RESUMO
Maize comes in a variety of colors, including white, yellow, red, blue, and purple, which is due to the presence of phytochemicals such as carotenoids, anthocyanins, flavonoids, phytosterols, and some hydroxycinnamic acid derivatives. In Mexico, maize is primarily grown for human consumption; however, maize residues comprise 51-58% of the total maize plant weight (stalks, leaves, ears, and husks) and are mainly used as livestock feed. These residues contain numerous bioactive compounds that interest the industry for their potential health benefits in preventing or treating degenerative diseases. This review explores the current knowledge and highlights key aspects related to the extraction methods and different techniques for identifying the bioactive compounds found in maize by-products.
RESUMO
Resumen: El maíz contiene un gran número de compuestos antioxidantes, muchos de ellos unidos a componentes de la pared celular, por lo que requieren tratamientos para liberarlos, como el uso de enzimas o procesos de fermentación. La fermentación en medio sólido (FMS) con Rhizopus oryzae se ha aplicado para aumentar la capacidad antioxidante (CA) y el contenido fenólico en cereales y leguminosas. El objetivo del presente trabajo fue evaluar el efecto de la FMS con R. oryzae sobre la CA y el contenido de fenoles totales (CFT) del maíz. La FMS se realizó en bolsas zip-lock (25 cm2) a 30 °C/72 h, con un inóculo de 1 x 106 esporas/g. Se tomaron muestras cada 12 h, el extracto se recuperó con etanol al 80 % y se utilizó para determinar el CFT y la CA (ensayo ABTS+, DPPH y FRAP). Los valores más altos se obtuvieron a las 60 h de cultivo, con un CFT de 1.92 mg/ gramos de materia seca (gms) y una CA de 1.47 mg de equivalentes Trolox por gramo de materia seca (mg ET/gms), 1.27 mg ET/gms y 5.8 mg Fe+2/gms para los ensayos de ABTS+, DPPH y FRAP, respectivamente. El uso de FMS permitió aumentar hasta 0.83 y 1.25 veces el CFT y la CA del maíz, con respecto al tiempo 0 h. El maíz fermentado con R. oryzae mostró potencial para ser empleado como materia prima para el desarrollo de alimentos funciona les, al incrementar su CA a través de un bioproceso.
Abstract: Maize contains a large number of antioxidant compounds. However, many of them are not in free form, as they are bound to components of the cell wall of maize kernels. For this reason, the use of treatments is required to release them, such as the use of enzymes or fermentation processes. Fermentation in solid medium (FMS) with Rhizopus oryzae has been applied to increase the antioxidant capacity (AC) and phenolic content in cereals and legumes. The objective of the present work was to evaluate the effect of FMS with R. oryzae on AC and total phenolic content (TPC) of maize. Fermentation on solid medium was carried out in zip-lock bags (25 cm2) at 30 °C for 72 h, with an inoculum of 1 x 106 spores/g. Samples were taken every 12 h, the extract was recovered with 80% ethanol, and used to determine TPC and AC (ABTS+, DPPH and FRAP essay). The highest values were obtained at 60 h of culture, with a TPC of 1.92 mg/gram dry metter (gdm) and an AC of 1.47 mg TE/gmd, 1.27 mg TE/gdm and 5.8 mg Fe+2/gdm for the ABTS+, DPPH and FRAP assays, respectively. The use of FMS allowed to increase up to 0.83 and 1.25 times the CFT and CA of corn, with respect to time zero. Corn fermented with R. oryzae showed potential to be used as a raw material for the development of functional foods, by increase its AC through a bioprocess.