While most of the rice available on the market is white or brown rice of various varieties, there are also other types of rice distinguished by their processing. Let’s talk about them.

Parboiled Rice

The first of these rice products, and perhaps the most widely marketed worldwide, is parboiled rice, also known as vaporized or precooked rice. The origin of this rice dates back more than 2000 years and became popular in the Indian subcontinent due to its advantages for the processing methods of that time, where husking treatments were very aggressive. The main advantages were that this rice hardly breaks during the husking process and that it better resists insect attacks.

The process to obtain this rice begins with clean, unhusked rice grains. The grains are soaked for about half an hour in hot water (60-75°C) to prevent germination or microbial growth and to accelerate water penetration into the grain. After soaking, the grains undergo a thermal treatment with steam. Thanks to this treatment, the starch gelatinizes, and the grain is sterilized. Subsequently, the grains must be dried to levels close to 12-13%. This process starts quickly (at higher temperatures) initially and then transitions to slower drying in the final stages, which are more critical. Once dried, the grains are processed like any other rice grain, undergoing husking and polishing to remove the husk and bran.

These grains have a much harder texture than the original ones due to the gelatinization and subsequent retrogradation of starch. Therefore, they are much more resistant during processing, and the number of broken grains is almost zero. However, this hardness also makes them more resistant to insect attacks. Despite being well-received in the Indian subcontinent, it did not catch on in other parts of the world. Currently, this region still accounts for 90% of the production and consumption of this type of grain, which represents more than half of the rice consumed in India.

At the end of the 19th century, interest in this type of rice increased due to its nutritional characteristics. During processing, some nutrients from the outer layers of the grain transfer to the endosperm, where they remain after the thermal treatment. For this reason, this type of rice has a higher content of vitamins, mainly from the B group, and minerals compared to conventional rice, although slightly less than whole grains. However, it’s also true that the fat content is slightly higher, and its colour changes to amber tones due to Maillard reactions and the presence of pigments from the bran.

These nutritional advantages are especially interesting in some Asian countries where part of the population’s diet is excessively based on white rice consumption, leading to significant nutritional deficiencies. Unfortunately, this alternative has not been successful, mainly due to its organoleptic characteristics such as its slightly different taste, colour, and firmer texture after cooking, which appeals to Indian taste but not to that of other Southeast Asian regions.

In recent decades, this type of rice has experienced some popularity in Western countries such as Spain, Italy, Brazil, or the USA, precisely because of the texture of this rice type and its ability to withstand overcooking. In fact, a well-known Spanish brand markets it as “rice that doesn’t overcook”. It’s clear that in the more developed world, we appreciate organoleptic quality and convenience more than other aspects.

It’s important to note that although these grains remain firmer after cooking, and there is less starch loss in this process, they also have a higher predisposition to rancidity due to the higher fat content of the grain, so they must be properly packaged. Additionally, the taste, aroma, and colour of the grains change slightly, and the cooking time is longer due to the grain’s greater compactness.

Enriched Rice

As we have discussed, there are certain parts of the world where diets are heavily based on white rice consumption, and neither whole nor parboiled rice has been successful. Various international organizations have attempted to offer alternatives to address some of the nutritional problems in these communities. In many countries where wheat flour products are the staple food, this issue has been addressed by fortifying flours with certain nutrients, such as B-group vitamins or iron, by law. However, this is not as simple in the case of rice.

Coatings with aqueous solutions rich in B-group vitamins, iron, and sometimes folic acid have been proposed. But after this coating, it is necessary to apply a new coating to fix these nutrients, so they do not release during cooking but do so in the intestine, usually due to the decrease in pH of the environment.

However, one of the methods that has been most successful is the production of synthetic grains, which are truly nutritional powerhouses. These grains are made through extrusion and subsequent drying, using flours and/or starches, minerals, and vitamins. It is crucial that they withstand cooking and have a very similar appearance to conventional grains so that consumers do not separate them. They are produced by specific companies and are later mixed in certain proportions with conventional rice grains.

Research has also been conducted through genetic modification of these grains to increase the content of certain nutrients in the endosperm. This has led to products such as “golden rice”, with a higher content of beta-carotenes, provitamin A, which not only enhances nutritional value but also gives the endosperm an attractive yellow-orange colour.

Quick Cooking Rice

One of the problems with rice for modern lifestyles, characterized by the limited time people have, or at least the time they want to spend cooking, is the long cooking time required. White rice usually requires about 20-30 minutes of cooking, while brown rice requires about 45-60 minutes due to the outer layers hindering water penetration. Among the varieties, those that are more starchy, less compact, and with more cavities inside will require shorter times than those that are more vitreous and compact. For this reason, parboiled rice also requires longer cooking times.

To solve this problem and speed up cooking times, channels can be created for water to be introduced “artificially”. For this, it is enough to precook (or partially cook) the grain industrially. In this precooking, water penetrates the grain, increasing its volume and enlarging those channels through which water penetrates. Unlike parboiled or precooked rice, in this case, the treatment is applied to white grain (after removing the bran and husk), and only reaches 60% humidity, compared to the 80% of conventional cooking, to avoid starch gelatinization, due to both the lack of water and the shorter treatment time. After this partial cooking, the grains are dried, maintaining the channels created.

These grains are somewhat more opaque or starchy due to their lower compactness than the original ones and have a slightly larger size for the same reason. The cooking time is about 5 minutes (10-15 minutes in the case of whole grains), four times less than conventional rice. And they are usually sold in microperforated bags to facilitate cooking.

However, cooking these grains still requires heating water to its boiling point. A time that many consumers already find excessive, at least at certain times of the day. To solve this problem, precooked rice has been developed. To preserve them, freezing can be used, but also sterilization, using canning industry technology. That is, cooked rice is placed in a can or jar and sterilized once closed. This process can also be carried out in a plastic container capable of withstanding the high temperatures necessary for sterilization or in an aseptic packaging. In these cases, it is necessary to consider that excessive thermal treatment can overcook the grains, increasing their stickiness and pasty character. To avoid this, cooking times and temperatures must be very carefully controlled, and it may be interesting to pre-fry the rice before cooking. For these preparations, long-grain varieties, or indica, are usually preferred due to their higher amylose content and their ability to remain looser and firmer after cooking. In the market, there are rice products of this type in cans, glass jars, and plastic containers. The latter facilitate heating the grains once the container is opened, in the microwave.