Tagatose is a prebiotic monosaccharide which is chemically similar to fructose and is naturally present at low levels in heat-treated dairy products. Despite having a sweetness level only a little less than that of sugar, it is low-calorie (less than 1.5kcal/g) and tooth-friendly.
Moreover, it is only minimally absorbed in the upper gastrointestinal tract. The undigested part is fermented in the intestines, causing a change in the proportions of short chain fatty acid which, in turn, creates a favourable environment for probiotic bacteria to thrive.
The researchers from Wacker Fine Chemicals and Auburn University in the US set out to test the potential for tagatose's use in cookies as a sucralose replacer. They were motivated particularly by the drive towards healthier eating and the appearance of nutraceutical ingredients that can bring health benefits to mainstream foods.
The team made batches of cookies in which they used tagatose (supplied by Arla Food Ingredients) instead of sucrose at levels of 25 per cent (18.75g), 50 per cent (37.5g), 75 per cent (56.25g) and 100 per cent (75g).
They also cookies using fructose as a replacer for sucrose in the same proportions, and a control cookie containing 100 per cent (75g) sucrose.
The control cookie required 15 minutes of cooking, while this proved to be too long for the tagalose-containing cookies. They only required 12 minutes.
The recipes were prepared and baked at least three times, on different days, and analysis of the baked cookies took place within 12 hours. After cooling they were stored in Ziploc bags.
The researchers first analysed the cookie dough, however, for its rheological properties - that is, hardness, adhesiveness, cohesiveness and resilience.
They found that these properties were similar between the tagatose cookies and the sucrose control.
Next, the researchers looked at the physical properties of the baked cookies - their spread, colour and hardness.
The tagatose cookies were seen to be harder, darker, and have a lower spread than the sucrose control.
In terms of the sensory properties, the researchers recruited 53 untrained panelists who ranked the cookies on a nine-point hedonic scale that ranged from dislike extremely to like extremely.
The panelists said they liked the brown colour of the tagatose cookies more than the control, but they preferred the sweetness level of the 100 per cent sucrose cookie.
Overall, the cookie containing 100 per cent sucrose was best liked. However of the tagatose cookies, the 50 per cent tagatose one was seen to be "not significantly different" in overall likeness.
"Sensory studies (based on likeness scores) suggest that an acceptable cookie can be prepared using a blend of sucrose and tagatose," concluded the researchers. "Such a cookie may help reduce the amount of metabolizeable sugars contributed to the diet while providing the beneficial prebiotic effect associated with tagatose."
Journal of Food Science DOI: 10.111/j.1750-3841.2007.00653.x
Title: "Physical properties and consumer liking of cookies prepared by replacing sucrose with tagatose"
Authors: TP Taylor, O Fasina, LN Bell.