Natural Colourants Extraction and Characterisation from Oilseeds.

Sruthi Rose, Thomas (2013) Natural Colourants Extraction and Characterisation from Oilseeds. [Student Project Report] (Submitted)

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Abstract

Colour is an important attribute to the quality of a food product, not only affecting the appearance but also acceptance of the product. Food colourants may be classified into synthetic, nature-identical, inorganic, and natural colourants. Man-made synthetic colourants have dominated the food industry because of their stability and cost effectiveness. The use of synthetic dyes is gradually receding due to an increased environmental awareness, harmful health effects and their non-biodegradable nature. There is resurgence in the use of natural colourants, which are perceived to be safe and eco-friendly. The focus of the current study was to extract and characterise colours from the hulls of oilseeds, namely sesame and mustard, which are a by-product of oilseed processing. Different solvents were used for the extraction of pigments from four varieties of sesame (A and C - white; B and D - black varieties) and black mustard. Sodium hydroxide (NaOH) solution was found to be the best, yielding dark extracts with the lowest lightness (L*) values. The extracts were also found to possess significant antioxidant activity, comparable to that of BHT (known synthetic antioxidant), determined using DPPH radical scavenging activity and FRAP assay. Lipoxygenase inhibitory activity of the NaOH extracts was found to increase dose dependently, confirming the antioxidant activity of these extracts. These extracts were further purified by acid hydrolysis and pigment (black and brown coloured) was obtained in powder form, with D variety of sesame giving the highest yield of 142 mg/g hull. These pigmentswere identified as melanin-like pigments using chemical tests and spectroscopic properties (UV-Visible & FT-IR), comparable to synthetic melanin. Stability of these extracted pigments was checked in order to determine its potential to be used as a natural colourant. Although continuous exposure to ambient temperature and light led to loss of colour, the refrigerated samples were stable with minimum loss of colour for a period of one month. All these results points out that the melanin-like pigment, can be used in various fields, including food industry, and can be obtained from oilseed hulls (sesame and mustard), thereby adding value to an otherwise by-product waste of oilseed processing.

Item Type:	Student Project Report
Uncontrolled Keywords:	natural colour, oilseed hull, melanin-like pigment, antioxidant activity, stability
Subjects:	600 Technology > 08 Food technology > 14 Physical properties > 01 Colours 600 Technology > 08 Food technology > 19 Lipids-oils/fats > 01 Oilseeds
Divisions:	Protein Chemistry and Technology
Depositing User:	Food Sci. & Technol. Information Services
Date Deposited:	06 May 2014 05:17
Last Modified:	06 May 2014 05:17
URI:	http://ir.cftri.res.in/id/eprint/11542

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