条浒苔中铝的存在形态及其对食用安全性的影响

Enteromorpha prolifera is a resource-rich and large-scale economic algae of China, it is also one of the favorite edible algae for coastal residents. In recent years, exceeding problems of aluminum in enteromorpha prolifera have been widely concerned. A lot of researches showed that aluminum have risk to human health and there is potential connection between aluminum and diseases. The current aluminum test for the food safety analysis is mainly the detection of total content of aluminum. However, the toxicity of aluminum is not determined by its total content. It is closely related to the specific speciation of aluminum. Lots of researches were related to the inorganic aluminum of algae. However, there are no extensive studies for the organic aluminum, which has the highest content. Algae can absorb aluminum from their growing environment. These aluminum become steady and low-toxic organic aluminum when they combined with the macromolecular compounds of algae, such as polysaccharide. The mechanism of absorption is still not clear. In this project, we will extract and quantitatively analyze the different forms of aluminum in an edible enteromorpha clathrate. We will also compare the molecular composition of polysaccharide before and after aluminum stress experiment using Fourier transform ion cyclotron resonance mass spectrometry technique, and reveal the mechanism of aluminum absorption. In addition, we will discuss the transformation and bioavailability of different forms of aluminum in digestion by an in vitro digestion system, and evaluate the edible safety. From these results we will get a better understanding of knowledge for the aluminum speciation in algae and their edible safety evaluation.

浒苔是我国资源丰富的大型经济藻类，也是沿海居民喜食的海藻之一。近年来浒苔中铝含量超标的问题已经引起广泛关注。大量研究表明铝会对人体健康造成危害，并且与各种疾病存在联系。目前食品中铝的检测方法主要是测定总铝含量，但铝的毒性并非由总铝含量决定，而是与其具体的存在形态相关。当前对海藻中无机态铝的研究已相对成熟，而对总铝中含量最高的有机态铝却尚未深入。海藻会从生长环境中吸附铝，这部分铝与海藻中的多糖等复杂有机物吸附会形成相对稳定且毒性较低的有机态铝，其吸附机理尚未阐明。本项目以一种可食用的条浒苔为原料，对其不同形态的铝进行提取和定量分析，并通过高分辨质谱技术探究多糖在铝胁迫前后的分子组成变化，揭示铝在多糖上的吸附机理。此外，通过体外模拟消化实验，探究各形态铝在肠胃消化过程中的变化情况和生物利用率，并对其食用安全性进行评价。研究成果将为海藻中铝的形态分析和食用安全性评价提供基础理论依据。

浒苔是我国资源丰富的大型经济藻类，具有较高的食用和药用价值。近年来浒苔等藻类产品的铝超标问题引起了广泛关注。铝的毒性与其存在形态密切相关，不同形态铝的毒性相差甚远。铝在浒苔等藻类中的含量非常高，其吸附机制尚未阐明，食用安全性也需要进行评估。本项目以江浙沿海条浒苔为原料，建立和优化了一套适用于条浒苔的铝形态分析方法，探讨了条浒苔中不同形态铝的含量和分布情况。通过研究铝胁迫在条浒苔生长过程中对其品质的影响以及对比铝胁迫前后条浒苔中与多糖结合的有机铝含量和红外光谱变化，探究了铝在条浒苔多糖上的吸附机理。由体外模拟消化后条浒苔中不同形态铝的转化情况，对其食用安全性进行了评估。研究结果表明：条浒苔中的铝主要是以有机铝和活性铝两种形式存在。其中87.76%~90.21%的铝是与蛋白、多糖、纤维等有机物结合的稳定态铝，而毒性最强的羟基态铝和Al3+仅占2.37%~2.82%。因此仅用总铝含量评价浒苔的食用安全性并不科学。条浒苔对铝具有一定的耐受性，经铝胁迫后条浒苔的细胞表面、元素分布会发生显着变化。通过条浒苔多糖吸附铝的前后红外光谱分析可知，铝可能会与多糖中的的酯基或O-乙酰基C-O、吡喃环的C-O-C、C-O-H、α-糖苷键和β-D-吡喃葡萄糖环等基团进行反应和吸附。通过体外模拟消化液实验证明，37℃下利用模拟胃液-模拟肠液连续浸提的方法溶出铝量仅占总铝含量的9.52%。尽管正常食用条浒苔对人体健康造成威胁的可能性较小，但是本项目仍建议应对藻类中的铝尽早建立明确科学的限定标准。本项目的研究成果可为海藻中铝或其他金属的毒性研究及食用安全性评价提供基础理论依据。