Vol. 7, Issue 12, Part C (2025)

Neem (Azadirachta indica) seed cake, a major by-product generated after oil extraction, remains largely underutilized despite its considerable protein content. The present study aimed to optimize protein extraction from defatted neem seed cake by systematically evaluating the effects of particle size, extraction solvent, and precipitation pH. Two particle size fractions (<0.5 mm and 0.5-1.0 mm) were investigated using three extraction systems: distilled water with pH adjustment, alkaline extraction with 0.25 M sodium hydroxide (NaOH), and 0.2 M potassium hydroxide (KOH). Protein solubilization was followed by acid precipitation at pH levels ranging from 2 to 5 and protein yield was determined on a dry weight basis.

Results demonstrated that particle size significantly influenced protein recovery, with the finer fraction (<0.5 mm) consistently yielding higher protein across all extraction methods due to enhanced surface area and improved solvent accessibility. Among the solvent systems, alkaline extraction methods were markedly more effective than distilled water. Distilled water with pH adjustment yielded a maximum protein recovery of 31.67% at pH 3 for the fine fraction. NaOH extraction achieved its highest yield of 29.78% at pH 4, whereas KOH extraction produced the highest overall recovery, reaching 37.89% at pH 5 for particles smaller than 0.5 mm.

Precipitation pH played a critical role in determining protein yield, with optimal recovery generally observed between pH 3 and pH 5, depending on the solvent system employed. The findings confirm that an integrated extraction approach combining particle size reduction, appropriate solvent selection and optimized precipitation pH can substantially improve protein recovery from neem seed cake.

Overall, this study highlights the potential of neem seed cake as a valuable and sustainable plant protein source and provides a scientific basis for its valorization in food, feed and industrial applications through optimized processing strategies.