Leek Detection

The detection of leeks is an important part of ensuring their quality and safety, mainly including the following aspects:

Pesticide residue detection
- **Organophosphorus pesticide residues**: Organophosphorus pesticides are commonly used insecticides in the process of leek cultivation. When testing, gas chromatography (GC) or liquid chromatography-tandem mass spectrometry (LC-MS/MS) is usually used. For example, to detect pesticide residues such as chlorpyrifos and methamidophos, the leek samples are subjected to pretreatment steps such as crushing, extraction, and purification, and then analyzed by instruments. The type and content of pesticide residues are determined by comparing the retention time and peak area with the standard. If the residues of these pesticides are too high, they will cause damage to the human nervous system, etc.
- **Pyrethroid pesticide residues**: This type of pesticide is also commonly used for leek pest control. The detection method is similar to that of organophosphorus pesticides, but it is different in terms of chromatographic conditions. For example, high-performance liquid chromatography (HPLC) can be used to detect pyrethroid pesticide residues such as cypermethrin and deltamethrin. Excessive residues of these pesticides may cause human poisoning, dizziness, nausea and other symptoms.

Heavy Metal Detection
- **Lead Detection**: Leeks may absorb lead from the soil, irrigation water and other environments. Atomic absorption spectrometry (AAS) or inductively coupled plasma mass spectrometry (ICP-MS) is generally used to detect lead content. The leek sample is first digested to make the lead exist in the form of ions, and then detected by instrument. After entering the human body, lead will accumulate in the body, causing harm to multiple systems such as the human nervous system and blood system.
- **Cadmium Detection**: Similarly, cadmium is one of the heavy metals that are focused on detection. The detection method is similar to that of lead. Cadmium can affect the normal function of organs such as the kidneys of the human body.
- **Mercury Detection**: The content of mercury in leeks can be detected by cold atomic absorption spectrometry or atomic fluorescence spectrometry. Mercury and its compounds are extremely harmful to the central nervous system, kidneys, etc. of the human body.

Nutritional Components Detection
- **Vitamin Detection**: Leeks are rich in vitamins, such as vitamin C, vitamin B group, etc. Vitamin C content can be detected by 2,6-dichloroindophenol titration, and its content can be determined by titration reaction. Vitamin detection helps to understand the nutritional value of leeks.
- **Mineral detection**: The content of minerals such as potassium, calcium, and iron in leeks is also important. For example, calcium and iron content are detected by flame atomic absorption spectrometry, and potassium and other minerals are detected by inductively coupled plasma emission spectrometry (ICP-OES). These minerals play an indispensable role in maintaining normal physiological functions of the human body.
- **Dietary fiber detection**: Leeks are a good source of dietary fiber. The enzyme-weight method can be used to detect dietary fiber content. This method removes digestible carbohydrates and other components through enzymatic hydrolysis. The remaining residue is dried, weighed, and other steps to calculate the dietary fiber content, which helps to evaluate the contribution of leeks to human intestinal health.

Microbial detection
- **Total colony count detection**: The leek sample is made into a homogenate, and the total colony count is detected by the plate count method. Various microorganisms may be attached to the surface of leeks. Too high a total colony count may indicate that the leek is contaminated and there is a risk of deterioration.
- **Coliform bacteria detection**: According to the national standard method, coliform bacteria are detected through lactose fermentation test and other steps. The presence of coliform bacteria may indicate that leeks are contaminated by feces and may cause intestinal diseases after consumption.
- **Pathogenic bacteria detection**: Such as detection of pathogenic bacteria such as Salmonella, Shigella, Staphylococcus aureus. Through complex steps such as selective culture medium and biochemical identification, it is determined whether leeks are contaminated by these harmful bacteria to ensure the food safety of consumers.