Mucilagem do rizoma de taro: técnicas de extração e de caracterizações físicas e químicas

Abstract

The mucilage from the rhizome of taro (Colocasia esculenta) (MT) may play an important role of interest in the food industry as a natural emulsifier, especially when added to bakery products. However, there is not a standard technique of its extraction, consequently, lead to the variation of the chemical components and may altering its technological property. Therefore, it was developed in the present work, the characterization of various forms of extraction MT (Gross Mucilage - MB, Gross Mucilage precipitated with ethanol - MBE, Mucilage extracted at hot temperature - MQ, Mucilage extracted hot and precipitated with ethanol - MQE and Mucilage extracted cold - MF), with the aim of eliminating components that interfere with its emulsifying property. From scanning electron microscopy (SEM) and by iodine test detected the presence of starch in all extractions, except in MF. The protein was detected by the biuret test and by the infrared spectrum with attenuated total reflectance (FTIR-ATR) in all mucilages. This macromolecule is responsible for the hydrophobic part of the emulsifying action of the MT, so it is important their presence. The hydrophilic part is due to glycidic fraction and not starchy. The sample with higher activity and emulsifying stability was MF, due to complete removal of starch and thus higher concentration of emulsifier molecule. By the spectra of principal component analysis (PCA) of FTIR-ATR it was possible to show that the MF is different from the others, due mainly to specific protein bands (1552 cm-1 and 1570 cm-1) and a specific band of carbohydrates (980 cm-1). With the purification of the mucilage cold technique can increase the protein and ash content, and decrease the glycidic fraction due to the absence of starch and soluble carbohydrates into ethanol. Furthermore, the purified mucilage (MP) is formed mainly of arabinogalactan and can be linked to proteins, forming the glycoprotein AGP (arabinogalactan-protein), which may be responsible for the macromolecule emulsifying power, as occurs in gum arabic. Regarding the thermal behavior, both MP and MB demonstrate greater weight loss to the average temperature of 200 ° C, which prevents its use above this temperature. Therefore, MP, that is extracted at 4 ° C, it can be used as a natural additive that aids in enhancing the MB due to the removal of impurities from a simple cold process and precipitation with ethanol.