油茶果干燥应力破蒲失水特征及冷榨原油质量的变化

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

摘要:

为更好地了解油茶果干燥应力破蒲技术以实现油茶籽和果蒲（壳）的高效、高品质分离，该文通过开展干燥应力破蒲试验，考察了不同干燥温度（50、60、70、80 ℃）条件下干燥应力破蒲失水动力学特征以及破蒲过程对后续冷榨原油质量的影响，建立了干燥应力破蒲失水过程模型，开发了变温干燥应力破蒲工艺。研究发现，干燥应力破蒲过程中油茶果失水速率曲线呈阶梯状下降趋势，且存在提速段及多个近似恒速段；干燥温度升高，油茶果失水曲线变陡，到达破蒲终点湿基含水率（32.00%）时所需时间显著缩短。新建的半经验模型（R2≥0.999 7，RMSE≤0.428 6%）可以准确模拟油茶果干燥应力破蒲失水过程。随着温度的升高，油茶籽冷榨原油酸价数值从0.08 mg/g显著增加至0.39 mg/g，总色差从76.27显著增加至83.63，出油率从23.43%显著降低至18.84%。低温干燥应力破蒲有利于提高油茶籽冷榨原油质量和出油率。经变温干燥应力破蒲后，油茶果破蒲率为98.35%，碎籽率为0%，冷榨原油酸价（以KOH计）、过氧化值分别为1.00 mg/g、0.009 9 g/100 g，水分及挥发物为0.35%，出油率为21.08%。该研究可为优化油茶果干燥应力破蒲技术工艺及设备开发提供依据。

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 coldpressed 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 shellbreaking 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.