Szonyi Barbara, Huang Guangwei, Birmingham Tim, Gizachew Dawit
Department of Chemistry and Physics, Purdue University Northwest, Hammond, IN 46323, USA.
Almond Board of California, 1150 Ninth St., Ste. 1500, Modesto, CA 95354, USA.
J Food Prot. 2025 Jun 23;88(7):100531. doi: 10.1016/j.jfp.2025.100531. Epub 2025 May 6.
Almond hulls are economically important by-products marketed as dairy cattle feed in California. This study investigated the ability of Aspergillus flavus and Aspergillus parasiticus to grow and produce aflatoxins on almond hulls. In-hull almond kernels and hull fragments were incubated at 0.92-0.98 a and 20-35 °C for 20 days. There was no growth and aflatoxin production at 0.92 a by either fungus. Both A. flavus and A. parasiticus were able to grow at 0.95-0.98 a and 20-35 °C on almond hulls. While Aspergillus flavus grew well on the in-hull almonds at 0.95-0.98 a and 27-35 °C, it did not produce any aflatoxins under any of the study conditions. In contrast, A. parasiticus produced aflatoxins B, G, B and G. On the in-hull kernels, A. parasiticus synthesized the highest levels of total aflatoxins (>100 µg/kg) at 27 °C and 0.95-0.98 a. On the hull fragments, 20 °C and 0.95 a were the ideal conditions for aflatoxin production, where the average total aflatoxin production was 35 µg/kg. The predominant aflatoxin synthesized by A. parasiticus was AFG, accounting for up to 100% of the total aflatoxin produced on the hulls, which highlights the need to measure and report total aflatoxins (rather than AFB only) for almond hulls. Further studies are needed to determine the factors that limit AFB synthesis by A. flavus and A. parasiticus on almond hulls. Also, the types of phenolic acids present in California almond hulls need to be identified.
杏仁壳是加利福尼亚州作为奶牛饲料销售的具有经济重要性的副产品。本研究调查了黄曲霉和寄生曲霉在杏仁壳上生长并产生黄曲霉毒素的能力。带壳杏仁仁和壳碎片在水分含量0.92 - 0.98 a和20 - 35°C下培养20天。两种真菌在水分含量0.92 a时均不生长且不产生黄曲霉毒素。黄曲霉和寄生曲霉在水分含量0.95 - 0.98 a和20 - 35°C下都能在杏仁壳上生长。虽然黄曲霉在水分含量0.95 - 0.98 a和27 - 35°C的带壳杏仁上生长良好，但在任何研究条件下都不产生任何黄曲霉毒素。相比之下，寄生曲霉产生了黄曲霉毒素B、G、B₁和G₂。在带壳果仁上，寄生曲霉在27°C和水分含量0.95 - 0.98 a时合成的总黄曲霉毒素水平最高（>100 μg/kg）。在壳碎片上，20°C和水分含量0.95 a是黄曲霉毒素产生的理想条件，此时平均总黄曲霉毒素产量为35 μg/kg。寄生曲霉合成的主要黄曲霉毒素是AFG₂，占壳上产生的总黄曲霉毒素的100%，这突出了对杏仁壳测量和报告总黄曲霉毒素（而不仅仅是AFB₁）的必要性。需要进一步研究以确定限制黄曲霉和寄生曲霉在杏仁壳上合成AFB₁的因素。此外，还需要确定加利福尼亚杏仁壳中存在的酚酸类型。
