Development and characterization of edible films based on mucilage of Opuntia ficus-indica (L.).

Mucilage of Opuntia ficus-indica (OFI) was extracted and characterized by its composition and molecular weight distribution. Mucilage film-forming dispersions were prepared under different pHs (3, 4, 5.6, 7, and 8) and calcium concentration (0% and 30% of CaCl(2), with respect to mucilage's weight), and their particle size determined. Mucilage films with and without calcium (MFCa and MF, respectively) were prepared. The effect of calcium and pH on mucilage films was evaluated determining thickness, color, water vapor permeability (WVP), tensile strength (TS), and percentage of elongation (%E). The average molecular weight of the different fractions of mucilage was: 3.4 x 10(6) (0.73%), 1 x 10(5) (1.46%), 1.1 x 10(3) (45.79%), and 2.4 x 10(2) Da (52.03%). Aqueous mucilage dispersions with no calcium presented particles with an average size d(0.5) of 15.4 microm, greater than the dispersions with calcium, 13.2 microm. MFCa films showed more thickness (0.13 mm) than the MF films (0.10 mm). The addition of calcium increased the WVP of the films from 109.94 to 130.45 gmm/m(2)dkPa. Calcium and pH affected the mechanical properties of the films; the largest TS was observed on MF films, whereas the highest %E was observed on MFCa films. The highest differences among MF and MFCa films were observed at pHs 5.6 and 7 for TS and at pHs 4 and 8 for %E. No effect of pH and calcium was observed on luminosity and hue angle. Chroma values were higher for MF when compared with MFCa, and increased as pH of the films increased. Practical Application: In this study mucilage from nopal was extracted and characterized by its ability to form edible films under different pHs, and with or without the addition of calcium. Opuntia ficus-indica mucilage had the ability to form edible films. In general, it can be considered that mucilage films without modification of pH and without the addition of calcium have the best water vapor barrier properties and tensile strength. Mucilage from nopal could represent a good option for the development of edible films in countries where nopal is highly produced at low cost, constituting a processing alternative for nopal.

[Effect of high hydrostatic pressure on water imbibition, cooking times and microstructure of Phaseolus vulgaris]. / Efecto de la alta presión hidrostática (APH) en la imbibición de agua, tiempos de cocción y microestructura del Phaseolus vulgaris.

The effect of high hydrostatic pressure (HHP) on water imbibition, cooking times, and microstructure of cotyledons and seed coats of black beans was evaluated. High pressure treatments at 275, 410, 550 or 690 MPa and 25 degrees C for 5 min increased the rate of water imbibition of black beans. The saturation degree of HHP treated black beans was reached 50% faster than the saturation degree of untreated black beans. High hydrostatic pressure treatments reduced the cooking times (CT) of unsoaked black beans by 25% to 39%, similar to black beans soaked for 3 h. The microstructure of HHP treated beans exhibited protein aggregation in cell protoplasm and swelling of cell walls and starch granules. Seed coats of HHP treated black beans were less smooth than seed coats of untreated black beans. The swelling of palisade, hourglass, and parenchyma cells was also observed in HHP treated black beans such as soaked beans. High hydrostatic treatment is an alternative for reducing the preparation long times of Phaseolus vulgaris.

Efecto de la alta presión hidrostática (APH) en la imbibición de agua, tiempos de cocción y microestructura del Phaseolus vulgaris / Effect of high hydrostatic pressure on water imbibition, cooking times and microstructure of Phaseolus vulgaris

The effect of high hydrostatic pressure (HHP) on water imbibition, cooking times, and microstructure of cotyledons and seed coats of black beans was evaluated. High pressure treatments at 275, 410, 550 or 690 MPa and 25 degrees C for 5 min increased the rate of water imbibition of black beans. The saturation degree of HHP treated black beans was reached 50 faster than the saturation degree of untreated black beans. High hydrostatic pressure treatments reduced the cooking times (CT) of unsoaked black beans by 25 to 39, similar to black beans soaked for 3 h. The microstructure of HHP treated beans exhibited protein aggregation in cell protoplasm and swelling of cell walls and starch granules. Seed coats of HHP treated black beans were less smooth than seed coats of untreated black beans. The swelling of palisade, hourglass, and parenchyma cells was also observed in HHP treated black beans such as soaked beans. High hydrostatic treatment is an alternative for reducing the preparation long times of Phaseolus vulgaris.