nutriFOODchem unit, Department of Food Safety and Food Quality (partner in Food2Know), Faculty of Bioscience Engineering, Ghent University, Belgium; Laboratory of Food Analysis, Department of Bioanalysis (partner in Food2Know), Faculty of Pharmaceutical Sciences, Ghent University, Belgium.
Laboratory of Food Microbiology and Food Preservation, Department of Food Safety and Food Quality (partner in Food2Know), Faculty of Bioscience Engineering, Ghent University, Belgium.
Int J Food Microbiol. 2016 Jul 2;228:44-57. doi: 10.1016/j.ijfoodmicro.2016.03.015. Epub 2016 Mar 19.
The growth and mycotoxin production of three Aspergillus flavus isolates and an Aspergillus parasiticus isolate were studied in whole black peppercorns (Piper nigrum L.) using a full factorial design with seven water activity (aw) (0.826-0.984) levels and three temperatures (22, 30 and 37°C). Growth rates and lag phases were estimated using linear regression. Diverse secondary models were assessed for their ability to describe the radial growth rate as a function of individual and combined effect of aw and temperature. Optimum radial growth rate ranged from 0.75±0.04 to 2.65±0.02mm/day for A. flavus and 1.77±0.10 to 2.50±0.10mm/day for A. parasiticus based on the Rosso cardinal estimations. Despite the growth failure of some isolates at marginal conditions, all the studied models showed good performance to predict the growth rates. Validation of the models was performed on independently derived data. The bias factors (0.73-1.03), accuracy factors (0.97-1.36) and root mean square error (0.050-0.278) show that the examined models are conservative predictors of the colony growth rate of both fungal species in black peppers. The Rosso cardinal model can be recommended to describe the individual aw effect while the extended Gibson model was the best model for describing the combined effect of aw and temperature on the growth rate of both fungal species in peppercorns. Temperature optimum ranged from 30 to 33°C, while aw optimum was 0.87-0.92 as estimated by multi-factorial cardinal model for both species. The estimated minimum temperature and aw for A. flavus and A. parasiticus for growth were 11-16°C and 0.73-0.76, respectively, hence, achieving these conditions should be considered during storage to prevent the growth of these mycotoxigenic fungal species in black peppercorns. Following the growth study, production of mycotoxins (aflatoxins B1, B2, G1, G2, sterigmatocystin and O-methyl sterigmatocystin (OMST)) was quantified using LC-MS/MS. Very small quantities of AFB1 (<LOQ-9.1μg/kg) were produced only by A. parasiticus. OMST was not produced in any growth conditions by both species. Sterigmatocystin (<LOQ-76.7μg/kg) was the dominant mycotoxin found. High variability in mycotoxin production restricted the modelling of mycotoxin production in black pepper.
采用完全因子设计，在整个黑胡椒粒（Piper nigrum L.）中研究了三个黄曲霉（Aspergillus flavus）分离株和一个寄生曲霉（Aspergillus parasiticus）分离株的生长和产毒情况，该设计涉及七个水分活度（aw）（0.826-0.984）水平和三个温度（22、30 和 37°C）。使用线性回归估计生长率和滞后期。评估了各种二次模型，以评估它们描述 aw 和温度单独和联合作用下的径向生长率的能力。根据 Rosso cardinal 估计，黄曲霉和寄生曲霉的最佳径向生长速率分别为 0.75±0.04 至 2.65±0.02mm/天和 1.77±0.10 至 2.50±0.10mm/天。尽管在边缘条件下一些分离株的生长失败，但所有研究的模型都显示出良好的性能，可以预测生长速率。使用独立获得的数据对模型进行了验证。偏差因子（0.73-1.03）、准确度因子（0.97-1.36）和均方根误差（0.050-0.278）表明，所检查的模型是对黑胡椒中两种真菌物种的菌落生长率的保守预测因子。Rosso cardinal 模型可用于描述 aw 的单独影响，而扩展的 Gibson 模型是描述 aw 和温度对两种真菌物种在胡椒粒中生长速率的联合影响的最佳模型。通过多因子 cardinal 模型估计，两种真菌的温度最佳范围为 30-33°C，aw 最佳范围为 0.87-0.92。估计黄曲霉和寄生曲霉生长的最低温度和 aw 分别为 11-16°C 和 0.73-0.76，因此，在储存过程中应考虑到这些条件，以防止这些产毒真菌在黑胡椒粒中生长。在生长研究之后，使用 LC-MS/MS 定量了产毒（黄曲霉毒素 B1、B2、G1、G2、桔青霉素和 O-甲基桔青霉素（OMST））。只有寄生曲霉产生了极少量的 AFB1（<LOQ-9.1μg/kg）。在任何生长条件下，两种真菌都没有产生 OMST。发现桔青霉素（<LOQ-76.7μg/kg）是主要的霉菌毒素。霉菌毒素产生的高度变异性限制了黑胡椒中霉菌毒素产生的建模。
