Cold gelation of leaf protein concentrate for nanoencapsulation of vitamins

Abstract

Nowadays, the necessity for dietary nutrient encapsulation emerges largely since the action of digestive enzymes causes the loss of structural integrity and function of nutrients. Proteins have high nutritional value and thus are considered as the most nutritionally beneficial carriers; moreover, due to their versatility, proteins can be generated in a variety of structures (nanoparticles, nanofilms, nanofibers, coacervates, and hydrogels), allowing for the delivery of hydrophobic or hydrophilic nutrients. Proteins of vegetable origin have broader application potential over proteins of animal sources. Thus, the modern research focuses on waste leaf biomass, such as pumpkin leaves, as a rich source of plant proteins, specifically the most abundant protein in the world, ribulose-1,5-bisphosphate carboxylase-oxygenase, RuBisCo protein. The aim of this work was to isolate the water-soluble proteins, mostly RuBisCO protein, from pumpkin leaves in order to utilize it as a carrier for folic acid (FA) encapsulation. The resulting protein leaf concentrate was lyophilized and used as such to form nanoparticles. Leaf protein nanoparticles were prepared by employing a Ca-induced cold gelation method. Results and conclusions. The results showed that the Ca-induced protein nanoparticles have a small particle size (58–208 nm), polydispersity index (PDI) of 0.241 to 0.377, and negative zeta potential (-16.2 to -23.9 mV). Protein leaf nanoparticles exhibited uniform unimodal size distribution and spherical shape with a unique honeycomb-like core structure. Nanoparticle characteristics including size, surface charge and hydrophobicity could be adjustable by changing calcium chloride concentration from 2 to 10 mM and environmental pH (7 to 9). All manufactured nanoparticles demonstrated good stability over seven days, with no significant changes in zeta potential or formation agglomerates. Release studies showed that the leaf protein nanoparticles with FA, encapsulation efficiency amounted 40.2%, were resistant to pepsin and low pH in simulated gastric fluid (10% of initial FA amount was realized), but released the encapsulated FA in simulated intestinal conditions was enriched, even another 50% was achieved. Pumpkin leaf protein nanoparticles have a promising possibility for bioactive ingredient delivery owing to the characteristics described above. These findings would be of great importance for the development of food-grade nanoparticles suitable for the formulations of functional foods.