The effects of grinding (medium-coarse) and extraction time (14–22 h) on the physicochemical and sensorial properties of cold brew coffee produced using two types of Colombian specialty coffees (Huila and Nariño) were evaluated. Cold coffee brewed under coarse grinding and 22 h of extraction exhibited the highest values of total dissolved solids, extraction yield, pH, titratable acidity (TA), and total phenolic content. The type of coffee used mainly affected the TA and pH. All cold brew coffee samples had lower TA values than their hot counterparts. Nariño cold brew samples had higher TA values than those of Huila in all treatments evaluated. Higher scores were reported in the sensorial evaluation of cold brew coffee when prepared using the shortest time (14 h) and coarse grinding for both coffee types. These coffees were characterized by strong sweetness, fruity and floral flavours, medium bitterness and acidity, and a creamy body. Furans, pyrazines, ketones, aldehydes, pyrroles, esters, lactones, furanones, and phenols were detected as odour-active compounds. The findings of this study demonstrate that the particle size, contact time, and coffee type affect the physicochemical and sensorial characteristics of cold brew coffee, leading to cold brew coffees with different flavour profiles.

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The progressive freeze concentration of sucrose solutions was tested. The effect of the initial concentration of the solution (C 0), the temperature of the refrigerant (T) and the stirring speed (ω) on the final concentration of the solution was determined. The effects were significant on the freeze concentration, for both individual and combined effects. The maximum concentration achieved in the progressive freeze concentration was 53º Brix, when the initial concentration was 35º Brix, at a speed of 800 rpm and a temperature of refrigerant of-20°C. The best values of the concentration index are obtained at low concentrations, high stirring speed and low temperature. The average distribution coefficient increased with the initial concentration of the solution. The average yield parameter at different initial concentrations is around 0.6 kg ice•kg sol-1 •h-1 .

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