Improving the stability of an hem-based food colorant by means of spray-drying encapsulation

Abstract

This work is part of a research project that aims to produce a natural red food colorant, stable during long-term cold storage, with a wide range of applications, using hemoglobin from porcine blood as raw material. The objective of this study was specifically to assess the suitability of the spray-drying technology to microencapsulate the hem-derivative into a protective matrix, aiming at obtaining a red powder able to maintain its red color in a wide range of pH. To achieve the objective, three separate formulations of haemoglobin derivatization, were prepared by addition of 3.5% nicotinamide as well as, 10% sucrose and the convenient quantity of encapsulation polysaccharide (E1 or E2) in A and C experiments, and 6% of sucrose, 0,1% of E1 and 4 % of a chelating agent in experiment B. Every hem-derivative was then encapsulated and dried in a spray-dryer. After dehydration process, several quality parameters of each encapsulation product, such are the proximate composition, the color, and the water activity, were used to assess the suitability of the encapsulation method and the matrix that leaded to the better quality characteristics. Moreover, gelatine gels were used as a model system to test the coloring power of both encapsulated products at different pH conditions. The results showed that all the spray-drying encapsulation of hem-derivatives permitted obtaining powders showing water content and water activity (aw) low enough to warrant the microbiological stability without favoring iron oxidation reactions. Immediately after dehydration, all the products exhibited an acceptable bright red color, whatever the encapsulation agent used in the derivatization of hemoglobin. The colorant containing polysaccharide E1 showed better color stability than the two products containing polysaccharide E2. The red color of the E1 powder remained constant over 2-month chill storage. The partial substitution of sucrose by a chelating agent in the products containing the polysaccharide E2 negatively affected the color stability of the dehydrated products. At pH 6-7 all the gelatins containing the hem-colorants showed a bright red color. Nevertheless, only the formulation with combination of chelating agent and polysaccharide E2 was able to preserve the red color at pH below 5. At pH 4.5 the formulation with the same combination did not succeed to complete stabilize redness during storage, since a 30% decrease in a* values occurred after 7-day chill storage. However, final a* values of these gelatins were even 3-fold higher than the initial ones in gelatins containing E1 or E2 without the chelating agent. At pH above 5, although there were significant differences in b* and L* parameters, the a* coordinates showed to be similar for all the treatments at the end of 7-day chill storage, the mean reduction from the initial values being in the range from 6 to 11%