Soil Drenching with Wood Distillate Modifies the Nutritional Properties of Chickpea (Cicer arietinum L.) Seeds by Increasing the Protein Content and Inducing Targeted Changes in the Proteomic Profile

The production of food with a naturally enriched protein content is a strategic response to the growing global demand for sustainable protein sources. Wood distillate (WD), a by-product of the pyrolysis of woody biomass, has previously been shown to increase the protein concentration and bioavailability in chickpea seeds. Here, we evaluated the effect of 0.5% (v/v) WD soil drenching on chickpea productivity, nutritional profile, and proteomic pattern. WD treatment significantly improved the yield by increasing plant biomass (+144%), number of pods and seeds (+148% and +147%), and seed size (diameter: +6%; weight: +25%). Nutritional analyses revealed elevated levels of soluble proteins (+15%), starch (+11%), fructose (+135%), and polyphenols (+14%) and a greater antioxidant capacity (25%), alongside a reduction in glucose content, albeit not statistically significant, suggesting an unchanged or even lowered glycemic index. Although their concentration decreased, Ca (−31%), K (−12%), P (−5%), and Zn (−14%) in WD-treated plants remained within normal ranges. To preliminary assess the quality and safety of the protein enrichment, a differential proteomic analysis was performed on coarse flours from individual seeds. Despite the higher protein content, the overall protein profiles of the WD-treated seeds showed limited variation, with only a few storage proteins, identified as legumin and vicilin-like isoforms, being differentially abundant. These findings indicate a general protein concentration increase without a major alteration in the proteoform composition or differential protein synthesis. Overall, WD emerged as a promising and sustainable biostimulant for chickpea cultivation, capable of enhancing both yield and nutritional value, while maintaining the proteomic integrity and, bona fide, food safety.