Abstract
Objective: To improve the counting efficiency and realize the traceability of raw data. The applicability, accuracy, precision and repeatability of the automatic colony counter were verified by experiments, Determine the applicability of colony count in the detection of dairy products and raw and auxiliary materials. Methods: The plate pouring method and test piece method are selected for verification test, including psychrophilic bacteria, aerobic spores, thermophilic aerobic spores, lactic acid bacteria count, total number of colonies, coliform, mold, yeast, Staphylococcus aureus and other items. The manual count is compared with the automatic colony counter to determine its feasibility, applicability and accuracy. Results: The colony count of normal Petri dish without background interference was compared with that of 3M test piece. The paired t-test was carried out by visual method and instrument method, <I>P </I>= 0.17, greater than 0.05. There was no significant difference in statistical results, and the colored medium had no significant effect on automatic counting. The counting effect of the instrument is poor when there are needle shaped colonies, the color of colonies is close to that of the culture medium, the contour of colonies is not obvious, the colonies spread greatly and the edges of colonies are irregular, there are food particles and colonies in the culture medium at the same time, or the color of colonies is close to that of food particles, which can not meet the accuracy requirements. Conclusion: For samples with uniform texture, the accuracy and precision of automatic colony counting are relatively good, the work efficiency is high, the operation time of experimental personnel is saved, and the original experimental data and images can be stored in the instrument for a long time. It is a counting method worthy of popularization in the laboratory. However, for the samples and culture medium with interference in the test verification, appropriate measures can be taken to change the counting conditions and manually correct the counting results of the instrument, but the counting efficiency will be reduced, and the laboratory can choose to use it according to the situation.
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