When cooked, the naturally sticky grain of rice produces a sticky result. This stickiness can be annoying when it sticks to your teeth while chewing or your fingers while handling it, but in other contexts and uses, stickiness is beneficial. Reducing the stickiness of rice is important for food manufacturers because it affects profits, product shelf life, and delivery. For example, excess starch on raw rice makes sifting necessary before milling; high moisture content makes uncoated paddy unsuitable for exports; high sugar content reduces luster and increases fumigation costs; too much bran increases milling costs due to excessive waste, and broken kernels reduce extractable starch by up to 25%. This blog post will explore how to make rice less sticky by looking at different methods used in production.
How To Make Rice Less Sticky
- Reduce the moisture content of the raw rice before cooking.
- Reduce the amount of bran and germ in the raw rice after milling.
- Cook the rice with a high-temperature steam treatment to achieve a lower water content than usual.
- Improve starch extraction by milling at low temperatures and using a high-temperature steam treatment, or by using an emulsifier during processing (such as by adding an emulsifying agent to milled rice).
- Reduce the number of broken kernels in the final product by removing them from the final product after milling, by milling at low temperatures, or both.
- Use a low-temperature steaming treatment to achieve a lower water content than usual.
- Increase the temperature of the raw rice during cooking to increase the water content, which will reduce stickiness.
- Use an emulsifier during processing to increase starch extraction and reduce stickiness.
- Reduce bran and germ content in the raw rice after milling by removing or grinding them out with a milling machine, or by improving milling conditions such as reducing temperature or increasing pressure. increasing the amount of water added to the raw rice.
- Use a low-temperature steaming treatment to reduce the stickiness by increasing the water content.
Types of Rice
- The most commonly consumed rice is the Long Grain variety, which is made up of two main varieties: the A-type and the B-type. The A-type has a higher starch content than the B-type, which makes it more sticky.
- Basmati rice is an aromatic long-grain variety that is grown in India. It takes longer to mature and therefore has a lower starch content than other types of rice. It also has less moisture content and less protein. Basmati rice can be used in any situation where regular long-grain rice would normally be used, but it has fewer applications in Asia because of its cost compared to other types of rice.
- Sushi rice is a short grain variety that is grown in Japan and Southeast Asia (Malaysia). Both white and brown sushi rice are produced, but brown sushi rice contains more nutrients than white sushi rice due to its higher nutrient level (higher protein, calcium, iron). The brown color has different meanings in different countries. In Japan, brown rice is more expensive and is used as a topping for sushi and sweet rice desserts. In Malaysia, brown rice is less expensive than white, but it can be used to make fried rice or fried noodles.
- Jasmine rice is a high-gluten type of long-grain rice that has a slight aroma of green tea. It has low starch content and high moisture content (about 60% of the total weight). It is grown in Thailand, Vietnam, Indonesia, and Malaysia.
- Paddy rice or paddy grain refers to the unhusked grains of long-grain rice harvested from paddies that are flooded with water during the growing process (Figure 1). These grains are steamed for about one hour and then dried in an oven at 65°C for 12 hours until they become crispy but still chewy and sticky (Figure 2). The main advantage of this method over other methods such as the mill is used for making rice porridge, as well as for making desserts, snacks, and savory dishes. In Thailand and Cambodia, brown rice is used to make plain porridge and desserts.
Rice Sticky Problem
- The amount of starch in raw rice is a major problem, which is why rice is sifted before milling. The amount of starch in raw rice can vary from as little as 0.1% to as much as 10%.
- The sticky condition of the raw rice during milling also affects milling efficiency and product quality. Excess bran on raw rice reduces the water content, resulting in a higher moisture content, which reduces the extractable starch content and increases the cost of milling. Excess bran also affects the ejection rate (paddy) and extractable starch content by up to 25%.
- Broken kernels reduce extractable starch by up to 25%, which may be due to excessive bran or broken kernels in paddy. Broken kernels result in a reduction of water absorption during cooking, which causes sticky rice that sticks to other foods or people’s fingers or teeth when handled and eaten; broken kernels also reduce the extraction rate from paddy, which in turn reduces extractable starch content.
- Excessive sugar content reduces luster and increases fumigation costs. If a rice variety has too much sugar, it may not be exported to some countries with high fumigation requirements because excessive sugar causes a sticky rice product, which makes the rice unusable for export.
- The amount of bran on raw rice affects the amount of water absorbed during cooking and thereby affects the quality and taste of cooked rice. Excess bran may also reduce milling efficiency and extractable starch content, as well as increase fumigation cost when exported to certain countries with high fumigation requirements (e.g., Japan, and China).
Rice Shattering Problem
1. Rice bran
Rice bran is the outer layer of the rice kernel that contains a lot of non-starch polysaccharides (NSP), which are not digestible by human beings. With a high moisture content, rice bran can increase the viscosity of rice milling and make it difficult to separate from the starch. This problem is especially severe in Asian countries with a large proportion of sticky rice, such as China and Thailand. In these countries, excess bran is often added to sticky rice, or extra bran is produced by mechanical separation. The excess bran in the milling process makes sifting necessary before milling; the high moisture content reduces uncoated paddy exports; fumigation costs increase when sugar content increases; broken kernels reduce extractable starch by up to 25%.
2. Broken kernels
Broken kernels are caused by improper milling procedures and excessive moisture content in raw paddy. When broken kernels are present, the brain cannot be separated from the starch, which reduces extractable starch by up to 25%.
3. Sticky rice
Sticky rice is a type of cooked rice that has a high moisture content and an excessive amount of bran. The sticky nature of sticky rice makes it difficult to separate the bran from the starch during milling and causes excessive waste. The stickiness is also a nuisance when it sticks to your teeth while chewing or your fingers while handling it. This sticky quality reduces profits by making sifting necessary before milling; limits exportability when sugar content increases; reduces luster and increases fumigation costs when too much bran is present in raw paddy and can reduce extractable starch by up to 25% when broken kernels are present in raw paddy.
Use of rice bran to reduce stickiness
1. Reduce the amount of bran
The traditional approach to reducing stickiness is to reduce the rice bran content. The rice bran is a part of the rice kernel that is very sticky in its natural state, and it is usually removed during milling. However, there are some instances when it may be left on during milling, especially if it can be used as a nutritional supplement for animals. This is because it is useful for the animals, and it does not affect the quality of the rice.
2. Use an inhibitor to remove the bran
Rice bran contains proteins that are sticky in their natural state and inhibit milling. These proteins interfere with milling, and an inhibitor can be used to break down these proteins and remove them from the rice bran during milling. An inhibitor can be added to the rice bran before milling or during milling. The rice bran can also be treated with an inhibitor during roasting, drying, and shelling.
3. Add a high-moisture content to the rice bran
The high-moisture content in the bran affects the stickiness of the raw rice kernel. A high-moisture content in the brain can be achieved by adding a lot of water to it during drying and/or shelling. This will reduce stickiness but will also reduce the nutritional value of the end product as compared to unprocessed raw rice, as it is not possible to remove all water from it without affecting nutritional value. Therefore, this method should only be used if it is necessary for food manufacturers that need low-cost raw materials to make products that are nutritious at affordable prices.
When rice is processed, the bran and germ layers are removed. This makes the rice less nutritious and less sticky. To reduce the stickiness, additives such as rice bran can be used. If the bran is not added, other additives such as starch can be used.