Common chemical properties analyzed in foods include the following:
- pH - Acidity
- Fat and oil quality
- Fat content
- Protein analysis
The pH is an indicator of the amount of acid or base present in a food. For canned foods, a pH of 4.6 or lower would prevent microorganisms such as Clostridium botulinum to grow if proper sterilization time and temperature are used. The pH also affects flavor, color and texture. The pH is measured using a pH meter. Here are some examples of the pH range for different food products.
|Description||pH Range||Example of Products|
|Low Acid||6.5-5.3||Bacon, canned vegetables, fresh meat|
|Medium Acid||5.3-4.5||Canned soup, soft cheese, pickled cucumbers|
|Acid||4.5-3.7||Mayonnaise, yogurt, orange juice|
|High Acid||<3.7||Pickles, canned sauerkraut|
|The pH scale ranges from 0-14. A pH of 0 is extremely acid. A pH of 14 is extremely alkaline.|
Fat and oil quality
This depends on the composition of the product, size of the product, type of processing and type of oil used. Higher fat products are more susceptible to rancidity. This defect is defined as the amount of free radicals that can cause an off-odor or off-flavor in foods. Rancidity is measured by the peroxide value, TBA test, Schaal test, or smoke point.
This is measured using equipment that can evaluate solid and semisolid foods. An example is the Foss-Let instrument. Analysis can take 5-8 minutes to complete.
Protein is typically measured using the Kjeldahl method. There are more rapid analyses to measure protein. These instruments can also measure oil, moisture, starch, fiber and sugar content.