Int J Biol Macromol, 2018, Volume 117: Pages 919 - 927. doi: 10.1016/j.ijbiomac.2018.06.010.

Characterization of mucilages extracted from different flaxseed (Linum usitatissiumum L.) cultivars: A heteropolysaccharide with desirable functional and rheological properties.

Kaur, M. Kaur, R. Punia, S.

Key Findings

The large amount of flaxseed carbohydrate is indigestible and comprises of soluble fibre and insoluble fibre. Cellulose and lignin constitute the major insoluble fibre fraction while soluble fibre is largely gum or mucilage. Flaxseed mucilage represents 3 to 9% of the total seed and is composed of 50–80% carbohydrates, 4–20% proteins and 3–9% ash. Flaxseed mucilage is composed of water soluble heteropolysaccharides of high molecular weight and consists of an acidic fraction (17%) comprising of a mixture of L-rhamnose, L-fucose, L-galactose and D-galacturonic acid and a neutral fraction (83%) consisting of L-arabinose, D-xylose and D-galactose. The potential utilisation of flaxseed gum as a commercially viable product requires selection of cultivars that produce consistent gum. The utilisation of mucilage gums depends on their unique functional properties, such as viscosity, emulsifying and foaming properties, gelation and water binding as well as on their bioactive role in the prevention and or treatments of certain diseases. In this study, mucilage was extracted from different Indian flaxseed cultivars for their chemical, functional, microstructural, rheological and thermal properties.   The results suggested that polysaccharide mucilage extracted from different flaxseed cultivars exhibited significant variations in their chemical composition and functional properties. All mucilage samples had presence of high proteinaceous components in them which contributed to their foaming and rheological properties. All mucilages showed high decomposition onset temperature thereby indicating their thermal stability. All the properties examined in the present study were found to be cultivar dependent. “LC-2023” cv. mucilage can be recommended as a potential cultivar on account of its low lead and cadmium, high pentose and total sugar contents, WAC, OAC, FC, more resistant to increasing shear rate and greater thermal stability and can be further explored for incorporation in various food products.

ABSTRACT

Flaxseed mucilage is composed of water soluble heteropolysaccharides of high molecular weight representing about 3 to 9% of the total seed. In the present study mucilages were extracted from six Indian flaxseed cultivars and their chemical, functional, microstructural and rheological properties were investigated. The extracted mucilages differed significantly (P < 0.05) in their yield (5.56-6.54%), ash (4.80-7.23%), protein (7.68-12.33%), pentose (0.48-0.80 mg/ml) and total sugar (1.58-3.06 mg/ml) contents. Copper (18.87-148.08 mg/kg) and zinc (15.43-53.43 mg/kg) were found to be the most abundant minerals in mucilages. “LC-2023” cv. mucilage exhibited lower values for lead, chromium and cadmium. The mucilage solutions exhibited high foaming (>40%) and solubility (64.5-69.15% at 80 °C) characteristics. Rheological data revealed shear rate dependent behaviour of aqueous mucilage solutions irrespective of cultivar type and concentration used. Frequency sweep tests demonstrated that at high frequency range investigated, storage modulus was higher than loss modulus thereby suggesting viscoelastic fluid behaviour of flaxseed mucilage. All mucilages exhibited endothermic as well exothermic transitions with high decomposition onset temperatures. Mucilage is of special research interest owing to its desirable functional properties, so the outcomes of the present study could be used to identify cultivars for producing mucilages for a desired end use.

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