Soy protein from by-product to offer low-cost isolate?

"To date, no studies were reported on the preparation of isoflavones enriched soy protein isolate directly from soy hypocotyls to our best knowledge," wrote lead author Jun Yu from Southern Yangtze University.

"Therefore, this utilization would greatly increase the value of soy hypocotyls and make it an alternative to the applications of soy hypocotyls for the soy protein industry."

The overall European market for soy products currently standing at more than €1.5bn a year is expected to grow at roughly 10 per cent per year.

The US market for soy foods is currently estimated at $1.75 billion in annual sales and is experiencing double-digit growth.

With such growth food formulators are constantly on the lookout for cheaper alternatives of the same product, and the new research, a collaboration between researchers in China and the Florida Department of Citrus, taps into this trend.

The research, published in the journal LWT - Food Science and Technology , looked into the development of a functional food, isoflavones enriched soy protein isolate from soy hypocotyls.

Hypocotyls are formed during germination and are the primary organ for growth of a plant and ultimately developing into the stem.

Hypocotyls were traditionally removed during the production of soy protein isolates since they are reported to affect flavour due to bitterness.

High quality soy hypocotyls (donated by Kaifeng Soy Protein) were defatted using supercritical carbon dioxide in order to reduce the oil content, producing defatted soy hypocotyls (DSH) with an oil content of only 0.2 per cent.

Supercritical CO2 offers advantages over solvent extraction, said the researchers, because it is economically efficiency and does not leave any solvent residue "Additionally, DSH obtained in this study had less off-flavours than those obtained by solvents, which the authors believed was resulted from the removal of off-flavours causing matters like aldehydes, ketones, furans and alcohols," wrote the authors.

The isolate was extracted from DSH (pH 6.0, DSH to water solution ratio of 1:10) and then freeze-dried to produce a soy protein isolate with a protein content of 92.46 g/100 g and 640 mg/100 g of isoflavones.

Isoflavones from soy have been shown to provide a number of health benefits, including the promotion of heart health and the maintenance of bone health in post-menopausal women.

Source: LWT - Food Science and Technology (Elsevier) 2007, Volume 40, Issue 5, Pages 800-806 "Preparation of isoflavones enriched soy protein isolate from defatted soy hypocotyls by supercritical CO2" Authors: J. Yu, Y.-F. Liu, A.-Y. Qiu and X.-G. Wang