Bran is good, Big Bran is better. A rice with bigger bran for multiple micronutrients

By Ronald Yu, Xiaoba WuNovember 16th, 2022

In a world where nutrient deficiencies are common and food costs are rising, could a healthier form of rice be a solution?

A global staple: rice is cheap and certainly filling, but not as nutritious as it could be. Scientists have been developing a solution to change that.

Developing a future crop with multiple micronutrients

We know that micronutrients are good for us. In Australia, we can get all the nutrients we need from a diverse diet including antioxidants from cherries, unsaturated fatty acids from salmon or nuts, fibre from vegetables, and vitamins from fruits.

These nutrients are vital to achieving everything from an active brain, functioning organs, high energy levels, and even how we physically look.

But scan your eyes down towards the bottom of your supermarket receipt and you can see how fresh, healthy foods might not be affordable for everyone to include into their everyday diets.

In comparison, food products from cereal crops such as rice and wheat are relatively cheap, and easy to find. However, they do come with a different cost. Refined-grain products of rice and wheat are low in micronutrients.

To overcome this, researchers from CSIRO Agriculture and Food are working with the Institute of Botany at the Chinese Academy of Science to increase multiple micronutrients in rice.

Left: Regular rice with a thin outer bran (aleurone) layer.  Right: Rice with a thicker multilayer aleurone phenotype.

More bran with more micronutrients

Rice grains have a thin outer layer called the bran, which is usually composed of one cell layer. The bran accounts for 10 per cent of the grain, but it provides us with 70 per cent of its nutrients. So, if bran is good, a big bran is better. We call this “the Big Bran Theory”. After significant work, our research showed we were able to increase the thickness of the rice bran layer from one to six cell layers. Just like building a stronger wall to protect our body, this bigger bran gives you:

  • 20 per cent more iron and zinc
  • 30 per cent more B vitamins
  • 50 per cent more unsaturated fatty acids
  • 60 per cent more fibre
  • 80 per cent more antioxidants.

A bigger bran content can help you in two ways.

Firstly, nutrition. The minerals and vitamins in the bran are essential to our bodily functions. Fibre is important for our bowel health, reduces blood glucose levels, and protects us from diabetes. A bigger bran would contain more of these valuable vitamins and minerals.

Secondly, ongoing health. Antioxidants in the big bran can stop damage from reactive oxygen species and protect us from oxidative DNA damage and cancers. Meanwhile, unsaturated fatty acids, also found in the bran, are the “healthy fats” for our cardiovascular system.

So how did we develop this new rice with bigger bran?

CSIRO researchers Dr Xiaoba Wu (left) and Dr Ronald Yu (right) have been developing a healthier variety of rice with a bigger bran content.

A great collaboration between two countries

This challenge was tackled by a successful collaboration between CSIRO Agriculture and Food and the Institute of Botany, Chinese Academy of Science (IBCAS) led by Dr Phil Larkin (CSIRO) and Professor Chun-Ming Liu (IBCAS).

Professor Chun-Ming’s team from IBCAS, including Dr Xiaoba Wu and Dr Jinxin Liu, applied microscopy with high-throughput screening technology to examine 36,000 seeds to find a handful of seeds with a bigger bran.

We then conducted a detailed genetic mapping to study how a small change in DNA can result in a big difference in bran thickness. This provided a new hypothesis on how DNA demethylation can control the bran (aleurone) development in rice.

Dr Larkin’s team from CSIRO, including Dr Ronald Yu, also collaborated with CSIRO Health and Biosecurity, led by Dr Anthony Bird, to measure the comprehensive nutritional profile of the big bran rice.

We detected an increase in fibre, antioxidants, minerals such as iron, zinc, potassium, magnesium, sulphur, increase in vitamins B3, B6, and B9, and change in total lipid and fatty acid composition. Also, we figured out that the bigger bran may not be fully filled, and provided perspectives to achieve even greater filling of this bigger bran, making it even better.

Big bran rice and beyond

So, we have established a healthier rice with bigger bran. But what we eat most of is white rice, which is without bran. In comparison to white rice, we can eat purple rice with bran. We successfully integrated our big bran trait into purple rice, which retains its bran during processing before it hits the supermarket shelf and tasted our big-bran purple rice congee. (That’s the privilege of being a crop scientist. You can eat your innovation.)

“But what about other types of food?”

Following this first success in rice, we are aiming to apply the technology to other cereals such as wheat, sorghum, and barley for healthier wholegrain cereal food products.

We actually have a good track record of commercialising our research developments. We work in the same team that previously had success with ultra-low gluten barley, BARLEYmax®, and high-amylose wheat.

We envisage that big bran rice can be the next success to find itself on your dinner plate.

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