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What is Paddy Parboiling Process?
Parboiling is a hydrothermal treatment process of soaking, steaming and drying of the paddy, which are performed before the milling operation.The two main ingredients used in the parboiling process are: Water and Heat. The primary purpose of the parboiling process is to 1. increase the final rice yield and 2. Reduce the breakage of the rice grain during the milling process.
Paddy undergoes various mechanical stages of harvesting, threshing, drying, dehulling and milling, which forces rice grains to crack under tension and increase the percentage of broken rice during final output. Consequently, broken rice brings market losses, price reduction, decreased product output from milling procedures, and storage issues.
Therefore, the parboiling process revolutionized the paddy production industry and became the breakthrough solution to deal with rice breakage. In summary, the hydro-method of parboiling causes the paddy to produce a gel-like substance inside the starch. This process is called gelatinization, where it heals all the fractures and also strengthens the rice grain which, in result, increases the total yield of the rice production during polishing. The gelatinization also de-localize the rice grain inside the husk which makes it easier to separate edible rice from its husks during the de-husking process.
In fact, though, the method of parboiling was developed with a preliminary objective of hardening the kernel to maximize head rice yield- it was later scientifically discovered the nutritional value and health benefits of consuming parboiled rice compared to raw rice which created the awareness and importance of parboiling among consumers and manufacturers worldwide, particularly in Asian countries and the estimated percentage of parboiled rice production in India is about staggering 60%, making them a most preferred rice type compared to non-parboiled rice.
Steps Involed In Parboiling Process
The parboiling process involves soaking, steaming and drying. The soaking increases the moisture content in the paddy and steaming causes gelatinization of starch and increases the grain strength.
There are various parboiling techniques for paddy. Here we will look at the basic steps involved in paddy processing.
Soaking Process
Once the paddy is cleaned and de-stoned, the initial parboiling process involves water soaking the paddy for a certain period of time. During the soaking stage, the water molecules penetrate through the micro-pores of husk and are absorbed by starch granules to become moisture hydrated and swell inside the husk, making it loose in the process.
At the same time, micro-toxins- which are naturally occurring unsafe residues, produced by certain fungi are entirely dismantled and wiped-out at such high levels of moisture content. This moisture saturation also activates enzymes in the paddy.
The moisture content of soaked paddy is about 30%-35%. The soaking duration can be minimized by maintaining a constant water temperature. Elevated temperature also reduces steaming time. Even steaming time can be cut-down by continuously recirculating and reheating of the water. Moisture content in the soaked paddy is about 30%-35%. For better soaking, paddy grain size should be uniform.
Steaming Process
After the soaked paddy drained from the container and then transferred to the steaming container. Steam is pressured between 0.5 – 3 bar depending on the paddy type. At this process, the moisture content in the grain gelatinizes the starch during the steaming process which causes physio-chemical reactions such as pigment transformations and enzymes deactivations. This brings improved flavor, color change and cooking characteristics of the rice.
Moisture content of paddy increases to 38% during steaming as a result, the splitting of the husk indicates completion of the steaming process, however, splitting is not a necessary condition and paddy can be completely parboiled without any splitting.
Drying
Drying evaporates the moisture and compresses the gelatinous starch together in a compact mass and delocalizes it from the husk making dehusking (milling) easier. Process of drying will also stop microbial pathogens from developing on steamed paddy. An efficient and uniform drying process requires high-performing paddy dryers. For more information on paddy dryers. See here.
Related: Types of Paddy Parboiling Process Explained In Detail
Major Benefits Of Parboiling Rice Process
| S.No | Benefit | Description |
|---|---|---|
| 1 | Higher Milling Yield | Parboiling strengthens the grain structure, resulting in fewer broken grains and improved head rice recovery. |
| 2 | Easier & Cost-Effective Dehusking | Rubber roll dehullers work more efficiently on parboiled paddy, reducing dehusking cost and increasing productivity. |
| 3 | Translucent & Shiny Appearance | Parboiled rice becomes glossy and translucent, increasing its market acceptance and premium pricing. |
| 4 | Resistant to Insects & Microorganisms | Heat-gelatinized endosperm prevents germination and makes grains compact, reducing vulnerability to pests. |
| 5 | Non-Sticky & Firm Texture | During cooking, parboiled rice stays firm, separate, and is less likely to turn mushy or sticky. |
| 6 | Lower Breakage During Husking | Strengthened grain structure reduces breakage during the husking and milling stages. |
| 7 | Reduced Nutrient Loss | Nutrients such as thiamine and minerals remain intact even after washing and cooking. |
| 8 | Higher Water Absorption | Parboiled rice absorbs more water during cooking, giving longer and fluffier grains. |
| 9 | Lower Fat Absorption | Cooked parboiled rice absorbs less oil from spices and condiments, stays fresh longer, and resists rancidity. |
| 10 | Retains More Nutrients | Parboiling enhances retention of proteins, vitamins, and minerals within the rice kernel. |
| 11 | Easier Shelling | Hardened husk–kernel bond reduces friction, making shelling smoother and faster. |
| 12 | Better Digestibility | Parboiled rice is easier to digest with fewer solids lost in the cooking water, beneficial for all age groups. |
| 13 | Higher Bran Oil Content | Bran produced from parboiled rice contains more extractable oil, increasing by-product profitability. |
| 14 | Superior Cooking Quality | Firmer cooked grains with better texture, consistency, and reduced stickiness make parboiled rice ideal for commercial kitchens. |
Conclusion
Rice is one of the cereals that belongs to the grass family and considered as an important plant for the supply of staple food to over half of the world’s population. In general, rice is considered as the source of carbohydrates and supplies energy to the body through diet. The parboiling paddy process plays a crucial role in both retaining the nutritional content in the rice kernel and reducing the rice breaking during the milling operation.
Contact SKF ELixer for more information on the paddy parboiling plant model.
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