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紫外联合冷等离子体降解玉米中黄曲霉毒素B1及对玉米品质的影响

Degradation of aflatoxin B1 in maize by ultraviolet combined with cold plasma and its effect on maize quality

  • 摘要: 为开发绿色、高效的玉米物理脱毒技术,该研究将紫外辐照与冷等离子体联合处理应用于黄曲霉毒素B1(aflatoxin B1,AFB1)降解,系统评估其对不同基质中 AFB1 的去除效果、降解产物特征以及对玉米籽粒主要品质的影响。该研究将AFB1分别加标到玻璃平皿和玉米籽粒上,检测不同处理时间(5、10、15、20、25、30 min)后的AFB1残留量,通过液质联用分析可能的降解产物结构,并测定处理后玉米籽粒的水分含量、脂肪酸值、色泽、淀粉糊化特性、淀粉含量、蛋白含量、表面种皮及横截面胚乳淀粉颗粒微观结构。结果表明,紫外联合冷等离子体可有效降解AFB1,降解率随处理时间的延长而提高,玻璃基质处理30 min后降解率达98.96%,而玉米籽粒处理60 min(每面各30 min)后降解率为39.40%,玉米基质的复杂性延缓了降解进程;分析得到11种主要的降解产物,作用位点涉及AFB1的呋喃环、甲氧基、内酯环和羰基等,初步解析了降解产物结构式及降解路径;品质分析显示,处理后玉米籽粒的水分含量和脂肪酸值有所下降,淀粉糊化特性略有变化,而色泽、淀粉与蛋白含量、表层种皮及胚乳淀粉颗粒微观形态均未发生显著改变(P>0.05),表明紫外联合冷等离子体技术处理未对玉米籽粒品质造成负面影响。该研究可为紫外联合冷等离子体对玉米中AFB1防控脱毒的潜在应用提供理论参考。

     

    Abstract: Aflatoxin B1 (AFB1) with strong carcinogenic, teratogenic and mutagenic properties is mainly produced by Aspergillus flavus. Maize, due to its high moisture content, is prone to Aspergillus flavus growth and subsequent AFB1. Both ultraviolet irradiation and cold plasma are non-thermal physical techniques with fungal inactivation and mycotoxin degradation capabilities. Ultraviolet combined with cold plasma technology can overcome the limitations of individual technologies, such as low penetration depth and inefficiency. However, there is little research on the effect of ultraviolet combined with cold plasma on degradation of AFB1 in maize. Therefore, this article aims to explore the degradation efficacy, products and pathways of AFB1, as well as effects on maize kernels quality treated by ultraviolet combined with cold plasma. AFB1 standard was spiked onto glass dishes and maize kernels, respectively. The residual AFB1 content was quantified after different ultraviolet combined with cold plasma treatment durations (5, 10, 15, 20, 25, 30 min). Liquid-chromatography mass spectrometry (LC-MS) was employed to analyze the potential structure of degradation products and degradation pathways. A comparison was mad on the moisture content, fatty acid value, color parameters (L*, a*, b* and △E value), starch gelatinization properties, starch content, protein content, surface seed coat microstructure, and cross-sectional microstructure of endosperm starch granules of maize kernels before and after ultraviolet combined with cold plasma treatment. A systematic investigation was implemented to explore the effect on the quality of maize kernels. The results showed that ultraviolet combined with cold plasma treatment effectively degraded AFB1, with degradation rates increasing progressively with prolonged treatment time. On glass substrates, the degradation rate of AFB1 reached 98.96% after 30 min treatment. For maize kernels, which required turning to expose both sides, the degradation rate was 39.40% after a total treatment time of 60 min (30 min per side). A slower degradation process was observed in the complex food matrix. LC-MS analysis identified 11 major degradation products. The peak areas of most degradation products initially increased and then decreased, indicating their further degradation. This trend was more pronounced for products 1-6 compared to products 7-11. The primary reaction sites involved the furan ring, methoxy group, lactone ring, and carbonyl group of AFB1. Structural modifications occurred at known toxicogenic sites of AFB1, suggesting a potential reduction in toxicity. However, further toxicological assessment was required. Degradation pathways were proposed, suggesting initial formation of six products (products 1-6) via substitution, addition, or demethylation reactions. Product 6 underwent furan ring cleavage to form an intermediate (C16H14O7), which subsequently yielded products 7-11 through oxidation, demethylation, demethoxylation, and ring-opening reactions. Regarding maize quality, ultraviolet combined with cold plasma treatment caused a significant decrease (P<0.05) in moisture content and fatty acid value, which was actually of benefit to the long-term storage stability of maize kernels. Starch gelatinization properties were slightly altered, with breakdown value, peak viscosity, trough viscosity, and final viscosity all showing a trend of initially decreasing followed by an increase. Meanwhile, the setback value, pasting time, and pasting temperature remained largely unaffected (P>0.05). These phenomena did not cause quality of maize deterioration. Moreover, color, starch content (including amylose and amylopectin), protein content, and the microstructure of surface seed coat and endosperm starch granules showed no significant changes (P>0.05). Overall, ultraviolet combined with cold plasma treatment did not adversely affect quality of maize kernels. In conclusion, ultraviolet combined with cold plasma technology can effectively degrade AFB1 while ensuring maize kernels do not exhibit significant deterioration in quality. The finding can provide a theoretical reference for the application of ultraviolet combined with cold plasma in the control and detoxification of AFB1 in maize.

     

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