Food Analysis and Inspection Review Questions
1. Multiple choice questions
1. What is measured with a pH meter is food ( )
A. Total acidity B. Effective acidity C. Volatile acidity D. True acidity
2. The hammer value of the sugar solution measured at 30°C is 20, which is equivalent to the hammer value of the standard condition of 20°C ( )
A、20 B、20.68 C、19.32 D、19.68
3. The following ( ) is the abbreviation of Codex Alimentarius Commission
A、AOAC B、ISO C、CAC D、OIE
4. When measuring water-insoluble ash, you need to use ( ) to dissolve the total ash first, filter it, and then treat it at high temperature.
A. Distilled water B. Purified water C. Deionized water D. Mineral water
5. The ultraviolet light source of the UV-visible spectrophotometer is emitted by ( )
A. Xenon lamp B. Deuterium lamp C. Tungsten lamp D. Hollow cathode tube
6. In the gas chromatograph, the sample is combined with the mobile phase in the form of ( ) and enters the chromatographic column
A. Solid B. Liquid C. Gas D. Semi-solid
7. When measuring acidity, the ( ) in the sample needs to be removed during sample processing to avoid interference with the measurement results.
A. Carbon dioxide B. Silica C. Nitrogen dioxide D. Sulfur dioxide
8. The following ( ) are suitable for measuring fluids with higher viscosity
A. Capillary viscometer B. Rotational viscometer C. Sliding ball viscometer D. Texture analyzer
9. Acid-insoluble ash is also ( )
A. Water-soluble ash B. Water-insoluble ash C. Alkali-soluble ash D. Alkali-insoluble ash
10. The nitrogen content in a sample measured by Kjeldahl method is 15 grams, then the protein content in the sample is estimated to be ( )
A. 240 grams B. 140 grams C. 93.75 grams D. 160 grams
11. ( ) determination is the basis for saccharide quantification.
A reducing sugar B non-reducing sugar C glucose D starch
12. Direct titration method uses ( ) as an indicator when measuring the reducing sugar content.
A Potassium ferrocyanide B Color of Cu2+ C Boric acid D Methylene blue
13. In order to eliminate the interference of the red Cu2O precipitation produced by the reaction on the titration, the reagent added is ( )
A Potassium ferrocyanide B Potassium ferrocyanide C The role of lead acetate, D NaOH
14, and K2SO4 in the digestion process in the nitrogen determination method is ().
A. Catalysis B. Color development C. Oxidation D. Increase temperature
15. After alkaline distillation by Kjeldahl method, use ( ) as the absorption liquid.
A. Boric acid solution B. NaOH solution C. Naphthalene test paper D. Distilled water
16. Ash content is an indicator marked ( ).
A Total amount of inorganic components B Organic components C Total amount of polluted sediment and iron, aluminum and other oxides
17. When measuring the total acidity of grapes, the measurement results are expressed in ( ).
A Citric acid B Malic acid C Tartaric acid
18. When measuring the reducing sugar content of food by direct titration, the calibration solution used is ( )
A. Filmlin's reagent B. Sample C. Glucose D. Sodium methyl tartrate
19. When potassium permanganate is used to determine the reducing sugar content of food, the calibration solution used is ( )
A. Fehling's reagent B. Methylene blue C. Glucose D. Potassium permanganate
20. When extracting sugar from fruits with water, the sample liquid should be adjusted to ( ).
A. Acidic B. Neutral C. Alkaline
2. Multiple choice questions
1. The dry ashing method for processing samples requires the following ( ) equipment
A. Crucible B. Volumetric flask C. Muffle furnace D. Weighing bottle
2. The basic taste of sensory testing refers to ( )
A. sour B. sweet C. salty D. bitter
3. When using distillation method to measure moisture content, choose ( ) as the solvent
A. Benzene B. Carbon tetrachloride C. Xylene D. Toluene
4. There are two types of chromatograms in high performance liquid chromatography ( )
A. Normal phase chromatography B. Reversed phase chromatography C. Transverse chromatography D. Longitudinal chromatography
5. Lipids in food include ( )
A. Diglycerides B. Triglycerides C. Lipids D. Alcohols
6. The following ( ) can be used to measure the concentration of sugar solution
A. Baume meter B. Hammer meter C. Milk consistency meter D. Refractometer
7. Which of the following liquid chromatography detectors is ( )
A. Optical property detector B. Thermal battery detector
C. Electrical and electrochemical detectors D. Thermal property detectors
8. When detecting the following ( ) elements, dry digestion is not suitable for sample processing.
A、Ca B、Hg C、As D、Mg
9. The food sensory inspection room is composed of ( )
A. Inspection area B. Conference area C. Office D. Sample preparation area
10. The most commonly used extractants for lipid determination are ( )
A. Ether B. Benzene C. Petroleum ether D. Xylene
11. The following ( ) samples should use ethanol as the extraction agent.
A white lemon B chocolate C biscuit D. bread
12. ( ) can also be added as a catalyst during digestion.
A. Potassium sulfate B. Copper sulfate C. Copper oxide D. Mercury oxide
13.．Which type of sample should be added with refined sea sand before drying ( )
A. Vegetables B. Jam C. Bread D. Meat
14. When extracting fat with ether, the heating method that cannot be used is ( ).
A Heating by electric furnace B Heating by water bath C Heating by oil bath D Heating by electric heating mantle
15. Which of the following is a reducing sugar ( )
A lactose B maltose C glucose D sucrose
16. Before measuring fat-soluble vitamins, the sample must pass ( )
A Saponification B Water washing C Organic solvent extraction D Concentration
17. To measure volatile acid directly, you can use ( ) to collect the volatile acid and then titrate it with sodium hydroxide.
A Distillation method B Drying method C Solvent extraction D Vacuum method
18. The absorption cell of UV-visible spectrophotometer is made of ( ) two materials
A glass B quartz C crystal D sodium halide
3. Fill in the blanks
1. When measuring volatile acid, an appropriate amount of phosphoric acid should be added to the processed sample. Its function is
2. When using sensory testing methods to distinguish the difference between two samples, you can use the differential testing method.
or law.
3. In addition to measuring the relative density, the preliminary judgment of whether the milk is adulterated can also be measured .
4. The two-phase substances in chromatography are and
5. UV-visible spectrophotometer consists of , , , and
6. There are three types of detectors in gas chromatograph :
7. Soxhlet extractor consists of , , and
8. In the measurement of ash content, the ash content reflects the degree of pollution such as sediment.
9. In food analysis, total sugar refers to and .
10. The main structure of the atomic absorption spectrophotometer consists of , , and
11. The Kjeldahl nitrogen determination method is to convert the protein content by measuring the total nitrogen content of the sample. This is because _______________________________________________.
12. The role of H2SO4 in the Kjeldahl digestion process is _______; the role of CuSO4 is ______________.
13. New electrodes or dry electrodes that have not been used for a long time must be soaked in ____________________ for more than __________ hours before use. The purpose is to ____________________.
14. Ash in food can be divided into ____________________, __________ and ____________________.
15. Density refers to ____________________, and relative density (specific gravity) refers to __________.
16. For thick samples, the effect of adding refined sea sand or anhydrous sodium sulfate before measurement is _______________.
17. When measuring the reducing sugar content, the pigments, proteins, soluble pectin, starch, tannins and other impurities contained in the extract that affect the determination must be removed. The commonly used method is __________, and there are three types of clarifiers used: __________, __________ ,__________.
18. The purpose of using dithizone when determining the limiting elements in food is __________.
19. The function of ascorbic acid used in the determination of tin is __________.
4. Questions and Answers/Calculation Questions
- Precisely weigh 20mg of the VB12 standard, add water to accurately dilute it to 1000ml, place this solution in an absorption cell with a thickness of 1cm, and measure the absorbance A at l = 361nm to be 0.414. There are also two samples, one is VB12 Precisely weigh 20mg of the raw material drug and add water to accurately dilute it to 1000ml. The absorbance A is also measured at b=1cm and l =361nm to be 0.400. One is VB12 injection. Precisely draw 1.00ml and dilute it to 10.00ml. The absorbance is also measured to be 0.518. Try to calculate the percentage content of VB12 raw material and the concentration of injection solution (mg/ml).
2. Why is the protein content in food measured by the Kjeldahl nitrogen determination method the crude protein content?
3. Now, 10 kilograms of Shuanghui brand ham sausages produced by Shuanghui Group in soft plastic packaging (sample batch number is 2004062518) are required to be measured for crude protein content.
1) An analytical inspector weighed 0.50g of minced and mixed ham into a 100mL Kjeldahl flask. Please write down the subsequent sample processing steps.
2) After cooling the digestion liquid, transfer it to a 100mL volumetric flask and set the volume. Remove 10mL of the digestion diluent into the reaction tube of the micro-Kjeldahl nitrogen distillation device, distill it with water vapor, and absorb it with 2% boric acid. The distillate is then Titrate 0.0998mol/L hydrochloric acid to the end point, consuming 5.12mL of hydrochloric acid. Calculate the crude protein content in the ham sausage.
4. When measuring the reducing sugar content of food by direct titration, why is it necessary to calibrate the copper tartrate solution?
5. Use the direct titration method to determine the reducing sugar content of hard candies produced by a certain factory. Weigh 2.000 grams of sample, dissolve it with an appropriate amount of water, and adjust the volume to 250 mL. Take 5.00mL each of alkaline copper tartrate A and B solutions into an Erlenmeyer flask, add 10.00mL water, heat to boiling and titrate with the above hard candy solution until the end point consumes 9.65mL. It is known that 10.00ml of calibrated cupric tartrate solution consumes 10.15ml of 0.1% mg/mL glucose solution. What is the reducing sugar content in the hard candy?
Answer
1. Multiple choice questions
1.B 2.B 3.C 4.C 5.B 6.C 7.A 8.C 9.B 10.C 11.A 12.D 13.B 14.D 14.A 16.A 17.C 18.B 19.D 20.B
2. Multiple choice questions
1.AC 2.ABCD 3.CD 4.AB 5.BC 6.BD 7.ACD 8.BC 9.AD 10.AC 11.CD 12.BD 13.BD 14.AC 15.ABC 16.ABCD 17.AC 18.AB
3. Fill in the blanks
1. Free the bound volatile acid
2. Unilateral inspection Bilateral inspection
3. Milk consistency
4. Mobile phase stationary phase
5. Light source, monochromator, absorption cell, detector and recording system
6.TCD (thermal conductivity cell detector) ECD (electron capture detector) FID (mass differential detector)
7. Receiving bottle, filter paper cylinder, extraction tube, condenser tube
8.Acid insolubility
9. Reducing sugar: sucrose that can be hydrolyzed into reducing monosaccharides under the measurement conditions.
10.Light source, atomizer, spectroscopic system, detection system
11. Generally, the nitrogen content of protein is 16%
12. Dehydrate, carbonize and catalyze organic matter, indicating the arrival of the end point of digestion
13. Distilled water or 0.1mol/L hydrochloric acid solution 24 to form a hydration layer with good ion exchange capability on the surface of the glass electrode ball membrane
14. Water-soluble ash Water-insoluble ash Acid-insoluble ash
15. The mass of a substance per unit volume. The ratio of the density of a substance to the density of a reference substance under specified conditions.
16. Prevent crusting and coking on the surface of the sample and hinder the evaporation of internal water.
17. Add clarification agent: neutral lead acetate, zinc acetate-potassium ferrocyanide solution, copper sulfate-sodium hydroxide solution
18. Combine metal ions with their chelates to form metal chelates, and use organic solvents to extract and separate them.
19. Masking agent
4. Answer/calculate questions
1.96.6% 0.25mol/L
2. Because samples often contain non-protein nitrogen-containing compounds such as alkaloids, alkaloids, nitrogen-containing lipids, porphyrins, and nitrogen-containing pigments.
3.
1) Add finely ground copper sulfate, potassium sulfate and concentrated sulfuric acid to the Kjeldahl flask, shake gently, install the digestion device, place a funnel at the mouth of the Kjeldahl flask, and tilt it at 45° on a small Asbestos net with holes, heat it with an electric stove over low heat. After the contents are all carbonized and the foam stops producing, increase the firepower and keep the liquid in the bottle slightly boiling until the liquid in the bottle turns blue-green and transparent. Continue heating for 30 minutes, stop heating, and cool down. , slowly add distilled water to the Kjeldahl flask and cool
2) 8942.08g
4. The reaction between reducing sugar and copper sulfate in alkaline solution does not comply with the equimolar relationship, and the reducing sugar content cannot be calculated based on the reaction formula. Therefore, it is necessary to calibrate the alkaline copper tartrate solution with a reducing sugar standard solution of known concentration and calculate the reducing sugar factor.
5.0.01315g/100mg