Ultrasound-Assisted Extraction of Bioactive Compounds from Annatto Seeds, Evaluation of Their Antimicrobial and Antioxidant Activity, and Identification of Main Compounds by LC/ESI-MS Analysis.

This study evaluated the antimicrobial activity (i.e., against Bacillus cereus and Staphylococcus aureus) and the antioxidant activity (i.e., ABTS, FRAP, and DPPH) of annatto seeds extract obtained by ultrasound-assisted extraction. A response surface design with three levels such as pH (2-11), solvent concentration (50-96 %), seed-to-solvent ratio (1:2-1:10), and treatment time (0-30 min) was employed to determine the optimal experimental conditions. Thus, a pH of 7.0, seed-to-solvent ratio of 1:7, and treatment time of 20 min were selected as optimal rendering an extract having a 0.62% of bixin, 3.81 mg gallic acid/mg equivalent of polyphenol compounds (ABTS 1035.7, FRAP 424.7, and DPPH 1161.5 µM trolox/L), and a minimal inhibitory concentration against Bacillus cereus and Staphylococcus aureus of 32 and 16 mg/L, respectively. Further, the main bioactive compounds identified by LC/ESI-MS were bixin and catechin, chlorogenic acid, chrysin, butein, hypolaetin, licochalcone A, and xanthohumol.

Rheology: a feasible tool to assess the viscoelastic behavior of natural ingredients / La reología: una herramienta factible para evaluar el comportamiento viscoelástico de los ingredientes naturales

Rheology studies the flow and deformation of materials. Thus, the knowledge of the rheological and mechanical properties is important for product design, production, quality control, and for predicting shelf storage stability. Rheology studies can assist scientists in formulating optimal products (1). Conventionally, a single-point viscosity tests are widely used, but they not adequate in characterizing the full rheological profile of these materials, and thus, it is better to generate the full viscosity curves to capture a wide range of material responses (2). There are several tests conducted to characterize a material. The first one implies plotting viscosity as a function of a stress ramp at constant temperature and within a specific time interval. Usually, at low stresses viscosity might remain constant, and then a critical stress point is reached were viscosity decreases abruptly. The magnitude of the resulting slope confirms the shear sensitivity of the material (3). Another highly used plot involves the viscosity versus shear rate. Usually, at low shear rates viscosity remains constant and then it decreases steadily. Further, from the stress ramp test the minimum shear stress required to initiate flow (Yield stress) is determined. The higher the yield value, the more readily a dispersion will maintain particles in suspension with minimal sedimentation. However, a low yield stress might be useful for a product to improve the sensorial properties such as the ease of spreading onto a surface forming a short-term thin layer (4).