Low-glycaemic index barley proves healthy alternative

CSIRO Plant Industry released its new low-glyceaemic index barley last week: BARLEYMax, developed from a mutant form of an old 'lab rat' strain of barley called Himalaya.

Research has recently shown that blueberries have the highest levels of protective antioxidants of any fruit, and protect your heart and brain, and ward off cancer by zapping reactive oxygen free radicals.

Meanwhile, BARLEYMax provides protection against bowel cancer and cardiovascular disease by reducing serum cholesterol and cutting the risk of obesity and type 2 diabetes. So tucking into a couple of BARLEYMax blueberry muffins for morning tea will not only be enjoyable, it will demonstrably benefit your health.

Dr Matthew Morell's research team developed BARLEYBax from a most unlikely germplasm storage facility: a shoebox in the office of his Plant Industry colleague Dr Peter Chandler.

In the mid-1990s, Chandler performed chemical mutagensis on an old two-row barley cultivar, 'Himalaya'. It was around 50 years old and was never grown commercially in Australia, but it made an ideal 'lab rat' for cereal geneticists.

Chandler's experiments with random chemical mutagenesis of Himalaya produced a variety of mutants -- plants with different habits, leaf densities and a range of grain shapes and sizes. He grew a few, but consigned the remaining seed to a shoebox on a shelf in his office.

"One day in 1997 I asked him what he had in his collection, and he pulled out the shoebox and told me to help myself," Morell said.

"We recognised that, in addition to the physical differences in the seed, the mutagenesis would probably have resulted in grain with different starch compositions."

A new cuiltivar

In 1998, a member of Chandler's team identified a Himalaya scion that carried a mutant SS2 (starch synthase) gene. The mutation impaired the conversion of sucrose to starch.

Using DNA marker technology, CSIRO breeders tracked the mutation through a rapid back-crossing program, to create high yielding BARLEYMax cultivars for commercial production. From the time the mutation was identified, it took less than seven years to produce the new cultivar, compared with the typical 10 years required in the past.

The result was a grain rich in the cholesterol-lowering soluble fibre b-glucan. It also has a significantly reduced glycaemic index because of the presence of high levels of so-called resistant starch, and a sweeter taste due to unconverted sucrose.

Dr David Topping's research group at CSIRO Health and Nutrition has shown that BARLEYMax is also high in insoluble fibre, because unlike most commercial barley varieties, the grain holds onto its husk until it is milled.

The typical Australian diet is low in resistant starch, which comprises long chains of oligosaccharides. Resistant starch takes longer to digest, and results in a low glycaemic load (GL).

Low GI/GL foods do not trigger the rapid rise blood insulin levels associated with rapidly digested starchy or sugary foods with high glycaemic indexes. Low GI foods can cause health problems in people with type 2 diabetes.

Both animal and human trials suggest that resistant starch also fosters a healthy bowel flora.

A trial by Topping's group has shown that 100 grams of a BARLEYMax-based breakfast cereal per day has favourable effects on several important indices of bowel health.

Compared with a commercial barley breakfast cereal, the BARLEYMax cereal had a much lower glycaemic index -- 50 compared with 77 on a 100-point scale (pure glucose has a GI of 100). It also resulted in a glycaemic load 40 per cent lower, and a markedly reduced insulin response.

Test products developed by CSIRO, Food Science Australia and food industry partners have shown that BARLEYMax has excellent processing properties for extruded and rolled breakfast cereals, breads, crackers and ... muffins.

In preliminary taste tests, consumers rated the test foods well above equivalent products made with refined or wholemeal wheat flour -- the grain's natural sweetness in the absence of added sugar was an attraction.