How to Reduce Discoloration of Rice Grains

How to Reduce Discoloration of Rice Grains

How to Reduce Discoloration of Rice Grains

A question that many rice mill owners have is — how can we reduce the discolouration of rice grains during the parboiling process? Grain discolouration means that the quality of the seeds is poor and people don’t want to consume it. It could mean that there are unwanted microorganisms present on the glumes, kernels, or both, and the rice is most likely to be infected with fungi such as B. oryzae, A. padwickii, Pyricularia oryzae, F. So reducing discolouration of rice as much as possible is very important. 

Reasons For Discoloration of Rice Grains. 

There are several reasons for discolouration happening during the parboiling process. 

  • With the conventional parboiling process, only 80-85% of the rice gets steamed properly and the remaining is untreated. This leads to variations from batch to batch and even grain to grain.
  • During the parboiling process, it’s necessary to control factors such as the soaking temperature, steam pressure and resting time — which most of the conventional parboiling systems do not allow for.
  • Colour that is required at the end is mainly dependent on the soaking temperature versus resting time. There is an inverse relationship between soaking temperature and resting time — so the parameters will vary depending on the colour of rice that is required and the variety of rice that is being processed. 
  • The discolouration of rice during parboiling is caused by a non-enzymatic browning reaction called Maillard type reaction, which is a chemical reaction between amino acids and reducing sugars that give the rice a brown colour. This reaction speeds up when there is fluctuation in the soaking and steaming process parameters. 

Colour changes of rice during soaking (by total water absorption) are attributed to inward diffusion of red and yellow pigments and outward migration of bran compounds at the rice surface, and in the steaming process due to the migration of bran pigments toward the endosperm.

What does this mean? It means that if you have control over the process parameters, you can have full control over the output quality of rice.

How APIT Technology Reduces Discoloration of Rice Grains 

With the latest technology, it is actually possible to have full control over the parameters affecting the rice during the parboiling process. We at Agri-Process Innovation Technology (APIT) – the world’s best Paddy Process Specialists for Parboiled Rice Plants, Steam Rice (Accelerated Aged Rice) Plants or the process

engineering for rice – have developed a parboiling and steam curing system that gives you full control over the process, which in turn gives us you uniform degree of starch gelatinization resulting in uniformity of colo ur, texture and other important quality parameters. 

The APIT Gel Cook system results in up to 98% of the rice getting steamed properly, which means that the discolouration is reduced to 0.02%. 

Gel cook stations are the key to quality rice paddy from any parboiling plant. APIT, with the inputs from the world’s greatest grain scientist Dr Kshirod Bhattacharya, has developed a unique gel cook station for producing High Quality parboiled paddy. Unlike the conventional type of cookers where the body is cylindrical and the steaming process is intense, the state-of-the-art APIT Gel Cook stations have a contoured internal design to facilitate proper mixing of paddy while it is steamed. This comprises of intermediary non-steaming zones to facilitate absorption of steam before steaming again and this alternate steaming and resting while in transit without compromising the FIFO method of grain flow ensures that hydrated paddy gelatinizes completely and the disarray of the amylose is corrected. 

This revolutionary concept introduced by APIT ensures uniformity in colour, texture and quality of rice. Are you a rice mill owner? Do you want to increase your high-quality output and reduce the amount of discoloured rice? 

FAQs About Discolouration of Rice

Is it good to parboil rice before cooking?

With parboiled rice, you can be sure that it won’t burn before it has cooked completely. So you won’t get rice that is soggy or undercooked. Parboiling rice also helps to remove the excess starch, preventing the cardboard taste that you usually get if the rice isn’t washed well before cooking.

Which is healthier — brown rice or parboiled rice?

Both brown rice and parboiled rice have a higher nutritional value compared to milled white rice. However, if you’re looking for firmer rice that has more vitamins, parboiled rice is a better option. 

What is the purpose of parboiling of rice?

Parboiling is the process of partially boiling the rice paddy before milling so that the rice is high in nutrients. This process also improves the texture of the rice and reduces the number of broken grains during milling. Moreover, parboiled rice is easier to cook, takes less time and is less sticky too.

Should you rinse parboiled rice?

Generally, it is advisable to wash all non-parboiled varieties of rice until the water runs clearly — this means that all the excess starch is gone. However, you don’t really need to rinse or wash parboiled rice. 

What are the common pests and diseases that affect rice?

The most common pests and diseases that affect rice are rice blast, bacterial blight, sheath blight, and tungro virus. Rice blast is a fungus that attacks the rice plants in its seedling stage, leading to critical damage. Bacterial blight also affects the rice paddy at the seedling stage causing the infected leaves to turn greyish green and roll-up.

Contact us to learn more about the cutting-edge parboiling systems.

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