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    Home > Chemicals Industry > Chemical Technology > Determination of synthetic colorants in food (1)

    Determination of synthetic colorants in food (1)

    • Last Update: 2021-07-11
    • Source: Internet
    • Author: User
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    Coloring agent, also known as food coloring, is a type of food additive that can color food and improve the color of food
    .


    According to its source, it can be divided into two types: edible natural pigments and edible synthetic pigments


    (1) Principle The artificial synthetic colorant in food is extracted by polyamide adsorption method or liquid-liquid partition method, made into aqueous solution, injected into high performance liquid chromatograph, separated by reverse phase chromatography, qualitatively based on retention time and comparison with peak area Quantitative
    .


    Calculate as follows:

    In the formula, X——the content of colorant in the sample, mg/g

    m 1 ——the quality of the colorant in the sample solution, ug

    V 2 ——Injection volume, mL

    V 1 ——Total volume of sample dilution, mL

    m 2 ——the mass of the sample, g

    (2) Chromatographic reference conditions

    Chromatographic column: YWG-C 18 , 10um stainless steel column, 4.
    6mm(id.
    )×250mm
    .

    Mobile phase: methanol - ammonium acetate solution (pH=4, 0.
    02mol/L)
    .

    Gradient elution: methanol: 20%~35%, 3%/min; 35%~98%, 9%/min; after 98%, continue for 6 minutes
    .

    Flow rate: 1mL/min.
    Ultraviolet detector: 254nm wavelength
    .

    (3) The main points suggest that the minimum detection amount of this method: 5ng for new red, 4ng for lemon yellow, 6ng for amaranth , 8ng for carmine , 7ng for sunset yellow , 18ng for erythrosin, and 26ng for brilliant blue
    .

    5.
    Determination of antioxidants in food

    Antioxidants are a type of food additives that can prevent or delay the oxidative deterioration of food ingredients, improve food stability and prolong the storage period
    .


    According to its solubility, it can be divided into oil-soluble antioxidants and water-soluble antioxidants


    Antioxidants are mainly used in fats and high-fat foods.
    The mechanism of their action is to prevent the oxygen in the air from reacting with the -C=C- in the fat to form a peroxide chain, thereby preventing the fat from oxidizing rancidity
    .

    There are 14 kinds of antioxidants currently allowed in our country, including BHA and BHT
    .


    There are three national standard methods for the determination of BHA and BHT: gas chromatography, thin layer chromatography and colorimetry


    (1) Principle The tert-butyl hydroxyanisole (BHA) and 2,6-di-tert-butyl-p-cresol (BHT) in the sample are extracted with petroleum ether , and the BHA and BHT are purified through a chromatography column.
    After concentration, After being separated by gas chromatography, it is detected by a hydrogen flame ionization detector and quantified according to the peak height of the sample and the standard peak height
    .

    (2) Reagent

    ① Petroleum ether (boiling range 30~60℃)
    .

    ② Dichloromethane (analytical grade)
    .

    ③Carbon disulfide (analytical pure)
    .

    ④ Anhydrous sodium sulfate (analytical grade)
    .

    ⑤Silica gel G (activate at 120°C for 4 hours on 60-80 days and put it in the dryer for later use)
    .

    ⑥ Florisil (60-80 mesh activated at 120°C for 4 hours and placed in a desiccator for later use)
    .

    ⑦BHA and BHT mixed standard stock solution: accurately weigh 0.
    1g each of BHA and BHT (purity 99.
    9%), dissolve with carbon disulfide after mixing , and dilute to a 100mL volumetric flask.
    This solution contains 1.
    0mg BHA per 1mL.
    BHT
    .


    Store in the refrigerator


    ⑧BHA and BHT mixed standard use solution: Pipette 4.
    0mL of standard stock solution into a 100mL volumetric flask, and dilute to 100mL with carbon disulfide .
    This solution contains 0.
    040mg BHA and BHT per 1mL respectively
    .


    Store in the refrigerator


    (3) Instruments

    ①Gas chromatograph: with FID detector


    ②Evaporator: 200mL in volume


    ③Oscillator


    ④Chromatography column: 1cm×30cm glass column with piston


    ⑤Gas Chromatography Column: A glass column with a length of 1.


     

     

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