Student explorations of calcium alginate bead formation by varying pH and concentration of acidic beverage juices
Student explorations of calcium alginate bead formation by varying pH and concentration of acidic beverage juices
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DOI：
10.1515/cti-2021-0027
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发表时间：
2022-08-01
期刊：
影响因子：
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通讯作者：
Wissinger, Jane E.
中科院分区：
文献类型：
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作者：
Buenaflor, Jeffrey P.;Lydon, Cassandra K.;Wissinger, Jane E.
涉及可食用，可生物降解的海藻酸钙珠的教学实验作为一个有吸引力的模型系统，通过可持续消费品的创新，向高中年龄的学生介绍核心化学主题。介绍了一个由海藻酸钠和乳酸钙这两种食品安全的可再生材料合成海藻酸钙水凝胶珠的教学实验。珠的外膜是藻酸盐链的羧酸根基团与它们之间的二价钙阳离子之间的离子相互作用的结果，从而形成交联聚合物。藻酸盐链上的羧酸根基团的质子化降低了影响珠粒形成的交联密度。首先，使用各种浓度的柠檬酸来降低海藻酸钠溶液的pH，并观察对海藻酸钙珠粒形成的影响。pH值和珠的形状和硬度之间的相关性。这些信息然后用于探索具有不同天然酸度的果汁。该实验适合在课堂上或作为家庭活动实施。学习成果包括酸碱反应，化学键，聚合物结构和绿色化学概念。学生考虑包装中使用的传统塑料的环境挑战，以及创新的新商业产品如何试图提供解决方案。
Teaching experiments involving edible, biodegradable calcium alginate beads serve as an attractive model system to introduce upper secondary age students to core chemistry topics through innovations in sustainable consumer products. A teaching experiment is described that engages students with the synthesis of calcium alginate hydrogel beads from sodium alginate and calcium lactate, two food-safe and renewable materials. The beads' outer membranes are a result of ionic interactions between carboxylate groups from alginate strands and the divalent calcium cations between them, thus forming cross-linked polymers. Protonation of the carboxylate groups on the alginate strands decreases crosslinking density affecting bead formation. First, various concentrations of citric acid are used to lower the pH of the sodium alginate solution and the effect on the calcium alginate bead formation is observed. A correlation between pH and bead shape and firmness is derived. This information is then used to explore juices with varying natural acidities. The experiment is amenable to implementation in the classroom or as an at-home activity. Learning outcomes include acid-base reactions, chemical bonding, polymer structures, and green chemistry concepts. Students consider the environmental challenges of traditional plastics used in packaging and how innovative new commercial products are attempting to provide solutions.