The production lines for pasteurized milk and yogurt have partial overlap in process flow, but there are also key differences. The following is the two production line process and key points of analysis:
pasteurized milk production line process
Raw milk acceptance
Detect the fat content of milk, protein, microbial indicators (such as total colony count, somatic cell count), antibiotic residues, etc., to ensure compliance with national standards.
Filtration and Cooling
Remove impurities through multi-stage filtration (e.g. 100 mesh screen), and rapidly cool to below 4℃ to inhibit bacterial reproduction.
Pre-treatment (standardization)
Adjust the fat content (e.g. whole milk, low-fat milk) and standardize the ingredients by centrifugal separation and mixing.
Pasteurization
- Core equipment: Plate heat exchanger
- Process parameters: 72-85°C/15-30 seconds (commonly used HTST: High Temperature Short Time Sterilization), killing pathogenic bacteria while retaining some beneficial bacteria and flavor.
Homogenization
Pressure 15-25MPa, break the fat balls to prevent the cream from layering and improve the taste.
Cooling and storage
After sterilization, the product is quickly cooled down to 4℃ and put into the buffer tank to wait for filling.
Filling and Packaging
- Equipment type: aseptic filling machine (roof box, glass bottle) or common filling line (plastic bag).
- Key points: avoid secondary contamination, packaging materials need to be pre-sterilized.
Refrigerated Storage
Finished products are stored in 2-6℃ cold storage, shelf life is usually 7-15 days.
Yogurt production line process
Raw Milk Processing
Similar to pasteurized milk, but may require higher protein content (can be adjusted by evaporation or addition of whey protein).
Standardization and homogenization
Adjust fat/non-fat milk solids ratio, homogenization parameters similar to milk.
Heat treatment (higher intensity sterilization)
Process: 90-95°C/5-10 minutes to completely kill stray bacteria and provide a pure environment for fermentation strains.
Cooling and Inoculation
Cool to 40-45°C, add fermentation agent (e.g. Lactobacillus bulgaricus + Streptococcus thermophilus).
Fermentation
- Equipment: Fermenter (with temperature control system).
- Conditions: 42-43°C/4-6 hours, terminate fermentation when acidity reaches 70-80°T.
Breaking curd and flavoring (for stirred yogurt)
Stirring and breaking curd, adding jam, sugar and other auxiliary ingredients, need to be operated under aseptic environment.
Filling
Filling and fermentation of curdled yogurt (e.g. old yogurt) directly; fermentation of stirred yogurt followed by filling.
Ripening and Refrigeration
Refrigerate at 2-6℃ for 12-24 hours to promote the formation of flavor substances, with a shelf life of about 21 days.
the key differences and equipment comparison
| Session | Pasteurized milk | Yogurt |
| Sterilization intensity | 72-85 ℃ / 15-30 seconds (retaining some microorganisms) | 90-95 ℃ / 5-10 minutes (complete sterilization) |
| Core equipment | Plate sterilizer, homogenizer | Fermenter, aseptic mixing system, fruit adders |
| Process focus | Retaining fresh milk flavor, rapid cooling | Precise temperature-controlled fermentation, preventing contamination by stray bacteria |
| Packaging requirements | Cold chain preservation | Cold chain preservation is also required, but the sealing requirement is higher |
the main points of production line design
- Hygiene standards: CIP (cleaning in place) and SIP (steam sterilization) system, in line with GMP/HACCP specifications.
- Automation: PLC control system, real-time monitoring of temperature, pH (yogurt) and other parameters.
- Flexibility: part of the equipment can be shared (e.g. filtration, homogenization), but the fermentation section needs to be designed independently.
- Capacity matching: yogurt fermentation time is long, need to plan enough fermentation tank capacity to balance the production rhythm.
Extended Knowledge
Pasteurized milk vs. room temperature milk: pasteurized milk needs refrigeration and has a short shelf life; room temperature milk is sterilized by UHT (135℃/2-4 seconds) and can be stored at room temperature.
Yogurt types: stirred (such as flavored yogurt), solidified (such as traditional cup yogurt), drinking (homogenized after fermentation), etc., with slightly different processes.
By rationally designing the production line, enterprises can simultaneously layout pasteurized milk and yogurt products, share pre-treatment equipment and reduce investment costs, but need to pay attention to the independent control of key links.