In the earlier article (Can chocolates go bad? A look into the shelf life of chocolates) we discussed in brief about the shelf life of chocolates, what it means , and some tips to ensure that the chocolates and the chocolate products have a good shelf life.

In this article we will discuss about the different types of testing which are done to check the shelf life of a chocolate product and the methodology of these tests. This should give an idea about the various types of tests done for shelf life, their procedures and the industry acceptable test results.

Chemical Analysis Test

Peroxide Value Test (PV Test)

The purpose of this test to measure the extent of Fat oxidation which will happen when the chocolate moves into the real world environment, which will be a primary indicator of rancidity and chocolate spoilage.

In this procedure the Lipids are extracted from the chocolate. The PV is determined using iodometric titration according to the Association of Official Analytical Chemists(AOAC) protocols, where the peroxides present, liberate the iodine from Potassium Iodide, and the iodine is titrated with sodium thiosulfate. The result is expressed in 10^-3 equivalents of active oxygen per kilogram of fat.

The generally accepted Critical threshold for chocolate is that the PV should not exceed 10meq O2/kg Fat.

Free Fatty Acid Test

The purpose of this test is to indicate the hydrolytic rancidity or lipid degradation of the chocolate.

Here the chocolate fats are extracted and titrated against standardized alkali using phenolphthalein as an indicator. The FFA percentage indicates product degradation over time. A good threshold is 1.75% of FFA. Any more the FFA percentage, the chocolate product is more viable to rancidity, off flavors. In pure chocolates it can also deter the crystallisation characteristic of cocoa butter , resulting in a different temperature range where the most stable form of chocolate, Beta V is obtained. Read more about the crystalline characteristics and their important in our article Understanding Fats in Your chocolate – Part 2.

Moisture Content

We have gone in detail about the effect of moisture content in chocolate in our previous article. This test is done to check the moisture in chocolate.

Here the chocolate sample is dried in an oven at 105 Degree C until constant weight is achieved. The weight which is lost is the moisture percentage. Less than 2% is ideal.

The test results are also mentioned in Aw also called Water Activity. Higher the Aw, higher are the chances of the chocolate going bad faster and the chocolate having a lower shelf life. An acceptable value of Aw is lower than 0.3-0.4.

Microbial Testing 

Total Plate Count

The purpose of this test is to detect general bacterial load.

Here the chocolate is homogenized in sterile buffered peptone water and the dilutions are plated on Plate Count Agar, which are in turn incubated at 30-37 degree C for 24-28 hours. After this period the colonies are counted , and reported as CFU/g. TPC values of less than 10^3 CFU/g are acceptable.

Yeast and Mold Count

This test determine the fungal spoilage agents.

Samples are diluted as before and then plated onto Malt extract Agar or Czapek Dox Agar. These plates are incubated at 25 Degree C for 5 days and then the colonies are counted. Acceptable values are less than 10 CFU/g.

Pathogen Screening 

This test is done to determine presence of Pathogens in the chocolate.

The sample is dipped in selective broths and streaked by selective agars (these selective broths and selective agars respond differently to different pathogens) and then tested by PCR based identification.

Physical Tests

These tests are basic tests which are done to confirm the physical attributes of the chocolate. A small to medium chocolate making facility can easily do these tests as the equipment needed are not so expensive and the method of the tests are not so complex.

Texture Profile Analysis

The purpose of this test is to evaluate hardness, brittleness and mouthfeel changes during storage and transport.

The procedure is to us a texture analyzer , a compression instrument to apply force to the chocolate and record resistance or break point.

Colorimetry

The purpose of this test to detect bloom or discoloration.

The test is done on a Colorimeter ( For eg MINOLTA Chroma meter) on chocolate surfaces, reporting objective color values (L, a,b)

Sensory (Organoleptic) Evaluation

This test assesses apperance, aroma, flavor, mouthfeel and overall acceptability of chocolate product during its storage and transport.

Trained sensory panels of chocolate tasters rate the chocolate product based on standard norms and forms generally acceptable, assessing parameters such as visual appearance, instance and persistance of flavour, aftertaste, aroma and texture. The test is random and most of the times a blind test to avoid bias. Some manufacturers also include industry leader’s chocolate product in these tests to see how their product fares.

Accelerated Shelf Life Testing

The purpose of this test to predict a “best before” date, which is achieved in a shorter time by simulating real world environment and aging factors.

Chocolates are stored at elevated temperatures and humidity. Tests mentioned above such as PV test, moisture test , sensory test are then conducted at fixed intervals of time. The Arrhenius equation is then used to model reaction rates and extrapolate shelf life during normal storage and transport conditions.

Different labs have different procedures where they may vary slightly in carrying out these tests and the orders of the chemical reagents, but all of them are based on validated scientific protocols.

The protocols follow strictly the code as mentioned in the regional certifying organisation such as FSSAI, FSSC, BRC and the manufacturer can ask for the protocol followed during testing to counter with the data available on the certifying organisations data available on public forum.

We hope the above information has helped in identifying your chocolate shelf life questions and information about the different testing methods.