Preservation of Mimosa tenuiflora Antiaflatoxigenic Activity Using Microencapsulation by Spray-Drying.

Mimosa tenuiflora aqueous extract (MAE) is rich in phenolic compounds. Among them, condensed tannins have been demonstrated to exhibit a strong antioxidant and antiaflatoxin B1 activities in Aspergillus flavus. Since antioxidant capacity can change with time due to environmental interactions, this study aimed to evaluate the ability of encapsulation by spray-drying of Mimosa tenuiflora aqueous extract to preserve their biological activities through storage. A dry formulation may also facilitate transportation and uses. For that, three different wall materials were used and compared for their efficiency. Total phenolic content, antioxidant activity, antifungal and antiaflatoxin activities were measured after the production of the microparticles and after one year of storage at room temperature. These results confirmed that encapsulation by spray-drying using polysaccharide wall materials is able to preserve antiaflatoxin activity of Mimosa tenuiflora extract better than freezing.

Mimosa tenuiflora Aqueous Extract: Role of Condensed Tannins in Anti-Aflatoxin B1 Activity in Aspergillus flavus.

Aflatoxin B1 (AFB1) is a potent carcinogenic mycotoxin that contaminates numerous crops pre- and post-harvest. To protect foods and feeds from such toxins without resorting to pesticides, the use of plant extracts has been increasingly studied. The most interesting candidate plants are those with strong antioxidative activity because oxidation reactions may interfere with AFB1 production. The present study investigates how an aqueous extract of Mimosa tenuiflora bark affects both the growth of Aspergillus flavus and AFB1 production. The results reveal a dose-dependent inhibition of toxin synthesis with no impact on fungal growth. AFB1 inhibition is related to a down-modulation of the cluster genes of the biosynthetic pathway and especially to the two internal regulators aflR and aflS. Its strong anti-oxidative activity also allows the aqueous extract to modulate the expression of genes involved in fungal oxidative-stress response, such as msnA, mtfA, atfA, or sod1. Finally, a bio-guided fractionation of the aqueous extract demonstrates that condensed tannins play a major role in the anti-aflatoxin activity of Mimosa tenuiflora bark.

Twin-screw extrusion encapsulation of MCT-oil in a maltodextrin matrix using compatibilizing biopolymers.

Carbohydrates are the most recurrent materials employed for active components encapsulation using twin-screw extrusion. However, the influence of process parameters on the properties of the final product remains a challenge. In this paper, special attention was given to the incorporation of a hydrophobic model compound (MCT-oil), in a maltodextrin matrix with a compatibilizing biopolymer. The effects of the extrusion parameters, as well as the influence of different formulations were analyzed. The mild extrusion conditions allowed obtaining blends with acceptable texture and viscosity to enhance the dispersion of the active compound. The encapsulation systems obtained were in a glassy state at room temperature and they remained stable at 60 % RH for a long time. Satisfactory incorporation rates of MCT-oil were found reaching encapsulation efficiencies up to 90 %. These results showed that the chosen compatibilizing agent enhanced the dispersion and stabilization of the MCT-oil within the matrix and significantly improved encapsulation.