Supercritical carbon dioxide (SC‐CO₂) technology offers new opportunities for green processing of lipids; however, there is little information of the melting behavior and volumetric expansion of solid lipids in pressurized CO₂. In this study, melting behavior and volumetric expansion of two different solid lipid classes and the effect of the structural differences within the same lipid class on the melting behavior in pressurized CO₂ were investigated. The melting point of the solid lipids decreased linearly with increasing pressures up to a certain level; then, it stayed constant. The highest melting point depression was observed for soybean oil monoacylglycerol (SO‐MAG) at 51.5 °C/110 bar, whereas the lowest was for fully hydrogenated soybean oil (FHSO) containing 30% SO‐MAG at 55.0 °C/79 bar. Melting point depression depended on lipid class. SO‐MAG exhibited a higher melting point depression than FHSO (triacylglycerol form), and its blends with SO‐MAG. There was no difference in melting point depression between glyceryl 1,2‐distearate and glyceryl 1,3‐distearate up to 200 bar (P > 0.05). A positive correlation between the melting point depression and volumetric expansion of solid lipids was observed. The highest volumetric expansion was for SO‐MAG in the linear region of the melting point depression curve, achieving 14.4% expansion compared to 9.3% for FHSO (P < 0.05). The highest dT/dP value (0.17 °C bar⁻¹) was obtained for SO‐MAG, whereas the FHSO (0.09 °C bar⁻¹) had the lowest one. Findings of this study will help optimize solid lipid‐involving SC‐CO₂ processes for better protection of heat‐sensitive compounds while improving energy efficiency.

中文翻译：

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固体脂质基质的化学结构对其在加压二氧化碳中的熔融行为和体积膨胀的影响

超临界二氧化碳（SC-CO ₂）技术为脂质的绿色加工提供了新的机会。然而，关于加压CO ₂中固体脂质的熔融行为和体积膨胀的信息很少。在这项研究中，两种不同的固体脂质类别的熔融行为和体积膨胀以及同一脂质类别内的结构差异对加压CO ₂的熔融行为的影响被调查了。固体脂质的熔点随着压力增加到一定水平而线性下降；然后，它保持不变。在51.5°C / 110 bar下观察到大豆油单酰基甘油（SO-MAG）的最高熔点降低，而在55.0°C / 79 bar下包含30％SO-MAG的完全氢化大豆油（FHSO）的最低熔点下降。熔点降低取决于脂质类别。与FHSO（三酰基甘油形式）相比，SO-MAG的熔点降低程度更高，并且与SO-MAG混合。在不超过200 bar的条件下，1,2-硬脂酸甘油酯和1,3-硬脂酸甘油酯的熔点降低没有差异（P > 0.05）。观察到熔点下降与固体脂质的体积膨胀呈正相关。SO-MAG的最大体积膨胀在熔点降低曲线的线性区域，达到14.4％的膨胀，而FHSO为9.3％（P  <0.05）。SO-MAG的dT / dP值最高（0.17°C bar ^-1），而FHSO的dT / dP值最低（0.09°C bar ^-1）。这项研究的结果将有助于优化涉及固态脂质的SC-CO ₂工艺，以更好地保护热敏化合物，同时提高能效。