Soybean waste to offer cost-effective natural antioxidants
healthy alternative to synthetic antioxidants that prolong the
shelf life of food, suggests a study from India.
"The present studies may be of importance in varietal improvement, nutraceuticals, bio-pharmaceuticals and utilization of agri-wastes as possible cost-effective natural antioxidants," wrote lead author Dhan Prakash from the National Botanical Research Institute in Lucknow, India. Oxidation processes in food can lead to organoleptic deterioration in taste, colour and texture. The food industry has long been aware of this, and is increasingly seeking natural solutions rather than artificial additives, such as like butylhydroxyanisole (BHA) and butylhydroxytoluene (BHT), to extend the shelf life of milder-tasting products. According to a 2003 report by Frost and Sullivan, the synthetic antioxidant market is in decline, while natural antioxidants, such as herb extracts, tocopherols (vitamin E) and ascorbates (vitamin C) are growing, pushed by consumer desire acceptance and easier market access. The new study, published in the journal Food Chemistry, investigated the antioxidant potential of 30 soy variety seeds and agri-waste (leaves, twigs and pod pericarp). Total phenolic content (TPC), flavonoids and antioxidant activity (AOA) were used to measure the potential of the waste extracts as natural antioxidant food ingredients. The TPC ranged from 6.4 to 81.7 mg gallic acid equivalents (GAE) per gram, flavonoids from 3.5 to 44.6 mg quercetin equivalents (QE) per gram, and AOA from 7.5 to 74.7 per cent. The agri-wastes of some of the more promising varieties, like Alankar, Kalitur, NRC-37 and PK-472, had TPC ranging from 27 to 167 mg GAE/g, flavonoids from 10 to 64 mg QE /g and AOA from 13 to 85 per cent. "In general, the amounts of TPC (98.6-167 mg GAE/g), flavonoids (39.7-63.8 mg QE/g) and AOA (69.8-84.7 per cent) were higher in the leaves, followed by pod pericarp and twigs," stated the researchers. Analysis using high-performance liquid chromatography (HPLC) and mass spectrometry (MS/MS) showed that the seeds of Kalitur were higher in genistin, while the seeds and leaves of Alankar contained the most diadzin and gallic acid. "The appreciable concentrations of flavonoids, along with phenolic acids and other antioxidant phytochemicals present in different soybean cultivars and their agri-wastes under study, might be responsible for their efficient free radical-scavenging activity," wrote the researchers. The research taps into the growing trend for sourcing natural antioxidants from waste sources, and then using them as nutraceutical or functional ingredients. Indeed, last year researchers taking part in the EC CRAFT project FAIR 98-9517, looked at the practical, economic, and industrial viability of waste products from juice production, waste from the canning industry, or remains from the harvesting of 11 different fruits and vegetables. The study focussed on two important aspects for the extracts: Firstly, if the plant waste extracts have potential as antioxidants compared to established ones, and, secondly, if the research could lead to practical and economic applications. Initial screening of red beet, apple, strawberry and pear residues from juice production; tomato, artichoke and asparagus from the canning industry; chicory, endive, cucumber and broccoli remains from harvesting; and golden rod herb and woad herb extracts showed that all of wastes yielded polyphenols. The advantages of using these natural antioxidants could offer important opportunities for food preservative producers. Source: Food Chemistry (Elsevier) 2007, Volume 104, Issue 2, Pages 783-790 "Antioxidant and free radical-scavenging activities of seeds and agri-wastes of some varieties of soybean (Glycine max)" Authors: D. Prakash, G. Upadhyay, B.N. Singh and H.B. Singh