热处理过程中肌肉蛋白与萜类化合物相互作用机制

    Interaction mechanisms for the muscle proteins with terpenoid compounds during heat treatment

    • 摘要: 为明确热处理过程中肌肉蛋白与萜类化合物的相互作用规律及机制,以肌原纤维蛋白(myofibrillar protein,MP)和肌浆蛋白(sarcoplasmic protein,SP)为研究对象,测定不同加热时间下表面疏水性、总巯基含量、粒径、二级结构含量等理化特性。选取炖煮猪肉中3种关键萜类化合物(3-蒈烯、柠檬烯、芳樟醇),结合气相色谱-质谱联用,探究热处理过程中MP和SP对萜类化合物吸附能力与蛋白构象变化的相关性,并通过分子对接揭示肌肉蛋白与萜类化合物结合机制。结果表明:随加热时间延长,MP和SP的表面疏水性和总巯基含量先上升后下降,粒径持续上升,α-螺旋结构转化为β-折叠和无规则卷曲结构。加热5 min内,MP和SP二级结构展开,结合位点暴露,对萜类化合物吸附能力增强;继续加热后,MP和SP聚集使结合位点被掩埋,对萜类化合物吸附能力降低,且由于SP更高的聚集程度,加热10~60 min内吸附能力弱于MP。分子对接结果证明,疏水相互作用为3-蒈烯和柠檬烯与肌肉蛋白结合的主要驱动力,而芳樟醇通过疏水相互作用和氢键与肌肉蛋白结合。结果表明热处理可以通过改变肌肉蛋白构象控制风味结合位点暴露或掩埋,从而影响肌肉蛋白与萜类化合物的相互作用,研究结果可为热加工肉制品的风味调控提供理论指导。

       

      Abstract: The interaction between muscle proteins and aroma compounds during processing can lead to a loss of aroma in the meat products, thereby altering the aroma profile for the consumer preference. Heat treatment has been commonly used in meat processing. The addition of spices during stewing meat can be used to eliminate the off-flavor for the enhanced color and the fragrance. Among them, terpenoid compounds are the key volatile flavor compounds in spices. But it is unclear on the mechanism of their interaction with muscle proteins. Myofibrillar protein (MP) and sarcoplasmic protein (SP) also play important roles as components of muscle proteins. This study aims to clarify the patterns and mechanisms of the interaction between muscle proteins and terpenoid compounds during heat treatment. Various physicochemical properties of MP and SP were determined at different heating times, such as surface hydrophobicity, total sulfhydryl content, particle size, and secondary structure content. Three terpenoid compounds (3-carene, limonene, and linalool) which significantly contributed to the aroma of stewed pork, were selected to investigate the interaction between aroma compounds and muscle proteins. Solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) was used to study the changes in the aroma absorption ability of proteins with heating time. The correlation was examined between aroma absorption and conformational changes of MP and SP. Moreover, the molecular docking analysis was also implemented to reveal the mechanism of muscle proteins binding to the terpenoid compounds. The results indicated that the heat treatment significantly altered the conformation of MP and SP. The surface hydrophobicity and total sulfhydryl content of MP and SP initially increased and then decreased, as the heating time increased, due to their unfolding and aggregation behaviors. Both MP and SP exhibited an increase in particle sizes during heating, particularly with a higher degree of SP aggregation, due to the lower thermal stability. Furthermore, the secondary structure content analysis showed that the intramolecular hydrogen bond of proteins was rearranged into intermolecular hydrogen bond, and then the ordered structure was transformed into a random coil conformation following heating, resulting in a decrease of α-helix structure content and an increase of β-sheet and random coil structure content. MP and SP demonstrated enhanced aroma adsorption during the initial 5 min of heating, due to their unfolded secondary structures and exposed binding sites. However, the continued heating led to the aggregation of MP and SP, burying the binding sites, and reducing their adsorption ability. Although the MP and SP exhibited similar adsorption within 0-5 min of heating, the SP displayed weaker adsorption than the MP after 10-60 min of heating. This difference was attributed to the higher degree of aggregation in the SP, which resulted in greater steric hindrance and the burial of more aroma-binding sites. Molecular docking results demonstrated that the hydrophobic interactions dominated the interactions between 3-carene/limonene and muscle proteins, whereas the linalool bound to muscle proteins through hydrophobic interactions and hydrogen bonds. Overall, the heat treatment can be expected to modify the conformation of muscle proteins, and then regulate the exposure or burial of aroma binding sites. Consequently, there was some impact on the interaction between muscle proteins and terpenoid compounds. The findings can provide theoretical guidance to control the aroma retention/release behavior during the thermal processing of meat products for the higher quality of meat products.

       

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