Abstract:

The objective of this study was to optimize the ultrasonic-assisted extraction of protein from walnut dregs as
a byproduct from the production of cold-pressed walnut kernel oil. A comparative study was carried out to optimize the
extraction process using orthogonal array design and Box-Behnken design. The results showed that response surface
methodology was more suitable to optimize protein extraction from walnut dregs than orthogonal array design. The
extraction yield of protein was influenced in decreasing order by pH, liquid-to-solid ratio, extraction temperature, and
ultrasonication time. The optimized extraction process was determined as extraction using an alkali solvent (pH 8.7) at
48 ℃ with a liquid to solid ratio of 25:1 (mL/g) by ultrasonication for 60 min at a power of 150 W followed by protein
precipitation by acidification to pH 5.0, resulting in an extraction yield of 69.62%.

Key words: walnut dregs, orthogonal array design, response surface methodology, walnut protein, optimization