Moisture Loss Characteristics and Quality Changes in Cold-pressed Oil of Camellia oleifera during Shell-Breaking Caused by Drying Stress

XU Jianguo; CHEN Jiajun; SHI Jinsong; GU Zhen; XU Gang; ZHANG Xukun

doi:10.13982/j.mfst.1673-9078.2025.12.1363

Abstract：The shell breaking process of Camellia oleifera fruit relies on drying stress to separate the seeds from the shells.Shell-breaking experiments were performed to analyze the moisture loss characteristics during shell-breaking caused by drying stress at different drying temperatures(50,60,70,and 80℃)and the influence of the shell-breaking process on the quality of cold-pressed oils.A model for moisture loss characteristics during shell-breaking caused by drying stress was established,and a variable temperature shell-breaking process was developed.The moisture loss curves of C.oleifera fruit during shell-breaking demonstrated a decreasing trend,and the moisture loss rate showed a decreasing trend with a ladder pattern,exhibiting an initial acceleration stage,followed by several nearly constant-rate stages.With the increase in drying temperature,moisture loss curves became steeper,and the time to reach the endpoint moisture content of 32.00%(w.b.)for C.oleifera was significantly reduced.The newly established mathematical model with R2≥0.999 7 and RMSE≤0.428 6%can accurately describe the moisture loss process during the shell-breaking of C.oleifera fruit caused by drying stress.With increasing shell-breaking temperature,the acid value of the cold-pressing oil prepared using C.oleifera seeds increased from 0.08 mg/g to 0.39 mg/g.The total color difference value increased from 76.27 to 83.63,and the crude oil yield decreased from 23.43%to 18.84%.Shell-breaking caused by drying stress at low temperature improved the quality and crude oil yield of cold-pressed oil from C.oleifera seeds.After variable temperature shell-breaking caused by drying stress,the shell-breaking and seed-breaking ratios of the C.oleifera fruits were 98.35%and 0%,respectively.The acid(based on KOH)and peroxide values of the cold-pressing crude oil were 1.00 mg/g and 0.009 9 g/100 g,respectively.The moisture and volatile matter content was 0.35%,and the crude oil yield was 21.08%.The results of this study will provide reference data for the optimization of shell-breaking technology.