LAUSR

BACKGROUND In this study, the foamability and foam stability of nitrogen-infused cold brew coffee, as affected by coffee variety (Arabica and Robusta), degree of roast (light, medium, dark), brewing temperature (4, 20, 35 °C), brew ratio (1:5-1:15 w/w; coffee/water), particle size (712, 647, and 437 μm volume mean diameter) and beverage temperature (4, 20, and 35 °C), were investigated. RESULTS The results showed that the dynamic surface tension of cold brew was about 65-70 mN/m at 0.1s bubble lifetime, and it reduced to about 60 mN/m at 1 s. At these surface tensions, infusing the cold brew (70 mL) with nitrogen gas for 30 s at 50 mL/min generated 30-40 mL of foam head. Overall, the foamability of the brews correlated positively with foam stability. At the same degree of roast, brews prepared from Arabica beans had more stable foam than those from Robusta. Foam stability increased with increasing degree of roast, increasing brewing temperature, and decreasing particle size, but increasing the beverage temperature dramatically destabilized the foam. By contrast, brew ratio had minimal effects on foaming properties. Nitrogen-containing constituents present in the 80% (v/v) ethanol-soluble fraction (55.9% of total dissolved solids) of the brew were important contributors to foaming, while the 80% (v/v) ethanol-insoluble fraction (42.3% of total dissolved solids) that contained polysaccharides was important in stabilizing the foam. CONCLUSION The foaming properties of cold brew were determined by its physicochemical properties, especially concentrations of the low molecular weight nitrogen-containing compounds and high molecular weight polysaccharides. This article is protected by copyright. All rights reserved.