MFHPB-03 Determination of the pH of foods including foods in hermetically sealed containers
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87D008CBD54245018116022D74491C52 |
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文件大小(MB)： |
0.08 |
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页数： |
5 |
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日期： |
2024-7-30 |
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Published on the Food Directorate’s (Health Canada's) website at http://www.hc-sc.gc.ca/food-aliment.,Government of Canada Gouvernement du Canada,HPB Method MFHPB-03,February 2003,HEALTH PRODUCTS AND FOOD BRANCH,OTTAWA,DETERMINATION OF THE PH OF FOODS,INCLUDING FOODS IN HERMETICALLY SEALED CONTAINERS,Dev C. Nundy,Food Section,Ottawa Laboratory (Carling),Canadian Food Inspection Agency,Ottawa, Ontario, K1A 0C6,e-mail: dnundy@inspection.gc.ca,with Carol Crawford (CFIA, Vancouver), Donna Douey (CFIA, Calgary),and Yvon-Louis Trottier (CFIA, St.-Hyacinthe).,1. APPLICATION,This method is designed to measure the equilibrium pH of foods, including thermally processed and foods,in other hermetically sealed containers. This revised method replaces MFHPB-25H, dated October 1991.,2. PRINCIPLE,This method is based upon the determination of the hydrogen ion concentration of food by direct,immersion of a single (combination) electrode into the food or a prepared sample of the food that has been,blended to paste consistency. This determination is recorded in terms of pH. Modern instrumentation and,availability of wide variety of electrode types and styles have made the measurement of pH simple and,convenient with very low maintenance.,3. DEFINITION OF TERMS,See Appendix A of Volume 2.,4. COLLECTION OF SAMPLES,See Appendix B of Volume 2.,5. MATERIALS AND SPECIAL EQUIPMENT,1) pH Meter,2) Combination electrode with Ag/Agcl Reference or Solid State Combination pH Electrode,MFHPB-03,- 2 - February 2003,3) Sieve or strainer,4) Buffer solutions, pH 3, 4, 5, 7, 10,5) Lab Blender, homogenizer or mixer,6) Lab Stomacher,7) Distilled water, recently boiled (CO2 free),8) Separatory funnel or centrifuge,6. PROCEDURE,6.1 Handling and Preparation of sample units,6.1.1 Store perishable foods in the refrigerator (4/C) until day of analysis. Store non-perishable,canned (normal or flat) or low moisture foods at room temperature. Store frozen foods at,-20/C.,6.1.2 Samples must be at room temperature before testing the pH. Thaw frozen samples at,refrigeration temperatures and then bring to room temperature before analysis.,6.1.3 For food in containers (such as canned), follow MFHPB-01 for the identification of the,container, removal and identification of the label, opening of the container, and mixing the,contents, as appropriate.,.,6.1.4 For other foods, handle as for other analysis, keeping in mind that many samples will,be undergoing microbiological testing and therefore must be handled,appropriately. Use aseptic technique and sterile equipment and avoid cross,contamination with other products, as appropriate.,6.2 Preparation of the food samples,The amount or weight of sample tested will depend on the amount of sample available. For,homogenized products, weigh a representative portion of the sample, in an appropriate amount,(approximately 100 g). Smaller amounts may be used in cases where the amount of sample,available is insufficient to test 100 g.,NOTE: A small amount of added water will not alter the pH of most food products, but,caution must be exercised concerning poorly buffered foods. When adding water,to a food matrix, the amount specified (i.e., 50 mL of water to 100 g of sample) is a,guideline only. Use as little water as possible to obtain the proper consistency.,This is particularly important with poorly buffered foods.,Some food products may consist of a mixture of liquid and solid components that differ in acidity.,Other food products may be semisolid in character. The following methods of sample preparation,should be used for pH testing, as appropriate.,6.2.1 Solids,Blend the sample to a paste consistency and determine the pH. Where more fluidity is,required add a small amount of recently-boiled distilled water to facilitate the blending. No,more than 50 mL of distilled water should be added to each 100 g of the product.,6.2.2 Liquid and solid component mixtures,MFHPB-03,- 3 - February 2003,Mixtures of solids and liquids can be tested either by blending the mixture to a paste,consistency and measuring the pH directly or by separating the solid and liquid portions,and testing each portion separately.,If separating the solid and liquid portions, drain the contents of the container by using a,suitable strainer or sieve. Standard sieve sizes of 8 to 20 are available for this procedure,and will be dependant on the particle size of the sample. Retain and test each portion,separately, preparing the solid component as in 6.2.1.,If the liquid portion contains sufficient oil to cause electrode fouling, separate the phases,with a separatory funnel or centrifuge and retain the aqueous phase for pH determi……
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