Application and stability of fungal pigments using jelly sweets as a food model system

Natural pigments have seen an increase in usage over the past decades due to their acclaimed safety and active biological properties. This is in line with the shift in consumer market preferences requiring a source replacement for synthetic colourants. Filamentous fungi are amongst the natural sources currently explored for pigment production. In this study, the heat, pH and UV light stability of fungal pigments produced by Penicillium multicolour (dark brown), P. canescens (green) and P. herquie (yellow). Talaromyces verruculosus (red) and Fusarium solani (orange) were evaluated. The antioxidant properties of the pigments as influenced by these conditions were ascertained using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. The pigments were also applied in a jelly sweet formulation and incubated at ambient temperature for 4 weeks. It was demonstrated that the pigment extracts of P. multicolour and T. verruculosus were significantly affected by higher pH (7.0 and 9.0), where the decline in antioxidant activity was observed. As far as high temperature and UV light exposure are concerned, all the pigment extracts, with exception of P. herquie, maintained an antioxidant activity above 35%. On the other hand, the L*a*b* values showed no overall significant change for heat and UV light exposure with the exception of P. canescens across the four pH levels (3.0, 4.0, 7.0 and 9.0), where an increase in the -a (green index) coupled with a decline in brightness (L* index) and b* (blue index) was observed. Finally, there was no significant change in colour over the 4 weeks of incubation. In conclusion, fungal pigments are generally stable at normal storage conditions (ambient temperature and normal light) and can be suitably applied in jelly sweets.