EVALUATION OF VACUUM DRYING ON AROMA COMPOUNDS OF DRIED HOPS

Vacuum drying of fresh hops was conducted at various pressures (0.2, 1 atm) and temperatures (40°C, 50°C, 60°C), and its impact on flavor and aroma compounds was evaluated. It was observed that hops dried faster at higher temperatures and at lower pressures, and a regression model was developed that calculates the drying time as a function of process conditions. Vacuum drying hops at 50°C and 60°C led to the retention of more aroma-active compounds (beta pinene, myrcene, limonene, linalool, caryophyllene, humulene, geraniol), humulones (alpha and beta acids), and free polyfunctional thiols such as 3MHA compared to drying hops without vacuum at high temperatures. Vacuum-dried hops tended to have the most mono- and sesquiterpenes and the least oxidation products, such as caryophyllene oxide. Vacuum-dried hops also had the most alpha acids, beta acids, and free polyfunctional thiols. These results indicate that more aroma retention results from vacuum drying compared to hot air drying.