Microbial contamination is the main factor affecting product quality in the production and processing of dairy products. If the residue on the equipment surface and pipe wall is not thoroughly cleaned, it will inevitably produce microbial contamination and cause product deterioration. Cleaning in Place (CIP) is an indispensable program in the production process of dairy products. CIP, also known as cleaning positioning or positioning cleaning, is a technology that thoroughly cleans all equipment or pipelines in the factory without the need to disassemble equipment, pipelines, and valves. It is widely used in food and beverage production lines with high mechanization, such as beverages, dairy products, juice, jam, and alcohol. The principle is to use composite alkaline cleaning agents and composite acidic cleaning agents to remove dirt on the surface of objects, and use chemical cleaning agents to chemically transform, dissolve, and peel off pollutants to achieve the purpose of degreasing, rust removal, and decontamination. The conventional CIP cleaning procedure is water washing → alkali washing → water washing → acid washing → water washing, which takes a long cleaning time, has low production technology efficiency, and has high energy consumption and pollutant discharge pressure.
The following measures can be taken to improve the conventional CIP cleaning system for dairy production using acid free cold disinfection technology.
(1) Using acid free cleaning instead of conventional CIP cleaning, the improved cleaning procedure is water washing → alkali washing → water washing. Based on the production scale and the use of cleaning solution, single batch use of CIP system, reusable CIP system, and multiple use CIP system are selected to reduce production costs and reduce wastewater treatment pressure.
(2) Use cold disinfection instead of hot disinfection during the cleaning process. Cold disinfection is a safe and efficient sterilization method that does not increase or limit the temperature of food during the sterilization process.
It not only helps to maintain the physiological activity of food functional components, but also helps to maintain color, aroma, taste, and nutritional components. Cold disinfection is effective for all microorganisms, and after dilution, it is generally non-toxic and not affected by water hardness. It forms a thin film on the surface of the equipment, making the concentration easy to measure and measure, thus achieving energy-saving and efficiency enhancing effects.
1.1 Acid free cleaning and enhanced cleaning
Start the acid free cleaning program, first perform a 7-day acid free cleaning program on all equipment except for the sterilizer and sterile tank. To achieve the cleaning purpose, acid and alkali cleaning can be carried out on the 8th day, which is equivalent to a strengthened cleaning. Then recycle and use single alkali cleaning. After each cleaning, the effect is verified, microbial application experiments are conducted, and the pH of the pipe wall is measured.
The concentration of the disinfectant used is 0.13%~0.26%. All equipment to be disinfected should strictly follow a continuous week of cold disinfection, followed by another hot disinfection. After each execution, it must be verified by ATP application testing, and microbial residues meet the requirements before proceeding with the next production process. The cleaning standards should follow the following two points. (1) Odor. Fresh and odorless, allowing for slight odors during special processing or stages without affecting the safety and quality of the final product. (2) Visual. Clean the surface with a bright surface and no accumulated water, film, dirt or other impurities.
After CIP treatment, the production and processing capacity of the equipment has significantly changed, and the hygienic indicators and microbiological indicators have met the relevant requirements, which cannot lead to the improvement of other hygienic indicators of the product.
2.1 Determination of alkali residue caused by incomplete water passing
Drop a few drops of indicator (phenolphthalein indicator) on the surface of the equipment. If the solution turns pink, it indicates that there is residual alkali on the equipment, and the equipment is not thoroughly watered after alkaline washing.
Drop a few drops of phosphoric acid solution onto the dirt on the equipment. If bubbles are released, it indicates that the dirt is carbonate water with high hardness; After 2-3 minutes, rinse with water. If the dirt is removed, it indicates that the dirt is alkaline. The equipment needs to be cleaned and neutralized with acidic products.
2.3 Determination of protein membrane
Drop a few drops of colorant onto the dirt on the surface of the equipment, let it stand for 1-2 minutes, thoroughly rinse with a washing solution (a 1:1 mixture of acetic acid and ethanol), and gently rinse with drinking water. If there is a blue layer present, it indicates that the dirt is protein based. Clean with a chlor alkaline cleaning agent.
Residual analysis after CIP cleaning
3.1 Determination of acidic dirtDrop a few drops of 30% Na OH onto the dirt on the surface of the equipment, rinse with water after 2-3 minutes. If the dirt can be removed, it indicates that the dirt is acidic, and the equipment can be cleaned with alkaline products.
Place 2-3 particles of iron reagent on the pre wetted surface, wet the particles with water, and let them stand for 1-2 minutes. If the surface contains iron or/or magnesium, the particles will turn orange and should be removed when washing the dirt layer.
If there is a white and greasy feeling on the surface and water droplets hang on the surface, the dirt layer is likely to be fat scale. Use a clean cloth containing a wetting agent to scrub the surface area, and then rinse with water. If the greasy feeling and water droplets hang on the surface decrease, it indicates that the dirt layer is fat scale.
Based on the nature of the dirt and ATP application verification, if the total number of bacterial colonies is ≥ 150 CFU · m L-1, it is considered unqualified and needs to be cleaned again.
Raw milk with high protein and fat content produces ultra-high temperature sterilized milk. The residual milk scale on the surface of the UHT section inner tube is hard. Element analysis shows that the milk scale is a composite structure mainly composed of inorganic substances, and the alkali in traditional cleaning processes cannot play a targeted role. Optimize the cleaning process by adjusting the acid cleaning frequency of the UHT pretreatment section and the cleaning concentration, cleaning time, and cleaning temperature of the UHT section to change the physical state of the dirt, accelerate the chemical reaction speed, and increase the solubility of the dirt, facilitating the detachment of impurity solutions during cleaning, thereby improving the cleaning effect and shortening the cleaning time.
By optimizing the cleaning process and standardizing the CIP cleaning operations of each section of the workshop production line, the cleaning is carried out according to certain requirements, procedures, and quality to achieve the predetermined goals. All tools, pipelines, and equipment that come into contact with materials are fully cleaned, without any dead corners or pollution sources. And it has reduced the discharge of chemical substances and waste liquid in the cleaning agent, shortened the cleaning time, improved the utilization rate of factory equipment, and achieved the goals of water conservation and energy conservation and emission reduction.
