The non-destructive testing of liquid milk UHT products is a new generation quality control method based on the combination of modern computer identification technology and inertial kinetic energy system. As a new technical means for the detection of microbial contamination of UHT products with accurate, high efficiency and non-destructive characteristics, its application in the dairy industry in China has positive significance.

First of all, the application of non-destructive testing technology can reduce the huge loss of packaging materials and production costs caused by the previous open package inspection.

Secondly, non-destructive testing can reduce the pressure of increasing testing costs, so that according to the objective requirements of quality management, the number of samples in the quality control link can be increased, the representativeness of the test samples can be further improved, and the scientific quality of product quality control can be continuously improved. And reliability.

The principle of non-destructive testing, the biological basis of non-destructive testing technology, in the production of liquid milk UHT, when producing microbial contamination such as Bacillus, Actinomycetes, Lactobacillus, Streptococcus lactis, Enterogastric bacteria, Pseudomonas, etc. Both are accompanied by reactions such as fat breakdown, protein coagulation, and changes in pH.

Based on the above-mentioned product performance of microbial contamination in UHT products, the traditional method of detection is to use wet chemical methods to open the package to detect changes in pH. The new generation of non-destructive testing technology does not need to open the package, using the computer inertial kinetic energy recognition system to directly detect the degree of change in physical properties such as fat decomposition and protein solidification in UHT products.

This change in physical properties can be manifested as a change in the inertia attenuation ratio and the decay period in a computer inertial kinetic energy system. As long as the computer's inertial kinetic energy system can achieve a sufficiently high repeatability, such as 0.3%, it is possible to detect the excess sample in the UHT product where the fat is decomposed and the protein is solidified by more than 0.3% of the set value.

Sample basis for non-destructive testing 1. Statistical analysis of microbial contamination samples: Statistics on more than 100,000 packs of 250m1 Tetra Pak pure milk test samples show that microbial contamination products can be roughly classified into acid packs and solidified acid packs. And 3 types of ups and downs. The rising package can be directly detected by visual inspection; the detection accuracy of the rising package and the solidified acid package in the computer inertial kinetic energy system can reach more than 99%; therefore, the statistical analysis focuses on the acid package.

The acid package can be divided into two types: slightly acid (pH between 6.0 and 6.5) and severe acid package (pH between 5.0 and 6.0). Depending on the nature of casein, a slight drop in pH usually results in a slight decrease in viscosity, and a sharp drop in pH leads to a re-elevation. Therefore, the micro acid package will cause an error of about 50% in the non-destructive testing; the detection accuracy of the severe acid package can reach more than 90%.

Specific to the composition of microbial contamination samples, statistics show that the bad packets caused by packaging materials accounted for 15.1% of the total amount of bad packets, the probability of occurrence of simple acid packets was 8%, and the probability of occurrence of micro-acid packets was 81%, which was serious. The probability of acid pack is 19%, and the probability of false detection of non-destructive testing is about 4.3%. The joint caused a bad package, accounting for 14.2% of the total amount of bad packets, and the probability of miscalculation of simple acid packets was 2.4%. P strips caused bad packets, accounting for 11.3% of the total number of bad packets, and the probability of misjudgment of simple acid packets was 2.0%. Suspension and shutdown caused bad packets, accounting for 9.4% of the total number of bad packets, and the probability of misjudgment of simple acid packets was 2.89%. Randomly caused bad packets, accounting for 16% of the total number of bad packets, the probability of misidentification of acid or coagulating acid packets is 1.7%. Startup and temporary opening cause bad packets, accounting for 34% of the total amount of bad packets. Due to the existence of a large number of simple acid packets, it is recommended to open the package inspection. In this way, the false detection rate caused by the opening and opening of the package and the non-destructive testing of other samples is about 1.83%.

2. Error analysis of non-destructive testing The error of non-destructive testing can be divided into two cases: bad packet judgment and bad packet judgment. The probability of judging a good package depends mainly on the set value of the test. According to the theoretical formula of the calibration, the probability of badly determining the good package is generally 0.3%.

The probability of judging bad packets depends mainly on the repeatability of the non-destructive testing system, the rationality of the testing method, and the sample characteristics. For example, the statistics of Tetra Pak 250m1 pure milk sample show that under the condition that the repeatability of the detection system is high enough and the detection method is reasonable, the probability of the bad packet in the random sample is about 1%, and the purpose sample (starting sample, The probability of temporary injection is about 2%, and the probability of quality tracking is about 0.1%.

The application effect of non-destructive testing technology At present, the non-destructive testing technology of liquid milk UHT finished products has been initially applied in China's dairy industry. According to the statistics of the test samples of more than 1 million packs of dairy companies such as Yili, Guangming, Mengniu and Nestle, the technical indicators and performance-price ratio of China's non-destructive testing system can meet the quality control level of UHT products in China. Claim.

The promotion and application of non-destructive testing technology in China's dairy industry will help enterprises to further reduce production costs, improve product quality and competitive advantages, and enhance the overall technical content of the dairy industry in terms of resource utilization and food safety. The dairy industry maintains a steady growth with a solid scientific and technological foundation.