Penicillium Expansum Growth Research Articles

Effect of Red Extractives of Plantation Woods on Bamboo Mildewing

Bamboo is so easily Mouldy that bamboo products have no high value added utilization. Therefore, the effect of red extractives from 18 plantation woods on bamboo biology moulding was studied based on full-factor test. The results were: (1) The red extractives of plantation could mostly inhibit the growth of Penicillium expansum, but a few could inhibit the growth of Aspergillus niger. (2) The red extractives of Cunninghamia lanceolata bark and shavings, Deodar cedar branch, Eucalyptus dunnii bark, Eucalyptus tereticornis bark, Bagasse, Eucalyptus camaldulensis branch and shaving were the most effective in controlling spore germination of Penicillium expansum, and the one raphiolepsis branch was the most effective in controlling spore germination of Aspergillus niger. (3) The effect of the red extractives from Cunninghamia lanceolata bark and shaving, Deodar cedar branch, cypress branch, Eucalyptus tereticornis branch on bamboo moulding was highly remarkable on outdoor test. So the plantation woods could be used as biologic mould inhibitor for bamboo.

Modelling growth of Penicillium expansum and Aspergillus niger at constant and fluctuating temperature conditions

The growth of Penicillium expansum and Aspergillus niger, isolated from yogurt production environment, was investigated on malt extract agar with pH = 4.2 and a w = 0.997, simulating yogurt, at isothermal conditions ranging from − 1.3 to 35 °C and from 5 to 42.3 °C, respectively. The growth rate ( μ) and (apparent) lag time ( λ) of the mycelium growth were modelled as a function of temperature using a Cardinal Model with Inflection (CMI). The results showed that the CMI can describe successfully the effect of temperature on fungal growth within the entire biokinetic range for both isolates. The estimated values of the CMI for μ were T min = − 5.74 °C, T max = 30.97 °C, T opt = 22.08 °C and μ opt = 0.221 mm/h for P. expansum and T min = 10.13 °C, T max = 43.13 °C, T opt = 31.44 °C, and μ opt = 0.840 mm/h for A. niger. The cardinal values for λ were very close to the respective values for μ indicating similar temperature dependence of the growth rate and the lag time of the mycelium growth. The developed models were further validated under fluctuating temperature conditions using various dynamic temperature scenarios. The time–temperature conditions studied included single temperature shifts before or after the end of the lag time and continuous periodic temperature fluctuations. The prediction of growth at changing temperature was based on the assumption that after a temperature shift the growth rate is adopted instantaneously to the new temperature, while the lag time was predicted using a cumulative lag approach. The results showed that when the temperature shifts occurred before the end of the lag, they did not cause any significant additional lag and the observed total lag was very close to the cumulative lag predicted by the model. In experiments with temperature shifts after the end of the lag time, accurate predictions were obtained when the temperature profile included temperatures which were inside the region of growth, showing that the assumption that μ is adopted instantaneously to the current temperature is concrete. In contrast, for scenarios with temperatures close or outside the growth region the models overestimated growth, indicating that fungi were stressed by this type of temperature shifts. The present study provides useful data for understanding the behavior of P. expansum and A. niger at dynamic temperature conditions while the developed models can be used as effective tools in assessing the risk of fungal spoilage and predicting shelf life of foods.

Development of an LC-MS/MS method for the determination of pesticides and patulin in apples

A method for the simultaneous determination of 33 pesticides or degradation products together with patulin in apples by liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed. The method involved homogenization of the apples, extraction with ammonium acetate–acetic acid solution in methanol–water by ultrasonication, filtration, and determination by LC-MS/MS. The repeatability and within-laboratory reproducibility for the three spiking levels 0.02, 0.04 and 0.2 mg kg−1 were between 4% and 35%. In general, the repeatability and reproducibility were about 10–20%. The limits of quantification (LOQs) were between 0.01 and 0.14 mg kg−1. The method was used on incurred samples from parts of the ISAFRUIT project financed by the European Commission under the 6th Framework Programme. Samples were analysed at four different stages: after harvest, after storage (controlled), after a water bath, and after 28 days at room temperature. Pesticide residues were found at all stages, but no significant differences in the concentration were seen between the stages analysed. The concentration decreased significantly only for tolylfluanid after storage at room temperature for 28 days when only 0–6% of the original amount of tolylfluanid remained in the apples. No patulin was found in the apples stored for 28 days at room temperature and no growth of Penicillium expansum was observed on these apples. However, when the apples were inoculated with a spore suspension of P. expansum, high concentrations of patulin were found.

Effect of storage temperature on the growth of Penicillium expansum and its production of patulin in apples

The relationship between the effect of storage temperature, the growth of Penicillium expansum and its production of patulin on apple were studied. To prevent fungal spoilage and patulin production it was demonstrated that apples needed to be stored just below 0 °C. It was also shown that once fungal decay had commenced, it spread relatively quickly and that patulin was produced, even when apples were stored at +1 °C. However, when apples were stored at +5 °C or below there was some time lag before decay and the onset of patulin formation. Therefore it was concluded that it is very important to store apples at +5 °C or less as soon as possible after harvest.

Control of Penicillium expansum and patulin accumulation on apples by quercetin and umbelliferone

The effectiveness of seven phenolic compounds (esculetin, ferulic acid, quercetin, resveratrol, scopoletin, scoparone and umbelliferone) in controlling Penicillium expansum growth and patulin accumulation was evaluated by both in vitro and in vivo studies. The in vitro screening showed that quercetin and umbelliferone were the most effective compounds in controlling Penicillium growth and patulin accumulation, respectively. Quercetin and umbelliferone, resulted to be effective also in the in vivo screening, were further tested (alone and in combination) on Granny Smith and Golden Delicious apples. The efficacy in controlling Penicillium growth was better expressed on Golden Delicious than on Granny Smith apples, with quercetin providing a better control of both incidence of decay and disease severity as compared to umbelliferone. Both compounds exerted a considerable control of patulin accumulation on the two apple cultivars. Quercetin and umbelliferone can be considered as natural compounds to be used as alternative strategy to chemical fungicides in postharvest control of P. expansum infections on apples.

Growth of Phytopathogenic Fungi in the Presence of Partially Acetylated Chitooligosaccharides

Four phytopathogenic fungi were cultivated up to six days in media containing chitooligosaccharide mixtures differing in average DP and FA. The three different mixtures were named Q3 (which contained oligosaccharides of DP2-DP10, with DP2-DP7 as main components), Q2 (which contained oligosaccharides of DP2-DP12, with DP2-DP10 as main components) and Q1 (which derived from Q2 and contained oligomers of DP5-DP8 with hexamer and a heptamer as the main components). The novel aspect of this work is the description of the effect of mixtures of oligosaccharides with different and known composition on fungal growth rates. The growth rate of Alternaria alternata and Rhizopus stolonifer was initially inhibited by Q3 and Q2 at higher concentrations. Q1 had a growth stimulating effect on these two fungi. Growth of Botrytis cinerea was inhibited by Q3 and Q2, while Q1 had no effect on the growth of this fungus. Growth of Penicillium expansum was only slightly inhibited by higher concentrations of sample Q3, while Q2 and Q1 had no effect. The inhibition of growth rates or their resistance toward chitooligosaccharides correlated with the absence or presence of chitinolytic enzymes in the culture media, respectively.

Effect of biocontrol agents Candida sake and Pantoea agglomerans on Penicillium expansum growth and patulin accumulation in apples

Penicillium expansum is the major responsible of fruit pome decaying in cold storage. Apples spoiled by P. expansum are expected to contain patulin, a mycotoxin which is proven to affect human health. The use of chemicals is the most common procedure to prevent rots in postharvest but legislation is becoming more and more restrictive. The use of biocontrol agents (BCA) as an alternative tool is currently being proposed. The aim of this study was to evaluate the effect of two BCA ( Candida sake CPA-2 and Pantoea agglomerans CPA-1) on P. expansum growth and patulin accumulation in cold storage and further deck (ambient) storage. Wounded apples were inoculated with a cell suspension of either C. sake or P. agglomerans and with a P. expansum conidial suspension. Apples were cold stored at 1 °C until lesion diameter reached 2 or 4 cm. Half the apples of each treatment were further stored at 20 °C for three days before patulin analyses. Both BCA tested controlled blue rot and patulin accumulation during cold storage. The control of P. expansum growth was enhanced in C. sake treated apples. On the other side, control of patulin accumulation in P. agglomerans treated apples seemed to be more efficient. BCA treatment could not control blue rot and patulin accumulation during further storage at room temperature and in some cases, an increase in P. expansum aggressiveness was observed.

Inoculum size and intraspecific interactions affects Penicillium expansum growth and patulin accumulation in apples

Penicillium expansum is the most important fungal species causing spoilage in cold stored apples. P. expansum produces patulin, a toxic secondary metabolite. The aim of this work was to study the changes in growth parameters and patulin accumulation that may occur when two different isolates of P. expansum germinate and develop in the same wound. The effect of the inoculum size was also studied. For that purpose, apples were point inoculated with two different isolates of P. expansum at two different conidia concentrations. Both isolates were also inoculated together. Apples were cold stored at 1 °C or incubated at 20 °C until lesion diameter reached 2.5 cm. Patulin from decayed tissue was analysed at the end of cold storage/incubation. It seems that intraspecific interactions occur. The interactions resulted in slower growth in which patulin content was lower. A competition for resources followed by either a “combat-like” interaction may be involved in this. Higher inoculum size led to shorter lag phase, which reflects the importance of the hygiene in packinghouses facilities. The inoculum size also affected growth rate and patulin accumulation, which suggests that interactions between individuals of the same strain may occur. Competition for resources and a combat-like interaction may take place. In vitro studies should be carried out in order to assess the patterns of the interactions observed.

The effect of inoculum size on the growth of Penicillium expansum in apples

Penicillium expansum is the most important cause of blue mould rot, a major post-harvest disease of apples worldwide. The objective of this study was to evaluate the effect of the inoculum size on the germination and growth parameters of P. expansum under different storage conditions in apples. Growth of P. expansum was observed in more than 90% of the inoculations, when the inoculum was equal or higher than 2×10 4 spores. The use of a low inoculum level resulted in longer lag phases and a larger variability of the estimated lag phase. This indicates that more replications are necessary to estimate the lag phase of the mould in the specified circumstances. At lower temperature, more inoculum was necessary to reduce the variability of the estimated lag phase, showing that this effect is temperature dependent. Moreover, the effect of the inoculum level on the lag phase is even more pronounced for a slower growing strain. These results imply that the inoculum size influences the estimated growth parameters and should be considered in quantitative risk assessments and for the design of challenge tests and experiments to gather data for predictive growth models.

Postharvest control of blue mold rot of pear by microwave treatment and Cryptococcus laurentii

The potential of using microwave power alone or in combination with an antagonistic yeast for the control of blue mold rot of pear, and its effects on postharvest quality of fruit was investigated. In vitro test, growth of Penicillium expansum was completely inhibited by a 2450MHz microwave heating for 2 or 3min. The population density of P. expansum in surface wounds of fruit treated with microwave for 2–3min was significantly lower than that of control. In vivo test, microwave power and antagonist yeast, as stand-alone treatments, were capable of reducing the percentage of infected wounds from 100% to 72.6% and 65.5%, and lesion diameter from 2.81mm to 2.20mm and 1.85mm respectively. However, in fruit treated with combination of microwave power and Cryptococcus laurentii, the percentage of infected wounds and lesion diameter was only 20.2% and 1.1mm respectively, incidence of natural decay on treated fruits were similar to that of inoculated fruit. None of the treatments did impair quality parameters of fruit. Thus, the combination of microwave and C. laurentii could be an alternative to chemicals for the control of postharvest blue mold rot on pear fruits.

(34) Maintaining the Analytical and Microbial Quality of Fresh-cut Apple Slices using Hot Water Pretreatment and a Low pH Dip Treatment

A calcium ascorbate processing formulation is commercially used to prevent browning on fresh-cut apple slices but has little to no antimicrobial activity. Intact apples were surface-sanitized with chlorine water at 20 °C or water at 60 °C, processed into fresh-cut slices, and the slices dipped in a calcium ascorbate formulation or a solution of isoascorbic acid, calcium, and N-acetylcysteine at pH 2.0. The commercial and experimental dip treatments similarly maintained cut surface color, Kramer firmness, and aromatic volatile concentrations during 3 weeks of storage at 5 °C in air. Freshly prepared experimental dip treatment reduced the native bacterial population of the apple slices prepared from sanitized apples better than the calcium ascorbate treatment. With repeated use, the experimental dip solution became adulterated with apple tissue and juice and rapidly lost its antibacterial activity. Concomitantly the pH of the dip solution increased to 2.6 or higher. The lost antibacterial activity could be restored in highly contaminated experimental dip solutions by back titrating to pH 2.0. The experimental dip treatment also reduced the overall yeast and mold population, but specifically enhanced growth of Penicilliumexpansum on slices prepared from chlorine-sanitized apples. A hot water pretreatment of intact apples at 60 °C for 3 min prior to fresh-cut processing essentially eliminated P. expansum contamination on the slices. The results indicate that the experimental dip treatment is a promising alternative to calcium ascorbate treatment for analytical and microbial quality retention of fresh-cut apple slices during storage, especially when the apple slices are processed from hot water-treated apples.

Editorial

Penicillium expansum growth and patulin production occur mainly at post-harvest stage during the long-term storage of apples. Low temperature in combination with reduced oxygen concentrations is commonly applied as a control strategy to extend apple shelf life and supply the market throughout the year. Our in vitro study investigated the effect of temperature and atmosphere on expression of the idh gene in relation to the patulin production by P. expansum. The idh gene encodes the isoepoxydon dehydrogenase enzyme, a key enzyme in the patulin biosynthesis pathway. First, a reverse transcription real-time PCR (RT-qPCR) method was optimized to measure accurately the P. expansum idh mRNA levels relative to the mRNA levels of three reference genes (18S, β-tubulin, calmodulin), taking into account important parameters such as PCR inhibition and multiple reference gene stability. Subsequently, two P. expansum field isolates and one reference strain were grown on apple puree agar medium (APAM) under three conditions of temperature and atmosphere: 20 °C — air, 4 °C — air and 4 °C — controlled atmosphere (CA; 3% O2). When P. expansum strains reached a 0.5 and 2.0 cm colony diameter, idh expression and patulin concentrations were determined by means of the developed RT-qPCR and an HPLC-UV method, respectively. The in vitro study showed a clear reduction in patulin production and down-regulation of the idh gene expression when P. expansum was grown under 4 °C — CA. The results suggest that stress (low temperature and oxygen level) caused a delay of the fungal metabolism rather than a complete inhibition of toxin biosynthesis. A good correlation was found between the idh expression and patulin production, corroborating that temperature and atmosphere affected patulin production by acting at the transcriptional level of the idh gene. Finally, a reliable RT-qPCR can be considered as an alternative tool to investigate the effect of control strategies on the toxin formation in food.

Effect of fludioxonil on germination and growth of Penicillium expansum and decay in apple cvs. Empire and Gala

Penicillium expansum is the predominant fungal pathogen responsible for blue mold of apple. The sensitivity of three thiabendazole-sensitive (TBZ S) and three thiabendazole-resistant (TBZ R) isolates of P. expansum, collected from apple stores in Ontario, to fludioxonil was determined in vitro (conidial germination and colony diameter on fludioxonil amended medium) and in vivo (apples). On fungicide amended medium, the concentration of 50% inhibition (EC 50 ) of germination for the TBZ S and TBZ R isolates of P. expansum ranged from 0.079 to 0.113 μg a.i. of fludioxonil/ml and for mycelial growth from 0.013 to 0.023 μg a.i. of fludioxonil/ml. Harvested apples were wounded and co-treated with a suspension of conidia of P. expansum and the fungicides by drenching. Fludioxonil at a concentration of 100 μg a.i./ml was found effective against blue mold induced by both TBZ S and TBZ R isolates of P. expansum on apple cv. Empire. In post-inoculation treatments, wounded apples were inoculated with P. expansum and incubated for 18–20 h at 13°C, and then drenched with appropriate concentrations of fungicides and incubated at 20°C for 6 days. Fludioxonil at a concentration of 100 μg a.i./ml controlled blue mold in the co-treatment and in the post-inoculation treatment on cvs. Empire and Gala. The activity of fludioxonil on two or more stages, conidial germination and mycelial growth, of life cycle of P. expansum and on decay formation in two cultivars of apples suggests that this compound potentially can provide an alternative to TBZ in post-harvest control of blue mold of apple, where any TBZ R conidia are present.

The Effect of Modified Atmospheres and Packaging on Patulin Production in Apples

This study was undertaken to determine the effectiveness of modified atmospheres and packaging materials on the growth of Penicillium expansum and patulin production in apples. Granny Smith apples were surface sterilized with 76% ethanol and inoculated with 0.1 ml of a 1.1 × 107 spore/ml P. expansum spore suspension. The apples were packaged either in polyethylene (PE) or polypropylene (PP) and treated with three different gas combinations, viz., 58% CO2/42% N2, 48% CO2/52% N2, and 88% CO2/12% N2, and were then incubated for 14 days at 25°C. Fungal growth was monitored every 2 to 4 days by measuring radial growth from the point of inoculation. After the 14th day, apples were pulped, and patulin was extracted, purified, and quantified by high-performance liquid chromatography. PP did not inhibit fungal growth in any of the atmospheres tested, and it only inhibited patulin production in atmospheric gas and 58% CO2/42% N2. PE was very effective and inhibited fungal growth by four- or fivefold, depending on the modified atmosphere. Patulin production in PE-packaged apples was almost completely inhibited by all three gas combinations. Gas chromatographic analysis of the PE-packaged samples before and after the incubation period showed that CO2 levels dropped and N2 levels increased for all of the atmospheres tested. Our studies showed conclusively that PE is an excellent packaging material for the storage of apples since it inhibited the growth of P. expansum, thereby allowing <3.2 μg/ml of patulin to be produced, regardless of gaseous environment.

Osmotic Dehydration of Apple Slices Using a Sucrose/CaCl2 Combination To Control Spoilage Caused by Botrytis cinerea, Colletotrichum acutatum, and Penicillium expansum

The efficacy of sucrose combined with CaCl2 during osmotic dehydration (OD) was tested for the control of Botrytis cinerea, Colletotrichum acutatum, and Penicillium expansum growth on lightly processed apple slices. The objective of this work was to determine whether the addition of CaCl2 in the osmotic solutions would limit the proliferation of fungal decay organisms. Slices were submitted to OD for 1 h at 25°C in solutions containing 5 to 65% sucrose. Calcium chloride was added to a similar set of sucrose solutions at 0 to 8%. Control slices were made of untreated slices, and slices were processed in water. The mass ratio of the slices did not vary when fruit pieces were processed in solutions containing 5 to 65% sucrose. These slices showed a high susceptibility to spoilage compared to the control slices not submitted to OD: a significant twofold and 60% increase in decay area caused by B. cinerea and P. expansum, respectively, was observed when slices were processed in 50% sucrose/0% CaCl2; C. acutatum showed a significant 50% increase in decay area when slices were processed in 20% sucrose/0% CaCl2. Calcium uptake was significantly increased when slices were processed in CaCl2 solutions, and the highest Ca content was observed when processed in 8% CaCl2, reaching 40 times that of the control slices processed in water. Calcium-treated slices were less susceptible to spoilage by all three pathogens, and the most effective combination in reducing apple slice spoilage was 20 to 30% sucrose combined with 2% CaCl2.

Antimicrobial Activity of Gaseous Allyl Isothiocyanate

A simple model system was constructed to evaluate the microbistatic and microbicidal properties of gaseous allyl isothiocyanate (AIT) against bacterial cells and fungal conidia deposited on agar surfaces. Salmonella typhimurium , Listeria monocytogenes Scott A, and Escherichia coli O157:H7 were inhibited when exposed to 1,000 μg AIT per liter. Pseudomonas corrugata , a Cytophaga species, and a fluorescent pseudomonad failed to grow in the presence of 500 μg AIT per liter. Germination and growth of Penicillium expansum , Aspergillus flavus , and Botrytis cinerea conidia was inhibited in the presence of 100 μg AIT per liter. Bactericidal and sporicidal activities varied with strain and increased with time of exposure, AIT concentration, and temperature. E. coli O157:H7 was the most resistant bacterial species tested.

Hexanal Vapor Is a Natural, Metabolizable Fungicide: Inhibition of Fungal Activity and Enhancement of Aroma Biosynthesis in Apple Slices

Hexanal vapor inhibited hyphae growth of Penicillium expansum and Botrytis cinerea on potato dextrose agar (PDA) and on apple (Malus domestica Borkh.) slices. After 48 hours exposure to 4.1 μmol·L-1 (100 ppm) hexanal, the hyphae growth of both fungi was about 50% that of untreated controls. At a concentration of 10.3 μmol·L-1 (250 ppm), neither fungus grew during the treatment period, however, some growth of both fungi occurred 120 hours after treatment. At concentrations of hexanal vapor of 18.6 μmol·L-1 (450 ppm) or more, the growth of both fungi ceased and the organisms were apparently killed, neither showing regrowth when moved to air. When fungi were allowed to germinate and grow for 48 hours in hexanal-free air, a subsequent 48-hour exposure to 10.3 μmol·L-1 hexanal slowed colony growth relative to controls for several days and a 48-hour exposure to 18.6 μmol·L-1 stopped growth completely. Concentrations of hexanal that inhibited fungal growth on PDA also retarded decay lesion development on `Golden Delicious' and on `Jonagold' apple slices. Hexanal was actively converted to aroma volatiles in `Jonagold' and `Golden Delicious' apple slices, with hexanol and hexylacetate production strongly enhanced after 20 to 30 hours treatment. A small amount of butylhexanoate and hexylhexanoate production was also noted. Within 16 hours after treatment, no hexanal could be detected emanating from treated fruit. Since hexanal was metabolized to aroma-related volatiles by the fruit slices, the possibility of hexanal being an essentially residue-less antifungal agent seems likely. The possibility of developing a system for treating apple slices with hexanal in modified-atmosphere packages was also examined. The permeability of low-density polyethylene (LDPE) film to hexanal and hexylacetate was, respectively, about 500- and 1000-fold higher than LDPE permeability to O2. The permeability of both compounds increased exponentially with temperature, with hexanal permeability increased 6-fold while hexylacetate increased only 2.5-fold between 0 and 30 °C.

Growth Inhibition of Penicillium expansumby Several Commonly Used Food Ingredients

Several compounds (cinnamon oil, cinnamaldehyde, clove oil, eugenol, and potassium sorbate) were assayed to evaluate their potential as inhibitors of Penicillium expansum growth on apples and in apple juice. The effectiveness of inhibitor was dependent on the apple cultivar treated. Both 0.1% cinnamon oil and 0.5% potassium sorbate decreased spoilage as measured by lesion diameter in most of the cultivars studied. Patulin was not detected in apple juice containing 0.3% cinnamon oil or 0.5% sorbate after incubation with P. expansum for 7 d at 25°C. The addition of benomyl (0.5–5 ppm) increased patulin production by P. expansum grown in apple juice. These results indicate that surface application of cinnamon oil or potassium sorbate might be an effective postharvest treatment for apples, and addition of these compounds to apple juice products that do not receive additional heat treatment, such as ‘fresh’ apple cider, would prevent patulin production by P. expansum.

Inhibition of growth and patulin synthesis in Penicillium expansum by potassium sorbate and sodium propionate in culture.

Potassium sorbate and sodium propionate brought about a marked inhibition in the growth of Penicillium expansum and a proportionally greater inhibition in the synthesis of patulin by the mold. At inhibitor concentrations used commercially in bakery products, propionate inhibited growth less efficiently than sorbate did but was a more effective inhibitor of patulin synthesis.

Mycotoxins in foodstuffs

The optimal temperature for the growth ofAspergillus parasiticus and the formation of aflatoxins B1 and G1 on whole wheat bread (sliced and packed) was 25°C. The optimal “total acid content” (Sauregrad) was 5.0. Incubation in light caused no reduction in aflatoxin yields. The optimal temperature for the growth ofPenicillium expansum on whole wheat bread was 10°C and was between 20° and 25°C for the biosynthesis of patulin. Patulin formation was not influenced by the “total acid content” but was greater under the influence of light than darkness. With increase of incubation time the yields of patulin decreased, probably due to an inactivation by SH-compounds.