Characterization of starch and gum Arabic-maltodextrin microparticles encapsulating Acacia tannin extract and evaluation of their potential use in ruminant nutrition.

Objectives: The use of tannin extract and other phytochemicals as a dietary additive in ruminants is becoming more popular due to their wide biological values such as in methane mitigation, bypass of dietary protein, control intestinal nematode, among other uses. Unfortunately, some have strong astringency, low stability and bioavailability, and negatively affecting dry matter intake and digestibility. To circumvent these drawbacks, an effective delivery system may offer a promising approach to administer these extract to the site where it is required. The objectives of this study were to encapsulate Acacia tannin extract (ATE) with native starch and maltodextrin-gum Arabic and to test the effect of encapsulation parameters on encapsulation efficiency, yield and morphology of the microparticles obtained as well as the effect on rumen in vitro gas production.

Methods: Acacia tannin extract was encapsulated with the wall materials, and the morphological features of freeze-dried microparticles were evaluated by scanning electron microscopy. The in vitro release pattern of microparticles in acetate buffer, simulating the rumen, and its effect on in vitro gas production was evaluated.

Results: The morphological features revealed that microparticles encapsulated with maltodextrin/gum-arabic were irregular shaped, glossy and smaller, compared with those encapsulated with native starch, which was bigger, and more homogenous. Maltodextrin-gum Arabic could be used up to 30% loading concentration compared with starch, which could not hold the core material beyond 15% loading capacity. Encapsulation efficiency ranged from 27.7%±6.4- 48.8%±5.5 in starch and 56.1%±4.9- 64.8%±2.8 in maltodextrin-gum Arabic encapsulated microparticles. Only a slight reduction in methane emission was recorded in encapsulated microparticles when compared with the samples containing only wall materials.

Conclusion: Both encapsulated products exhibited the burst release pattern under the pH conditions and methane reduction associated with tannin was marginal. This is attributable to small loading percentages and therefore, other wall materials or encapsulation methods should be investigated.