Methods and Benefits of Puffing Pulses

Puffing is one of the oldest and most practical methods of transforming raw pulses into ready-to-eat snack foods. Roasting or puffing of legumes by subjecting them to high temperatures for a short time has been practised across Asia, the Middle East, and South America for centuries. Today, the same principle drives a multi-crore snack food industry, where Bengal gram (chickpea) and peas are converted into light, crispy, protein-rich snacks through a carefully controlled sequence of soaking, roasting, and dehusking. Understanding how this process works – and why it works so well – is essential for anyone studying pulse processing.

What is pulse puffing? 🔗

Bengal gram (Cicer arietinum L.) is one of the longest-cultivated pulses known in Asia and Europe, and accounts for nearly 40% of Indian pulse production. Along with peas, it is among the most suitable pulses for puffing – a thermal processing technique that converts dense, hard legumes into expanded, lightweight, and porous grains. Puffing is one of the primary processing methods practised for many years in the Indian subcontinent, producing snack foods that are cheap, nutritious, and widely consumed across all demographics.

Puffed legumes are among the most affordable and popular foods for the common person, with puffing effected by manual or mechanical roasting of conditioned legumes in hot sand. The resulting increase in size is 1.5 to 2 times the original grain size.

The traditional puffing process 🔗

The traditional method follows a precise sequence of steps. Each step serves a specific function, and deviating from any one of them affects the quality of the final product.

Step 1: Soaking 🔗

The process begins with a brief soaking of chickpeas or peas in water for 15 to 20 minutes, followed by draining. This is not the extended overnight soaking used for cooking; rather, it is a controlled moisture addition. After draining, the wet grains are kept in a closed vessel to allow moisture to equilibrate uniformly within the grain. This equilibration step is critical – it ensures that the moisture is distributed evenly inside the kernel, not just on the surface.

Step 2: Roasting with heated sand 🔗

The moisture-conditioned grains are then roasted in a hot iron vessel containing sand at 190-200°C for 60 to 80 seconds. The sand acts as a heat-transfer medium, providing uniform and rapid heat contact with every grain surface. During the roasting process, the moisture inside the chickpea changes from liquid into vapour, and the grain expands – likely due to the steam pressure pushing on the compact internal structure of the grain. Because most starch granules do not gelatinize during roasting, the amount of water is considered the major factor in swelling.

For puffing to succeed, the temperature just before expansion must be high enough to generate sufficient water vapour pressure without burning the outer pericarp. The rate of temperature increase must also be fast enough to build the required pressure before the water simply evaporates. Kernels that are too dry often puff only feebly, which is why moisture content has a pronounced effect on popping behaviour.

In the traditional Indian snack industry, roasted chana (phutana) is prepared by puffing chickpea seeds in hot sand maintained at 200 to 300°C, with temperature variation depending on the specific product style and regional practice.

Step 3: Dehusking 🔗

As the grains puff, the husk splits and loosens naturally. The grains then undergo dehusking to remove the outer skin and reveal the porous, expanded interior. This step refines the final product’s texture and eating quality. Dehusking is an essential component of pulse processing that enhances the digestibility of essential nutrients in the grain. Without this step, the residual husk would result in a coarser, less palatable texture in the finished product.

The commercial puffing process 🔗

While the traditional method works well at the household or small-scale level, commercial production requires consistency, food safety compliance, and the ability to process large volumes efficiently. The commercial process upgrades each stage of the traditional method using mechanised equipment.

Heated revolving drums 🔗

In commercial units, the hot sand and iron vessel are replaced by heated revolving drums. These drums maintain precise temperature control while the continuous rotation ensures even heat distribution across all grains. The movement prevents hot spots and guarantees that every grain in the batch receives the same heat treatment, resulting in uniform puffing throughout. This is a significant improvement over traditional hand-stirring, where heat application can be uneven.

Mechanical dehusking 🔗

Following puffing, mechanical dehusking systems efficiently remove the outer husk from the expanded grains. These machines use controlled air currents, vibration, or friction to separate the lighter, loosened husks from the puffed grains. Mechanical dehusking offers higher throughput, better consistency, and significantly lower labour costs compared to manual methods. The systems are calibrated to remove the husk cleanly while minimising breakage of the delicate puffed grains – an important consideration for maintaining product weight and appearance.

Output and yield 🔗

The commercial process yields a product that is 1.5 to 2 times the size of the original raw grain. This expansion ratio is not just a measure of physical change – it directly affects packaging volume, product presentation, and consumer perception of value. Puffed chickpeas possess many desirable sensory attributes to meet the demand for healthy snacks, and the global snack food market for such products is expanding rapidly.

Why puffing works: the science behind expansion 🔗

The expansion during puffing is a result of rapid phase change – liquid water inside the grain converts to steam almost instantaneously when subjected to intense heat. This steam generates internal pressure that forces the grain to expand. The porous structure that forms when this steam escapes is what gives puffed pulses their characteristic light, airy texture.

The grain’s internal starch and protein matrix sets around this expanded structure as the surface temperature stabilises, locking in the porous form. Studies have revealed that substantial structural changes occur during processing – the raw chickpea is tightly packed with no air pockets, while a large number of air pockets form in the cotyledon after roasting.

Nutritional value of puffed pulses 🔗

A key advantage of the puffing method is that the nutritional quality of the pulse is largely preserved. Research on puffed Bengal gram and garbanzo snacks shows that the protein content remains at 21-22%, and the mineral content of the puffed product is around 3%. Critically, the protein content was not damaged by either the air fryer or infrared puffing methods tested.

The pulse proteins are rich in lysine and have low sulphur-containing amino acids, making them particularly valuable in preventing malnutrition among vegetarian children, nursing mothers, and older adults. Since puffing uses no oil – unlike deep frying – the process produces a low-fat, high-protein snack, which is a distinct nutritional advantage over most commercial snack alternatives.

Additionally, the heat treatment involved in puffing helps reduce some antinutritional factors naturally present in raw pulses, such as tannins and certain enzyme inhibitors, improving the overall digestibility of the snack. Processing techniques applied to chickpeas have long been recognised as essential for better digestibility and enhanced nutritive value, and puffing fits well within that framework.

Product characteristics and applications 🔗

Puffed pulses are classed as value-added products in food processing. Their primary characteristics – light weight, porous texture, expanded size, and extended shelf life – make them suitable for a range of food applications beyond direct consumption as snacks.

Common uses include:

• Ready-to-eat snacks – sold plain or coated with spices, salt, and flavourings. Puffed chickpeas are commonly coated with suitable spices and sold in various markets across India.
• Breakfast food ingredients – incorporated into ready-to-eat breakfast mixes and trail mixes.
• Confectionery and snack formulations – used as a crunchy ingredient in combination products. Puffed pulses have found popularity as ingredients in ready-to-eat breakfast foods, confectionery, and snack formulations.
• Nutrition supplements for children – traditionally, parched Bengal gram has been used in the treatment of protein-calorie malnutrition in children.

The low water activity of puffed pulses (the moisture available for microbial growth is minimal after puffing) also contributes to a longer shelf life compared to raw or boiled pulses, making them suitable for packaging and distribution.

Factors that affect puffing quality 🔗

Not all pulse varieties or batches puff equally well. Several factors determine the final quality of the puffed product:

Moisture content of the grain is the single most important variable. Too little moisture means insufficient steam pressure, resulting in poor or incomplete expansion. Too much moisture can cause the grain to become soft and sticky rather than crispy. The brief soaking and equilibration step in the traditional method is specifically designed to hit the right moisture window.

Variety selection also plays a major role. Research from the Grains Research and Development Corporation (GRDC) in Australia confirms that understanding which seed attributes are important for puffing is key to opening new market avenues for chickpeas. Bold-seeded desi cultivars of Bengal gram are generally preferred for puffing over kabuli types due to their seed coat characteristics.

Temperature and duration of roasting must be precisely managed. Overheating burns the pericarp; insufficient heat produces under-puffed, hard grains. In commercial operations, the revolving drum system handles this through automated temperature monitoring and controlled retention times.

What do you think? Given that puffing retains most of the protein content of raw pulses while producing an oil-free snack, do you think it could serve as a scalable solution for addressing protein-calorie malnutrition in developing regions? And as modern food technology introduces infrared and hot-air puffing methods alongside traditional sand-roasting, which approach do you think better balances nutritional retention, energy efficiency, and food safety for commercial-scale production?

References

1. https://www.usapulses.org/technical-manual/chapter-5-applications/applications
2. https://link.springer.com/article/10.1007/s42535-025-01188-z
3. https://www.grdc.com.au/resources-and-publications/grdc-update-papers/tab-content/grdc-update-papers/2013/02/improving-the-value-of-australian-pulses-through-puffing
4. http://ecoursesonline.iasri.res.in/pluginfile.php/154233/mod_resource/content/1/Lesson_16.htm
5. https://agritech.tnau.ac.in/postharvest/pht_pulses_valueaddtn.html
6. https://www.tourism.rajasthan.gov.in/content/dam/agriculture/Rajasthan%20Agricultural%20Competitiveness%20Project/Disclosure_of_Reports/Borrower_Completion_Report_BCR/Agribusiness/RACP_ABPF_Tech%20DPR_Roasted%20Chana.pdf
7. https://pmc.ncbi.nlm.nih.gov/articles/PMC4252399/
8. https://www.sciencedirect.com/science/article/abs/pii/S0023643817307934