0.25 ppm) EO. Samples were subjected to physico-chemical, sensory, anti-oxidant and microbiological analysis and the results revealed that increasing the herbal EOs levels in burfi led to increase in anti-microbial and anti-oxidative attributes but simultaneously decreased the sensory attributes. Physico-chemical attributes remained unaffected upon EOs incorporation. Principal component analysis revealed 81.5% relation between the burfi samples and its quality attributes (DPPH activity, ABTS activity, total phenolic content, sensory attributes, standard plate count, yeast and mould count, moisture content, water activity, lightness, L* value, redness, a* value and yellowness, b* value). Herbal EOs i.e. CRYF@0.10 ppm and CLVB@0.20 ppm on khoa basis were found optimum for incorporation into burfi for enhancing storage stability without compromising the sensory acceptability.

Improvement of Fermented Fish Flour Quality Using Essential Oil Extracted From Fresh Leaves of Pimenta racemosa (Mill.) J. W. Moore

The aim of this study was to evaluate the efficacy of the essential oil extracted from fresh leaves of Pimenta racemosa in the improvement of fermented fish flour producing technology. Essential oil of Pimenta racemosa was extracted by hydrodistillation and its chemical composition was determined by GC and GC/MS. Different types of fermented fish flours from Lesser African Threadfin (Galeoides decadactylus) were produced by the modification of the traditional processing technology and the introduction of a step of essential oil adjunction during the process. Three different essential oil concentrations (0.5, 1.0 and 2.0 μL g^-1) were investigated. Physicochemical, microbiological and nutritional analyzes were performed in order to evaluate the quality of the fermented fish flour produced. Results obtained revealed that the essential oil of Pimenta racemosa investigated has a chemical composition characterized by the presence of myrcene (25.1%), chavicol (7.5%) and eugenol (51.1%). Fermented fish flour produced have a good nutritional potential. However, on the microbiological level, only samples produced by adjunction of essential oil have a low level of microbial contamination, with an absence of pathogenic microorganisms.

Antifungal activity evaluation of Mexican oregano (Lippia berlandieri Schauer) essential oil on the growth of Aspergillus flavus by gaseous contact

The antifungal activity of Mexican oregano (Lippia berlandieri Schauer) essential oil by gaseous contact on the growth of Aspergillus flavus at selected essential oil concentrations (14.7, 29.4, 58.8, or 117.6 μl of essential oil per liter of air) and temperatures (25, 30, or 35°C) was evaluated in potato dextrose agar formulated at water activity of 0.98 and pH 4.0. Mold growth curves were adequately fitted (0.984 < R(2) < 0.999) by the modified Gompertz model. The effect of the independent variables (concentration of essential oil and temperature) on the estimated model parameters (reciprocal of growth rate [1/ν(m)] and lag time [λ]) were evaluated through polynomial equations. Both ν(m) and λ were significantly (P < 0.05) affected by the independent variables; ν(m) decreased and λ increased as essential oil concentration increased and temperature decreased, which suggests that Mexican oregano essential oil retards or inhibits mold germination stage. Further, minimum fungistatic and fungicide essential oil concentrations at 30 and 35°C were determined. Mexican oregano essential oil applied in gas phase exerts important antifungal activity on the growth of A. flavus, suggesting its potential to inhibit other food spoilage molds.

Inhibitory activity of Indian spice plant Cinnamomum zeylanicum extracts against Alternaria solani and Curvularia lunata, the pathogenic dematiaceous moulds

BACKGROUND

Dematiaceous moulds are pathogenic microorganisms and act as etiological agents of mycoses with different degrees of severity in humans and animals. These moulds also cause loss of food crops and storage food products. The information regarding antimicrobial efficacy of the plant preparations on these moulds is scanty. The present study reveals phytochemical characterization and the effect of bark and leaf extracts of Indian spice plant, Cinnamomum zeylanicum (Cz), against the growth of two species of dematiaceous moulds, Alternaria solani and Curvularia lunata.

METHODS

Cz bark and leaf samples were sequentially extracted in different solvents using Soxhlet apparatus. Phytochemical analyses of extracts were done as per standard protocols. The antifungal bioassay of extracts was done by hanging drop technique. The inhibition of fungal spore germination was monitored under influence of three different concentrations of extracts.

RESULTS

The lowest test concentration (50 microg/ml) of extracts of Cz bark prepared into acetone and that of Cz leaf into petroleum ether and ethanol exhibited complete inhibition (100%) of spore germination in both the moulds. At 100 microg/ml concentration all the extracts showed about 50 to 100% inhibition. However, the treatment of the spores of the two fungal species with highest concentration (500 microg/ml) of bark and leaf extracts in all the solvents showed 100% fungicidal activity as it completely arrested the germination of spores. Relatively lower activity of aqueous extracts at 50 and 100 microg/ml concentrations suggests that the antifungal ingredients present in Cz bark and leaf are more soluble in organic solvents than water.

CONCLUSION

The results demonstrated that the Cz bark and leaves contain certain fungicidal constituents exhibiting potential antimould activity against A. solani and C. lunata.

Physiological traits of Penicillium glabrum strain LCP 08.5568, a filamentous fungus isolated from bottled aromatized mineral water

Penicillium glabrum is a ubiquitous fungus distributed world wide. This fungus is a frequent contaminant in the food manufacturing industry. Environmental factors such as temperature, water activity and pH have a great influence on fungal development. In this study, a strain of P. glabrum referenced to as LCP 08.5568, has been isolated from a bottle of aromatized mineral water. The effects of temperature, a(w) and pH on radial growth rate were assessed on Czapeck Yeast Agar (CYA) medium. Models derived from the cardinal model with inflection [Rosso et al., 1993 An unexpected correlation between cardinal temperatures of microbial growth highlighted by a new model. J. Theor. Bio. 162, 447-463.] were used to fit the experimental data and determine for each factor, the cardinal parameters (minimum, optimum and maximum). Precise characterisation of the growth conditions for such a fungal contaminant, has an evident interest to understand and to prevent spoilage of food products.

Mycoflora of two types of Portuguese dry-smoked sausages and inhibitory effect of sodium benzoate, potassium sorbate, and methyl p-hydroxybenzoate on mold growth rate

The mycoflora of chouriqo types Alentejano and Ribatejano, two varieties of Portuguese dry-smoked sausages, have been investigated after a producer-defined shelf life period (120 days at 20 +/- 5 degrees C) in modified atmosphere packaging (55% N2 and 45% CO2). On the basis of morphological and physiological characteristics, the isolates were identified as Penicillium, Aspergillus, Fusarium, Rhizopus, Monilia, Absidia, and Cephalosporium. The species identified were as follows: Penicillium terrestres (43.4%), Penicillium sp. (13.3%), Fusarium sp. (10%), Aspergillus glaucus (10%), Aspergillus versicolor (6.8%), Monilia fruticola (3.3%), Absidia sp. (3.3%), Cephalosporium sp. (3.3%), Rhizopus stolonifer (3.3%), and Fusarium tricinctum (3.3%). Additionally, the effects of three preservatives (potassium sorbate [PS], sodium benzoate [SB], and methyl p-hydroxybenzoate [MHB]) were studied on the growth rate of mold representative isolates. MHB showed a greater inhibitory effect than SB and PS in all fungi isolates, except in A. glaucus [Tm30(A)], in which the inhibitory effect of MHB was similar to PS. At 0.05% (wt/vol), all fungi were inhibited with MHB, except for R. stolonifer [Tm25(A)], which started to decrease the growth rate only at a concentration higher than 0.1%. PS was more effective at inhibiting mold growth than SB, except in Absidia sp. [Tm16(R)], in which both showed a similar inhibitory effect. MHB showed great promise as an application to the surface at 0.1% (wt/vol) to improve the stability and safety of the product through the inhibition of potential spoilage and toxigenic molds.

Antifungal activity of Mexican oregano (Lippia berlandieri Shauer)

Antifungal and sensorial properties of spices have been recognized for years. The antifungal compounds are products of the plant's secondary metabolism, and the action of those compounds could be used to inhibit the growth of spoilage and pathogenic microorganisms in food. Mexican oregano (Lippia berlandieri) grows wildly in the desert zone of Mexico and is usually added to regional foods. The goal of this study was to evaluate the antifungal activity of Mexican oregano versus food-contaminant fungi. Fungi were isolated from spoiled fruit and vegetables and identified according to morphological characteristics. The antifungal activity of oregano was evaluated by radial growth measurement on potato dextrose agar added with dried oregano (0.25 to 4.0%). The essential oil antifungal activity of oregano was also evaluated by the diffusion well test. Twenty-one fungal strains were isolated, which included Penicillium, Geotrichum, Aspergillus, and Bipolaris. In seven of the 21 strains, no inhibitory effect was observed at either concentration of oregano. An increase in growth at the lower or higher concentrations of oregano, when compared to the control, was observed in two fungal strains; in 12 strains, a strong inhibitory effect of oregano was evident. The oregano essential oil was inhibitory to all fungal strains, but there were differences in the extent of the effect. Although the antifungal effect of oregano is strongly established, there was a differential effect with the fungal strains studied. Besides pathogenic fungi and bacteria, microbial spoilage flora should be considered when the addition of spices for food preservation is proposed.

Determination of growth characteristics and lipolytic and proteolytic activities of Penicillium strains isolated from Argentinean salami

The growth of Penicillium spp. on the surface of meat-based dry fermented sausages provides them with a protective effect against some undesirable microorganisms. Penicillium also acts as an antioxidant, minimizes the risk of excessive drying, and it is responsible for flavor development due to the decomposition of proteins, free fatty acids and lactic acid. With the aim of developing starter cultures, important physiological properties such as growth and proteolytic and lipolytic activities were evaluated on 13 mold strains belonging to the genera Penicillium. These strains were isolated from Argentinean dry fermented meat sausages named "salami". The selection was based on color, mycellium appearance and growth characteristics. The most important factors of the drying process of salami, such as temperature (14 and 25 degrees C), water activity (aw) (0.90, 0.95 and 1.00) and presence of 2.5% sodium chloride (NaCl), were analyzed. Although all strains analyzed were able to grow under the different conditions evaluated, they showed different growth velocity (K = mm/day) in response to temperature, aw and presence of NaCl in the media. All strains showed both proteolytic and lipolytic activities under the studied factors of the drying process. Nevertheless, differences in inter-species and even intra-species were found. The addition of NaCl gave a stimulant effect to the proteolytic activity at 25 degrees C, but the response at 14 degrees C was variable. The same variability was observed in the presence of salt, both at 25 and 14 degrees C, when the lipolytic activity was assayed. According to our results, detailed assays of the physiological capacities of indigenous strains proposed as starter cultures are required.

Moulds isolated from Istrian dried ham at the pre-ripening and ripening level

The aim of this study is to define the mould strains growing on the surface during the pre-ripening and the ripening phases of Istrian ham, and their toxic potential. The mould microflora was predominantly represented by five genera, which were isolated on the ham surfaces of three different producers investigated. The identified species were similar in the both tested periods, demonstrating that the contamination came mainly from the air and the ripening chambers (seasoning rooms), rather than the raw meat. Eurotium spp., Aspergillus spp. and Penicillium spp. were the main strains isolated. The presence and growth of the different strains depended on the temperature of ripening and the relative humidity in the ripening chambers, since the hams were home made products and not matured in controlled conditions. The toxic potential of isolated strains was also investigated. None of the tested moulds can produce mycotoxins and for this reason the Istrian hams do not represent a health hazard.