The food lab pdf free download

If samples analyzed glasses at all times. Petroleum ether and ether liquid by these methods can be tested by an instrumen- wastes must be disposed of in designated hazardous tal method for which equipment is available in your waste receptacles. Snack foods are suggested for analysis and compari- Supplies son by the Soxhlet and Goldfish methods, and milk by the Mojonnier and Babcock methods. Fat analysis. Wearing plastic gloves, remove three predried cellulose extraction thimbles from the desic- Data from moisture analysis: cator.

Place the three samples in a Soxhlet extractor. Cool dried samples in a desiccator then 1 reweigh. The Soxhlet extraction procedure utilized petroleum ether.

What were the advantages of using the Soxhlet extraction Name of Snack Food: method rather than the Goldfish extraction method? Solvent continuously Rep g Thimble g wool g g wool g drips through the sample to extract the fat.

Fat con- 1 tent is measured by weight loss of sample or weight 2 of fat removed. Follow Steps 1—4 in Soxhlet procedure. Place the thimble in the Goldfish condenser bracket. Push the thimble up so that only about 1 cm. Follow Steps 6 and 7 in Soxhlet procedure.

If the fat content 1. What would be the advantages of using ethyl ether rather of the food you analyzed was given on the label, report than petroleum ether in a solvent extraction method, such this theoretical value. Label serving size g : 3. Make triplicate determinations on both the sample and reagent blanks.

The Principle procedure given here is for fresh milk. Other samples may need to be diluted with distilled water in step 2 and require Fat is extracted with a mixture of ethyl ether and petro- different quantities of reagents in subsequent steps. Consult leum ether. The extract containing the fat is dried and the instruction manual or AOAC International Official Methods expressed as percent fat by weight. The assay uses not only ethyl ether and petroleum ether, but also ammonia and ethanol.

Ammonia dis- Procedure solves the casein and neutralizes the acidity of the Instructions are given for analysis in triplicate. Ethanol prevents gela- tion of the milk and ether, and aids in the separation 1. Turn on power unit and temperature controls of the ether—water phase. Ethyl ether and petroleum for oven and hot plate on the fat side of the ether serve as lipid solvents, and petroleum ether Mojonnier unit.

Warm milk samples to room temperature and mix well. Chemicals 3. CAS No. Hazards Handle dishes from this point on with tongs or gloves. Use three dishes for each type of milk Ammonium Corrosive, dangerous for the samples, and two dishes for the reagent blank. Cool dishes in cooling desiccator for 7 min. Weigh dishes, record weight of each dish and its Petroleum Harmful, highly flammable, identity, and place dishes in desiccator until use. Weigh samples accurately ca. If weighing rack is used, fill curved pipettes and place in rack on the balance.

Weigh Hazards, Precautions, and Waste Disposal each sample by difference. Add chemicals for the first extraction in the Ethanol, ethyl ether, and petroleum ether are fire haz- order and amounts given below. After each ards; avoid open flames, breathing vapors, and contact addition of chemicals, stopper the flask and with skin. Ether is extremely flammable, is hygro- shake by inverting for 20 s.

Ammonia is a corrosive; avoid contact and breathing vapors. Oth- erwise, adhere to normal laboratory safety procedures. First extraction Second extraction Wear gloves and safety glasses at all times.

Petroleum Chemicals Step Amount ml Step Amount ml ether and ether liquid wastes must be disposed of in designated hazardous waste receptacles. The aqueous Ammonia 1 1.

Carefully pour off the ether solution of each Notes sample into a previously dried, weighed, and Reagents must be added to the extraction flask in the follow- cooled fat dish. Most or all of the ether layer ing order: water, ammonia, alcohol, ethyl ether, and petroleum should be poured into the dish, but none of the ether. The burets on the dispensing cans or tilting pipets are remaining liquid must be poured into the dish.

List possible causes for high and low results in a Mojon- Repeat the extraction procedure a second nier fat test. How would you expect the elimination of alcohol from the following the sequence and amount given in Mojonnier procedure to affect the results? Again, after each addition 3. How would you propose to modify the Mojonnier procedure of chemicals, stopper the flask and shake by to test a solid, nondairy product? Explain your answer. Centrifuge the flasks again, as described above.

If this is done, repeat the Principle centrifugation. Sulfuric acid is added to a known amount of milk Pour ether extract into respective fat dish sample in a Babcock bottle. The acid digests the pro- i. Centrifugation poured into the same fat dish used for that and hot water addition isolate the fat into the graduated sample from the first extraction , taking care neck of the bottle. The Babcock fat test uses a volumetric to remove all the ether but none of the other measurement to express the percent of fat in milk or liquid in the flask.

Complete the evaporation of ether, either very carefully on the hot plate this can be problem- Note atic and a fire hazard or open in a hood. The specific gravity of liquid fat at that temperature is not fast enough to cause splattering. If the approximately 0. The calibration on the gradu- plate appears to be too hot and boiling is too ated column of the test bottle reflects this fact and enables one fast, only part of the dish should be placed to make a volumetric measurement, which expresses the fat on the hot plate.

If instead using an operating content as percent by weight. Chemicals When all the ether has been evaporated from the dishes, place the dishes in the vacuum CAS No. Sulfuric acid Corrosive Cool the dishes in the desiccator for 7 min. Accurately weigh each dish with fat. Record weight. Hazards, Precautions, and Waste Disposal Concentrated sulfuric acid is extremely corrosive; avoid Data and Calculations contact with skin and clothes and breathing vapors.

Calculate the fat content of each sample. Subtract the Wear gloves and safety glasses at all times. Otherwise, average weight of the reagent blank from the weight of adhere to normal laboratory safety procedures. Sulfuric each fat residue in the calculation. Add glymol red reader to top of fat layer.

Equipment Immediately use a divider or caliper to mea- sure the fat column to the nearest 0. Procedure 9. Reject all tests in which the fat column is milky Instructions are given for analysis in triplicate.

Adjust milk sample to ca. The fat should be clear and spar- homogenous. Using a standard milk pipette, kling, the upper and lower meniscus clearly pipette After the pipette has emptied, blow out should be clear.

Record the readings of each test and determine bottle. Allow milk samples to adjust to ca. Dispense ca. Mix the milk and acid thoroughly. Be careful not to get 1 any of the mixture into the column of the bottle 2 while shaking. Be sure bottles are counterbalanced. Position bot- Questions tles so that bottlenecks will not be broken in horizontal configuration.

Be sure that the heater 1. What are the possible causes of charred particles in the fat column of the Babcock bottle? What are the possible causes of undigested curd in the 4. Centrifuge the bottles for 5 min after reaching Babcock fat test? Why is sulfuric acid preferred over other acids for use in upon the diameter of the centrifuge head. Carefully permit the water to flow Resource Materials down the side of the bottle. Again, centrifuge the bottles for 2 min.

In: Nielsen SS top graduation of the scale. Again, centrifuge ed Food analysis, 4th edn. Springer, New York the bottles for 1 min. Remove the bottles from the centrifuge and place examination of dairy products. Hazards The protein content of foods can be determined by numerous methods. Both Hydrochloric acid, Corrosive methods are official for the purposes of nutrition conc. HCl labeling of foods. While the Kjeldahl method has Methyl red been used widely for over a hundred years, the recent Sodium hydroxide NaOH Corrosive availability of automated instrumentation for the Sulfuric acid, conc.

Protein analysis. Add dd water Objective to make up to 4. In a 4-L flask, dissolve g boric acid in ca. Mix and then add an additional 1. Principle of Method Cool to room temperature under tap water cau- The Kjeldahl procedure measures the nitrogen content tion: glassware may break due to sudden cooling of a sample. The protein content then, can be calculated or leave overnight. When using the rapid proce- assuming a ratio of protein to nitrogen for the specific dure, the flask must be shaken occasionally to food being analyzed.

The Kjeldahl procedure can be prevent recrystallization of the boric acid. Add basically divided into three parts: 1 digestion, 2 40 ml of bromocresol green solution mg distillation, 3 titration.

In the distilla- ethanol. Dilute to 4 L with water and mix care- tion step, the digested sample is made alkaline with fully. The con- of ammonia nitrogen in this solution is quantified by tents of the flask should then be a neutral gray. A reagent blank If not, titrate with 0. Calculate the amount of NaOH titrant required for this blank is subtracted from each solution necessary to adjust the boric acid solution determination.

Fit the dispenser Add the calculated amount of 0. Mix well. Verify Kjeldahl tube. Set the bottle with dispenser on a tray the adjustment results by distilling a new blank to collect spills. Place adjusted solution into a bottle equipped with a ml repipettor.

HCl to 4 L with dd water. Add 3—5 drops indicator Equipment 3 parts 0. Note the acid volume used and calculate the normality as described below. Procedure Calculation to standardize HCl solution: Instructions are given for analysis in triplicate. Digestion Write the normality of the standardized HCl 1. Turn on digestion block and heat to appro- solution on the stock container. Accurately weigh approximately 0. Record the weight. Leave in a drying digestion tube. Repeat for two more samples.

Let cool in a desiccator. Add one catalyst tablet and appropri- a 1-L volumetric flask, dissolve 1. Dilute to volume. Concentrated sodium hydroxide is a corrosive. Place rack of digestion tubes on digestion Wear corrosion resistant gloves and safety glasses at block. Cover digestion block with exhaust all times. Perform the digestions in an operating hood system turned on. Let samples digest until digestion is complete.

Allow samples to cool in the hood before remov- The samples should be clear but neon green , ing the aspirating fume trap from the digestion unit.

Otherwise, adhere to normal laboratory safety proce- 6. Take samples off the digestion block and allow dures. The waste of combined sulfuric acid and sodium to cool with the exhaust system still turned on. Carefully dilute digest with an appropriate ensure it is pH 3—9 , so it can be discarded down the volume of dd water. Swirl each tube.

However, for disposing any chemical wastes, follow good laboratory practices out- II. Distillation lined by environmental health and safety protocols at 1. Follow appropriate procedure to start up your institution. In this distillation process, a set volume of NaOH solution will Blank 1 — — — — be delivered to the tube and a steam generator 2 — — — — will distill the sample for a set period of time.

Upon completing distillation of one sample, Sample 1 proceed with a new sample tube and receiv- 2 ing flask. Titration Questions 1. Record the normality of the standardized 1. H2SO4 was used to digest the sample, how many millili- 2. How to calibrate the instrument.

Put a magnetic would your results have been changed if the alkali pump stir bar in the receiver flask and place it on a timer had malfunctioned and delivered only 15 ml of the stir plate. Molarity of conc. Could phenolphthalein be used as an indicator in the Kjeldahl titration? Why or why not? Titrate each sample and 3. Describe the function of the following chemicals used in blank to an endpoint pH of 4. Record vol- this determination: ume of HCl titrant used. If using a colorimetric endpoint, put a b Borate magnetic stir bar in the receiver flask, place c H2SO4 it on a stir plate, and keep the solution stir- d NaOH ring briskly while titrating.

Titrate each 4. Why was it not necessary to standardize the boric acid sample and blank with the standardized solution? HCl solution to the first faint gray color. Explain how the factor used to calculate the percent pro- Record volume of HCl titrant used. Data and Calculations 6.

For each of the disadvantages of the Kjeldahl method, give Calculate the percent nitrogen and the percent pro- another protein analysis method that overcomes at least tein for each of your duplicate or triplicate corn flour partially that disadvantage. The corn flour sample you analyzed was not a dried sample.

Use 6. Determine the protein content of corn flour using the nitrogen combustion method. In the assay, the the appropriate slot for the sample number. Sample and to release nitrogen gas and other products i. The other products are removed, and the nitrogen is quantitated by gas chromatography using Data and Calculations a thermal conductivity detector. Record the percent nitrogen content for each of your duplicate or triplicate corn flour samples.

Calculate Chemicals protein content from percent nitrogen data, and determine the average percent protein. The corn flour CAS No. Hazards sample you analyzed was not a dried sample. Report percent protein results on a wet weight basis wwb and Ethylenediaminetetraacetic acid, Irritant on a dry weight basis dwb.

The other chemicals used are specific to each manufac- turer for the columns within the instrument. Supplies Questions 1. What are the advantages of the nitrogen combustion Used by students method compared to the Kjeldahl method? If you analyzed the corn flour sample by both the Kjeldahl Equipment and nitrogen combustion methods, compare the results.

Chang SKC Protein analysis. Springer, New York sample cup on an analytical balance. Sample weight AOAC International Official methods of analysis, will be coordinated with sample number in autosam- 18th edn, ; Current through revision 2, On-line. Remove sample from Method Although the method detects almost all carbohydrates, the absorptivity of the different carbohydrates varies. These compounds then react with phenol to produce a yellow-gold color. Wear gloves and safety glasses at all times, at nm.

For products that are high in hexose sugars, and use good lab technique. The concentrated H2SO4 is glucose is commonly used to create the standard curve, very corrosive e. The phe- and the absorption is measured at nm. The color nol is toxic and must be discarded as hazardous waste.

In this experiment, you will create a standard curve with a glucose standard solution, use Supplies it to determine the carbohydrate concentration of soft drinks and beer, then calculate the caloric content of Used by students those beverages. Carbohydrate analysis. Then, pipette 1. Dilute to volume with dd water. Seal flask with Para- Instructions are given for analysis in duplicate. Record caloric content from label: You will ana- volumetric flask, and dilute to volume lyze for total carbohydrate content: 1 a regular with dd water.

Seal flask with Parafilm and and diet soft drink of the same brand, or 2 a mix well. Before 5. Phenol addition: To each tube from Parts you proceed with the sample preparation and 1 and 4 containing a total volume of 2 ml, analysis, record the caloric content on the nutri- add 0.

Mix on a Vortex test 3. Decarbonate the beverages: With the bever- tube mixer. Shake 5. The sulfuric acid reagent should gently at first try not to foam the sample if it be added rapidly to the test tube. Direct the is beer and continue gentle shaking until no stream of acid against the liquid surface rather observable carbon dioxide bubbles appear. If than against the side of the test tube in order there is any noticeable suspended material in to obtain good mixing.

These reactions are the beverage, filter the sample before analysis. Sample tubes: So the sample tested will contain of H2SO4 to an aqueous sample.

After ized. Mix on a Vortex test tube mixer. Let tubes dilution as indicated, pipette 1. Ana- for 10 min i. Vortex the test tubes again before reading the absorbance. Dilution Volume assayed ml 7. Reading absorbance: Wear gloves to pour Soft drink samples from test tubes into cuvettes. Do not Regular 1 rinse cuvettes with water between samples.

Retain this blank sample in one Lite 1 cuvette for later use. Read your standard Sample table: curve tubes from low to high concentration i. Absorbance Spectra: Use one of the duplicate 18 Soft drink, 1: 1 ml 0. Determine the absorbance spectra from to nm by reading Sample calculation for soft drink, regular: the tube at 10 nm intervals.

Construct a standard curve for your total carbo- ond table below. Calculate the concentration of glucose in your into account the dilution and volume assayed. Note: Glucose equivalent 4.

Plot the absorbance spectra obtained by measur- 11 Std. What are the advantages, disadvantages, and sources of diet error for this method to determine total carbohydrates? Your lab technician performed the phenol—H2SO4 analysis on 17 Beer, reg. What most likely 6. Was it best to have read the absorbance for the standard caused these results? Describe what happened. Explain why a wave- 3. If you started with a glucose standard solution of 10 g length in this region is appropriate for this reaction.

Show all calculations. If you had not been told to do a fold dilution of This laboratory was developed with input from Dr a soft drink sample, and if you know the approximate Joseph Montecalvo, Jr.

In: Nielsen content on the food label? Springer, New York ries explain any differences? The U. Food and Drug Administration requires approximately 50 mg ascorbic acid preferably U. The instability of Vitamin C makes it more dif- dard. Record this weight. Transfer to a mL volu- ficult to ensure an accurate listing of Vitamin C content metric flask. Dilute to volume immediately before use on the nutrition label. While this To 50 ml deionized distilled dd water in a method is not official for other types of food products, ml beaker, add and stir to dissolve 42 mg it is sometime used as a rapid, quality control test sodium bicarbonate, then add and stir to dis- for a variety of food products, rather than the more solve 50 mg 2, 6-dichloroindophenol sodium time-consuming microfluorometric method AOAC salt.

Dilute mixture to ml with dd water. Method Close the bottle with a stopper or lid and store refrigerated until used. Official Methods of Analysis, 18th ed. Method 20 ml acetic acid. Add and stir to dissolve 7. Dilute mixture to ml Pegg, R. Vitamin with distilled water. Filter through fluted filter analysis. Close the bottle with a stop- Springer, New York. Filter juices through cheesecloth to avoid problems with pulp when pipetting. Record Principle of Method from the nutrition label for each product the Ascorbic acid reduces the indicator dye to a colorless percent of the Daily Value for Vitamin C.

At the endpoint of titrating an ascorbic acid- containing sample with dye, excess unreduced dye is Hazards, Precautions, and Waste Disposal a rose-pink color in the acid solution. The titer of the Preparation of reagents involves corrosives.

Use appro- dye can be determined using a standard ascorbic acid priate eye and skin protection. Otherwise, adhere to solution. Food samples in solution then can be titrated normal laboratory safety procedures. Waste likely may with the dye, and the volume for the titration used to be put down the drain using a water rinse, but follow calculate the ascorbic acid content.

Prepare blanks: Pipette 7. Record the initial and final readings and calcu- Notes late the difference to determine the amount of dye used for each titration. Quantities of supplies and reagents specified are adequate for each student or lab group to standardize Data the dye and analyze one type of orange juice sample in triplicate. Buret start Buret end Vol. Pipette 5 ml metaphosphoric acid—acetic acid Blank 1 solution into each of three ml Erlenmeyer 2 flasks.

Add 2. Using a funnel, fill the buret with the indophe- 3 nol solution dye and record the initial buret reading. Place the Erlenmeyer flask under the tip of the Calculations buret.

Slowly add indophenol solution to stan- 1. Swirl the flask as you add the indophenol solution. Repeat steps 3—5 for the other two standard samples. How do results available for the juice samples analyzed 1. Why was it necessary to standardize the indophenol Sample solution? Why was it necessary to titrate blank samples? Why might the Vitamin C content as determined by 1 this method be underestimated in the case of the heat 2 processed juice samples? In: Nielsen SS ed Food analysis, 4th edn.

This blue color is the endpoint of the Background titration. Stoichiometry of the reaction is nesium. This reaction can be used to determine the 1 mol of calcium complexing with 1 mol of EDTA. Endpoints in the titration are detected Chemicals using indicators that change color when they complex with mineral ions.

Calmagite and eriochrome black CAS No. Hazards T EBT are such indicators that change from blue to pink when they complex with calcium and magne- Ammonium chloride Harmful sium. The pH affects a com- for the plexometric EDTA titration in several ways, and must environment be carefully controlled. Such test strips are available Ethylenediaminetetraacetic Irritant from various companies. E and Carpenter, C. Traditional methods Magnesium sulfate, for mineral analysis.

In 50 ml deionized distilled dd Principle of Method water, dissolve 1. Combine complex with calcium or magnesium at pH Store in a tightly black T EBT , are pink when complexed to metal stoppered Pyrex or plastic bottle to prevent ions but blue when no metal ions are complexed to loss of ammonia NH3 or pickup of carbon them. The indicators bind to metal ions less strongly dioxide CO2. Dispense this buffer solution than does EDTA.

When the indicator is added to a with a repipette system. Discard buffer when solution containing metal ions, the solution becomes 1—2 ml added to a sample fails to give pH pink. When EDTA is added as titrant to the mineral- Transfer to a ml Erlen- meyer flask. HCl:H2O , a little Adhere to normal laboratory safety procedures. Wear at a time, until all the CaCO3 has dissolved gloves and safety glasses at all times. The buffer make sure all the CaCO3 in the neck of the flask solution, which contains ammonium hydroxide, has been washed down with HCl.

Add ml should be disposed of as hazardous waste. Adjust to pH 3. HCl:H2O , as required. Transfer by environmental health and safety protocols at your quantitatively to a 1-L volumetric flask, and institution. Dilute to 1 L Used by students with dd water. Mix carefully. Use 1 ml per 30 ml solution to be titrated. With increasing pH, the sharpness of the endpoint increases. However, at high pH, the indi- Procedure cator dye changes color and there is risk of precipi- Modified from Method Hardness, Standard Meth- tating calcium carbonate CaCO3 or magnesium ods for the Examination of Water and Wastewater, 21st ed.

The tendency toward CaCO3 precipita- Instructions are given for analysis in triplicate. Certain inhibitors 1. Adjust to pH Magnesium salt of 1,2-cyclo- If possible, do this pH adjustment with the hexanediaminetetraacetic acid MgCDTA , which buffer in an operating hood, due to its odor. However, for samples with pH adjustment. Color may first appear lavender or purple, 1 2 but will then turn to blue. Complete titration 3 within 5 min from time of buffer addition.

Prepare samples in triplicate. Record the volume of EDTA solution used 1. If a sample of water is thought to have a hard- for each titration. Data and Calculations 2. Other similar test strips could be used. The strips are dipped into the water to test Note: Test the same tap water, tap distilled water, and for total hardness caused by calcium and magnesium. The calcium displaces the magnesium bound to EDTA, and the released magnesium binds to Calmagite, caus- 1.

Dip the test strip into a beaker filled with ing the test strip to change color. Follow instructions on strip about how to read it, relat- Chemicals ing color to ppm CaCO3. Compare and discuss the accuracy and precision and concentrated HCl. No precautions are needed in use of the test strip. Adhere to normal laboratory safety procedures. Wastes likely may be put down the drain using a water rinse, but follow Resource Materials good laboratory practices outlined by environmental health and safety protocols at your institution.

American Public IN. Several chromogens daily. Wear tify the mineral in beef samples. Waste may be put down the In this experiment, meat samples are first ashed to drain using water rinse. The acid is necessary Supplies to keep the mineral in solution. Ferrozine complexes only with ferrous iron and not with ferric iron. Traditional methods for mineral analysis.

Instructions are given for analysis in duplicate. Objective Determine the iron content of food samples using the Ashing ferrozine method. Principle of Method 2. Heat on the hot plate until the sample is well- Ferrous iron in extracts or ashed samples reacts with fer- charred and has stopped smoking. Iron is is white. Iron Measurement 1. Make dilutions using ca 0. Hazard s 2. In duplicate, put 0. Sigma P 4.

Add 1. Vortex and let set 10 min. Ammonium acetate 5. Vortex Calculation of total iron in sample: and let set in dark for 15 min. Plot the standard curve and determine the 7. Take two readings repeated measures, msmt mg iron for each tube at nm. How else could iron be determined using the wet ash digest? What would be the advantages and disadvantages 0 blank of the ferrozine method versus the other method you 2 identified?

These methods are official methods of analysis commercially available from companies that sell the for numerous specific products. All these methods electrodes : electrode rinse solution, ionic strength are faster and less expensive procedures than analy- adjustor, reference electrode fill solution, standard sis by atomic absorption spectroscopy or inductively solution, electrode storage solution.

Strength Adjustor to 1 L with deionized distilled dd water. For chloride electrode — Deionized Reading Assignment distilled water. For chloride electrode: 5 M NaNO3. HNO3 to 1 L with dd water. Sensing and reference Hazards, Precautions, and Waste Disposal electrodes are immersed in a solution that contains the Adhere to normal laboratory safety procedures.

Wear element of interest. The electrical potential that develops gloves and safety glasses at all times. Ammonium at the surface of the sensing electrode is measured by hydroxide waste should be discarded as hazardous comparing the reference electrode with a fixed potential. Other waste likely can be put down the drain The voltage between the sensing and reference electrodes using a water rinse, but follow the laboratory practices relates to the activity of the reactive species.

Remove from hot plate and cool to room temperature in the hood. Filter water extract Cat. NA II. Sample Analysis by ISE 1. Condition sodium electrode as specified by the Procedure manufacturer. Replicate the preparation and analysis of standards 2.

Assemble, prepare, and check sodium and and samples as specified by the instructor. Sample Preparation General Instructions 3. Connect electrodes to meter according to meter instruction manual. Prepare samples by adding 5 g or 5 ml of 4. For instruments with direct concentration sample prehomogenized if necessary, and readout capability, consult meter manual for diluted if necessary to a ml volumetric correct direct measurement procedures. Add 2 ml ISA, then dilute to volume 5.

Using the pH meter set on mV scale, determine with dd water. See instructions specific for the potential mV of each standard solution each type of food product below. Samples 1, 10, , , ppm , starting with the with high fat levels may require fat removal.

Use a uniform stirring Consult technical services of the company that rate, with a magnetic stir bar in each solution, manufactures the ISE. Prepare standards by adding 5 ml standard of 6. Rinse electrodes with electrode rinse solution proper dilution e. Measure samples and record the mV reading. Add 2 ml ISA, then dilute to volume with As you rinse electrodes with electrode rinse dd water. Therefore since samples that the hole is covered. After use, store sodium electrode and reference rection for this dilution needs to be made in electrode as specified by manufacturer.

Data and Calculations Specific Samples: 1. Prepare a standard curve using 5-cycle semilog Sports drink: No dilution is required before paper, with concentration plotted on the log a 5-ml sample is combined with the 2-ml ISA axis. Plot actual concentration values on the and dd water as described above. Concentrations may Catsup: Accurately weigh ca. Combine 5 ml of tion of the line.

Note: If the standard curve this diluted sample with 2-ml ISA and dd is really a curve and not a straight line, read water as described above. Use the standard curve and the mV readings containing a stir bar. Add ml 0. Show all Prepare approximately ml of the ca. Calculate sodium chloride content of each food, each student or lab group.

Students should based on the chloride content. Calculate the sodium content of each food, in the Procedure. Compare the sodium chloride contents of the Hazards, Precautions, and Waste Disposal foods you analyzed to those reported in the Wear gloves and safety glasses at all times, and use U.

Use of crystalline www. AgNO3 or solutions of the silver salt can result in dark brown stains caused by photodecomposition of Question the salt to metallic silver. These stains are the result 1. If you used both a sodium and chloride ISE, which elec- of poor technique on the part of the analyst, with trode worked better, concerning accuracy, precision, and spilled AgNO3 causing discoloration of the floor.

If time to response? Explain your answer, with appropriate you do spill this solution, immediately sponge up justification. Also, be sure to rinse all pipettes, burets, beakers, flasks, etc. Objective to remove residual AgNO3 when you are finished Determine the sodium content of various foods with this experiment. Otherwise, these items also using the Mohr titration method to measure chloride will stain, and drip stains are likely to appear on the content.

Potassium chromate and silver nitrate must be disposed of as a hazardous waste. Other waste likely can be put down the drain using a water rinse, Principle of Method but follow good laboratory practices outlined by The Mohr titration is a direct titration method to environmental health and safety protocols at your quantitate chloride ions, to then calculate sodium ions.

The chloride-containing sample solution is titrated with a standard solution of silver nitrate. Procedure 4. Filter each solution through glass wool. Transfer Instructions are given for analysis in triplicate.

Add 1 ml of potassium chromate indicator to I. Standardization of ca. Titrate each solution with standardized ca. Transfer ml of the 0. This solution will be standard- color that persists for 30 s. Record the volume of ized, then used to titrate the food samples. Fill a titrant used. Accurately weigh to four decimal places about mg KCl into 1. Weigh accurately approximately 5 g of potato three ml Erlenmeyer flasks. Dissolve in chips in duplicate into ml beakers, then add dd water about 25 ml , add 2—3 drops of 95 ml boiling dd water to each beaker.

Stir the mixture vigorously for 30 s, wait for mate may cause serious skin sensitivity reac- 1 min, stir again for 30 s, then let cool to room tions! Put a magnetic stir bar in each flask with 3. Transfer the KCl solution, and place the beaker on a 50 ml of each solution to ml Erlenmeyer magnetic stir plate below the buret for titration. Using the AgNO3 solution in the buret, titrate 4. Add 1 ml of potassium chromate indicator to the KCl solutions to the appearance of the first each 50 ml of filtrate.

Note: you 5. This color that persists for 30 s. Record the volume of endpoint is due to the formation of Ag2CrO4. Pipette accurately 5 ml of sports drink in 4. Record volume of AgNO3.

Calculate and record molarity of AgNO3. Stir the mixture vigorously for 30 s, wait for gKC1 1molKC1 ml 1 min, stir again for 30 s. Add 1 ml of potassium chromate indicator to 6. Label bottle of AgNO3 with your name and the each 50 ml of prepared sample. Record the volume of II. Sample Analysis by Mohr Titration titrant used. Cottage Cheese Data and Calculations 1. Accurately weigh 10 g of cottage cheese in triplicate into ml beakers.

Calculate the chloride content and the sodium 2. Mix to a thin paste using a glass then calculate the mean and standard deviation stirring rod or spatula. Add another ca.

Note that answers must titration, b Volhard titration? The reaction of silver dichromate with ml chloride ions produces a white column of silver chloride in the strip. When the strip is completely saturated with the liquid, a moisture-sensitive signal across the top of Buret Buret Vol. The value on the numbered scale is read 3 at the tip of the color change, and then is converted to percent salt using a calibration table. Would this Mohr titration procedure as described above work well to determine the salt content of grape juice or Dilute 5 ml of the stock solution to ml with catsup?

How did this method differ from what would be done sodium chloride solution to use as a standard using a Volhard titration procedure? Repeat Steps 1—5 given above using the 0. Stir mixture vigorously for 30 s, wait for 1 min, stir as NaCl.

Company, Elkhart, IN, Contact 3. Instructions are given for analysis in triplicate. Transfer 50 ml of the 0. Note that each lot of chloride solution to a ml beaker. Fold a piece of filter paper into a cone-shaped sure to use the correct calibration chart i.

Multiply the result by the dilution factor 20 3. Using the 0. Weigh accurately approximately 5 g of potato than 2. Crush chips with a 4. Thirty seconds after the moisture-sensitive sig- glass stirring rod. Add 95 ml boiling dd water nal string at the top of the titrator turns dark and stir.

Filter water extract into a ml volumetric reading at the tip of the yellow-white peak, to flask, using a funnel with glass wool. Let cool the nearest 0. Using the calibration chart included with the Transfer to a ml beaker. Follow Steps 3—7 from the procedure for cottage ing to percent sodium chloride NaCl and cheese.

Be Catsup sure to use the correct calibration chart i. Weigh accurately approximately 5 g of catsup control number on the product being used must into a ml beaker. Add 95 ml boiling dd match the control number on the bottle. Transfer to a ml beaker. Product electrode titration titrator label Data 3. Follow Steps 3—7 from the procedure for cot- — tage cheese.

Follow Steps II. Questions Data and Calculations 1. Based on the results and characteristics of the methods, discuss the relative advantages and disadvantages of each From calibration chart Corrected for dilution factor method of analysis for these applications. Include in the table the sodium cheese, indicating strip method. Part The aim of coupled plasma-atomic emission spectroscopy. In this experiment, the term AES will be amount of energy emitting from the hollow cathode used rather than OES, but the two terms are inter- lamp and that reaching the detector.

Absorption is lin- changeable. This experiment specifies the preparation of stan- Atomic emission is based on atoms emitting energy, dards and samples for determining the sodium Na after heat energy from a flame has converted molecules and potassium K contents by AAS and ICP-AES. The to atoms, and then raised the atoms from ground state samples suggested for analysis include two solid food to an excited state. One measures the amount of emit- product that does not a clear sports drink, or a clear ted energy of a wavelength specific for the element of fruit juice.

Emission is linearly related to concentration. Procedures for both wet ashing and dry ashing Chemicals of the solid samples are described. Experience can be gained with both types of ashing, and the results of the two methods can be compared. Sodium results from this CAS No.

Lanthanum chloride LaCl3 Irritant The limit of detection for sodium is 0. Skip to content Search for:. A grand tour of the science of cooking explored through popular American dishes, illustrated in full color.

How to roast a succulent, moist turkey forget about brining! In The Food Lab, Kenji focuses on the science behind beloved American dishes, delving into the interactions between heat, energy, and molecules that create great food. In hundreds of easy-to-make recipes with over 1, full-color images, you will find out how to make foolproof Hollandaise sauce in just two minutes, how to transform one simple tomato sauce into a half dozen dishes, how to make the crispiest, creamiest potato casserole ever conceived, and much more.