As a leading food processing consultant and food industry consultant, PMG Engineering supports clients in designing and optimizing dairy processing plants for products like Dahi (curd). This article explores industrial and traditional methods of Dahi production, quality and packaging standards, and best practices to enhance shelf life while maintaining product safety.
What is Dahi?
Dahi, also known as curd, is a semi-solid fermented dairy product made by inoculating heat-treated milk with lactic acid bacteria. These probiotic cultures ferment milk sugars (lactose) to produce lactic acid, acetic acid, and volatile compounds like diacetyl, which contributes to the characteristic aroma and flavor of Dahi. A balanced combination of acid-producing and flavor-producing microorganisms is critical for achieving a firm texture and pleasant taste.
Composition Standards of Dahi
According to food consultancy services and food regulatory bodies:
- Fat and SNF (Solids-Not-Fat) content must match the source milk (buffalo, cow, etc.)
- Additional cane sugar may be added
- If no milk source is specified, buffalo milk standards apply
Methods of Dahi Preparation
1. Traditional Method
- Milk is boiled for 5–10 minutes and cooled to room temperature.
- Cooled milk is mixed with previous-day Dahi or buttermilk.
- The mixture is left undisturbed overnight for fermentation.
- Natural concentration of milk solids gives Dahi a custard-like consistency and prevents whey separation.
2. Industrial Method
As part of food manufacturing consultancy, the industrial production of Dahi involves precise steps to ensure hygiene, consistency, and scale:
a. Raw Material Selection
High-quality milk is selected based on microbial, physical, and chemical parameters.
b. Filtration/Clarification
Milk is heated to 35–40°C and filtered to remove foreign particles, improving clarity and purity.
c. Standardization
- Fat content: 0–5%
- SNF: 11–13% (enhanced with skim milk powder or condensed milk)
- This enhances protein and calcium content, resulting in a smooth texture and longer shelf life.
d. Homogenization
Performed at 175 kg/cm² to prevent cream separation and ensure uniformity.
e. Heat Treatment
Milk is heated at 90°C for 23 minutes:
- Coagulates proteins for better texture
- Destroys competitive microbes
- Enhances starter culture performance
f. Inoculation and Fermentation
- Milk is cooled to 37°C
- Starter culture (1–1.5%) is added
- The mix is poured into sealed food-grade cups (100g, 200g, 400g)
- Incubation occurs at 37–42°C until pH reaches 4.4–4.5
- Rapid cooling to <5°C follows
g. Storage
Dahi is stored at 4–5°C. Hygienic cold chain practices are vital to prevent contamination and maintain product integrity.
Packaging Solutions for Dahi
Through expert food technology consulting, modern dairies use polystyrene or polypropylene containers with automated filling and sealing machines (up to 400 cups/min). Cold storage logistics are essential to preserve quality.
Common Defects in Dahi
Even with robust systems, issues can arise:
- Souring due to over-acidification
- Yeast and mold growth due to contamination
- Whey separation caused by low SNF or improper fermentation
- Texture inconsistency in domestic (undefined cultures) vs. industrial (defined cultures) production
Conclusion
Dahi is a cornerstone of Indian fermented dairy products. Food consultants and dairy plant design experts emphasizes the importance of process standardization, starter culture control, and optimized packaging to ensure consistent quality in commercial Dahi manufacturing.
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