Resumen El maíz de calidad proteínica (MCP) combina la calidad proteínica de la mutante opaco-2 (o2) con un endospermo vítreo. Estas características han permitido a los programas de mejoramiento alrededor del mundo producir genotipos MCP que ayudan a aliviar la malnutrición de la gente en países en desarrollo de África, Asia y América Latina con una dieta basada en cereales. Sin embargo, el desarrollo de estos materiales ha sido poco eficiente debido al limitado conocimiento acerca de las bases moleculares de la conversión del endospermo suave o2 en un fenotipo vítreo en MCP. Esta conversión se ha asociado con el incremento en cuerpos proteínicos pequeños ricos en γ-zeína de 27 kDa, la síntesis de almidón con una mayor proporción de amilosa y ramificaciones de amilopectina cortas-intermedias que favorece la compactación de los gránulos de almidón, así como alteraciones en la envoltura de los amiloplastos que favorece la interacción entre gránulos de almidón y cuerpos proteínicos. Estudios adicionales sobre los mecanismos involucrados en la modificación del endospermo en MCP contribuirán a producir materiales con buenas características agronómicas y buena calidad proteínica.

Abstract Quality protein maize (QPM) combines the protein quality of the opaque-2 (o2) mutant with a vitreous endosperm. These characteristics have allowed breeding programs worldwide to produce QPM genotypes that help alleviate malnutrition of people in developing countries from Africa, Asia and Latin America with a cereal-based diet. However, the development of these materials has been inefficient due to the limited knowledge about the molecular basis of the soft o2 endosperm conversion into a vitreous phenotype in QPM. This conversion has been associated with an increase in small protein bodies rich in 27 kDa γ-zein, the synthesis of starch with a higher proportion of amylose and short-intermediate amylopectin chain branches that favors the compaction of the starch granules, as well as alterations in the amyloplast envelope that favors the interaction between starch granules and protein bodies. Additional studies about the mechanisms involved in the modification of the endosperm in QPM will contribute to produce materials with good agronomic characteristics and protein quality.

Abstract Pineapple slices were treated with three antioxidants and stored under passive modified atmosphere packaging (MAP) to evaluate the effect of these treatments on tissue browning (percentage of dark area) and the accumulation of ascorbic acid and total phenolics. Pineapple slices were immersed in ascorbic acid (AA), isoascorbic acid (IAA), and N-acetylcysteine (NAC) solutions for 2 min, and then were packed and stored at 5 °C under air (AIR) or MAP for 15 days. Water was used as control. The application of IAA and NAC under passive MAP reduced better the tissue browning index and maintained a good quality of the slices. The use of AA and IAA increased the contents of ascorbic acid and total phenolics. The application of IAA followed by storage under MAP conditions was effective in reducing tissue browning, which was associated with a higher retention of ascorbic acid and total phenolics contents of the pineapple slices.