Centre of Excellence for Food Safety Research (CEFSR), Faculty of Food Science and Technology, University Putra Malaysia, Serdang, Selangor Darul Ehsan, Malaysia.
J Appl Microbiol. 2011 Nov;111(5):1262-74. doi: 10.1111/j.1365-2672.2011.05134.x. Epub 2011 Sep 29.
This study was conducted to characterize the growth of and aflatoxin production by Aspergillus flavus on paddy and to develop kinetic models describing the growth rate as a function of water activity (a(w)) and temperature.
The growth of A. flavus on paddy and aflatoxin production were studied following a full factorial design with seven a(w) levels within the range of 0·82-0·99 and seven temperatures between 10 and 43°C. The growth of the fungi, expressed as colony diameter (mm), was measured daily, and the aflatoxins were analysed using HPLC with a fluorescence detector. The maximum colony growth rates of both isolates were estimated by fitting the primary model of Baranyi to growth data. Three potentially suitable secondary models, Rosso, polynomial and Davey, were assessed for their ability to describe the radial growth rate as a function of temperature and a(w). Both strains failed to grow at the marginal temperatures (10 and 43°C), regardless of the a(w) studied, and at the a(w) level of 0·82, regardless of temperature. Despite that the predictions of all studied models showed good agreement with the observed growth rates, Davey model proved to be the best predictor of the experimental data. The cardinal parameters as estimated by Rosso model were comparable to those reported in previous studies. Toxins were detected in the range of 0·86-0·99 a(w) with optimal a(w) of 0·98 and optimal temperature in the range of 25-30°C.
The influences of a(w) and temperature on the growth of A. flavus and aflatoxin production were successfully characterized, and the models developed were found to be capable of providing good, related estimates of the growth rates.
The results of this study could be effectively implemented in minimizing the risk of aflatoxin contamination of the paddy at postharvest.
本研究旨在描述黄曲霉在稻谷上的生长和产毒情况，并建立描述其生长速率与水分活度（a(w)）和温度关系的动力学模型。
采用全因子设计，在 0.82-0.99 范围内设置 7 个 a(w)水平和 10-43°C 之间的 7 个温度，研究黄曲霉在稻谷上的生长和产毒情况。用菌落直径（mm）每日测量真菌的生长情况，并用 HPLC 荧光检测器分析黄曲霉毒素。通过将 Baranyi 基本模型拟合到生长数据中，估算出两个分离株的最大菌落生长速率。评估了 Rosso、多项式和 Davey 三个潜在合适的二次模型，以描述其在温度和 a(w)下的径向生长速率。无论研究的 a(w)如何，两个菌株都无法在边缘温度（10 和 43°C）下生长，无论温度如何，在 a(w)水平为 0.82 时也无法生长。尽管所有研究模型的预测与观察到的生长速率都有很好的一致性，但 Davey 模型被证明是实验数据的最佳预测模型。Rosso 模型估计的特征参数与以前的研究报道相当。毒素在 0.86-0.99 a(w)范围内检测到，最佳 a(w)为 0.98，最佳温度范围为 25-30°C。
成功地描述了 a(w)和温度对黄曲霉生长和产毒的影响，所建立的模型能够很好地预测生长速率。
本研究的结果可有效地用于降低稻谷产后黄曲霉毒素污染的风险。
