Food Chemistry：Stability of stevioside in food processing conditions

Stevioside is a natural sweetener derived from the stevia plant. It has a high sweetness intensity and low-calorie content, making it attractive for diabetics and others on carbohydrate-controlled diets. However, stevioside is not stable under some food processing conditions, such as high temperature, low pH, and ethanol presence. It can undergo hydrolysis and degradation, resulting in loss of sweetness and formation of bitter compounds.
This paper investigates the stability of stevioside in different food processing conditions and its interaction with other sweeteners. The authors used high-performance liquid chromatography (HPLC) and mass spectrometry (MS) to analyze the changes in stevioside and its hydrolysis products in water and ethanol/water solutions at different pH values and temperatures. They also studied the synergistic effects of stevioside with sucrose, glucose, fructose, maltose, lactose, and xylitol on the sweetness intensity and sensory properties of the solutions.
The main findings of the paper are:

• Stevioside is stable at neutral pH and room temperature, but it is hydrolyzed at acidic pH and high temperature. The hydrolysis products include rubusoside, steviolbioside, steviol monoside, and steviol. The hydrolysis rate increases with increasing temperature, decreasing pH, and increasing ethanol concentration.

• Stevioside hydrolysis follows a pseudo-first-order kinetic model. The activation energy for stevioside hydrolysis is 83.6 kJ/mol in water and 86.9 kJ/mol in ethanol/water (50:50 v/v) solution.

• Stevioside hydrolysis also produces two previously unknown anomers: stevioside α-anomer and rubusoside α-anomer. These anomers are formed by the recombination of stevioside hydrolysis products in the electrospray ionization (ESI) source of the MS instrument. They have similar molecular weights but different retention times and fragmentation patterns than the original compounds.

• Stevioside shows a synergistic effect with sucrose, glucose, fructose, maltose, lactose, and xylitol on the sweetness intensity of the solutions. The optimal ratios of stevioside to other sweeteners vary depending on the type of sweetener and the concentration of stevioside. The synergistic effect is more pronounced at low concentrations of stevioside (<0.1 g/L).

• Stevioside also improves the sensory properties of the solutions by masking the bitter aftertaste of some sweeteners, such as sucrose and maltose. The optimal ratios of stevioside to other sweeteners for sensory quality are similar to those for sweetness intensity.

The paper concludes that stevioside is a promising natural sweetener that can be used in combination with other sweeteners to enhance the sweetness intensity and sensory quality of food products. However, its stability under food processing conditions should be considered and optimized to prevent loss of sweetness and formation of bitter compounds.