传统中式火腿加工过程中N-羟乙酰神经氨酸的动态变化

为探究传统中式火腿加工过程中不同形态N-羟乙酰神经氨酸（N-glycolylneuraminic acid，Neu5Gc）之间的关系，采用高效液相色谱-荧光检测（high performance liquid chromatography-fluorescence detector，HPLC-FLD）法测定样品中总Neu5Gc、游离态Neu5Gc、结合态Neu5Gc的含量。结果表明：上述3 种形态的Neu5Gc含量随着加工时间的延长均呈前期上升后期降低的趋势；浅层肌肉半膜肌和深层肌肉股二头肌中总Neu5Gc和结合态Neu5Gc的含量变化规律相似，因水分含量降低程度的不同而使股二头肌的变化规律滞后。发酵后期水分损失幅度变缓，股二头肌中Neu5Gc解离速率高于半膜肌；新鲜猪后腿原料中游离态Neu5Gc含量极少，甚至低于检测限，结合态Neu5Gc含量与总Neu5Gc含量（15.00～30.62 μg/g）接近。发酵半年、1 年和2 年的火腿中总Neu5Gc含量分别为（15.09±0.39）、（14.52±0.38）、（28.30±0.43）μg/g，均与猪后腿原料中的Neu5Gc含量相近。为进一步探究Neu5Gc的变化，对样品进行冷冻干燥处理以避免水分含量变化对Neu5Gc含量的影响，结果表明，随着加工时间的延长，总Neu5Gc、结合态Neu5Gc的含量逐渐降低，且发酵期降低明显，具有显著差异性（P＜0.05）；游离态Neu5G变化无明显规律，但与空白样品相比，其含量呈增加趋势。

Dynamic Change of N-Glycolylneuraminic Acid in Chinese Dry-Cured Ham during Processing

The purpose of this study was to explore the relationship between different forms of N-glycolylneuraminic acid (Neu5Gc) during traditional Chinese ham processing. The contents of total Neu5Gc, free Neu5Gc and conjugated Neu5Gc in samples, as determined by high performance liquid chromatography with fluorescence detector (HPLC-FLD), increased first and decreased later. The contents of total Neu5Gc and conjugated Neu5Gc in Semimembranosus muscle (SM) and Biceps femoris muscle (BF) changed in a similar trend, with BF lagging behind SM due to the different degrees of decrease in water content. In the late stage of fermentation, water was lost slowly, and the dissociation rate of Neu5Gc in BF was higher than that in SM. The content of free Neu5Gc in fresh hind legs was very low, even lower than the detection limit, and the content of conjugated Neu5Gc was close to the content of total Neu5Gc (15.00–30.62 μg/g). Total Neu5Gc contents in hams fermented for six months, one year and two years were (15.09 ± 0.39), (14.52 ± 0.38) and (28.30 ± 0.43) μg/g, which were similar to that in fresh hind legs. In order to further explore the change of Neu5Gc, the samples were freeze-dried to avoid the influence of water content change on Neu5Gc content. The contents of total Neu5Gc and conjugated Neu5Gc decreased gradually, especially during the fermentation period, with a significant difference being observed (P < 0.05). The content of free Neu5G changed irregularly, but showed an increasing trend compared with the blank sample.