Application of Anlerix pH510 acidity meter and CD510 conductivity meter in milk PH value monitoring

Under normal circumstances, the pH value of pure milk is between 6.4 and 6.8 , which is weakly acidic. The pH value can accurately reflect the freshness of milk. Reliable pH measurement is very important for the quality control of fresh milk. The importance of pH is that the on-line pH is mainly considered from the perspective of the freshness of milk and other media contamination in the production process. Freshness is also the focus on the acidity of the product, which will seriously affect the stability of your later products. If the product is reinforced, the pH value is the key basis for the release of the product. It is the quickest way to verify the sterilization effect of your product and whether the product is contaminated.

At the same time, dairy products can rely on pH to ensure that milk does not clump. This critical point is pH 4.3-4.6 , and the pH of the milk cannot be lower than this value anyway. This is the so-called isoelectric point of milk protein. When the pH value is within this range, the repulsion between the milk protein molecules is minimal and precipitation is easy. Therefore, the pH of the protein beverage needs to be adjusted to the isoelectric point, but the pH is generally Can not be higher than 6.8 , high pH is not conducive to product quality, and when the pH is higher than 6.8 , in the sterilization process, protein and reducing sugar are prone to Maillard reaction, product color browning.

The pH of milk is not easy to measure. They usually contain fat, protein, sulfides and many other substances, all of which interfere with electrode measurements and make measurement errors. In addition, the milk itself or the precipitated protein contaminates the junction of the electrode during the pH measurement of the milk, causing a change in the pH electrode calibration value (zero point and slope). They can also be very thick, very thin, very sticky or very hard, but we have to measure them and get fast and accurate results, so it is difficult to implement. However, if the electrodes are chosen correctly and used properly, your measurements are accurate and reliable. Ordinary pH electrodes will not be able to withstand such high pollution measurement environments, which will cause measurement errors due to poor relinearity of the electrode measurements. Anlai Lisi S3221 glass composite pH electrode adopts Swiss imported ceramic liquid junction and long-life reference system. It has large glass electrode contact area, is not easy to block, and can withstand high pollution. It is very suitable for measuring milk pH value.

Normal milk has a certain conductivity, and the change in conductivity increases or decreases as the temperature of the milk increases or decreases. The adulterated milk can be separated into electrolytes or non-electrolytes by using a conductivity meter to test adulterated milk. The conductivity of the electrolyte is significantly increased when the electrolyte is incorporated into the electrolyte. The more the amount of the mixture is, the more the change is. The conductivity of the non-electrolyte is reduced. Therefore, the conductivity of milk is measured by a conductivity meter. According to the change of conductivity, it is possible to determine whether the milk is adulterated, and provides a direction for further quantitative analysis of adulterants. The Anlerich high-precision conductivity electrode is suitable for the measurement of conductivity in this study.

In this experiment, the Anlerix pH510 main unit was equipped with S3221 glass composite pH electrode and T2132 temperature electrode to measure the pH value of pure milk of Liangming and Yili . The combination of Elanith CD510 conductivity meter and E2224T glass conductance was used. The electrodes measured the conductivity values ​​of the above two brands.

 

pH510 type PH meter pH of the milk during the measurement operation

1 Prepare the machine pH510 host with S3221 glass composite pH electrode for precise pH measurement , routine use in laboratory ; can be used in turbid liquid or colloidal solution , such as milk, jam, water-based paint, cosmetics, soil solution, sewage and sludge Wait. Prepare the sample with the T2132 temperature electrode.

2 connected to the power supply. Place the universal electrode holder.

3 Regularly calibrate the instrument using the standard pH buffer solution.

4 Wash the pH electrode with pure water and dry it, immerse it in the solution to be tested, and then put it aside after a little agitation, and wait for the LCD to display stable measured values ​​and The reading at the icon is the measured pH value.

Note Regular calibration:

1. Press the CAL key, to access the calibration mode, the bottom right LCD flashes 6.86 pH, suggesting for the first calibration point pH6.86 buffer solution.

2. Rinse the electrode with pure water and dry it, immerse it in a pH 6.864 buffer solution, and let it stand still after agitation to wait for the reading to stabilize. When the instrument is locked 6.86 pH LCD will display stable   Icon, then press the ENTER key instrument calibration, the calibration is successful display End icon to end the first point calibration.

3. If performing 3- point calibration, repeat step 2 by changing the buffer of pH4.003 and pH9.182 . The operation of 5- point calibration mode is the same as above, but the calibration solution and calibration sequence can be selected at will.

Experimental result

The picture below shows the well-known brand 1 and the famous brand 2 and the contrast of pure water pictures.

 

Test Data

 

Analysis: From the above experimental results, it can be seen that the pH values ​​of the two brands of Guangming and Yili used in this study are 6.61 and 6.67 , respectively , which are relatively close, and both are within the standard range of 6.4-6.8 .

Precautions
1. The protective bottle at the front end of the pH electrode has an appropriate amount of electrode soaking solution, and the electrode tip is immersed therein to maintain the activation of the glass bulb and the liquid junction.

2. The electrode plug must be kept highly clean and dry. If it is contaminated, it can be cleaned and dried with medical cotton 蘸 anhydrous alcohol to prevent short circuit at the two ends of the electrode plug, otherwise the measurement will be invalid.

3. The electrode protection bottle has an appropriate amount of electrode soaking solution, and the electrode head is immersed therein to keep the glass bulb moist and the liquid junction unblocked. When measuring, loosen the cap, pull out the electrode, and wash it with deionized water to use. After use, insert the electrode and tighten the cap. If the solution in the protective bottle is found to be turbid and moldy, the protective bottle should be washed in time and replaced with a new one.

4. The electrode usage period is about one year. After aging, the new electrode should be replaced in time.

 

 

CD510 conductivity meter measures pure milk conductivity value operation process

1. Connect the power supply.

2. Position the E2224T conductivity electrode to the position of the bayonet and insert it slowly. Tighten the socket nut.

3. Install the universal electrode holder.

4. conductivity electrodes set constant K.

5. Select the conductivity standard solution (default CH ), set the reference temperature (default 25.0 °C ), temperature coefficient (default 2.00 ), and TDS and conductivity conversion factor (default 0.71 ) as needed .

General calibration:

(Taking "1408 μS/cm" calibration as an example)

Rinse the electrode with pure water and dry it, then rinse with a small amount of calibration solution. Dip the electrode into the calibration solution, stand still after agitation and wait for the reading to stabilize.

2. Press the CAL key and the instrument enters the calibration mode. When the instrument is locked at 1408 μS/cm , the LCD will display the symbol.   At this time, press the ENTER key to calibrate the instrument. After the calibration is successful, the LCD displays the End icon and returns to the measurement mode.

To perform the calibration points 2-4 (note that the concentration of the calibration solution carried from low to high), repeat the steps above, until the calibration some are completed.

Tags: Li Si Anlai Acidity Conductivity Meter viscous samples