HOME / ARTICLES / DAHI PROCESSING: METHODS, QUALITY PARAMETERS, PACKAGING, SHELF LIFE, AND COMMON DEFECTS

ARTICLES

Dahi Processing: Methods, Quality Parameters, Packaging, Shelf Life, and Common Defects

Q: What fat and SNF levels should we standardise milk to for industrial Dahi?

For industrial Dahi manufacture, milk is standardised to a fat content of 0–5% and SNF of 11–13%, with SNF typically enhanced using skim milk powder or condensed milk. Raising the solids level increases protein and calcium content, which gives a smoother texture and a longer shelf life. Composition standards also require that fat and SNF match the source milk, with buffalo milk standards applying when no source is specified.

Q: What are the key process parameters in industrial Dahi production?

Industrial Dahi production follows defined parameters: milk is heated to 35–40°C for filtration or clarification, standardised to 0–5% fat and 11–13% SNF, homogenised at 175 kg/cm², heat treated at 90°C for 23 minutes, cooled to 37°C, inoculated with 1–1.5% starter culture, incubated at 37–42°C until pH reaches 4.4–4.5, then rapidly cooled to below 5°C and stored at 4–5°C.

Q: Why is whey separating out of our cups of Dahi?

Whey separation in Dahi is caused by low SNF or improper fermentation. Standardising SNF to 11–13% using skim milk powder or condensed milk, and controlling incubation at 37–42°C until pH reaches 4.4–4.5 before rapid cooling to below 5°C, addresses the problem. In the traditional method, natural concentration of milk solids gives a custard-like consistency and prevents whey separation.

Q: What packaging and filling capacity is used for commercial Dahi?

Modern dairies pack Dahi in polystyrene or polypropylene containers, filled and sealed on automated machines rated up to 400 cups per minute. Cup sizes commonly used are 100g, 200g and 400g, with the standardised milk poured into sealed food-grade cups before incubation. Cold storage logistics are essential downstream, as Dahi must be held at 4–5°C to preserve quality.

Q: Why heat milk at 90°C for 23 minutes instead of standard pasteurisation before making Dahi?

Heat treatment of milk at 90°C for 23 minutes serves three purposes in Dahi manufacture: it coagulates milk proteins to give better body and texture, destroys microbes that would compete with the starter culture, and thereby enhances starter culture performance. The milk is then cooled to 37°C before 1–1.5% starter culture is added for fermentation.

Q: What defects should we design our Dahi line to prevent?

The common defects in Dahi are souring from over-acidification, yeast and mould growth from contamination, whey separation caused by low SNF or improper fermentation, and texture inconsistency, which arises where undefined cultures are used in domestic production compared with defined cultures in industrial production. Process standardisation, starter culture control, hygienic cold chain at 4–5°C, and optimised packaging control these risks.

By PMG Engineering · 13 Oct 2023

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.

Frequently asked

What fat and SNF levels should we standardise milk to for industrial Dahi?

For industrial Dahi manufacture, milk is standardised to a fat content of 0–5% and SNF of 11–13%, with SNF typically enhanced using skim milk powder or condensed milk. Raising the solids level increases protein and calcium content, which gives a smoother texture and a longer shelf life. Composition standards also require that fat and SNF match the source milk, with buffalo milk standards applying when no source is specified.

What are the key process parameters in industrial Dahi production?

Industrial Dahi production follows defined parameters: milk is heated to 35–40°C for filtration or clarification, standardised to 0–5% fat and 11–13% SNF, homogenised at 175 kg/cm², heat treated at 90°C for 23 minutes, cooled to 37°C, inoculated with 1–1.5% starter culture, incubated at 37–42°C until pH reaches 4.4–4.5, then rapidly cooled to below 5°C and stored at 4–5°C.

Why is whey separating out of our cups of Dahi?

Whey separation in Dahi is caused by low SNF or improper fermentation. Standardising SNF to 11–13% using skim milk powder or condensed milk, and controlling incubation at 37–42°C until pH reaches 4.4–4.5 before rapid cooling to below 5°C, addresses the problem. In the traditional method, natural concentration of milk solids gives a custard-like consistency and prevents whey separation.

What packaging and filling capacity is used for commercial Dahi?

Modern dairies pack Dahi in polystyrene or polypropylene containers, filled and sealed on automated machines rated up to 400 cups per minute. Cup sizes commonly used are 100g, 200g and 400g, with the standardised milk poured into sealed food-grade cups before incubation. Cold storage logistics are essential downstream, as Dahi must be held at 4–5°C to preserve quality.

Why heat milk at 90°C for 23 minutes instead of standard pasteurisation before making Dahi?

Heat treatment of milk at 90°C for 23 minutes serves three purposes in Dahi manufacture: it coagulates milk proteins to give better body and texture, destroys microbes that would compete with the starter culture, and thereby enhances starter culture performance. The milk is then cooled to 37°C before 1–1.5% starter culture is added for fermentation.

What defects should we design our Dahi line to prevent?

The common defects in Dahi are souring from over-acidification, yeast and mould growth from contamination, whey separation caused by low SNF or improper fermentation, and texture inconsistency, which arises where undefined cultures are used in domestic production compared with defined cultures in industrial production. Process standardisation, starter culture control, hygienic cold chain at 4–5°C, and optimised packaging control these risks.

CITE THIS

PMG Engineering. (2023). Dahi Processing: Methods, Quality Parameters, Packaging, Shelf Life, and Common Defects. PMG Engineering. https://pmg.engineering/Article/263/dahi-processing-methods-quality-parameters-packaging-shelf-life-and-common-defects/

https://pmg.engineering/Article/263/dahi-processing-methods-quality-parameters-packaging-shelf-life-and-common-defects/