Fresh cream consistency measurement

PRINCIPLE OF THE TEST

Evaluation of the consistencies of whole and light Fresh Creams by retro-extrusion.

CONTEXT

Crème Fraîche is a cultured cream that is thickened with natural lactic acid bacteria to produce a delicate creamy texture. The high fat content of the product increases the moisture content, further softening the product.

Research has shown that the conditions of homogenization and pasteurization of the cream can affect the viscous and elastic properties of the Crème Fraiche. It is therefore necessary to monitor the texture of the Crème Fraiche. Using the CT3 texture analyzer with a rear extrusion cell, the consistency and firmness of the product can be determined. In the test, the extrusion piston compresses the sample a specified distance during which the sample is deformed and packaged more tightly in the remaining space available (under the descending probe). As the sample becomes very compact with limited air pockets, the force increases. Then the back extrusion begins with the sample of material flowing around the edge of the piston as it pushes down. The back-extrusion test is useful for viscous products,

METHOD

Equipment : CT3 with 4.5 kg load cell

Luminaire base table (TA-BT-KIT)

Rear extrusion cell with 38.1mm disc (TA-BEC)

TexturePro CT software

Settings :

Type of test: Compression

Pre-test speed: 1.0 mm / s

Test speed: 1.0 mm / s

Post-test speed: 1.0 mm / s

Target type: Distance

Target value: 30 mm

Trigger force: 10.0 g

SAMPLE PREPARATION

Samples can be tested from their original containers or placed in a standard size back extrusion container. If you use a standard extrusion container, the sample should not fill more than 75 % the depth of the container. Samples should also be tested immediately after removal from storage (refrigerator).

PROCEDURE

1. Attach the 38.1mm disc (extrusion piston) to the load cell.
2. Place the fixture base table on the instrument base and lightly tighten the thumbscrews to allow some degree of mobility.
3. Insert a plate (if you are testing the sample from its original container) onto the fixture base table and tighten in position using the side screws. Otherwise, the standard extrusion container containing the sample is placed directly on the base of the instrument.
4. Place the sample on the fixture base table if it is in its original container.
5. Lower the probe a few inches above the sample surface.
6. Position the sample container centrally under the extrusion piston by repositioning the base table of the fixture so that the probe can fully enter the container without touching the edge of the container.
7. When alignment is complete, tighten the thumbscrews on the fixture base table to prevent further movement.
8. Select a specified start distance, for example 10mm above the top of the container or the sample surface. This will ensure that the probe returns to the same position above the sample after each test, allowing the cohesion and “cohesive work” of the samples to be compared.
9. Start the penetration test.

Remarks :

Samples can be tested directly from their containers. When comparing between samples always make sure that the container size, temperature and sample volume are the same and mention them in the report. However, it is preferable to test directly from the sample containers in order to avoid any alteration of the fixed product.

The extrusion distance will vary depending on the depth of the sample in the container and the depth and shape of the container. As a general rule, the chosen depth should not exceed 75 % the depth of the sample. This will prevent base effects and instrument overload caused by the plunger contacting the base of the vessel.

The harder sample is best tested first in order to predict the maximum test range for subsequent samples.

RESULTS

The graphs show the consistencies and firmness of whole and lightened Fresh Creams by back extrusion.

Figure I shows the extrusion of whole cream and low fat preserved at 6 ° C by back extrusion. Tests were performed at room temperature and from the original sample containers. The maximum peak on the graph is a measure of the hardness of the sample. The area below the positive peak from the start of the test to the maximum load is a measure of the hardness work performed. The maximum negative peak is a measure of the bond strength. The area above the negative peak is a measure of the stickiness of the sample.

Figure II shows the force versus distance for the extrusion of whole, low fat crème fraîche. The maximum peak on the graph at the target distance of 30 mm is a measure of the hardness of the sample. The area below the positive peak between the start of the test and the target distance (30mm) is a measure of the hardness work performed. The maximum negative peak is a measure of the bond strength. The area above the negative peak is a measure of the stickiness of the sample.

OBSERVATIONS

When a triggering force of 10g has been reached at the sample surface, the extrusion piston compresses the sample a specified distance of 30mm. During this time, the sample is deformed and compressed to settle more tightly in the remaining space available (under the descending piston). When the sample becomes very compact with limited air pockets, the force increases rapidly and extrusion begins. When the specified distance is reached, the plunger begins to withdraw from the sample.

The maximum force on the graph is a measure of the firmness of the sample over the specified distance; the higher the value, the firmer the sample. The area under the curve is a measure of the consistency of the sample; the higher the value, the thicker the consistency of the sample. As the probe withdraws from the sample, the initial lift of the sample weight off the plunger surface produces the negative portion of the graph. The maximum negative force is a measure of the adhesive strength of the sample; the more negative the value, the more adhesive the sample is. The area under the negative curve is a measure of the stickiness of the sample. According to the graph, low-fat crème fraîche requires a higher compression force than whole crème fraîche.

The following table summarizes the hardness and the work done, the adhesion and the work done.