Plant leaf proteins for food applications: Opportunities and challenges.

Plant-based proteins are gaining a lot of attention for their health benefits and are considered as an alternative to animal proteins for developing sustainable food systems. Against the backdrop, ensuring a healthy diet supplemented with good quality protein will be a massive responsibility of governments across the globe. Increasing the yield of food crops has its limitations, including low acceptance of genetically modified crops, land availability for cultivation, and the need for large quantities of agrochemicals. It necessitates the sensible use of existing resources and farm output to derive the proteins. On average, the protein content of plant leaves is similar to that of milk, which can be efficiently tapped for food applications across the globe. There has been limited research on utilizing plant leaf proteins for food product development over the years, which has not been fruitful. However, the current global food production scenario has pushed some leading economies to reconsider the scope of plant leaf proteins with dedicated efforts. It is evident from installing pilot-scale demonstration plants for protein extraction from agro-food residues to cater to the protein demand with product formulation. The present study thoroughly reviews the opportunities and challenges linked to the production of plant leaf proteins, including its nutritional aspects, extraction and purification strategies, anti-nutritional factors, functional and sensory properties in food product development, and finally, its impact on the environment. Practical Application: Plant leaf proteins are one of the sustainable and alternative source of proteins. It can be produced in most of the agroclimatic conditions without requiring much agricultural inputs. It's functional properties are unique and finds application in novel food product formulations.

Effect of enzyme de-esterified pectin on the electrostatic complexation with pea protein isolate under different mixing conditions.

Native high methoxy citrus pectin (NP) was de-esterified by pectin methyl esterase to produce modified pectins [MP (42, 37, and 33)] having different degrees of esterification. Complex coacervation between a pea protein isolate (PPI) and each pectin was investigated as a function of pH (8.0-1.5) and mixing ratio (1:1-30:1, PPI-pectin). Complex formation was found to be optimal for biopolymer-mixing ratios of 8:1, 8:1, 25:1 and 25:1 for PPI complexed with NP, MP42, MP37 and MP33, respectively, at pHs 3.6, 3.5, 3.9 and 3.9. And, the critical pHs associated with complex formation (accessed by turbidity) was found to shift significantly to higher pHs as the degree of esterification of the pectin decreased, whereas the shift in the pH corresponding to their initial interactions was minimal with degree of esterification. Complexation of PPI with NP and MP42 greatly improved the protein solubility.

Effect of molecular mass and degree of substitution of carboxymethyl cellulose on the formation electrostatic complexes with lentil protein isolate.

The electrostatic interaction between lentil protein isolate (LPI) and carboxymethyl cellulose (CMC) of different molar mass (MM; 90 and 250 kDa) and degree of substitution (DS; 0.7, 0.9 and 1.2%) was examined during a turbidimetric pH acid-titration over a pH (8.0-1.5) and mixing ratio (LPI: CMC; 1:1-10:1) rang. For LPI-CMC (0.7% DS, 250 kDa) at a 1:1 ratio, pHs linked soluble (pHc) and insoluble complexes (pHϕ1) being formed, maximum coacervation (pHopt) and the dissolution of complexes (pHϕ2) occurred at pHs of 6.8, 2.6, 2.1 and 1.7, respectively. As the mixing ratio increased, pHc and pHϕ2 remained unchanged; however, pHϕ1 and pHopt shifted to higher pHs until plateauing at a 4:1 mixing ratio. Molecular mass and DS had no significant effect on critical pHs but did have an impact on the size and number of complexes formed. The maximum optical density at pHopt was found to decrease from 0.495 to 0.406 as the DS increased from 0.7% to 1.2% on the CMC (constant at 250 kDa), suggesting that complexes were likely smaller as they scattered less light. As the MM of CMC decreased from 250 to 90 kDa (at 0.7% DS), maximum optical density increased from 0.495 to 0.527, respectively. Confocal laser scanning microscopy preformed at pHopt showed an increasing number of aggregates as the DS or MM of CMC decreased. From isothermal titration calorimetry (ITC), larger enthalpy values in LPI-CMC with increased DS and MM were observed.

Effect of alkaline de-esterified pectin on the complex coacervation with pea protein isolate under different mixing conditions.

High methoxy citrus pectin (UM88) was saponified to produce modified pectin [M(72, 42, and 9)], with different levels of degree of esterification (DE), to investigate the complex coacervation of pea protein isolate (PPI) with pectin [UM88 and M(72, 42, and 9)]. Regardless of the DE value of pectin, the critical pH corresponding to when insoluble complexes form shifted to higher pH as the mixing ratio increased. The maximum amount of coacervates formed at a biopolymer-mixing ratio of 8:1, 8:1, 10:1 and 15:1 for PPI with UM88, M72, M42, and M9, respectively. Maximum interactions for the protein-pectin admixtures occurred between pH 3.70 and 3.85. PPI complexed with modified pectin displayed greater interactions under their optimal mixing conditions compared to the unmodified pectin. The de-esterification of pectin resulted in more rigid and stiffer pectin, which enhanced its interaction with PPI by shifting the critical parameters to a higher value.

Electrospun polylactic acid-chitosan composite: a bio-based alternative for inorganic composites for advanced application.

Fabricating novel materials for biomedical applications mostly require the use of biodegradable materials. In this work biodegradable materials like polylactic acid (PLA) and chitosan (CHS) were used for designing electrospun mats. This work reports the physical and chemical characterization of the PLA-CHS composite, prepared by the electrospinning technique using a mixed solvent system. The addition of chitosan into PLA, offered decrease in fiber diameter in the composites with uniformity in the distribution of fibers with an optimum at 0.4wt% CHS. The fiber formation and the reduction in fiber diameter were confirmed by the SEM micrograph. The inverse gas chromatography and contact angle measurements supported the increase of hydrophobicity of the composite membrane with increase of filler concentration. The weak interaction between PLA and chitosan was confirmed by Fourier transform infrared spectroscopy and thermal analysis. The stability of the composite was established by zeta potential measurements. Cytotoxicity studies of the membranes were also carried out and found that up to 0.6% CHS the composite material was noncytotoxic. The current findings are very important for the design and development of new materials based on polylactic acid-chitosan composites for environmental and biomedical applications.

Effect of the degree of esterification and blockiness on the complex coacervation of pea protein isolate and commercial pectic polysaccharides.

The complex coacervation of pea protein isolate (PPI) with commercial pectic polysaccharides [high methoxy citrus pectin (P90, 90 representing DE), apple pectin (P78) sugar beet pectin (P62), low methoxy citrus pectin (P29)] of different degrees of esterification (DE) [and galacturonic acid content (GalA)] and blockiness (DB), was investigated. The maximum amount of coacervates formed at a biopolymer weight mixing ratio of 4:1 for all PPI-pectin mixtures, with the exception of PPI-P29 where maximum coacervation occurred at the 10:1 mixing ratio. The pH at which maximum interactions occurred was pH 3.4-3.5 (PPI: P90/P78) and 3.7-3.8 (PPI: P62/P29). PPI complexed with pectins with high levels of DE (low levels of GalA) and DB displayed greater interactions at optimal mixing conditions compared to pectin having lower levels of esterification and blockiness. The addition of P78 to PPI greatly increased protein solubility at pH 4.5.