Physical-chemical properties and microstructural characterization of traditional mexican chili (Capsicum annuum L.) powders

Abstract

The chili (Capsicum annuum L.) (Solanaceae) is native of America, is consumed as vegetable, spice, and as source of vitamins A, C and E, carotenoids, and capsaicin which produce the characteristic pungency of Capsicum species. The chili in Mexico is usually processed in dried form to conserve its color and flavor. The main objective of this work was to evaluate the physical-chemical properties and characterize the microstructure of four varieties of traditional Mexican chili (Capsicum annuum L.) powders: “Arbol”, “Guajillo”, “Piquin” and “Mole ranchero” (Ancho chili). Physical-chemical properties of chili powders were evaluated by means of moisture content, particle size, aerated and tapped bulk density, Carr index, Hausner ratio, angle of repose (flow properties), capsaicin, and carotenoids content. Microstructure of samples was characterized by Confocal Laser Scanning Microscopy and Scanning Electron Microscopy. ANOVA analysis and Tukey test were performed to evaluate the significant statistical difference between samples at 95% of confidence level. “Arbol”, “Guajillo”, “Piquin” and “Mole Ranchero” chili powders presented a cohesive behavior respect to its flow properties related to aerated and tapped bulk density, angle of repose, Carr Index, and Hausner ratio values under moisture content between 6.59-14.48 g H2O/100g d.s. “Arbol” and “Piquin” chili powders presented the higher capsaicin content, while “Guajillo” and “Mole ranchero” showed the higher carotenoids content. FTIR spectra confirmed the presence of secondary amide, phenolic groups, alkanes, and aliphatic chains that belong to capsaicin structure at specific absorption bands. Microstructure of chili powders presented particles with surface imperfections as cracks and dents, and smooth surface that influence physical- chemical and flowability properties. Moisture content between 6.59 and 14.48 g H2O/100g d.s. influences the physical- chemical properties, flowability and microstructure of traditional Mexican chili powders. To improve physical- chemical properties and flowability behavior of chili powders is required that moisture content be lower than 6.59 H2O/100g d.s.