Effect of Extraction Time on the Yield, Chemical Composition, and Antibacterial Activity of Hop Essential Oil Against Lactic Acid Bacteria (Lactobacillus brevis and Lactobacillus casei) Beer Spoilage.

Hop essential oil (EO) generates interest for its antioxidant and antimicrobial properties, in addition to the volatile compounds that are responsible for the hop aroma in beer. Thus, the objective of this study was to evaluate the chemical composition, EO yield, and antibacterial activity of hop essential oil from hops of the Chinook variety against lactic acid bacteria (Lactobacillus brevis and Lactobacillus casei) at different times of extraction. EO extraction was performed by hydrodistillation at different times. By analyzing the chemical composition by gas chromatography and mass spectrometry, the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) were determined. The major compounds of hop EO were α-humulene, ß-myrcene, and ß-caryophyllene, and the extraction yields were 0.67, 0.78, and 0.85% mass of EO per mass of hops pelletized hops (m/m), for extractions of 90, 180, and 300 min, respectively. The EO obtained in 90 min was efficient against L. casei at 2.5 mg/mL (MIC) and 5.0 mg/mL (MBC), and the 300 min one against L. brevis at 2.5 mg/mL (MIC) and 25 mg/mL (MBC). The antibacterial activity was affected by the chemical makeup of the oil, revealing that the hop EO extracted in 300 min was the most efficient among the other extraction times.

Extraction of hops pelletized (Humulus lupulus) with subcritical CO2 and hydrodistillation: Chemical composition identification, kinetic model, and evaluation of antioxidant and antimicrobial activity.

Hop essential oil and hop extract using carbon dioxide (CO2) are products with high added value because they have bioactive and sensory properties. In this context, the objective of this study was to obtain and characterize essential oil and extracts from pelleted hops of El Dorado, Polaris, Hallertau Blanc and Callista varieties using hydrodistillation and subcritical CO2 extraction methods. Extraction yield ranged from 0.38 % to 1.97 % (m/m) for essential oils and from 8.76 % to 15.35 % (m/m) for extracts using subcritical CO2. The chemical compositions of the essential oils were mainly monoterpene (18.14 % to 29.91 %) and sesquiterpene (46.01 % to 59.03 %) hydrocarbons and for the extracts were sesquiterpene hydrocarbons (33.05 % to 71.90 %) and oxygenated sesquiterpenes (14.80 % to 34.89 %). The extracts showed better antioxidant activity than essential oils due to the presence of phenolic compounds and flavonoids. Hop extracts showed some antimicrobial activity, but essential oils did not demonstrate antimicrobial potential. Hop extracts obtained with subCO2 have the potential to be used in the brewing industry as a flavoring and as natural antioxidants.