Lu Yan, Dai Jinxia, Zhang Sen, Qiao Junqin, Lian Hongzhen, Mao Li
State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry & Chemical Engineering and Center of Materials Analysis, Nanjing University, Nanjing 210023, China.
Ministry of Education (MOE) Key Laboratory of Modern Toxicology, School of Public Health, Nanjing Medical University, Nanjing 211166, China.
Foods. 2023 Apr 3;12(7):1519. doi: 10.3390/foods12071519.
It is widely acknowledged that casein is an important allergenic protein in milk which may cause danger to customers. The identification and confirmation of caseins through mass spectrometry requires the selection of suitable characteristic peptides. In this study, by means of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), the three most representative specific peptides of caseins in cow milk were screened out with mass-to-charge ratios (/) of 830, 1195, and 1759, respectively. By comparing 2,5-dihydroxybenzoic acid (DHB) and -cyano-4-hydroxycinnamic acid (CHCA) MALDI matrices, it was found that DHB was more suitable for peptide detection with the limits of detection (LODs) of 0.1 mg/L for , -casein. Furthermore, on the basis of verifying the characteristic peptides of casein from cow milk, this protocol was applied to goat milk authentication. Cow milk addition in goat milk was investigated by using the screened specific peptides. The results showed that the adulteration could be identified when the proportion of cow milk was 1% or more. When applied to inspect adulteration in five brands of commercial goat milk, specific peptides of bovine casein were detected in four of them. The method has the advantages of strong reliability, high throughput, simple preprocessing, and fast speed, which can provide powerful help for prewarning dairy allergen.
人们普遍认为，酪蛋白是牛奶中一种重要的过敏原蛋白，可能会对消费者造成危害。通过质谱法鉴定和确认酪蛋白需要选择合适的特征肽段。在本研究中，借助基质辅助激光解吸电离飞行时间质谱（MALDI-TOF MS），筛选出了牛奶中酪蛋白的三种最具代表性的特异性肽段，其质荷比（m/z）分别为830、1195和1759。通过比较2,5-二羟基苯甲酸（DHB）和α-氰基-4-羟基肉桂酸（CHCA）两种MALDI基质，发现DHB更适合肽段检测，对于αs1-、αs2-酪蛋白的检测限（LOD）为0.1 mg/L。此外，在验证了牛奶中酪蛋白特征肽段的基础上，将该方法应用于山羊奶的掺假鉴定。利用筛选出的特异性肽段对山羊奶中添加牛奶的情况进行了研究。结果表明，当牛奶比例达到1%及以上时，掺假情况能够被识别。将该方法应用于检测五个品牌的市售山羊奶的掺假情况时，其中四个品牌检测到了牛酪蛋白的特异性肽段。该方法具有可靠性强、通量高、预处理简单、速度快等优点，可为乳制品过敏原预警提供有力帮助。
