Acessibilidade / Reportar erro

Growth modeling kinetics of Alternaria alternata in dried jujube at different temperatures

Abstract

Alternaria alternata is a fungus that infects jujube, causes black spot disease, and produces Alternaria mycotoxins, such as alternariol, alternariol monomethyl ether, and tenuazonic acid. This study aimed to apply models to predict growth and mycotoxin production by A. alternata isolated from jujube as a function of temperature and water activity. The practicability of the model was verified on jujube agar medium. The growth conditions were water activity of 0.99 or 0.90 aw and temperatures of 10, 15, 20, 25, 30, or 35 °C. The growth rate of A. alternata was highest at 0.99 aw and 25 °C, and the lag time was the shortest at 0.90 aw and 30 °C. The dry weight growth rate of mycelia increased gradually with the increase of temperature on PDA and jujube agar medium. Mycotoxin production by A. alternata was not correlated with growth, but no significant delay was detected in some cases. In general, the growth model predicted the growth of A. alternata.

Keywords:
Alternaria alternata; Alternaria mycotoxins; predictive modeling

1 Introduction

Jujube (Ziziphus jujuba Mill.) is a plant in the Rhamnoidea family that contains high concentrations of sugars, fatty acids, amino acids, minerals, vitamins, polyphenols, and other antioxidants (Li et al., 2020Li, N., Fu, L., Song, Y., Li, J., Xue, X., Li, S., & Li, L. (2020). Wax composition and concentration in jujube (Ziziphus jujuba Mill.) cultivars with differential resistance to fruit cracking. Journal of Plant Physiology, 255, 153294. http://dx.doi.org/10.1016/j.jplph.2020.153294. PMid:33070052.
http://dx.doi.org/10.1016/j.jplph.2020.1...
). It has good nutritional and medicinal value (Ji et al., 2020Ji, X., Hou, C., Yan, Y., Shi, M., & Liu, Y. (2020). Comparison of structural characterization and antioxidant activity of polysaccharides from jujube (Ziziphus jujuba Mill.) fruit. International Journal of Biological Macromolecules, 149, 1008-1018. http://dx.doi.org/10.1016/j.ijbiomac.2020.02.018. PMid:32032709.
http://dx.doi.org/10.1016/j.ijbiomac.202...
). China is the largest jujube producer in the world, and Xinjiang is the most important jujube producing area in China. The physical and chemical indices of the jujube cultivars differ among districts (Chen et al., 2019Chen, K., Fan, D., Fu, B., Zhou, J., & Li, H. (2019). Comparison of physical and chemical composition of three chinese jujube (Ziziphus jujuba Mill.) cultivars cultivated in four districts of Xinjiang region in China. Food Science and Technology, 39(4), 912-921. http://dx.doi.org/10.1590/fst.11118.
http://dx.doi.org/10.1590/fst.11118...
). Therefore, it is necessary to study the physiological characteristics of microorganisms leading to jujube disease in Xinjiang. The jujube is vulnerable to black spot. Alternaria alternata is a fungus that infects a variety of plants and causes black spot disease in jujube (Zhang et al., 2020Zhang, S., Wang, Q., Guo, Y., Kang, L., & Yu, Y. (2020). Carbon monoxide enhances the resistance of jujube fruit against postharvest Alternaria rot. Postharvest Biology and Technology, 168, 111268. http://dx.doi.org/10.1016/j.postharvbio.2020.111268.
http://dx.doi.org/10.1016/j.postharvbio....
), pear (Sardella et al., 2018Sardella, D., Gatt, R., & Valdramidis, V. P. (2018). Modelling the growth of pear postharvest fungal isolates at different temperatures. Food Microbiology, 76, 450-456. http://dx.doi.org/10.1016/j.fm.2018.07.010. PMid:30166173.
http://dx.doi.org/10.1016/j.fm.2018.07.0...
), apple (Ntasiou et al., 2015Ntasiou, P., Myresiotis, C., Konstantinou, S., Papadopoulou-Mourkidou, E., & Karaoglanidis, G. S. (2015). Identification, characterization and mycotoxigenic ability of Alternaria spp. causing core rot of apple fruit in Greece. International Journal of Food Microbiology, 197, 22-29. http://dx.doi.org/10.1016/j.ijfoodmicro.2014.12.008. PMid:25560914.
http://dx.doi.org/10.1016/j.ijfoodmicro....
), blueberry (Wang et al., 2021Wang, F., Saito, S., Michailides, T. J., & Xiao, C.-L. (2021). Postharvest use of natamycin to control Alternaria rot on blueberry fruit caused by Alternaria alternata and A. arborescens. Postharvest Biology and Technology, 172, 111383. http://dx.doi.org/10.1016/j.postharvbio.2020.111383.
http://dx.doi.org/10.1016/j.postharvbio....
), citrus (Sardar et al., 2022Sardar, M., Ahmed, W., Al Ayoubi, S., Nisa, S., Bibi, Y., Sabir, M., Khan, M. M., Ahmed, W., & Qayyum, A. (2022). Fungicidal synergistic effect of biogenically synthesized zinc oxide and copper oxide nanoparticles against Alternaria citri causing citrus black rot disease. Saudi Journal of Biological Sciences, 29(1), 88-95. http://dx.doi.org/10.1016/j.sjbs.2021.08.067. PMid:35002397.
http://dx.doi.org/10.1016/j.sjbs.2021.08...
) and cherry tomato (Pane et al., 2016Pane, C., Fratianni, F., Parisi, M., Nazzaro, F., & Zaccardelli, M. (2016). Control of Alternaria post-harvest infections on cherry tomato fruits by wild pepper phenolic-rich extracts. Crop Protection (Guildford, Surrey), 84, 81-87. http://dx.doi.org/10.1016/j.cropro.2016.02.015.
http://dx.doi.org/10.1016/j.cropro.2016....
).

Alternaria produces secondary metabolites called Alternaria mycotoxins. The main mycotoxins detected in food are alternariol (AOH), alternariol monomethyl ether (AME), and tenuazonic acid (TeA). These mycotoxins have mutagenic, carcinogenic, and genotoxic effects (Puntscher et al., 2019Puntscher, H., Cobankovic, I., Marko, D., & Warth, B. (2019). Quantitation of free and modified Alternaria mycotoxins in European food products by LC-MS/MS. Food Control, 102, 157-165. http://dx.doi.org/10.1016/j.foodcont.2019.03.019.
http://dx.doi.org/10.1016/j.foodcont.201...
). Exposure of Europeans to AOH was detected through urine tests but the risk was not characterized due to a lack of intake by a reference (Martins et al., 2019Martins, C., Vidal, A., De Boevre, M., De Saeger, S., Nunes, C., Torres, D., Goios, A., Lopes, C., Assuncao, R., & Alvito, P. (2019). Exposure assessment of Portuguese population to multiple mycotoxins: The human biomonitoring approach. International Journal of Hygiene and Environmental Health, 222(6), 913-925. http://dx.doi.org/10.1016/j.ijheh.2019.06.010. PMid:31253542.
http://dx.doi.org/10.1016/j.ijheh.2019.0...
). Temperature and water activity are key factors affecting fungal growth and mycotoxin production (Lahouar et al., 2017Lahouar, A., Marín, S., Crespo-Sempere, A., Said, S., & Sanchis, V. (2017). Influence of temperature, water activity and incubation time on fungal growth and production of ochratoxin A and zearalenone by toxigenic Aspergillus tubingensis and Fusarium incarnatum isolates in sorghum seeds. International Journal of Food Microbiology, 242, 53-60. http://dx.doi.org/10.1016/j.ijfoodmicro.2016.11.015. PMid:27883966.
http://dx.doi.org/10.1016/j.ijfoodmicro....
; Thanushree et al., 2019Thanushree, M. P., Sailendri, D., Yoha, K. S., Moses, J. A., & Anandharamakrishnan, C. (2019). Mycotoxin contamination in food: An exposition on spices. Trends in Food Science & Technology, 93, 69-80. http://dx.doi.org/10.1016/j.tifs.2019.08.010.
http://dx.doi.org/10.1016/j.tifs.2019.08...
). The shelf life of products depends on environmental conditions and exposure time (Oliveira et al., 2021Oliveira, C. C. M., Oliveira, D. R. B., & Silveira, V. Jr. (2021). Variability in the shelf life of table grapes from same batch when exposed under different ambient air conditions. Food Science and Technology, 41(Suppl. 1), 290-300. http://dx.doi.org/10.1590/fst.14220.
http://dx.doi.org/10.1590/fst.14220...
).

The fungal growth rules have been quantified and predicted by mathematical models (Garcia et al., 2009Garcia, D., Ramos, A. J., Sanchis, V., & Marín, S. (2009). Predicting mycotoxins in foods: a review. Food Microbiology, 26(8), 757-769. http://dx.doi.org/10.1016/j.fm.2009.05.014. PMid:19835759.
http://dx.doi.org/10.1016/j.fm.2009.05.0...
). As fungal growth leads to the release of mycotoxins from the substrate, control of fungal growth is essential according to predictive modeling (Marín et al., 2021Marín, S., Freire, L., Femenias, A., & Sant’Ana, A. S. (2021). Use of predictive modelling as tool for prevention of fungal spoilage at different points of the food chain. Current Opinion in Food Science, 41, 1-7. http://dx.doi.org/10.1016/j.cofs.2021.02.006.
http://dx.doi.org/10.1016/j.cofs.2021.02...
). Models have been used to evaluate the effects of different environmental factors on fungal growth and mycotoxin production in food. The effects of temperature, water activity (Bernáldez et al., 2017Bernáldez, V., Córdoba, J. J., Magan, N., Peromingo, B., & Rodríguez, A. (2017). The influence of ecophysiological factors on growth, aflR gene expression and aflatoxin B 1 production by a type strain of Aspergillus flavus. Lebensmittel-Wissenschaft + Technologie, 83, 283-291. http://dx.doi.org/10.1016/j.lwt.2017.05.030.
http://dx.doi.org/10.1016/j.lwt.2017.05....
), and pH (Casquete et al., 2017Casquete, R., Benito, M. J., Cordoba, M. G., Ruiz-Moyano, S., & Martin, A. (2017). The growth and aflatoxin production of Aspergillus flavus strains on a cheese model system are influenced by physicochemical factors. Journal of Dairy Science, 100(9), 6987-6996. http://dx.doi.org/10.3168/jds.2017-12865. PMid:28711264.
http://dx.doi.org/10.3168/jds.2017-12865...
) on the growth of Aspergillus flavus and the production of aflatoxin have been described by a linear model. A response surface analysis revealed an interaction between temperature and water activity on Fusarium mycotoxin production (Yu et al., 2021Yu, S., Jia, B., Li, K., Zhou, H., Lai, W., Tang, Y., Yan, Z., Sun, W., Liu, N., Yu, D., & Wu, A. (2021). Pre-warning of abiotic factors in maize required for potential contamination of fusarium mycotoxins via response surface analysis. Food Control, 121, 107570. http://dx.doi.org/10.1016/j.foodcont.2020.107570.
http://dx.doi.org/10.1016/j.foodcont.202...
).

The purpose of this study was to describe the effects of temperature and water activity on the growth of A. alternata and the production of Alternaria mycotoxins using predictive models. The results were verified on jujube agar medium.

2 Materials and methods

2.1 Preparation of spore and culture medium

An A. alternata (GenBank OL989878) strain was isolated and identified from dried jujube in Xinjiang, China. The strain produced high mycotoxin levels in preliminary tests. A. alternata was inoculated on potato dextrose agar (PDA) at 25 °C for 5 days, sterilized 0.05% Tween80 solution was added, and the mycelial suspension was scraped on the surface of the medium with a sterile rod, through four layers of gauze to filter the mycelium. Sterile water was diluted to 106 spores/mL using a blood count board. The water activity of the PDA was adjusted to 0.99 and 0.90 aw using glycerin instead of water. Water activity was measured with a water activity meter (HD-3A Smart Water Activity Meter, Wuxi Huake Instrument Co. Ltd., Wuxi, China). The jujube agar medium (JAM) was comprised of 3% jujube powder and 2% agar (25 °C, aw 0.903, pH 5.19).

2.2 Growth and dry weight evaluation

Growth was assessed daily by measuring two vertical diameters of the fungal colonies. The colonies were cut from the medium and transferred to a beaker filled with distilled water (about 100 mL), which was heated in a microwave for 10 min to melt the agar. The mycelia that remained intact were collected and transferred to dry pre-weighed filter paper and dried at 80 °C for 18 h (Garcia et al., 2013Garcia, D., Ramos, A. J., Sanchis, V., & Marín, S. (2013). Modeling kinetics of aflatoxin production by Aspergillus flavus in maize-based medium and maize grain. International Journal of Food Microbiology, 162(2), 182-189. http://dx.doi.org/10.1016/j.ijfoodmicro.2013.01.004. PMid:23422844.
http://dx.doi.org/10.1016/j.ijfoodmicro....
). Then, the filter paper was weighed and the dry weight of the biomass was calculated as the difference.

2.3 Mycotoxin detection

Three agar plugs were taken from different parts of the medium after 7 days of cultivation using a hole punch and placed together in a vial. One mL of methanol was added, and the extract was shaken and filtered (0.22 μm organic filter membrane) into a vial for 5 s. After 60 min, the extract was placed in another vial for the high-performance liquid chromatography (HPLC) analysis. UV was detected at 254 nm and 276 nm, respectively. The AOH, AME, and TeA standards were prepared in methanol. The HPLC analysis was performed using a Shimadzu HPLC system (Tokyo, Japan) equipped with a UV detector. The HPLC detection conditions were Agilent HC-C18 column (250 × 4.6 mm, 5 μm, Agilent Technologies, Santa Clara, CA, USA), column temperature of 35 °C, and a mobile phase system of water (A) and acetonitrile (B). The gradient elution procedure was 0 min, 20% B, 1 min, 40% B, 16 min, 80% B, 18 min, 80% B, 19 min, 20% B, and 22 min, 80% B. The injection volume was 10 μL, and the flow rate was 1.0 mL/min. The recovery rate of the method was > 80% when different amounts of Alternaria mycotoxins were added (range 0.1-100 mg/mL).

2.4 Growth model

The growth data at each temperature were subjected to the modified Gompertz model (Zwietering et al., 1990Zwietering, M. H., Jongenburger, I., Rombouts, F. M., & van ’t Riet, K. (1990). Modeling of the bacterial growth curve. Applied and Environmental Microbiology, 56(6), 1875-1881. http://dx.doi.org/10.1128/aem.56.6.1875-1881.1990. PMid:16348228.
http://dx.doi.org/10.1128/aem.56.6.1875-...
). The maximum radial growth rate (μmax, mm/d) and lag time (λ, d) were determined. The parameters obtained from the primary model were substituted into a secondary model affected by temperature, and the data were processed using IPMP (Huang, 2014Huang, L. (2014). IPMP 2013--a comprehensive data analysis tool for predictive microbiology. International Journal of Food Microbiology, 171, 100-107. http://dx.doi.org/10.1016/j.ijfoodmicro.2013.11.019. PMid:24334095.
http://dx.doi.org/10.1016/j.ijfoodmicro....
).

The Ratkowsky square-root model (Ratkowsky et al., 1983Ratkowsky, D. A., Lowry, R. K., McMeekin, T. A., Stokes, A. N., & Chandler, R. E. (1983). Model for bacterial culture growth rate throughout the entire biokinetic temperature range. Journal of Bacteriology, 154(3), 1222-1226. http://dx.doi.org/10.1128/jb.154.3.1222-1226.1983. PMid:6853443.
http://dx.doi.org/10.1128/jb.154.3.1222-...
).

μ m a x = a T T 0 1 e b T T m a x (1)

where μmax is the maximum radial growth rate (mm/d), a and b are coefficients, T is temperature (°C), T0 is the nominal/notational minimum temperature, and Tmax is the maximum estimated temperature.

The Huang square-root model (Huang et al., 2011Huang, L., Hwang, C. A., & Phillips, J. (2011). Evaluating the effect of temperature on microbial growth rate--the Ratkowsky and a Bělehrádek-type models. Journal of Food Science, 76(8), M547-M557. http://dx.doi.org/10.1111/j.1750-3841.2011.02345.x. PMid:22417595.
http://dx.doi.org/10.1111/j.1750-3841.20...
).

μ m a x = a T T m i n 0.75 1 e b T T m a x (2)

The same parameters as used in Equation 1.

The Rosso cardinal model (Rosso et al., 1993Rosso, L., Lobry, J. R., & Flandrois, J. P. (1993). An Unexpected correlation between cardinal temperatures of microbial growth highlighted by a new model. Journal of Theoretical Biology, 162(4), 447-463. http://dx.doi.org/10.1006/jtbi.1993.1099. PMid:8412234.
http://dx.doi.org/10.1006/jtbi.1993.1099...
).

μ m a x = μ o p t T T m a x T T m i n 2 T o p t T m i n T T o p t T o p t T m a x T o p t + T m i n 2 T T o p t T m i n (3)

where μmax is the maximum radial growth rate (mm/d), and µopt is the optimal radial growth rate (mm/d) at the optimum temperature (Topt). Tmin and Tmax are the minimum and maximum growth temperatures (°C).

2.5 Model validation

A f = 10 l o g μ p r e d i c t e d μ o b s e r v e d / n (4)
B f = 10 l o g μ p r e d i c t e d μ o b s e r v e d / n (5)
RMSE = μ m a x , p r e d μ m a x , o b s 2 n (6)

where μpredicted and μobserved are the predicted growth rate and observed growth rate respectively, and μmax,pred and μmax,obs are the maximum predicted growth rate and the observed growth rate, respectively. The accuracy factor (Af) and bias factor (Bf) were considered to evaluate model performance (Ross, 1996Ross, T. (1996). Indices for performance evaluation of predictive models in food microbiology. The Journal of Applied Bacteriology, 81(5), 501-508. http://dx.doi.org/10.1111/j.1365-2672.1996.tb03539.x. PMid:8939028.
http://dx.doi.org/10.1111/j.1365-2672.19...
). Af indicates how close the average predicted value is to the observed value. Bf evaluates the distance between the observed value and the prediction line (the closer Af and Bf are to 1, the better the model fit is). The performance of the regression analysis is reported as the root mean square error (RMSE).

2.6 Statistical analysis

Growth data and dry weight were fitted using StatGraphics 18 (Statgraphics Technologies Inc., The Plains, VA, USA). The toxin data were processed with Origin 2019 (OriginLab Corp., Northampton, MA, USA). The data are expressed as mean ± standard error.

3 Results

3.1 Primary model

The maximum radial growth rate (µ) and the lag time (λ) were estimated through the modified Gompertz primary model (Table 1). Up to and including 25 °C, the radial growth rate was 0.99 aw > JAM > 0.90 aw, but at 30 °C and 35 °C, JAM had the greatest growth rate, at 35 °C, 0.90 aw > 0.99 aw, suggesting that low water activity allows better survival at high temperatures. The lag times of 0.99 aw and 0.90 aw were similar at 10-25 °C. The JAM lag time was much higher than the other two. These results show that A. alternata grew earlier on PDA than on jujube agar medium.

Table 1
Radial growth rate (µ) and reciprocal lag time (1/λ) estimates using the modified Gompertz model of A. alternata on PDA with different water activity values (0.99 and 0.90 aw) and jujube agar medium (JAM).

3.2 Secondary model

The four different models were evaluated to describe the response of the fungus to the temperatures examined (Table 2). All parameters in Rosso cardinal model had physiological significance when estimating the initial parameters. However, the fitting parameters of the PDA differed greatly from the different water activity values. The optimum growth rate and optimum temperature were similar between JAM and 0.99 aw PDA. In the Ratkowsky Square-root model, the maximum growth temperatures of A. alternata in the three media were 36.75, 35.38, and 37.85 ℃, respectively (Equation 1). In the Huang Square-root model, the maximum growth temperatures of A. alternata were 36.64, 35.42, and 37.62 ℃, respectively (Equation 2). In the Rosso cardinal model, the maximum growth temperatures of A. alternata were 36.93, 35.30, and 38.11 °C, respectively, and the fungus did not grow at temperatures > 40 °C (Equation 3). The minimum temperatures of A. alternata in the Rosso cardinal model were 0.46, –9.63, and –4.20 °C respectively, with relatively low values and large differences. These results show the differences in strain growth between the different water activity values and different media. The optimum growth rates were 12.34, 8.68, and 11.07 mm/d, respectively. The predicted value of JAM was close to that of 0.99 aw PDA, and the observed growth rate of JAM was subjected to the 0.99 aw PDA predictive model for verification.

Table 2
The secondary models were used to evaluate the effect of temperature on growth rate.

3.3 Verification of the model

The observed and predicted values were compared intuitively, and prediction performance was evaluated numerically. The accuracy factor (Af) and bias factor (Bf) were used as mathematical indices (Table 3). As the secondary models only evaluated the effect of temperature on the radial growth rate of A. alternata, there was no difference in Af and Bf between the models. The accuracy factors were 1.1-1.2 (Equation 4), indicating large deviations between the predicted and observed values because the Af value depended on the medium. The bias factor was close to 1 (Equation 5), indicating a good correlation between the predicted and observed values. The Rosso cardinal model fit the experimental data well, as illustrated by the low RMSE (Equation 6).

Table 3
Accuracy factors (Af) and bias factors (Bf) for each of the growth predictive models.

3.4 Mycelial dry weight

On PDA and JAM, the dry weight of mycelia was positively correlated with the diameter (P < 0.05), and the dry weight growth rate of mycelia increased gradually with the increase of temperature (15-30 °C). The dry weight growth rate was 0.99 aw > 0.90 aw > JAM (Figure 1), and the growth rate on jujube medium was much lower than that on PDA medium at different temperatures, which was caused by the different medium components. A significant positive correlation was observed between the colony radius and dry biomass on maize agar medium, and toxin accumulation slowed before there was a decrease in dry biomass accumulation (Garcia et al., 2013Garcia, D., Ramos, A. J., Sanchis, V., & Marín, S. (2013). Modeling kinetics of aflatoxin production by Aspergillus flavus in maize-based medium and maize grain. International Journal of Food Microbiology, 162(2), 182-189. http://dx.doi.org/10.1016/j.ijfoodmicro.2013.01.004. PMid:23422844.
http://dx.doi.org/10.1016/j.ijfoodmicro....
).

Figure 1
Effect of temperature on the growth rate (μ) of Alternaria isolates by mycelial dry weight (a) 0.99 aw PDA; (b) 0.90 aw PDA; and (c) jujube agar medium (JAM).

3.5 Alternaria mycotoxins

PDA had the highest toxin content at 25 °C, JAM had the highest toxin content at 30 °C (Figure 2), and the mycotoxins produced by the Alternaria strains did not correlate well with maximum growth. The high aw resulted in higher toxin content at high temperature and a low aw resulted in higher toxin content at a low temperature on PDA. High aw and high temperature are more conducive to the production of mycotoxins. The toxin content of all media was mostly concentrated at 20-30 °C. No significant delay in toxin production or fungal growth was observed under the optimum conditions.

Figure 2
Effect of temperature on Alternaria mycotoxin content (a) 0.99 aw PDA; (b) 0.90 aw PDA; and (c) jujube agar medium (JAM).

3.6 Correlation between growth and mycotoxin

The colony diameter growth rate was significantly correlated with the dry weight growth rate of mycelia and daily Alternaria mycotoxin production (Table 4). Alternaria mycotoxin production was always correlated with the dry weight of mycelia when significant correlations were detected.

Table 4
Correlation among Alternaria mycotoxins and growth responses (Pearson coefficients).

4 Discussion

The growth and toxin production probabilities of mixed and single inoculations are very similar under non-isothermal conditions, considering the interactions between the same strains and the temperature changes (Aldars-García et al., 2015Aldars-García, L., Ramos, A. J., Sanchis, V., & Marín, S. (2015). An attempt to model the probability of growth and aflatoxin B1 production of Aspergillus flavus under non-isothermal conditions in pistachio nuts. Food Microbiology, 51, 117-129. http://dx.doi.org/10.1016/j.fm.2015.05.013. PMid:26187836.
http://dx.doi.org/10.1016/j.fm.2015.05.0...
). Growth models are used to predict growth boundaries and the models were applied to prevent toxin production. Polysporous inoculation resulted in a higher growth rate and a shorter lag period than monosporous inoculation, and the polysporous inoculation probability model is more accurate (Aldars-García et al., 2017Aldars-García, L., Sanchis, V., Ramos, A. J., & Marín, S. (2017). Single vs multiple-spore inoculum effect on growth kinetic parameters and modeled probabilities of growth and aflatoxin B1 production of Aspergillus flavus on pistachio extract agar. International Journal of Food Microbiology, 243, 28-35. http://dx.doi.org/10.1016/j.ijfoodmicro.2016.11.026. PMid:27940413.
http://dx.doi.org/10.1016/j.ijfoodmicro....
). Polyspore inoculation was used in this experiment, and the hysteresis period was relatively short, which was greatly affected by the inoculation amount.

The germination time of A. arborescens on tomato medium was the lowest at 0.995 aw, and 25 °C and 30 °C, and the maximum growth rate was 7.21 mm/d at 0.995 aw and 30 °C, and 6.97 mm/d at 25 °C (P > 0.05). AOH, AME, and TeA greatly accumulated at 0.975 aw and 30 °C, although a large number of toxins were detected at 25 °C (Vaquera et al., 2014Vaquera, S., Patriarca, A., & Fernandez Pinto, V. (2014). Water activity and temperature effects on growth of Alternaria arborescens on tomato medium. International Journal of Food Microbiology, 185, 136-139. http://dx.doi.org/10.1016/j.ijfoodmicro.2014.06.007. PMid:24964391.
http://dx.doi.org/10.1016/j.ijfoodmicro....
, 2016Vaquera, S., Patriarca, A., & Fernandez Pinto, V. (2016). Influence of environmental parameters on mycotoxin production by Alternaria arborescens. International Journal of Food Microbiology, 219, 44-49. http://dx.doi.org/10.1016/j.ijfoodmicro.2015.12.003. PMid:26708802.
http://dx.doi.org/10.1016/j.ijfoodmicro....
). The optimum temperature for maximum toxin content and maximum growth rate was the same, but the aw value was different. In this experiment, the growth rate of A. alternata on jujube agar medium was 11.25 mm/d at 25 °C. The total AOH, AME, and TeA contents accumulated at 25 °C, and a correlation was detected between the AOH, AME, and TeA contents and the maximum growth rate. Climate can also affect the growth and toxicity of A. alternata on tomato, including temperature and other factors (Van de Perre et al., 2015Van de Perre, E., Jacxsens, L., Liu, C., Devlieghere, F., & De Meulenaer, B. (2015). Climate impact on Alternaria moulds and their mycotoxins in fresh produce: The case of the tomato chain. Food Research International, 68, 41-46. http://dx.doi.org/10.1016/j.foodres.2014.10.014.
http://dx.doi.org/10.1016/j.foodres.2014...
). High or low temperatures can inhibit the production of mycotoxins. When the temperature at harvest time is close to the optimum temperature for fungal toxicity, the toxin content will increase, leading to deteriorated crops. Therefore, it is important to consider the effects of temperature during crop growth, harvest and storage, and use models to predict the effects of temperature on fungal growth and the toxins produced to take preventive measures in advance.

The optimum temperature for A. alternata on Sabouraud dextrose agar (SDA) was 23.99 °C, the minimum temperature was –4.06 °C, and the maximum temperature was 34.99 °C. Growth rates verified on pear culture medium were almost the same at the optimum temperature but were significantly lower on pears than on SDA (Sardella et al., 2018Sardella, D., Gatt, R., & Valdramidis, V. P. (2018). Modelling the growth of pear postharvest fungal isolates at different temperatures. Food Microbiology, 76, 450-456. http://dx.doi.org/10.1016/j.fm.2018.07.010. PMid:30166173.
http://dx.doi.org/10.1016/j.fm.2018.07.0...
). A. alternata has an optimum temperature of 25.18 °C, a minimum temperature of 0.46 °C, and a maximum temperature of 36.93 °C on PDA. The temperature range varies depending on the strain and medium. The boundaries of aflatoxin production and fungal growth on pistachios are the same, but the optimum growth temperature is different. The temperature at which the maximum toxin production occurs is earlier than the maximum fungal growth rate (Marín et al., 2012Marín, S., Ramos, A. J., & Sanchis, V. (2012). Modelling Aspergillus flavus growth and aflatoxins production in pistachio nuts. Food Microbiology, 32(2), 378-388. http://dx.doi.org/10.1016/j.fm.2012.07.018. PMid:22986204.
http://dx.doi.org/10.1016/j.fm.2012.07.0...
). Different from the results of this experiment, the maximum fungal growth rate was accompanied by maximum toxin accumulation, which may have been caused by differences between the strain and the substrate.

The independent black pepper experimental data were used to verify the established model, and the Bf (0.73-1.03) and Af (0.97-1.36) showed that the model examined was a conservative prediction of the growth rates of Aspergillus flavus and Aspergillus parasitica (Yogendrarajah et al., 2016Yogendrarajah, P., Vermeulen, A., Jacxsens, L., Mavromichali, E., De Saeger, S., De Meulenaer, B., & Devlieghere, F. (2016). Mycotoxin production and predictive modelling kinetics on the growth of Aspergillus flavus and Aspergillus parasiticus isolates in whole black peppercorns (Piper nigrum L). International Journal of Food Microbiology, 228, 44-57. http://dx.doi.org/10.1016/j.ijfoodmicro.2016.03.015. PMid:27088871.
http://dx.doi.org/10.1016/j.ijfoodmicro....
). Botrytis cinerea and Penicillium expansum tested in simulated grape juice medium and grape juice agar, the Bf is close to 1 indicates a safe prediction, the Af (1.11-1.29) is a large deviation (Judet-Correia et al., 2010Judet-Correia, D., Bollaert, S., Duquenne, A., Charpentier, C., Bensoussan, M., & Dantigny, P. (2010). Validation of a predictive model for the growth of Botrytis cinerea and Penicillium expansum on grape berries. International Journal of Food Microbiology, 142(1-2), 106-113. http://dx.doi.org/10.1016/j.ijfoodmicro.2010.06.009. PMid:20619474.
http://dx.doi.org/10.1016/j.ijfoodmicro....
). In this study, A. alternata was verified on jujube agar medium, and the accuracy factor indicated a large deviation, while the bias factor indicated that the model had a safe prediction.

A. tenuissima and A. arborescens produce AOH and AME in vitro and on apple fruits (Ntasiou et al., 2015Ntasiou, P., Myresiotis, C., Konstantinou, S., Papadopoulou-Mourkidou, E., & Karaoglanidis, G. S. (2015). Identification, characterization and mycotoxigenic ability of Alternaria spp. causing core rot of apple fruit in Greece. International Journal of Food Microbiology, 197, 22-29. http://dx.doi.org/10.1016/j.ijfoodmicro.2014.12.008. PMid:25560914.
http://dx.doi.org/10.1016/j.ijfoodmicro....
). However, the toxin-producing capacity of Alternaria strains between in vitro culture and its actual occurrence in food is not strongly correlated. Although AOH and AME are the toxins most commonly produced by isolates on medium, they are much less prevalent in pepper fruits. In contrast, TeA is produced in vitro by a smaller number of isolates, but more fruits are contaminated with this toxin (Masood et al., 2015Masood, M., Iqbal, S. Z., Asi, M. R., & Malik, N. (2015). Natural occurrence of aflatoxins in dry fruits and edible nuts. Food Control, 55, 62-65. http://dx.doi.org/10.1016/j.foodcont.2015.02.041.
http://dx.doi.org/10.1016/j.foodcont.201...
). Therefore, convenient and rapid toxin detection methods unique to different foods are an important tool for control strategies and are not limited to toxin models to reduce toxin risk.

5 Conclusion

In this study, primary and secondary models were established through the effects of different temperatures on A. alternata, and the applicability of the model was confirmed in jujube agar medium. No significant delay was observed in the production of Alternaria mycotoxins or fungal growth under the optimum conditions, which provided a theoretical basis for the risk assessment. The colony diameter growth rate was significantly correlated with the dry weight growth rate of mycelia and daily Alternaria mycotoxin production. It may be possible to build a growth model for harmful fungi isolated from different food substrates, compare the same and different growth conditions of the same fungus, set different correction factors, and apply them to actual food to prevent fungal toxins.

Acknowledgements

The authors wish to thank the anonymous reviewers, whose insightful comments and helpful suggestions significantly contributed to improving this paper.

  • Practical Application: The effects of temperature and water activity on the growth of Alternaria alternata were predicted by secondary models.
  • Funding

    This research was funded by Innovation and Development Pillar Program for Key Industries in Southern Xinjiang of Xinjiang Production and Construction Corps, grant number 2018DB002 and the Shihezi University Achievement Transformation and Technology Promotion Program, grant number CGZH201904.

[[Q1: Please confirm if the quote from Equation 6 can remain in this part of the text. Q1]]

References

  • Aldars-García, L., Ramos, A. J., Sanchis, V., & Marín, S. (2015). An attempt to model the probability of growth and aflatoxin B1 production of Aspergillus flavus under non-isothermal conditions in pistachio nuts. Food Microbiology, 51, 117-129. http://dx.doi.org/10.1016/j.fm.2015.05.013 PMid:26187836.
    » http://dx.doi.org/10.1016/j.fm.2015.05.013
  • Aldars-García, L., Sanchis, V., Ramos, A. J., & Marín, S. (2017). Single vs multiple-spore inoculum effect on growth kinetic parameters and modeled probabilities of growth and aflatoxin B1 production of Aspergillus flavus on pistachio extract agar. International Journal of Food Microbiology, 243, 28-35. http://dx.doi.org/10.1016/j.ijfoodmicro.2016.11.026 PMid:27940413.
    » http://dx.doi.org/10.1016/j.ijfoodmicro.2016.11.026
  • Bernáldez, V., Córdoba, J. J., Magan, N., Peromingo, B., & Rodríguez, A. (2017). The influence of ecophysiological factors on growth, aflR gene expression and aflatoxin B 1 production by a type strain of Aspergillus flavus. Lebensmittel-Wissenschaft + Technologie, 83, 283-291. http://dx.doi.org/10.1016/j.lwt.2017.05.030
    » http://dx.doi.org/10.1016/j.lwt.2017.05.030
  • Casquete, R., Benito, M. J., Cordoba, M. G., Ruiz-Moyano, S., & Martin, A. (2017). The growth and aflatoxin production of Aspergillus flavus strains on a cheese model system are influenced by physicochemical factors. Journal of Dairy Science, 100(9), 6987-6996. http://dx.doi.org/10.3168/jds.2017-12865 PMid:28711264.
    » http://dx.doi.org/10.3168/jds.2017-12865
  • Chen, K., Fan, D., Fu, B., Zhou, J., & Li, H. (2019). Comparison of physical and chemical composition of three chinese jujube (Ziziphus jujuba Mill.) cultivars cultivated in four districts of Xinjiang region in China. Food Science and Technology, 39(4), 912-921. http://dx.doi.org/10.1590/fst.11118
    » http://dx.doi.org/10.1590/fst.11118
  • Garcia, D., Ramos, A. J., Sanchis, V., & Marín, S. (2009). Predicting mycotoxins in foods: a review. Food Microbiology, 26(8), 757-769. http://dx.doi.org/10.1016/j.fm.2009.05.014 PMid:19835759.
    » http://dx.doi.org/10.1016/j.fm.2009.05.014
  • Garcia, D., Ramos, A. J., Sanchis, V., & Marín, S. (2013). Modeling kinetics of aflatoxin production by Aspergillus flavus in maize-based medium and maize grain. International Journal of Food Microbiology, 162(2), 182-189. http://dx.doi.org/10.1016/j.ijfoodmicro.2013.01.004 PMid:23422844.
    » http://dx.doi.org/10.1016/j.ijfoodmicro.2013.01.004
  • Huang, L. (2014). IPMP 2013--a comprehensive data analysis tool for predictive microbiology. International Journal of Food Microbiology, 171, 100-107. http://dx.doi.org/10.1016/j.ijfoodmicro.2013.11.019 PMid:24334095.
    » http://dx.doi.org/10.1016/j.ijfoodmicro.2013.11.019
  • Huang, L., Hwang, C. A., & Phillips, J. (2011). Evaluating the effect of temperature on microbial growth rate--the Ratkowsky and a Bělehrádek-type models. Journal of Food Science, 76(8), M547-M557. http://dx.doi.org/10.1111/j.1750-3841.2011.02345.x PMid:22417595.
    » http://dx.doi.org/10.1111/j.1750-3841.2011.02345.x
  • Ji, X., Hou, C., Yan, Y., Shi, M., & Liu, Y. (2020). Comparison of structural characterization and antioxidant activity of polysaccharides from jujube (Ziziphus jujuba Mill.) fruit. International Journal of Biological Macromolecules, 149, 1008-1018. http://dx.doi.org/10.1016/j.ijbiomac.2020.02.018 PMid:32032709.
    » http://dx.doi.org/10.1016/j.ijbiomac.2020.02.018
  • Judet-Correia, D., Bollaert, S., Duquenne, A., Charpentier, C., Bensoussan, M., & Dantigny, P. (2010). Validation of a predictive model for the growth of Botrytis cinerea and Penicillium expansum on grape berries. International Journal of Food Microbiology, 142(1-2), 106-113. http://dx.doi.org/10.1016/j.ijfoodmicro.2010.06.009 PMid:20619474.
    » http://dx.doi.org/10.1016/j.ijfoodmicro.2010.06.009
  • Lahouar, A., Marín, S., Crespo-Sempere, A., Said, S., & Sanchis, V. (2017). Influence of temperature, water activity and incubation time on fungal growth and production of ochratoxin A and zearalenone by toxigenic Aspergillus tubingensis and Fusarium incarnatum isolates in sorghum seeds. International Journal of Food Microbiology, 242, 53-60. http://dx.doi.org/10.1016/j.ijfoodmicro.2016.11.015 PMid:27883966.
    » http://dx.doi.org/10.1016/j.ijfoodmicro.2016.11.015
  • Li, N., Fu, L., Song, Y., Li, J., Xue, X., Li, S., & Li, L. (2020). Wax composition and concentration in jujube (Ziziphus jujuba Mill.) cultivars with differential resistance to fruit cracking. Journal of Plant Physiology, 255, 153294. http://dx.doi.org/10.1016/j.jplph.2020.153294 PMid:33070052.
    » http://dx.doi.org/10.1016/j.jplph.2020.153294
  • Marín, S., Freire, L., Femenias, A., & Sant’Ana, A. S. (2021). Use of predictive modelling as tool for prevention of fungal spoilage at different points of the food chain. Current Opinion in Food Science, 41, 1-7. http://dx.doi.org/10.1016/j.cofs.2021.02.006
    » http://dx.doi.org/10.1016/j.cofs.2021.02.006
  • Marín, S., Ramos, A. J., & Sanchis, V. (2012). Modelling Aspergillus flavus growth and aflatoxins production in pistachio nuts. Food Microbiology, 32(2), 378-388. http://dx.doi.org/10.1016/j.fm.2012.07.018 PMid:22986204.
    » http://dx.doi.org/10.1016/j.fm.2012.07.018
  • Martins, C., Vidal, A., De Boevre, M., De Saeger, S., Nunes, C., Torres, D., Goios, A., Lopes, C., Assuncao, R., & Alvito, P. (2019). Exposure assessment of Portuguese population to multiple mycotoxins: The human biomonitoring approach. International Journal of Hygiene and Environmental Health, 222(6), 913-925. http://dx.doi.org/10.1016/j.ijheh.2019.06.010 PMid:31253542.
    » http://dx.doi.org/10.1016/j.ijheh.2019.06.010
  • Masood, M., Iqbal, S. Z., Asi, M. R., & Malik, N. (2015). Natural occurrence of aflatoxins in dry fruits and edible nuts. Food Control, 55, 62-65. http://dx.doi.org/10.1016/j.foodcont.2015.02.041
    » http://dx.doi.org/10.1016/j.foodcont.2015.02.041
  • Ntasiou, P., Myresiotis, C., Konstantinou, S., Papadopoulou-Mourkidou, E., & Karaoglanidis, G. S. (2015). Identification, characterization and mycotoxigenic ability of Alternaria spp. causing core rot of apple fruit in Greece. International Journal of Food Microbiology, 197, 22-29. http://dx.doi.org/10.1016/j.ijfoodmicro.2014.12.008 PMid:25560914.
    » http://dx.doi.org/10.1016/j.ijfoodmicro.2014.12.008
  • Oliveira, C. C. M., Oliveira, D. R. B., & Silveira, V. Jr. (2021). Variability in the shelf life of table grapes from same batch when exposed under different ambient air conditions. Food Science and Technology, 41(Suppl. 1), 290-300. http://dx.doi.org/10.1590/fst.14220
    » http://dx.doi.org/10.1590/fst.14220
  • Pane, C., Fratianni, F., Parisi, M., Nazzaro, F., & Zaccardelli, M. (2016). Control of Alternaria post-harvest infections on cherry tomato fruits by wild pepper phenolic-rich extracts. Crop Protection (Guildford, Surrey), 84, 81-87. http://dx.doi.org/10.1016/j.cropro.2016.02.015
    » http://dx.doi.org/10.1016/j.cropro.2016.02.015
  • Puntscher, H., Cobankovic, I., Marko, D., & Warth, B. (2019). Quantitation of free and modified Alternaria mycotoxins in European food products by LC-MS/MS. Food Control, 102, 157-165. http://dx.doi.org/10.1016/j.foodcont.2019.03.019
    » http://dx.doi.org/10.1016/j.foodcont.2019.03.019
  • Ratkowsky, D. A., Lowry, R. K., McMeekin, T. A., Stokes, A. N., & Chandler, R. E. (1983). Model for bacterial culture growth rate throughout the entire biokinetic temperature range. Journal of Bacteriology, 154(3), 1222-1226. http://dx.doi.org/10.1128/jb.154.3.1222-1226.1983 PMid:6853443.
    » http://dx.doi.org/10.1128/jb.154.3.1222-1226.1983
  • Ross, T. (1996). Indices for performance evaluation of predictive models in food microbiology. The Journal of Applied Bacteriology, 81(5), 501-508. http://dx.doi.org/10.1111/j.1365-2672.1996.tb03539.x PMid:8939028.
    » http://dx.doi.org/10.1111/j.1365-2672.1996.tb03539.x
  • Rosso, L., Lobry, J. R., & Flandrois, J. P. (1993). An Unexpected correlation between cardinal temperatures of microbial growth highlighted by a new model. Journal of Theoretical Biology, 162(4), 447-463. http://dx.doi.org/10.1006/jtbi.1993.1099 PMid:8412234.
    » http://dx.doi.org/10.1006/jtbi.1993.1099
  • Sardar, M., Ahmed, W., Al Ayoubi, S., Nisa, S., Bibi, Y., Sabir, M., Khan, M. M., Ahmed, W., & Qayyum, A. (2022). Fungicidal synergistic effect of biogenically synthesized zinc oxide and copper oxide nanoparticles against Alternaria citri causing citrus black rot disease. Saudi Journal of Biological Sciences, 29(1), 88-95. http://dx.doi.org/10.1016/j.sjbs.2021.08.067 PMid:35002397.
    » http://dx.doi.org/10.1016/j.sjbs.2021.08.067
  • Sardella, D., Gatt, R., & Valdramidis, V. P. (2018). Modelling the growth of pear postharvest fungal isolates at different temperatures. Food Microbiology, 76, 450-456. http://dx.doi.org/10.1016/j.fm.2018.07.010 PMid:30166173.
    » http://dx.doi.org/10.1016/j.fm.2018.07.010
  • Thanushree, M. P., Sailendri, D., Yoha, K. S., Moses, J. A., & Anandharamakrishnan, C. (2019). Mycotoxin contamination in food: An exposition on spices. Trends in Food Science & Technology, 93, 69-80. http://dx.doi.org/10.1016/j.tifs.2019.08.010
    » http://dx.doi.org/10.1016/j.tifs.2019.08.010
  • Van de Perre, E., Jacxsens, L., Liu, C., Devlieghere, F., & De Meulenaer, B. (2015). Climate impact on Alternaria moulds and their mycotoxins in fresh produce: The case of the tomato chain. Food Research International, 68, 41-46. http://dx.doi.org/10.1016/j.foodres.2014.10.014
    » http://dx.doi.org/10.1016/j.foodres.2014.10.014
  • Vaquera, S., Patriarca, A., & Fernandez Pinto, V. (2014). Water activity and temperature effects on growth of Alternaria arborescens on tomato medium. International Journal of Food Microbiology, 185, 136-139. http://dx.doi.org/10.1016/j.ijfoodmicro.2014.06.007 PMid:24964391.
    » http://dx.doi.org/10.1016/j.ijfoodmicro.2014.06.007
  • Vaquera, S., Patriarca, A., & Fernandez Pinto, V. (2016). Influence of environmental parameters on mycotoxin production by Alternaria arborescens. International Journal of Food Microbiology, 219, 44-49. http://dx.doi.org/10.1016/j.ijfoodmicro.2015.12.003 PMid:26708802.
    » http://dx.doi.org/10.1016/j.ijfoodmicro.2015.12.003
  • Wang, F., Saito, S., Michailides, T. J., & Xiao, C.-L. (2021). Postharvest use of natamycin to control Alternaria rot on blueberry fruit caused by Alternaria alternata and A. arborescens. Postharvest Biology and Technology, 172, 111383. http://dx.doi.org/10.1016/j.postharvbio.2020.111383
    » http://dx.doi.org/10.1016/j.postharvbio.2020.111383
  • Yogendrarajah, P., Vermeulen, A., Jacxsens, L., Mavromichali, E., De Saeger, S., De Meulenaer, B., & Devlieghere, F. (2016). Mycotoxin production and predictive modelling kinetics on the growth of Aspergillus flavus and Aspergillus parasiticus isolates in whole black peppercorns (Piper nigrum L). International Journal of Food Microbiology, 228, 44-57. http://dx.doi.org/10.1016/j.ijfoodmicro.2016.03.015 PMid:27088871.
    » http://dx.doi.org/10.1016/j.ijfoodmicro.2016.03.015
  • Yu, S., Jia, B., Li, K., Zhou, H., Lai, W., Tang, Y., Yan, Z., Sun, W., Liu, N., Yu, D., & Wu, A. (2021). Pre-warning of abiotic factors in maize required for potential contamination of fusarium mycotoxins via response surface analysis. Food Control, 121, 107570. http://dx.doi.org/10.1016/j.foodcont.2020.107570
    » http://dx.doi.org/10.1016/j.foodcont.2020.107570
  • Zhang, S., Wang, Q., Guo, Y., Kang, L., & Yu, Y. (2020). Carbon monoxide enhances the resistance of jujube fruit against postharvest Alternaria rot. Postharvest Biology and Technology, 168, 111268. http://dx.doi.org/10.1016/j.postharvbio.2020.111268
    » http://dx.doi.org/10.1016/j.postharvbio.2020.111268
  • Zwietering, M. H., Jongenburger, I., Rombouts, F. M., & van ’t Riet, K. (1990). Modeling of the bacterial growth curve. Applied and Environmental Microbiology, 56(6), 1875-1881. http://dx.doi.org/10.1128/aem.56.6.1875-1881.1990 PMid:16348228.
    » http://dx.doi.org/10.1128/aem.56.6.1875-1881.1990

Publication Dates

  • Publication in this collection
    13 May 2022
  • Date of issue
    2022

History

  • Received
    27 Nov 2021
  • Accepted
    25 Jan 2022
Sociedade Brasileira de Ciência e Tecnologia de Alimentos Av. Brasil, 2880, Caixa Postal 271, 13001-970 Campinas SP - Brazil, Tel.: +55 19 3241.5793, Tel./Fax.: +55 19 3241.0527 - Campinas - SP - Brazil
E-mail: revista@sbcta.org.br