Food Chemistry and Analysis, Technische Universität Berlin, Gustav-Meyer-Allee 25, 13355 Berlin, Germany.
Institute for Food and Environmental Research e. V., Papendorfer Weg 3, 14806 Bad Belzig, Germany.
Molecules. 2021 Feb 19;26(4):1104. doi: 10.3390/molecules26041104.
Lipid oxidation and the resulting volatile organic compounds are the main reasons for a loss of food quality. In addition to typical compounds, such as alkanes, aldehydes and alcohols, methyl ketones like heptan-2-one, are repeatedly described as aroma-active substances in various foods. However, it is not yet clear from which precursors methyl ketones are formed and what influence amino compounds have on the formation mechanism. In this study, the formation of methyl ketones in selected food-relevant fats and oils, as well as in model systems with linoleic acid or pure secondary degradation products (alka-2,4-dienals, alken-2-als, hexanal, and 2-butyloct-2-enal), has been investigated. Elevated temperatures were chosen for simulating processing conditions such as baking, frying, or deep-frying. Up to seven methyl ketones in milk fat, vegetable oils, and selected model systems have been determined using static headspace gas chromatography-mass spectrometry (GC-MS). This study showed that methyl ketones are tertiary lipid oxidation products, as they are derived from secondary degradation products such as deca-2,4-dienal and oct-2-enal. The study further showed that the position of the double bond in the precursor compound determines the chain length of the methyl ketone and that amino compounds promote the formation of methyl ketones to a different degree. These compounds influence the profile of the products formed. As food naturally contains lipids as well as amino compounds, the proposed pathways are relevant for the formation of aroma-active methyl ketones in food.
脂质氧化和由此产生的挥发性有机化合物是导致食物质量损失的主要原因。除了典型的化合物，如烷烃、醛和醇外，甲基酮，如庚烷-2-酮，在各种食物中被反复描述为具有香气活性的物质。然而，目前还不清楚甲基酮是由哪些前体形成的，以及氨基酸化合物对形成机制有什么影响。在这项研究中，研究了选定的与食品相关的脂肪和油以及含有亚油酸或纯次级降解产物（烷-2,4-二烯醛、烯-2-醛、己醛和 2-丁基-2-辛烯醛）的模型体系中甲基酮的形成。选择高温来模拟烘焙、油炸或深炸等加工条件。使用静态顶空气相色谱-质谱联用（GC-MS）在牛奶脂肪、植物油和选定的模型体系中测定了多达七种甲基酮。这项研究表明，甲基酮是三级脂质氧化产物，因为它们是由二级降解产物如癸-2,4-二烯醛和辛-2-烯醛衍生而来。研究进一步表明，前体化合物中双键的位置决定了甲基酮的链长，并且氨基酸化合物以不同的程度促进甲基酮的形成。这些化合物影响产物形成的分布。由于食物中天然含有脂肪和氨基酸化合物，因此所提出的途径与食物中具有香气活性的甲基酮的形成有关。
