连续流动快速分析仪测定食品中的蛋白质

Determination of protein in foods by using continuous flow rapid analyzer

建立连续流动快速分析仪测定食品中蛋白质的方法.样品采用加压微波消解.对仪器仪器工作条件进行优化,样品和清洗剂管径:1.8 mm;缓冲溶液和显色剂管径:1.0 mm;混合后主管径:2.0 mm;蠕动泵转速:5 r/min;进样时间:1.5 min;清洗剂吸入时间:1.0 min;清洗剂吸入后再吸入空气时间:10 s.消解液中(NH4)2SO4-N的质量浓度在1.0~55.0 mg/L范围内与吸光度具有良好的线性关系,线性相关系数r=0.998,检出限为0.15 mg/L.对营养奶粉、核桃粉和纯牛奶进行加标回收试验,回收率为95%~103%,测定结果的相对标准偏差均小于3.5%(n=5).将该法的测定结果与传统手工操作凯氏定氮法的测定结果比较,两者无显著差异.该方法具有较好的准确度和精密度,可用于食品中蛋白质含量的快速批量测定.

A method for the determination of protein in food by continuous flow rapid analyzer was established. Samples were digested by pressurized microwave digestion. The optimized operating conditions: pipe diameter of sample and cleaning agent were 1.8 mm, pipe diameter of buffer solution and color developer were 1.0 mm, main pipe diameter after mixing was 2.0 mm;peristaltic pump speed was 5 r/min;injection time was 1.5 min;inhalation time of cleaning agent was 1.0 min;air inhalation time after cleaning agent inhalation was 10 s. The mass concentration of (NH4)2SO4–N in the digestion solution had a good linear relationship with the absorbance in the range of 1.0–55.0 mg/L,and the linear equation was A=0.012 85c +0.014 5,the correlation coefficient was r=0.998,and the detection limit was 0.15 mg/L. The recoveries of nutritious milk powder,walnut powder and pure milk were 95%–103%,and the relative standard deviation of determination results was less than 3.5%(n=5). The determination results of this method was no significant difference compared with traditional manual operation method(Kjeldahl method). The method had good accuracy and precision which can be used for the rapid batch determination of protein content in foods.