Guarana extract shows promise as preservative additive
and antibacterial properties, which could see the exotic berry
making a move into food preservatives, new research suggests.
"Due to their high antioxidant, antibacterial and antifungal activities the guarana seed extracts have promising potential as natural antioxidants in the food industries, in the preservation of foodstuffs against a range of food-related bacterial and fungal species or in the pharmaceutical and cosmetic industries," wrote lead author Lucija Majhenic in the journal Food Chemistry .
Interest is growing in plant-derived food additives as replacements to synthetic antioxidants like butylhydroxyanisole (BHA) and butylhydroxytoluene (BHT) to slow down the oxidative deterioration of food.
Indeed, according to a 2003 report by Frost and Sullivan, the synthetic antioxidant market is in decline, while natural antioxidants, such as herb extracts (particularly rosemary), tocopherols (vitamin E) and ascorbates (vitamin C) are growing, pushed by easier consumer acceptance and legal requirements for market access.
The researchers, from the University of Maribor in Slovenia, tested different solvents, including water, acetone, methanol and ethanol, to extract the antioxidant polyphenol content, which was then measured using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay.
The room temperature extraction produced an extract with highest total phenol content of 181 milligrams of gallic acid equivalents, containing 29.4 milligrams of proanthocyanidins.
"All tested guarana seed extracts displayed strong antioxidant and radical-scavenging properties," wrote the researchers.
Majhenic and co-workers then tested the guarana seed extracts against three food-borne fungi:
Aspergillus niger, Trichoderma viride and Penicillium cyclopium , and three health-damaging bacteria: Escherichia coli, Pseudomonas fluorescens and Bacillus cereus.
The extracts obtained using the alcoholic solvents were found to display stronger antimicrobial activity against the micro-organisms, compared to the extracts obtained using water "Results presented here may suggest that seed extracts of guarana possess strong antimicrobial and antioxidant properties, and they can therefore be used as a natural additive in food, cosmetic and pharmaceutical industries," wrote Majhenic.
"Future studies are required to determine the types of other bioactive compounds in seed extracts, as well as the efficiencies of individual phenolic compounds, caffeine and synergistic effects responsible for the antimicrobial and antioxidant activity of the guarana seed extract," she concluded.
Exotic fruits are increasing in popularity, with consumers tapping into reports that they may boost their mood and energy levels.
Indeed, in Europe the increased popularity of exotic fruit contributed significantly to a growth rate of 26 per cent for the European organic food industry between 2001 and 2004, according to market analyst Datamonitor, and the US market looks to be following suit.
Source: Food Chemistry (Elsevier) Volume 104, Issue 3, 2007, Pages 1258-1268 "Antioxidant and antimicrobial activity of guarana seed extracts" Authors: L. Majhenic, M. Skerget and Z Knez
