Traditional and Mechanized Methods for Making Rabri

Rabri is one of India’s most cherished traditional dairy desserts – a rich, sweetened, concentrated milk product defined by its characteristic layers of malai (clotted cream). For centuries, it has been prepared by halwais (traditional sweet-makers) using a slow, hands-on process. But as consumer demand grows and food safety expectations rise, the dairy industry has developed mechanized methods to produce rabri at commercial scale. Let’s explore both the traditional and mechanized approaches to making this iconic sweet.

What exactly is rabri? 🔗

Rabri is a heat-desiccated, sweetened whole milk product with visible layers of clotted cream mixed into concentrated, sweetened milk. It differs from other milk-based sweets like khoa because it retains a semi-liquid consistency and those distinctive flaky cream layers that give it a unique mouthfeel. The product is widely consumed across North and East India, either as a standalone dessert or as an accompaniment to jalebi, malpua, gulab jamun, and other sweets.

Buffalo milk is the preferred raw material for rabri preparation because its higher fat content (typically 6-7%) helps form thicker, more prominent malai layers. The fat content directly influences the richness and textural quality of the final product. The other key ingredients include sugar (added at about 5-6% of the milk volume), cardamom for flavouring, and dry fruits such as almonds, pistachios, and cashews for garnishing.

The traditional method of rabri preparation 🔗

The traditional process is deeply rooted in the practices of Indian halwais and remains the gold standard for flavour and texture, even though it has significant limitations for commercial production.

Step-by-step traditional process 🔗

The process begins with whole buffalo milk being taken in a wide, shallow, heavy-bottomed karahi (a type of open pan). The broad surface area of the karahi is important – it maximises the milk-air interface, which promotes the formation of the cream skin on the surface.

The milk is heated slowly at a simmering temperature, kept just below boiling point. This is critical: the milk must not be allowed to boil vigorously, because gentle heat is what allows a thin film of clotted cream (malai) to form undisturbed on the surface. As each layer of malai forms, the halwai carefully lifts it with a fork or ladle and places it on the cooler side of the karahi. This cycle of skin formation and removal is repeated continuously over several hours.

During this extended simmering, the milk gradually loses moisture through evaporation and becomes concentrated – typically to about 3 to 4 times its original concentration. Once the milk volume has reduced substantially, sugar at around 5-6% of the original milk volume is stirred into the concentrated milk. Finally, all the malai that was collected on the sides of the karahi is gently broken into smaller pieces and mixed back into the sweetened concentrated milk. Cardamom and chopped dry fruits are added at this stage.

Limitations of the traditional method 🔗

While the traditional approach produces rabri with exceptional flavour complexity, it has several drawbacks that make it unsuitable for large-scale commercial production:

Labour and time intensity: The process demands constant attention from a skilled person for several hours. Maintaining the right temperature and timing the cream layer collection requires experience and cannot be easily delegated.

Scale limitations: It is difficult to produce large, consistent batches. Each karahi can only handle a limited volume of milk, and increasing the quantity proportionally increases cooking time.

Hygiene concerns: Traditional rabri is often prepared in open environments and stored in shallow, uncovered containers. This exposes the product to contamination from dust, insects, and microorganisms, making it particularly vulnerable to microbial spoilage.

Seasonal inconsistency: During summer, when milk costs more and spoilage risk is higher, many halwais avoid making rabri altogether, leading to supply shortages and inflated prices.

Flavour variability: Because the process relies heavily on the skill of the individual maker, there is batch-to-batch variation in flavour, colour, and texture. While some view this as a positive quality, it poses a challenge for branded commercial products that need uniform quality.

The improved (semi-mechanized) method 🔗

To address some of the hygiene and consistency issues, dairy scientists have developed an improved version of the traditional method. This approach retains the fundamental steps of the traditional process but introduces key upgrades.

The most important change is the use of steam-jacketed vessels instead of direct-fire heating. Steam heating provides much better temperature control and eliminates the risk of smoky or burnt flavour defects that are common when milk is heated over open flames. The indirect heating through a steam jacket prevents direct contact between the heat source and the milk, reducing the chances of scorching.

In this improved process, milk is first standardised for fat and solids-not-fat content to ensure a consistent starting point. It is then heated in the steam-jacketed vessel, and the malai collection procedure follows the same principles as the traditional method. Sugar, cardamom, and dry fruits are added at the appropriate stages.

The key difference comes after manufacturing. The product is immediately chilled and packaged under hygienic conditions. This step is crucial because it sharply reduces post-manufacturing contamination – one of the biggest weaknesses of the traditional method. The improved method strikes a balance between preserving the authentic character of rabri and meeting modern food safety expectations.

The mechanized (large-scale) method 🔗

For true industrial-scale production, a fully mechanized approach has been developed that uses specialised dairy processing equipment. This method represents a significant departure from traditional techniques but aims to produce a product that closely resembles conventionally made rabri.

Role of the scraped surface heat exchanger (SSHE) 🔗

The core piece of equipment in mechanized rabri production is the scraped surface heat exchanger (SSHE), which is widely used in the dairy industry for the continuous manufacture of concentrated milk products like khoa. The SSHE works by passing milk through a heated cylindrical chamber where rotating scraper blades continuously remove product from the inner walls. This prevents fouling and ensures uniform heat transfer throughout the product.

In the mechanized rabri process, the SSHE is used for pre-concentrating the milk. Research conducted at the ICAR-National Dairy Research Institute in Karnal has shown that integrating an SSHE with a conical process vat (CPV) allows for efficient in-line rabri production. The optimised parameters from this research indicate that milk should be initially concentrated to approximately 30% total solids in the SSHE, followed by further concentration to 40% total solids in the CPV before sugar is added.

Replicating the malai texture 🔗

One of the biggest challenges in mechanized production is reproducing the characteristic flaky malai layers that define authentic rabri. Two approaches have been explored:

Separate malai preparation: In one method, buffalo milk is simmered in an open kettle to prepare malai separately, which is then added to the mechanically concentrated sweetened milk at a controlled ratio. Research has established an optimal clotted cream layer to sweetened concentrated milk (CCL:SCM) ratio of about 0.167 for the best sensory results.

Chhana/paneer substitution: In another approach, the flaky texture is simulated by incorporating shredded chhana or paneer into the concentrated milk. These coagulated milk products have a fibrous, flaky structure that can mimic the mouthfeel of traditional malai layers. While this is a practical solution for large-scale operations, sensory evaluations have shown that this method still needs refinement to fully match the taste and texture of traditionally prepared rabri.

Sugar and flavouring addition 🔗

In mechanized production, sugar is typically added at around 12% of the product weight once the milk has reached the target concentration. The mixture is then cooled to approximately 70°C before malai is incorporated. Cardamom and dry fruits are added at precisely timed stages. The ability to control the timing and temperature of these additions is a major advantage of the mechanized approach – it helps ensure consistent flavour across every batch.

Quality control and hygiene advantages 🔗

Mechanized production offers substantial improvements in food safety and quality assurance. The entire process takes place in a closed, controlled environment with regulated temperature, humidity, and air quality. Equipment is designed from food-grade stainless steel that is easy to clean and sanitise, meeting FSSAI food safety standards.

Every step of the process can be monitored, recorded, and traced – something that is simply not possible with traditional preparation. This traceability is increasingly important for commercial dairy products, as consumers demand greater transparency about how their food is made.

Packaging and shelf life 🔗

Traditionally prepared rabri has a very short shelf life – often just a day or two at room temperature – because of its high moisture content and exposure to environmental contaminants. Mechanized production addresses this through modern packaging technologies.

Research published in the Journal of Food Science and Technology has explored the use of modified atmosphere packaging (MAP) for extending rabri’s shelf life. In this technique, rabri samples are packed in polyethylene bags filled with specific gas compositions – such as a mixture of carbon dioxide and nitrogen, or pure nitrogen – and stored under refrigeration at 10°C. Samples packed with 100% nitrogen showed significantly better stability compared to those stored in regular air, with slower rates of chemical deterioration and microbial growth.

Vacuum packaging is another option being used commercially. By removing air from the package, oxidation and microbial activity are slowed considerably. These packaging technologies allow mechanized rabri to be distributed across much wider geographical areas, bringing the product to consumers in regions where freshly prepared rabri may not be available.

As per FSSAI packaging regulations, all commercially packaged rabri must use food-grade primary packaging materials, carry clear labelling with manufacturing date, best-before date, and storage instructions, and meet specified compositional standards.

Chemical composition of rabri 🔗

The composition of rabri varies depending on the type of milk used, the degree of concentration, sugar quantity, and the manufacturing method. However, a typical composition profile includes roughly 20-30% moisture, 20-25% fat, 15-20% sugar, 10-12% protein, and smaller percentages of minerals and other milk solids. The product must conform to the compositional standards set by FSSAI, and it should be free from adulterants like starch and blotting paper – a historically common form of adulteration in market-sold rabri.

Traditional vs. mechanized: how do they compare? 🔗

The comparison between these two approaches ultimately comes down to a trade-off between authenticity and scalability.

Traditional preparation often produces a more complex flavour profile. The natural variations in heating, the slow Maillard browning reactions, and the hands-on management of cream layers contribute to subtle flavour nuances that are difficult to replicate mechanically. Many consumers and connoisseurs still prefer rabri from experienced halwais for this reason.

Mechanized production, on the other hand, excels in consistency, hygiene, volume, and shelf life. Every batch tastes the same, the product meets food safety standards, it can be manufactured in large quantities, and it can be shipped to distant markets. For branded dairy companies looking to offer rabri as a packaged product, mechanization is essential.

A growing middle ground is emerging where artisanal producers adopt modern hygiene and storage practices while maintaining traditional preparation techniques. This hybrid approach aims to preserve the authentic taste while ensuring the product is safe for commercial distribution.

Future directions in rabri production 🔗

Research in rabri production continues to evolve. Current areas of focus include developing dietetic or low-calorie variants using sugar substitutes like aspartame and prebiotic ingredients like inulin. Scientists are also working on improving the sensory quality of mechanized rabri to more closely match its traditional counterpart. The integration of advanced technologies – such as response surface methodology for process optimisation – is helping fine-tune parameters for the best possible product quality.

There is also growing interest in standardising rabri production at the village level using small-scale steam-jacketed pans that provide the benefits of controlled heating without requiring full factory infrastructure. This could help small dairy entrepreneurs produce safer, better-quality rabri without losing the artisanal character that consumers value.

What do you think? As packaged, mechanized rabri becomes more widely available, do you believe it can ever match the depth of flavour found in traditionally prepared rabri? And how important is it for India’s dairy industry to preserve the artisanal knowledge of halwais even as it scales up production?

References

1. http://ecoursesonline.iasri.res.in/mod/page/view.php?id=148063
2. http://dairy-technology.blogspot.com/2014/01/preparation-of-rabri.html
3. https://pubmed.ncbi.nlm.nih.gov/25745264/
4. https://arccjournals.com/journal/asian-journal-of-dairy-and-food-research/DR-887
5. https://www.dairyprocessing.com/articles/2055-flexibility-with-scraped-surface-heat-exchangers
6. https://fssai.gov.in/upload/uploadfiles/files/Compendium_Packaging_Labelling_Regulations_05_06_2022.pdf
7. https://fssai.gov.in/upload/uploadfiles/files/Compendium_Packaging_Labelling_Regulations_04_08_2021.pdf