Tofu or curd consistency measure

APPLICATION

Determination of the resistance of the curd.

OBJECTIVE OF THE TEST

Determine the strength of the curd to help assess the quality of tofu and other curd products.

PRINCIPLE

TEST The sample of curd to be tested is placed on the test table. The curd probe kit consists of three probes used to compress the sample until it breaks. The curd strength is defined as the maximum breaking load.

CONTEXT

Tofu curd resistance testing has traditionally been performed using a motorized stage to lift the curd sample towards the test probe, which would unload a weighted spring causing the probe to apply a increasing force on the sample. The operator had to observe a mechanical pointer as it moved on a scale of 0 to 100 until it suddenly collapsed when the probe punctured the sample. The highest scale reading observed was considered to be curd strength.

Due to the limited load range of this machine, probes of three sizes were required. The small 5mm diameter probe was used to test the extra firm curd. This allowed a moderate load on the probe to apply relatively high stress to the sample. On the other hand, the 10 mm diameter probe was used to test the soft curd. This allowed the relatively low stress at break to cause a moderate load on the probe. The development of probes with a diameter of 10 mm, 8 mm and 5 mm was therefore necessary. The CT3 using a 1000g load cell offers sufficient capacity to test all three types of curds with a single probe. Three curd probes are provided to allow easy correlation with existing methods. This allows a seamless transition to modern equipment without the need to change the criteria for degrees of firmness.

Test: Normal

Trigger: 3 grams

Distance: 40 mm *

Speed: 4 mm / s

* varies by sample

EMPIRICAL FACTORS

The “trigger value” is the load in grams that must be exceeded to start the test. This is used to indicate the position of the sample surface and allows the test to begin. After triggering, the transducer will travel to the target distance at the preset speed.

When setting the target distance for the test, the thickness of the sample should be taken into account as well as the expected strain to failure. A soft curd 40 mm thick may rupture after only 10 mm of penetration, while an extra-firm product of the same thickness may deform 20 mm before breaking. The target distance should be high enough to exceed the strain required for failure.

RESULTS

DISCUSSION

In order to obtain accurate curd strength results for tofu puncture, test probes of specific geometry and dimensions are required. The probes are shown in the photo (Figure I). Typically, an extra firm tofu test uses the 5mm diameter TA46 probe. A test for firm tofu would use the 8mm diameter TA47 probe, and the test for soft tofu would use the 10mm diameter TA48 probe. These probes, when used with the CT3, provide identical results to those used in the traditional mechanical method described above, with one exception. The mechanical scale range of 0-100 is equivalent to 0-207g. The CT3 texture analyzer reads directly in grams, so the expected results should be correlated according to the table above.

CONCLUSION

The modern, user-friendly, low-cost texture analyzer Model CT3 can be used for quality control testing of tofu and other curd products. A set of Curd probes is the only item