Stability in Acid

The following chart illustrates the pH stability of stevioside in several acid systems over a range of storage time.


Temperature Stability

Stability of Stevioside at Elevated Temperatures

Incubation of the solid sweetener stevioside at elevated temperatures for 1 h showed good stability up to 120° C, whilst at temperatures exceeding 140° C forced decomposition was seen which resulted in total decomposition by heating at 200° C (Figure 2). As consequence, the application of stevioside as sweetening agent might not be suitable or recommended in baking or other processes requiring high temperatures. Crammer and Ikan (1987) expressed that since stevioside is stable at 95° C it is a suitable sweet additive to cooked and baked foods. On the other hand, Chang and Cook (1983) reported that stevia sweeteners have a high heat stability after one hour heating at 100° C. Besides, Tanaka (1988) who reported that stevioside and rebaudioside A are reasonably thermally stable under the elevated temperatures used in food processing and do not undergo browning or caramelization when heated.


Temperature and PH Stability

Stability of Stevioside at Different PH at Elevated Temperature

In aqueous solution stevioside is remarkably stabler over a widge range of pH values and temperatures. Under thermal treatment in a pH range of 1-10 over 2 h, practically no degradation of stevioside could be observed at 60° C and only slight losses up to 5% (pH 2 and 10) occurred on heading to a temperature of 80° C. Under strong acidic conditions (pH 1.0) forced decomposition of stevioside was observed which resulted in total decomposition after incubation at a temperature of 80° C for 2 h. These reutls are in accordance which that reported by Buckenhuskers and Omran (1997) who showed that the stevioside excellent heat stability is up to 100° C for 1 hr at pH range 3-9, but rapid decomposition occurs at pH level greater than 9 under these conditions.