Caramel colour pigments from black sapote (Diospyros digyna): obtention and food application

Abstract

This work aimed to develop a pigment from black sapote (Diospyros digyna) using lactic acid bacteria or yeasts for fermentation for use as a pigment in gummy bear formulations. Black sapote pulp was fermented with Lactobacillus casei, Lactobacillus rhamnosus, and Saccharomyces cerevisiae. Pigments were obtained by liquid–liquid extraction with an 80% ethanol solution and fermented purée in a 1 : 1 (v/v) ratio. The extract was added with 5% of maltodextrin–mesquite gum (1 : 1 w/w) blend and microencapsulated by spray drying at 150 °C (inlet temperature). The physical characteristics (yield, moisture content, water activity (a_w), colour and particle size), antioxidant capacity (AC), total phenolic compounds (TPC), and their stability at various pHs and temperatures were evaluated. The pigment powders were added at 1, 3, and 5% to the gummy bear formulations. Gummies were evaluated by colour (using a colorimeter) and some sensory characteristics. The results showed that the fermentation process increased the AC and TPC characteristics, particularly when fermentation was performed with L. rhamnosus. The AC was reduced during drying, but the light brown colour barely remained the same (L* = 61.87–67.18, a* = −0.09–4.6, and b* = 27.97–29.26). Powders obtained after fermentation with L. casei and L. rhamnosus rendered approximately 10% lower yields than the control and sample fermented with S. cerevisiae. The moisture content and a_w were lower than 9.04% and 0.190, respectively, in all the powders. The particle size of the powders was in the range 0.75 to 352 μm (due to agglomerations). The stability study showed that the pH significantly (p < 0.05) changed the pigment colour parameters (L*, a*, and b*). Temperature, on the other hand, changed the colour of reconstituted powders, showing a brownish-pale green colour. Finally, by increasing the pigment concentration in the gummy bear formulations, the colour changed from light brown to almost black; however, this did not influence the acceptability of the gummy bears by consumers.