Effect of fungi on dyes used in making Nigerian tie and dye cloths ('Adire') and shelf-life determination

Abstract

Dye quality and fastness properties could only be guaranteed for a finite period of time on shelf. In this study, the shelf-life of natural indigo dye and indigo VAT dye was studied for 360 days. Physico-chemical parameters monitored includes; total viable count, viscosity, pH, specific gravity, absorbance and transmittance from 360 days. Fungi isolated from the dyes on shelf were Achaetomium strumarium, Aspergillus niger, Aspergillus flavus, Duitina rugosa, Penicillium citrinum and Peyronellaea prosopidis. The fungal population count was monitored monthly throughout the shelf-life study period. Multiple linear regression model was used to predict the shelf-life of the dyes from the growth data of the isolated organisms and the physico-chemical parameters. The total fungal viable counts ranged from 1.267×10⁵ -3.213×10⁵ spores ml^-1 for indigo VAT dye and 1.453×10⁵ - 3.347×10⁵ spores ml^-1 for natural indigo dye over the 12 months study period. The changes in the physico-chemical parameters ranged from pH 12.94±0.00-10.39±0.01 and 12.54±0.00-10.01±0.01, specific gravity 1.279±0.00-1.106±0.005 and 1.445±0.00-1.176±0.001, viscosity 1.288±0.00-1.215±0.001 cSt and 1.283±0.00- 1.176±0.001 cSt, optical density 1.627±0.002-3.323±0.001 and 1.705±0.001- 3.315±0.002, transmittance 5.573±0.003-2.652±0.001 and 6.124±0.002-2.108±0.001 for indigo VAT dye and natural indigo dye respectively. The percentage dye exhaustion of the shelf-life products determined after the study period peaked at 88±0.001 and 90±0.001 % for indigo VAT dye and natural indigo dye respectively. The shelf-life were found to be 17 months and 10 months for indigo VAT dye and natural indigo dye respectively. The synthetic indigo VAT dye has a higher shelf-life than the natural indigo dye. Imported indigo VAT dye is however recommended based on its longer shelf-life. The results further buttressed the trend where textile dyers in Nigeria and indeed the West African region largely employ imported indigo VAT dye than locally produced natural indigo dye.

Keywords: Shelf-life; Nigerian tie and dye cloths 'Adire'; indigo VAT dye; natural indigo