Effects of different stevia-to-onion ratios and heating temperatures on physicochemical and sensory attributes of onion-stevia hot water extracts

Increased consumption of artificial and intense natural sweeteners have led to serious health implications and safety issues for intended consumers. Among all natural sweeteners, steviol glycosides (SGs: stevioside & rebaudioside-A) are popularly known as zero-caloric intense sweetening compounds of natural origin. Hot water extraction (HWE) is considered ecofriendly and less expensive, and HWE extracts are safe for human consumption as compared to organic solvents extraction. Onion (Allium cepa L.) and stevia (Stevia rebaudiana) were extracted using a single factor experimental approach to determine the optimal onion-stevia hot water extract (OSHE) extraction conditions. Physicochemical and sensory attributes of onion hot water extract (OHE) and OSHE extracted at varying stevia-to-onion ratios and temperatures were investigated. The results showed that total phenolic content (TPC) increased and total flavonoid content (TFC), L*, a* and b* values decreased with corresponding increases in stevia-to-onion ratio and extraction temperature. In contrast, total soluble solids increased with increase in onion-stevia ratio, whereas pH values declined with increasing temperature. Glucose was the most dominant organic sugar in OSHE followed by sucrose and fructose. In conclusion, OSHE obtained at 115 degrees C and 1:100 stevia-to-onion ratio (w/w) could be produced as a natural sweetener after concentration or drying and could be exploited in beverages and cooked foods without any deteriorating quality effects with improved thermal and pH stability and fermentation resistance. Furthermore, OSHE can be manufactured as a natural sweetener because it can be extracted at high temperature and pressure using stevia leaves with only the bound water content of onion without any additional moisture from external sources. As an eco-friendly alternative of expensive enzymatic digestion or organic solvent extraction.

Automated summary

Increased consumption of artificial and intense natural sweeteners have led to serious health implications and safety issues. Steviol glycosides, a natural sweetener derived from stevia, have zero-caloric intense sweetening properties. Hot water extraction is an eco-friendly and cost-effective method for obtaining safe extracts. The optimal extraction conditions for an onion-stevia hot water extract were determined through experimental tests, revealing improved stability and resistance to thermal and pH effects.