TEST PRINCIPLE
Evaluation of the hardness and crunchiness of candy.
BACKGROUND
Sweets (candy) are made by dissolving sugar in water or milk and boiling the syrup until it reaches the desired concentration (thickness or consistency) or starts to caramelize. There are different kinds of candy depending on the ingredients used and the length of time the syrup is boiled.
The final texture of a candy will depend upon the sugar concentration which in turn depends upon the boiling temperature. Higher boiling temperatures result in higher sugar concentrations as more of the water evaporates from the mixture producing hard and brittle candies. Lower boiling temperatures on the other hand, produces softer candies. Candy, therefore, comes in a variety of textures from soft and chewy to hard and brittle e.g., jelly beans, fudge, toffee, candy canes, lollipops and hard candy amongst others.
Other than the boiling temperature, a change in formulation for instance, will affect the texture of the end product. Therefore carrying out routine tests on the texture of the sweet product is necessary to ensure consistency from sample to sample.
Texture analysis using the Texture Analyzer with the confectionery jig and cylinder probe enables one to measure the firmness, fracturability, and quantity of fractures of hard candy. The robustness of the instrument also means that tests can be performed directly from the production line.
METHOD
| Equipment: | CTX Texture Analyzer with 50kg load cell |
| Fixture Base Table (TA-BT-KIT) | |
| 2mm Cylindrical probe (TA39) | |
| Confectionary Jig (TA-CJ) | |
| Texture Pro Software |
Settings:
| Test Type: | Compression |
| Pre-Test Speed: | 1mm/s |
| Test Speed: | 1mm/s |
| Post-Test Speed: | 1mm/s |
| Target Type: | Deformation |
| Target Value: | 15mm |
| Trigger Force: | 15g |
PROCEDURE
- Attach the 2mm cylindrical probe onto the probe shaft of the load cell.
- Place the Fixture Base Table to the base of CTX Texture Analyzer and tighten into position using the side screws.
- Place the confectionery jig onto the fixture base table and tighten into position using the thumbs screws.
- Put the sample into the confectionery jig such that it is centrally aligned to the aperture of the fixture then tighten into position using the four screws. Tightening should be to the point of first resistance from the sample. Any further tightening will compress the sample.
- Lower the probe to about 5mm above the confectionery jig.
- Align the aperture of the confectionery jig to the probe above by re-positioning the base table, and ensure that the probe can penetrate the aperture of the confectionery jig without friction effects with the sides of the jig.
- Once the alignment is complete, tighten the thumbs screws of the fixture base table to prevent further
movement. - Start the penetration test.
- After each test, clean the cylinder probe and fixture before proceeding to the next test.Samples were removed from refrigerator at 6.8°C.
Note: For comparison purposes, samples should be placed into the confectionery jig in the same orientation.
The sample in the confectionery jig must be placed centrally under the probe.
The distance of penetration chosen for the test depends on the height of the sample. For thicker samples, greater depths can be used. When making comparison, test conditions must be kept the same for all samples tested.
When optimizing test settings, the hardest sample should be tested first in order to anticipate the maximum testing range for subsequent samples. This will ensure that the force capacity covers the range for other future samples.
RESULTS
Figure I
Figure I shows the load vs. time graph for the hardness of the candy using a confectionery jig and a 2mm cylinder probe. The maximum peak force is a measure of candy hardness, this value correlates with the force required to penetrate the hard candy with the molars. The fracturability value is the force required to generate the first fracture and gives an indication of the brittleness of the product; the higher the value the less brittle the candy. The fluctuations on the graph represent the fractures generated in the test from which the quantity of fractures is calculated from to give candy crunchiness values.
Figure II
Figure II shows the load vs. distance graph showing the work done to penetrate the candy. This graph shows the candy hardness and fracturability but also the energy required to overcome the structural make-up of the candy when deforming it with the molars. This is the work done measured as the area under the graph.
OBSERVATIONS
When a trigger of 15g has been attained at the candy surface, the probe proceeds to compress and deform the candy over a chosen distance (in this example 15mm). As the probe deforms the sample, the force/load is seen by the rapid rise (see graphs). Candy hardness is determined by the maximum force on the graph (Figure I and II). This correlates with the force required to penetrate the candy with the molars.
The area under the graph on the load/distance graph (Figure II) is a measurement of work done that correlates with the energy required to overcome the strength of the internal bonds within the candy when deforming the candy. The quantities of fractures generated in the test (see Figure I and II) give an indication of the crunchiness of the sample; the higher the value, the crunchier the sample.
The breaking characteristics of candy (i.e., hardness, fracturability, and crunchiness) provides very useful information in the development process of the product for optimizing product formulation, cook times, moisture content of the product, as well as verifying the ideal sensory preference of the product.
The table below summarizes the average results taken from 12 samples:
| # | Sample Description Product Name | Hardness (g) | Work Done (mJ) | Quantity of Fractures |
| 1 | Candy | 14068± 1051 | 156.8± 42.3 | 17± 4 |
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