Department of Food Nutrition, College of Biosystems and Food Science, Zhejiang University, Hangzhou 310058, China.
Key Laboratory of Post-Harvest Handling of Fruits, Food Science Institute, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China.
Molecules. 2022 Jul 22;27(15):4689. doi: 10.3390/molecules27154689.
The traditional method for the determination of protein in food needs the operations of digestion, distillation, absorption, and titration; therefore, it is complicated and time-consuming and requires professional personnel. Is there a more convenient and faster detection method that can directly determine the ammonium ions in protein digestion solution to obtain the protein content of food and avoid the distillation−absorption−titration process? The feasibility of water ammonium ion test kits for food protein rapid detection was discussed here. After digestion, the protein in food transforms into ammonium ions in the digestion solution. Because of the variety of food, there are many different inorganic ions left in the food digestion solution, and at the same time, digestion agents are added in the digestion process and become potential interference factors in ammonium determination. Therefore, the detection accuracy of ammonium test kits needs to be evaluated first, including their anti-interference ability. The standard curve of ammonium was established by the test kit. When the ammonium concentration was 0.00−2.50 mg/L, the absorbance at 620 nm was linearly related to the ammonium concentration, the determination coefficient R2 was 0.9995, and the detection limit of this method was 0.01 mg/L. The influences of temperature, pH value, and reaction time on the test kit method were discussed. The precision was 0.90−3.33%; the repeatability was 1.71−4.86%; and the recovery rate of tap water, river water, and sea water was controlled within 90−103%. The anti-interference ability of the evaluated test kit was better than that of the national standard detection method. The test kit, combined with sample pretreatment and protein conversion formula, was used to detect protein in different types of food (milk powder, rice flour, wheat flour, soy, banana, milk, fish food, chicken food, and dog food). The results showed that there were no significant differences (ρ > 0.05) between the national method and the test kit method. The ammonium ion test kit method shortened the determination time and had higher sensitivity, showing its potential for the rapid determination of food protein.
传统的食品中蛋白质测定方法需要经过消化、蒸馏、吸收、滴定等操作，因此较为复杂繁琐，耗时较长，且需要专业人员进行操作。是否存在更方便、快速的检测方法，可以直接测定蛋白质消化液中的铵离子，从而得到食品中蛋白质的含量，避免蒸馏−吸收−滴定过程？本文探讨了水质铵离子测试盒用于食品蛋白质快速检测的可行性。食品中的蛋白质经消化后，在消化液中转化为铵离子。由于食品种类繁多，在食品消化液中还残留着多种不同的无机离子，同时在消化过程中加入消化试剂，这些也成为铵离子测定的潜在干扰因素。因此，需要首先对铵测试盒的检测准确性进行评价，包括其抗干扰能力。采用测试盒建立了铵的标准曲线，当铵浓度在 0.00-2.50mg/L 时，620nm 处的吸光度与铵浓度呈线性关系，测定系数 R2 为 0.9995，该方法的检出限为 0.01mg/L。探讨了温度、pH 值和反应时间对测试盒法的影响。精密度为 0.90-3.33%；重复性为 1.71-4.86%；自来水、河水和海水的回收率控制在 90-103%。评价的测试盒抗干扰能力优于国家标准检测方法。测试盒结合样品预处理和蛋白质转化公式，用于检测不同类型的食品（奶粉、米粉、面粉、大豆、香蕉、牛奶、鱼饲料、鸡饲料和狗饲料）中的蛋白质。结果表明，与国家标准方法相比，测试盒法无显著差异（ρ＞0.05）。铵离子测试盒法缩短了测定时间，灵敏度更高，显示出其在食品蛋白质快速测定中的应用潜力。
