Stone Grinding Method in Pulse (Dal) Milling

Pulse milling, commonly known as dal milling, is a vital process in preparing pulses for consumption. It involves three major steps: loosening the husk, dehusking, and splitting the pulses. These steps help transform raw pulses into edible dal, enhancing their cooking properties and digestibility. Among the various milling methods developed over time, one of the oldest and most traditional is stone grinding.

Stone grinding uses two circular stone surfaces—one stationary and one rotating—to crush and split the pulses. The gap between the stones is carefully adjusted based on the type of pulse being processed. This traditional technique is simple yet effective, relying on friction to gradually separate the husk and split the grain. Although modern mechanized mills have largely replaced stone grinders, this method remains in use in rural areas and small-scale operations where affordability and tradition are key factors.

The advantages of stone grinding are noteworthy. It is cost-effective, making it suitable for small or community-level production without the need for expensive machinery. The slow speed of the grinding process helps preserve nutrients, as there is less heat generation compared to high-speed mechanical mills. Additionally, operators can manually adjust the process to achieve a customized texture, producing dal that retains a natural flavor and coarser grain preferred by many consumers.

However, the method also presents several drawbacks. It is labor-intensive, requiring constant attention and physical effort to operate. The process can be messy, as ground material often spreads around the grinding area, increasing post-processing cleanup. Moreover, fine stone particles may mix with the dal if not carefully monitored, necessitating thorough cleaning before packaging or cooking.

Despite these limitations, stone grinding remains a valued technique for its simplicity, affordability, and ability to produce high-quality, traditional dal.
Stone Grinding Method in Pulse (Dal) Milling

Dal Milling Process: Steps from Whole Pulses to Edible Dal

Milling is the process of removing the husk and splitting whole lentils to produce edible dal. The effectiveness of this process directly influences the final product’s quality. Dal milling involves several stages designed to clean, treat, and process pulses to enhance digestibility and reduce cooking time.

1. Cleaning and Grading
Initially, lentils are cleaned to remove impurities like stones, dust, and other foreign matter, using sieves and air classifiers. They are then sorted by size.

2. Pitting
Cleaned pulses are passed through emery rollers that crack or scratch the husk—a process called pitting. This step helps loosen the husk and allows better absorption of oil and moisture during further treatment.

3. Pretreatment
Pitted pulses are lightly coated with edible oil, such as linseed oil, which aids in loosening the husk even further.

4. Conditioning
The oil-treated pulses undergo alternating wetting and drying—often sun-dried for a few days—to adjust moisture levels and prepare them for dehusking.

5. Dehusking and Splitting
Using emery roller machines (gota), husks are removed, and the pulses are split in half. Multiple passes are usually required to achieve complete dehusking.

6. Polishing
To enhance visual appeal, split dal may be polished using oil, water, or other methods like nylon, leather, or velvet polishing. Although it adds market value, polishing is not considered nutritionally beneficial.

7. Separation and Grading
Finally, the milled dal is sorted using sieves to separate whole dal, broken pieces, and husk, ensuring a uniform end product.
Dal Milling Process: Steps from Whole Pulses to Edible Dal