Sweetness and flies: insects help in the search for new sugars

CSIRO scientist Dr Anne Rae and her team went on the search for new types of sugars to act as healthy sweetening agents, using a novel testing approach with fruit flies as the test subject.

• 10 March 2011 | Updated 14 October 2011

Sucrose is a versatile sugar that is easy to produce and widely available but because it is so soluble and easily digested it can adversely affect metabolic health and provide a food source for teeth-damaging bacteria. 

A team of CSIRO Plant Industry scientists have recently completed a project to look for novel sugars and evaluate them for their role as healthy sweeteners. In completing this project, they used a very innovative method of testing preference for different types of sugars – fruit flies.

Using fruit flies as model insects to conduct sensory research is well-accepted. Even though their taste mechanisms are very different to those of humans, they tend to prefer similar types of tastes. 

Fruit flies are, in fact, more accurate predictors of acceptable tastes than more closely related species such as monkeys, and fruit flies tend to respond similarly to specific ‘sweet’ or ‘bitter’ tastes as humans. 

Past research has demonstrated, for example, that the flies will avoid bitter compounds like caffeine that humans also find bitter to the taste.

CSIRO scientist Dr Anne Rae and her team collected wild fruit flies and used blue and red food dye to indicate the flies’ relative preference for a particular sugar. 

The more they consumed one form of sugar, the more intensely red or blue coloured the flies’ abdomens became. If the flies demonstrated a preference for both sugars approximately equally, then the flies’ abdomens became a purple colour. 

This enabled the researchers to develop a scoring system that demonstrated the flies’ preferences for either sugar which could then be broadly equated to likely human preference.

This research is important in establishing a mechanism to evaluate some of the new sugar compounds being discovered, some of which are only available in very tiny amounts that makes using animals or humans as testers difficult. 

This method represents a low-cost way to quickly conduct screening of sugar compounds and correlate them with likely human preference.

The ideal sweetener would be one that humans perceive to be sweet like sucrose, but that doesn’t feed tooth-decaying bacteria or adversely affect blood sugar levels. 

The search continues for these compounds which will enable food to be sweetened without some of the adverse side effects that table sugar brings with it.

This project was supported by the Cooperative Research Centre for Sugar Industry Innovation through Biotechnology (CRC SIIB).

Read other articles from the CSIRO Plant Industry newsletter.