1. Describe 

The aluminum in alum is harmful to the human body. When alum is used as a food additive and consumed, it is essentially not excreted and remains permanently deposited in the body. Its toxic effects are primarily manifested in its ability to kill brain cells, leading to premature brain atrophy, dementia, and reduced cognitive function. Therefore, detecting alum in food is of significant importance.

During the processing of edible bird's nests, alum may potentially be used as an additive to enhance the whiteness or shape of the nests, while nitrites may originate from storage conditions or emerge during processing.

According to China's current food safety standards:

1. Alum is prohibited as an additive in bird's nest products.

2. Nitrite content is strictly limited to 30 mg/kg.

Therefore, all bird's nest products imported into China must comply with these regulations.

2. Limit of detection

25mg/kg. 

3. Kit composition 

Extracting Agent (6mL) ×1

Detection Solution A (80mL) ×1

Detection Solution B (80mL) ×1

50mL Centrifuge tubes x5

5mL Centrifuge tubes x 50

Colorimetric card ×1

User manual

The reagents and appliances may be required but not provided: grinder, 20-200µL pipette, 100-1000µL pipette, 200µL pipette tip, 1000µL pipette tip, purified or distilled water, ultrasonic apparatus.

4. Specifications 

50 tests 

5. Application

Intended to test alum in products such as fried dough twists, deep-fried dough cakes, fritters, instant noodles, sesame leaves, crispy bean shells, noodles, bread, steamed buns, cakes, biscuits, flour, rice flour, vermicelli, edible bird’s nest and jellyfish semi-quantitatively.

6. Procedure & steps 

6.1 Collect no less than 100g of representative samples (remove fillings from stuffed samples, and drain surface water from jellyfish

products). Thoroughly grind the sample using a grinder, then proceed with testing. 

6.2 Weigh 0.50g of the sample into a 50mL centrifuge tube, accurate to 0.01g. Add purified or distilled water to the 50mL mark, then add 0.1mL of the alum extracting agent. Mix thoroughly until the sample is completely dispersed, and then process ultrasound for 10 min. Shake it several times during this period (if ultrasonic condition are unavailable, let the mixture stand for 20 min for extraction). Use the supernatant as the test solution. 

6.3 Take 1mL of the supernatant into a 5mL centrifuge tube, add 1.5mL of Detection Solution A, followed by 1.5mL of Detection Solution B. Mix thoroughly and let it react for 5min. Compare the color with the standard colorimetric chart. If the result exceeds the range of the color chart, dilute the sample extract with purified water to an appropriate ratio and retest. Note: Detection Solution B should be shaken well to dissolve before use, as sediment may form over time.

7. Results determination

7.1 Read the corresponding color block on the colorimetric card as the detection result for the sample. If the color falls between two

blocks, follow the principle of taking the higher value. 

7.2 The detection result of the diluted sample test solution shouldbe multiplied by the corresponding dilution factor during interpretation. 

8. Attention

8.1 When preparing the sample, ensure it is finely ground, and fully disperse it during extraction; otherwise, alum extraction may be affected. 

8.2 Failure to shake and dissolve the sediment in Detection Solution B may result in lighter color development. 

8.3 The extracting agent is highly corrosive; if it comes into contact with skin, rinse immediately with clean water. 

8.4 The 50mL centrifuge tubes can be reused after being cleaned thoroughly.

9. Limit standard

The specific nitrite limit standards for food should be referenced according to local regulations. The table on the reverse side shows the standards in China, provided for reference only.

10. Storage conditions 

Stored at 4-30℃ with seal, at a cool and dry place within a shelf-life of 12 months.