The researchers said their results, published in the International Journal of Food Science and Technology, also showed that chocolate containing inulin with a higher degree of polymerisation (DP) had higher melting points, greater plastic viscosity and an increased flow behaviour index.
Rebaudioside A, also known as Reb A and rebiana, is a high-intensity sweetener derived from the stevia leaf. It is said to be approximately 200 times sweeter than sugar.
There has been a great deal of excitement about stevia and its high purity component Reb A since the US Food and Drug Administration said it considers the zero-calorie, natural sweetener to be GRAS (generally recognized as safe) in December 2008.
And the Food Standards Australia and New Zealand (FSANZ) approved the use of steviol glycosides as a food additive also in 2008. Meanwhile April of this year saw a positive opinion from EFSA on the safety of stevia, with final EU approval expected next year.
The authors, based at Victoria University in Melbourne, said that five batches (10 kg each) of chocolate were prepared following the same procedure, except for one experimental batch which had a whey protein isolated added to it to ascertain the success of this ingredient in partially reducing fat content.
Stevia extract was then added (0.5% w⁄ w) to all the batches and a control was also included in the experiment.
Resulting solidified chocolate was packaged in aluminium foil, and then the samples stored in a cool (15 °C) and dry place until required for analysis.
The researchers said that a sensory analysis panel, selected from students and staff at Victoria University in Melbourne, analysed five different samples (4 to 5 grams each) simultaneously for appearance, firmness, mouthfeel, smoothness, flavour, taste and overall acceptance.
The researchers found that polymerisation (DP) of inulin preparations may play a role in perception of flavour ⁄ taste of sucrose free chocolate, with the panelists opting first for the control chocolate followed by the chocolate sample with long chain inulin.
“Reduction of inulin DP resulted in apparent low flavour ⁄ taste acceptance,” said the scientists.
And replacing sucrose with stevia and with inulin and polydextrose as bulking agents also resulted in darker chocolate, found the authors.
They concluded that chocolate with inulin HP in combination with stevia and polydextrose resulted in very similar physico-chemical and sensory characteristics in comparison to sucrose sweetened milk chocolate.
“The size of the inulin chains may affect both the crystallisation and the aggregation processes and consequently visco-elastic properties of milk chocolate.
The longer chains have a lower solubility than the shorter ones and therefore they may crystallise more rapidly, which could explain the slight increase in visco-elastic behaviour of chocolate with inulin HP,” said the scientists.
They said that inulin HPX and GR due to their shorter chain length did not result in same physico-chemical, rheological and sensory properties as inulin HP.
The use of whey proteins for partial fat replacement in sucrose-free chocolate was not given a favourable rating in terms of rheological and sensory properties by the consumer testing panel, they added.
Source: International Journal of Food Science and Technology
Published online ahead of print
Sucrose-free chocolate sweetened with Stevia rebaudiana extract and containing different bulking agents - effects on physicochemical and sensory properties
Authors: A. B. Shah, G. P Jones, T Vasiljevic.