Writing in Food Research International, Cathleen Dobbs and Leonard Bell from Auburn University in the US report that the stability of tagatose is highest under low pH and in refrigerated products.
“These stability issues need to be considered by manufacturers who desire to use tagatose as a prebiotic in their food and beverage products,” wrote the researchers. “To obtain the prebiotic effect from tagatose, its degradation during product storage should be minimal.
“Shelf-stable beverages should be formulated using the lowest buffer concentration and pH possible to deliver the maximum amount of tagatose with the minimal discoloration from browning,” they added.
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.
Supply constraints
Initial developments of the sweetener on the market came from a joint venture between Arla and Nordzucker, with production of tagatose from dairy. However, the JV halted production in 2006 and, despite having novel foods approval, Belgium-based Nutrilab stepped into the breach and bought up existing stocks.
Arla and Nordzucker said it was not possible to identify a volume potential to justify continued investments. But Nutrilab saw potential to produce the sweetener using an enzymatic process and the raw material galactose, a waste product from a biofuels manufacturing group. It started working towards this goal in August 2007, once the patent on the tagatose molecule had expired.
For now, however, Nutrilab is not supplying tagatose to any other externally, as it uses up the stocks it inherited from Arla.
That could all change before the end of this year, however, as the Belgian company expects to begin commercial production tagatose via a fermentation method, pending agreement that it is substantial equivalent to chemically-produced tagatose
Study details
Dobbs and Bell tested the stability of tagatose in the presence of different buffers (phosphate and citrate buffers) and over a range of pH. The effect of temperature was also evaluated.
According to their data, all three variables influenced the stability of the ingredient, as evidenced by the degree of browing in the model beverage. Optimal conditions were observed at pH 3, storage at 40 Celsius, and in the presence of buffer at ta concentration of 0.1M. Under such conditions, only 5 per cent of the tagatose was lost over a six month period, said Dobbs and Bell.
“To deliver the prebiotic effect from tagatose, shelf-stable beverages should be formulated to the lowest buffer concentration and pH possible to optimize tagatose’s stability,” they concluded.
Source: Food Research International
Volume 43, Pages 382–386
“Storage stability of tagatose in buffer solutions of various compositions”
Authors: C.M. Dobbs, L.N. Bell