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Curd Processing: From Traditional Methods to Industrial-Scale Production
Introduction: What is Curd (Dahi)?
Curd, or dahi, is a semi-solid fermented dairy product made by inoculating milk with lactic acid bacteria (LAB). These cultures ferment lactose into lactic acid, giving curd its:
- Tart flavor
- Improved digestibility
- Therapeutic benefits
The Indian curd market is booming, expected to grow from ₹1365.5 billion (2022) to ₹3175 billion (2028) at a CAGR of 15.1%. This surge is fueled by:
- Rising demand for packed curd
- Health-conscious consumers
- Busy lifestyles requiring convenient food options
Nutritional Highlights of Whole Milk Curd
According to FSSAI (2011), dahi from whole milk is:
- Rich in calcium, potassium, phosphorus, and magnesium
- A source of vitamin D, supporting bone health
- A natural probiotic, aiding gut health and digestion
Industrial Curd Processing: Step-by-Step
While traditional dahi is still widely prepared at home, modern dairy plants follow a structured, hygienic, and scalable process.
1. Milk Filtration & Clarification
- Removes extraneous matter and microbial load
- Performed at 30–40°C using clarifiers and bactofuge machines
2. Milk Standardization
- Adjusts fat and SNF content
- Ensures uniform texture, protein content, and nutrient retention
3. Homogenization
- Conducted at 60°C, 175 kg/cm²
- Improves texture and reduces cream separation
- Enhances incubation consistency
4. Pasteurization
- 90–95°C for 10–20 minutes
- Destroys pathogens and air-borne contaminants
- Releases nutrients essential for fermentation microbes
5. Inoculation & Incubation
- Milk cooled to 37°C
- LAB culture added (1–1.5%)
- Incubated at 37–42°C for 8–10 hrs
- Target pH: 4.4–4.5
6. Packaging
- Primary packaging types:
- Plastic pouches
- Cups/jars
- Earthen pots
- Materials used: LDPE, LLDPE, EVOH, MLLDPE, PVC
Packaging may occur before or after incubation, depending on the product type (e.g., set curd vs stirred yogurt).
7. Cooling & Storage
- Rapid chilling to 4–7°C
- Halts fermentation
- Maintains texture, shelf life, and microbial stability
Curd Cultures and Their Role
⚠️ Possible Defects in Curd
- Whey separation (syneresis)
- Bitter or sour off-flavors
- Slimy or grainy texture
- Gas formation / bloating in sealed cups
These issues are typically caused by:
- Poor temperature control
- Inadequate pasteurization
- Unbalanced culture ratios
- Contaminated equipment
A food consultant helps set up SOPs, QC tests, and culture validation to prevent defects and product recalls.
Packaging Innovations in the Curd Industry
- Portion control cups for on-the-go use
- Multi-compartment packs for flavored/stirred curds
- Use of eco-friendly materials and UV sterilized packaging lines
Conclusion: Modern Curd Processing Marries Tradition and Technology
From age-old fermentation to CIP-automated dairy plants, curd remains a staple with massive commercial potential. Modern curd processing ensures:
- Safe, standardized production
- High market appeal with clean packaging
- Growth opportunities in health-based, probiotic, and regional variants
A professional food manufacturing consultant helps:
- Design curd plants with flow-optimized layouts
- Source appropriate equipment and packaging
- Implement FSSAI, ISO, and HACCP-compliant processing systems
Frequently asked
What temperature and time do we hold for pasteurizing milk intended for curd?
For industrial curd (dahi) production, milk is pasteurized at 90–95°C for 10 to 20 minutes. This destroys pathogens and air-borne contaminants, and also releases nutrients essential for the fermentation microbes that follow. It is a more severe heat treatment than fluid milk pasteurization, and it is what makes the subsequent lactic acid bacteria fermentation predictable and safe.
What incubation conditions and end-point pH should a curd line target?
After pasteurization the milk is cooled to 37°C, inoculated with 1–1.5% lactic acid bacteria culture, and incubated at 37–42°C for 8–10 hours. The target end-point is pH 4.4–4.5. Once that pH is reached, the product is rapidly chilled to 4–7°C to halt fermentation and lock in texture, shelf life and microbial stability.
Why is homogenization needed for curd, and at what pressure?
Homogenization for curd is carried out at 60°C and 175 kg/cm². It improves the final texture of the dahi, reduces cream separation in the cup or pouch, and gives more consistent behaviour during incubation. Combined with standardization of fat and SNF, it is one of the key steps that delivers a uniform set and repeatable protein content batch to batch.
We keep getting whey separation and gas formation in sealed cups. What usually causes this?
Common curd defects include whey separation (syneresis), bitter or sour off-flavors, slimy or grainy texture, and gas formation or bloating in sealed cups. These are typically traced to poor temperature control, inadequate pasteurization, unbalanced culture ratios, or contaminated equipment. Correcting them means tightening SOPs, QC testing and culture validation rather than changing the recipe alone.
Should curd be packed before or after incubation?
Both routes are used in curd manufacturing, and the choice depends on the product. Set curd is typically filled before incubation so it sets undisturbed in its final pack, while stirred yogurt style products are incubated in bulk and packed afterwards. Primary packaging options include plastic pouches, cups or jars and earthen pots, using LDPE, LLDPE, EVOH, MLLDPE or PVC.
How is the milk prepared before fermentation in an industrial curd plant?
Industrial curd processing begins with filtration and clarification at 30–40°C using clarifiers and bactofuge machines to remove extraneous matter and reduce microbial load. The milk is then standardized to adjust fat and SNF content for uniform texture, protein content and nutrient retention, followed by homogenization at 60°C and 175 kg/cm², then pasteurization before inoculation.
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PMG Engineering. (2023). Curd Processing: From Traditional Methods to Industrial-Scale Production. PMG Engineering. https://pmg.engineering/Presentation/56/curd-processing-from-traditional-methods-to-industrial-scale-production/