Impact of nitrogen fertilisation on cactus pear mucilage functionality

The spineless cactus pear (Opuntia ficus-indica) mucilage is a physically slimy, green extract that is sourced from the cladodes (modified stems) of the crop. The mucilage can be freeze-dried into a powder, and this powder has shown potential to be considered as a novel functional food biopolymer because it exhibits good functional properties, especially with regard to emulsification. The main objective of this study was to investigate whether nitrogen fertilisation had an effect on the functionality of O. ficus-indica (L.) Mill ‘Morado’ mucilage. The functionality of the mucilage was attributed to its protein content. Nitrogen is one of the main elements in soil that makes up proteins. Nitrogen fertilisers from three nitrogen sources (urea, limestone ammonium nitrate, and ammonium sulfate) were applied at four application levels (0 kg/ha, 60 kg/ha, 120 kg/ha and 240 kg/ha). The functionality of mucilage was also compared to high-protein content commercial food biopolymers known to have good functional properties. Of the parameters tested, the oil-holding and oil-absorption capacities of the mucilage were significantly affected by nitrogen fertilisation. Scanning electron microscopy revealed that all freeze-dried mucilage samples resembled broken glass or showed a flake-like structure. Different nitrogen fertilisation sources and levels appeared to have no visible morphological implications on the different freeze-dried mucilage samples evaluated.