Determination of Soluble Sugar in Vegetables and Products Shaffer-Somogyi
Some standard content:
ICS67.080.20
Agricultural Industry Standard of the People's Republic of China
NY/T1278--2007
Determination of Soluhle Sugar in Vegetables and ProductsShaffer-Somogyi
Published on April 17, 2007
Implemented on July 1, 2007
Published by the Ministry of Agriculture of the People's Republic of China
Appendix A of this standard is an informative appendix.
This standard is proposed and managed by the Ministry of Agriculture of the People's Republic of China. Drafting unit of this standard: Vegetable Quality Supervision, Inspection and Testing Center of the Ministry of Agriculture (Beijing) Main drafters of this standard: Wang Xiaoqin, Liu Su, Liu Zhongxiao, Yang Pu, Chen Najia, NY/T1278-2007
1 Scope
Determination of soluble sugar in vegetables and their products Copper reduction iodine method
This standard specifies the method for determination of soluble sugar in fresh vegetables and their products. This standard is applicable to the determination of soluble sugar in fresh vegetables and vegetable products. The linear range of this standard is 0mg~2.5mg reducing sugar. 2 Principle
NY/T 1278-2007
Cu2+ in reagent A reacts with reducing sugar to generate cuprous oxide (Cu2O) precipitate. After HSO4, the soda ore precipitate is decomposed to generate Cu+ ions, and K1O) in the reagent reacts with KI to generate I2 during acidification: KIO +5KI - 31S04-+3KSO, + 3H20+31 Then (a+ is oxidized:
2Cu++I2Cu2+-21
The remaining iodine in the solution is titrated with Na2SO standard solution as starch indicator: 2Na2SO3 + l-+Na2S.Oh 1 2Nal
At the same time, water is used instead of the sample solution to do blank titration, and the titration difference between the blank and the sample is substituted into the regression equation calculated by titrating the standard series solution, that is, the maximum content of reducing alcohol in the tested sample is obtained before: 3 Reagents and materials
Unless otherwise specified, only analytical reagents and water of at least grade 3 specified in GB/T6682 are used in the analysis. 3.1 Sodium hydroxide titration [c(NaOH)=1mol/Ll: Weigh 40.00g sodium hydroxide (V 3.2 Alkaline copper reagent: Dissolve 30.0 g potassium sodium tartrate (KNaCH4%·4HO) and 30.0 g anhydrous sodium phosphate (NazCO) in 200 mL hot water in a 1 L beaker, add 40 mL sodium hydroxide solution (3.1), 8.0 g copper sulfate (Cu545HO) in 80 mL hot water, and add to the above solution while stirring. , and then boil to eliminate dissolved air. Dissolve 120g of anhydrous sodium sulfate (AazSQ4) in 500tmiL of hot water, boil the rest, cool and add to the copper solution. Dissolve 8.0g of potassium iodide (KI) in a small amount of boiled water and add to the copper solution. Then use boiled water to transfer all the solution in the boiling flask into a 1I volumetric flask, accurately weigh 0.891.7g of potassium iodate (KIO) dried at 105℃ for 2h, dissolve it in boiled water, and transfer to the reverse osmotic pressure. 3.3 Hydrochloric acid solution [c(HKCI)-1mol/L]: Add about 500mL of water to a 1L beaker, measure 90mL of hydrochloric acid and slowly add it to the beaker, stirring while adding, and finally add water to 1L? 3.4 Potassium ferrocyanide solution [KFc(CN)]·3TLO=15%1: Weigh 150g of potassium ferrocyanide [K,Fe(CN)*3HO] and dissolve it in water, and make up to 1L. www.bzxz.net
3.5 Zinc sulfate solution: [w(ZnSO4·7H,0)-30%]: Weigh 300g of zinc sulfate (ZnSO47H2O) and dissolve it in water, and make up to 1L. 3.6 Sulfuric acid 1 oxalic acid solution: weigh 40.0g oxalic acid (HCO) + 21J0) and dissolve it in 800ml water, measure 56mL sulfuric acid (HSO4) and add it while stirring, cool and grind the water to 1L 3.7 Sodium thiosulfate solution 1c (Naz%3) = 0.1mol/Ll: weigh 25.00g sodium thiosulfate (Na2S2Og?5HgO) and 0.2g sodium carbonate (NaCO) without water and dissolve in boiled water. After cooling, dilute to 1I with previously boiled and cooled water, buy in brown bottle, and store in a dark place at low temperature.
3.8 Sodium thiosulfate working solution [(NazSOa)-0.005mol/L] is accurately diluted with sodium thiosulfate solution (3.7). Prepare before use, valid for 2411,
3.9 Starch indicator: weigh 0.50g of soluble starch into a beaker, add a small amount of cold water to make a paste, add 100mL of boiling water, continue to boil, cool, store in a dropper bottle, and store in a refrigerator. 3.10 Powder acid indicator: weigh 0.50g of phenolic acid and dissolve it in 100mL of 95% ethanol, put it in a dropper bottle, 3.11 Sodium hydroxide solution [c(Nal)H)=0.5mol/L]: dilute the sodium chloride solution (3.1) by 1 time. 3.12 Glucose standard solution: accurately weigh 0.1250g of inulin (CHz0s) dried at 80℃ for 2h, or 0.1.375g (C.HzQ-HO) dissolved in water, and make up to 250ml. This solution is 500rmg/L glucose standard solution. Prepare before use. 4 Instruments and equipment
4.1 Analytical balance, with a sensitivity of ±0.01g and ±0.0001g. 4.2 High-speed tissue masher.
4.3 Induction cooker, adjustable temperature electric stove or constant temperature water bath. 4.4 Burette, 25ml - acid type or thief type. 4.5 Blast drying oven:
5 Sample preparation
5.1 Fresh sample
Take representative samples, wash, remove water, sample by quartering method, chop, mix, and make a paste with a tissue masher: Juicy vegetables such as tomato and cucumber can be made into paste, and other vegetables can be weighed 100.0g of chopped and mixed sample and added with 100mL of water to make a paste. Vegetables with less water such as radish can be weighed 100.0g of chopped and mixed sample and added with 200ml of water to make a paste. Weigh the sample equivalent to 10g, accurate to 0.01g, wash it with water into a 100mL volumetric flask (V1), add 1ml of potassium ferrocyanide solution (3.4) and zinc sulfate solution (3.5) (such as vegetables/high-protein vegetables, add 2ml each). Shake the spoon to make up the volume, let it stand for a while, filter and separate the drug precipitation for use. 5.2 Dry products
Put the sample in 65℃12℃ air-dried, crush it with a grinder, and pass it through a 0.5mm sieve. Weigh 1.00g~2.00g of the crushed sample in a furnace, add a small amount of water to moisten it, wash it with water into a 100mL volumetric flask, heat it in a boiling water bath for 10min, cool it down, add potassium ferrous chloride solution (3.4) and zinc sulfate solution (3.5) each [ml., shake well and make up the volume, filter it and set it aside. 5.3 Products
Various pickles and pickled vegetables: weigh 100.0g of the chopped and mixed sample, add 100ml of water to make a slurry, and canned vegetables can be directly made into a homogenate. The following steps are the same as 5.1. After mixing the tomato sauce, you can directly weigh 5.00g of the sample and wash it with water into a 100ml volumetric flask, and operate in the same way as 5.1. For vegetable juice, weigh 20.00g of the mixed sample and wash it with water into a 100mL volumetric flask, and operate in the same way as 5:1. 6 Analysis steps
6.1 Determination of reducing sugar
6.1.1 Preparation of standard curve
Use a pipette to draw 0, 1.0, 2.0.3.0.4.0, 5.0mL of grape chrysanthemum standard solution (3.12) into a 100mL conical flask or a 200mm×25mm test tube, add water to each to a total volume of 5.0mL, add 5.00mL of copper reagent (3.2), cover the conical flask or test tube with a small funnel, fix it with a corresponding rack, and heat it in a boiling water bath for 15min. Immediately place it in cold water after taking it out and cool it to 25℃～30℃. Replace the covered small funnel with a surface test tube (do not shake it). Add 2mL of sulfuric acid + oxalic acid mixture (3.6) and shake it immediately to completely dissolve the precipitate of cuprous oxide 2
NY/T 1278--2007
When the sodium thiosulfate working solution (3.8) is titrated to a light yellow-green color, add about 0.5 ml of starch indicator (3.9) Titrate until the color disappears as the endpoint: take the content (mg) as the endpoint, the difference between the blank and the sugar solution titration as the endpoint, calculate the regression equation = b + a, and calculate the a value and b value. The standard curve is prepared every time the copper reagent and sodium thiosulfate stock solution are newly prepared: - times. 6.1.2 Determination of reducing sugar in the sample
According to the sugar content in different samples, use a pipette to draw 5mL~10mL (V2) of the filtrate into a 50ml. or 100mL (Vs) volumetric flask, and make up to volume with water (samples with low sugar content can be diluted without this dilution, such as potatoes, 2ml.~5mL of the filtrate can be directly drawn into a test tube or conical flask, and water can be added to 5.00nL for determination) Draw 5.00mL (Vs) of sample solution from the volumetric flask into a test tube or conical flask, and add 5.00ml. copper reagent (3.2). The following steps are followed in the preparation of the standard curve in 6.1.1 above. Record the titration value of the sample (V4). Meanwhile, use water to replace the sample as a blank (V4) (no heating is required): Substitute the difference between the blank and sample titration values into the regression equation to obtain the reducing sugar content in the sample. If the brick-red copper oxide precipitates more and no blue is visible after the sample reacts with the copper reagent, the sugar content of the sample is high. You can take 1mL4mL of the sample solution as appropriate, add water to 5.00mL for determination. The titration value should be less than the lowest point of the standard curve. 6.1.3 Determination of the total soluble sugar content of the sample
Pipette 5mL-10mL of the filtrate into a 50mL or 100mL volumetric flask, add 1mL of hot acid solution (3.3), heat in a boiling water bath for 10min, cool, add 1-2 drops of powdered acid indicator, neutralize with about 0.5mal/L sodium hydroxide solution (3.11) to red, and then adjust with dilute hydrochloric acid until the red color just disappears, and make up to volume. The following steps are followed for measuring reducing sugar. 7 Calculation of results
7.1 Reducing sugar
The content of reducing sugar in the sample is expressed as mass fraction and the unit is expressed as percentage (%). It is calculated according to formula (1): a1
The slope in the regression equation;
The intercept in the regression equation:
[a+b(Vo- V4)]× V,× Va
V2× V ×m ×1 000
Vg——Blank solution 0.005mol/L sodium thiosulfate solution titration volume, unit is milliliter (mL); Vi1——Sample fixed volume, unit is milliliter (rnL); V2Sample aliquot volume, unit is milliliter (mL): V3——Sample aliquot fixed volume, unit is milliliter (mL); V
——Sample solution 0.005mol/L sodium thiosulfate solution titration volume, unit is milliliter (mL); Vs—Sample solution volume absorbed during determination, unit is milliliter (mL): m—Sample mass, unit is gram (g):
1000——Convert from gram to gram.
Calculation result is expressed to two decimal places
7.2 Soluble total sugar (inverted sugar)
The content of potential total sugar in the sample is expressed as mass fraction 1, unit is expressed as percentage (%), and the calculation is the same as formula (1). 7.3 Sugar
The sugar content in the sample is expressed as mass fraction 2, expressed in white content (%), 2=(1 -- )×0.95
-the factor for converting invert sugar into sucrose.
The calculated result is expressed to one decimal place, (1)
NY/T1278—2007
8 Precision
The absolute difference between two independent test results obtained under repeatability conditions shall not exceed 5% of the calculated difference between the two measured values, provided that the difference does not exceed 5% of the calculated difference between the two measured values. Statistical data and other data obtained from the inter-laboratory test results are shown in Appendix A. 4
Specimen standard
Number of participants in the experiment
According to the validity of the result
Mean, ng/k
True value or acceptance value,
Standard deviation of repeatability (3,)
Coefficient of variation of repeatability, %
Reproducibility limit ()
Present standard (51)
Coefficient of variation of reproducibility, %
Reproducibility limit (R)
Appendix A
【Informative Appendix】
Statistical data and other data obtained from the results of inter-laboratory tests Table A.1
Statistical results
NY/T 1278—2007
Cabbage
Large household packaging
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