Multiple Choice Scheme for Identification of Indigo Aluminum Lake in the New Standard

    Today, when we advocate pure handwork and no additives, when we talk about food additives, we will naturally think that they are all harmful. In fact, this is not the case. Let's first clarify a concept: food additives ≠ illegal additives. Among them, indigo aluminum lake is a food blue pigment. It is mainly used for coloring sugar coating in pharmaceuticals, powder food, oil products, cakes, etc. in food industry, and can also be used for coloring food packaging materials, toys, ink, etc. In GB 2760-2014, the addition amount of indigo aluminum lake in various foods is limited, in which the addition amount of pickled vegetables does not exceed 0.01 g/kg at most, and the addition amount of other sweets except gum-based sweets does not exceed 0.3 g/kg. In the national standard GB 1886.357-2022 issued on June 30, 2022, spectrophotometric colorimetry was used as a simple and feasible method for the detection of food additive indigo aluminum lake. Before the standard was formally implemented (implemented on December 30, 2022), the meta-photometer laboratory used the research-grade ultraviolet-visible spectrophotometer Q-6 to verify this scheme.

    According to the determination requirements in the standard, it is necessary to put the sample solution in a 1 cm cuvette, take ammonium acetate solution as a blank, and measure the absorbance value with a spectrophotometer at the maximum absorption wavelength (about 610 nm), and the absorbance value should be controlled within the range of 0.3~0.7, otherwise, the concentration of the sample solution should be adjusted, and then the absorbance should be measured again. In addition to adjusting the concentration of the solution mentioned in the standard to control its absorbance within the range of 0.3~0.7, we can also reduce the sampling volume of the sample to achieve the purpose of testing. Q-6 research-grade UV-Vis spectrophotometer adopts a conventional single-hole frame, selects a variety of micro-cuvette cells, controls the optical path unchanged, and changes the concentration; In addition, according to Lambert beer's calibration, we can also control the absorbance within a certain range by changing the optical path. At this time, we can choose Q-6 test accessory variable optical path sample cell frame and matching cuvette to complete the test. In short, it is ok to choose the appropriate accessories and reduce the test error.