Mucilage Yield, Composition, and Physicochemical Properties of Cultivated Cactus Pear Varieties as Influenced by Irrigation

Opuntia spp. plants occupy an important socioeconomic role in arid and semiarid zones where water is scarce. Irrigation increases the productivity of these plants; however, its effect on the yield, composition, and physicochemical properties of the mucilage is unknown. Three irrigation regimens were tested: non-irrigated (rainwater), supplemental irrigation (irrigation between field capacity (0.28 m(3) m(-3)) and permanent wilting point (0.14 m(3) m(-3))), and full irrigation (100% of crop evapotranspiration), on the four cactus pear varieties ('Amarilla Olorosa' (Opuntia spp.), 'Cristalina' (Opuntia albicarpa Scheinvar), 'Dalia Roja' (Opuntia spp.), and 'Roja Lisa' (O. ficus-indica (L.) Mill)). Irrigation regimens were applied during the dry season (March to June in the northern hemisphere). Composite samples of cladodes per replicate and treatment were collected for mucilage extraction. The mucilage was characterized for yield, color, chemical composition, infrared spectroscopy, viscosity, and molar mass. The combination with the greatest yield was 'Amarilla Olorosa' with no irrigation (22.2%), while the least yield was from 'Cristalina' undergoing full irrigation (12.2%). In general, non-irrigated plants yielded more mucilage, their color was brighter and less green, and they had more protein and fiber. The viscosity and molar mass were greatest in non-irrigated plants. Total carbohydrate content was similar between non-irrigated and supplementally irrigated plants. Thus, for the cactus pear varieties studied here, either no irrigation or supplemental irrigation could be a feasible strategy to produce mucilage with good characteristics for agro-industrial and pharmaceutical use.