Departamento de Química, Faculdade de Filosofia, Ciências e Letras, Universidade de São Paulo, Av. Bandeirantes, 3900, 14040-901 Ribeirão Preto, SP, Brazil.
Int J Biol Macromol. 2019 Apr 1;126:507-516. doi: 10.1016/j.ijbiomac.2018.12.206. Epub 2018 Dec 22.
The dye extraction from turmeric rhizomes (Curcuma longa L.) is generated a residue with high starch content that in nature does not form film. Therefore, we decided evaluate how mechanical treatment (ball or cryogenic mill) and chemical treatment with alkali (NaOH 2.5% (1, 4, or 8 h) and bleaching with NaClO or HO at 25 or 45 °C affect the chemical structure of the starch and fibers in turmeric residue, and its filmogenic capacity. Ball milling decreased the turmeric residue particle size more effectively favoring the chemical procedures. Only two types of chemical treatment consisting in alkaline treatment for 4 h and bleaching with NaClO and HO, respectively, for 4 h, at 25 °C yielded turmeric residues with filmogenic capacity. The chemical treatments oxidized the starch granules causing to lose their crystal structure as verified by DRX, and removed amorphous fibers such as lignin and hemicellulose increasing cellulose content in turmeric residue. FTIR analyses also revealed that the starch granules were oxidized. As bleaching agent, NaClO caused greater starch oxidation (the highest carboxyl and carbonyl groups contents) affording films with the best mechanical and functional properties. Although chemical treatment reduced the turmeric residue phenolic compounds, the films still presented antioxidant activity.
从姜黄根茎（姜黄）中提取染料会产生一种含有高淀粉含量的残渣，而这种残渣在自然界中不能形成薄膜。因此，我们决定评估机械处理（球磨或低温粉碎机）和化学处理（NaOH 2.5%（1、4 或 8 小时），以及用 NaClO 或 HO 在 25 或 45°C 下漂白）对姜黄残渣中淀粉和纤维的化学结构及其成膜能力的影响。球磨更有效地减小了姜黄残渣的粒径，有利于化学处理。只有两种化学处理方法（碱性处理 4 小时和分别用 NaClO 和 HO 漂白 4 小时，均在 25°C 下进行）能够使姜黄残渣具有成膜能力。化学处理氧化了淀粉颗粒，导致其晶体结构丧失，这可以通过 X 射线衍射（DRX）来验证，并且去除了无定形纤维，如木质素和半纤维素，从而增加了姜黄残渣中的纤维素含量。傅里叶变换红外（FTIR）分析还表明淀粉颗粒被氧化。作为漂白剂，NaClO 引起了更大的淀粉氧化（最高的羧基和羰基含量），从而赋予薄膜最佳的机械和功能性能。尽管化学处理降低了姜黄残渣中的酚类化合物含量，但薄膜仍具有抗氧化活性。
