p‐Hydroxybenzoic acid (PHBA) plays a significant role in sustaining the oxidative stability of macadamia nut oil (MNO). However, PHBA undergoes thermal decarboxylation and loses its bioactive antioxidant properties. In this study, we determine PHBA degradation kinetics in oils at various heating temperatures, which provides fundamental understanding of PHBA thermal degradation in oils and oil quality changes during high‐temperature processing. PHBA degradation kinetics in MNO, olive oil, and corn oil were evaluated at temperatures typical for cooking and frying. PBHA headspace concentration was measured using selected ion flow tube mass spectrometry. PHBA decarboxylation followed a zero‐order reaction, where degradation could be affected by factors such as the type of oil matrix having different FA compositions, antioxidants, and component interactions. PHBA degradation activation energies (E _a) showed that PHBA was more stable against thermal decarboxylation in MNO (85 kJ mol^–1) than in olive oil (40 kJ mol⁻¹) or corn oil (22 kJ mol⁻¹). The higher enthalpy () of decarboxylation in MNO (82 kJ mol⁻¹) indicates that PHBA is more inhibited from decomposition than olive oil (37 kJ mol⁻¹) or corn oil (19 kJ mol⁻¹). Moreover, the negative entropy values () of PHBA degradation from MNO (−192 J mol⁻¹ K⁻¹), olive oil (−277 J mol⁻¹ K⁻¹), and corn oil (−325 J mol⁻¹ K⁻¹) indicates that these oils impart some inhibitory properties against PHBA thermal decarboxylation.

中文翻译：

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澳洲坚果油，橄榄油和玉米油中对羟基苯甲酸的热降解

p‐羟基苯甲酸（PHBA）在维持澳洲坚果油（MNO）的氧化稳定性方面起着重要作用。然而，PHBA经历热脱羧并失去其生物活性抗氧化剂性质。在这项研究中，我们确定了在各种加热温度下油中的PHBA降解动力学，这提供了对PHBA在油中的热降解和高温加工过程中油质变化的基本了解。在烹饪和油炸的典型温度下评估了MNO，橄榄油和玉米油中的PHBA降解动力学。使用选定的离子流管质谱仪测量PBHA顶空浓度。PHBA脱羧反应遵循零级反应，降解可能受到多种因素的影响，例如具有不同FA组成的油基质类型，抗氧化剂，和组件交互。PHBA降解活化能（E _a）表明，相比MNO （40 kJ mol ^-1）或玉米油（22 kJ mol ^-1），PHBA在MNO（85 kJ mol ^-1）中对热脱羧更稳定。MNO（82 kJ mol ^-1）中较高的脱羧焓（）表明，PHBA的分解作用比橄榄油（37 kJ mol ^-1）或玉米油（19 kJ mol ^-1）更受抑制。而且，PHBA由MNO（-192 J mol ^-1 K ^-1），橄榄油（-277 J mol ^-1 K ^-1）和玉米油（-325 J mol ^-1 K ）降解的负熵值（）^-1 ）表明这些油赋予PHBA热脱羧一些抑制性能。