Characterization of Hop Extracts and Extracts from some Selected Nigerian Plants by GC-MS and Brewing Qualities Analyses

Abstract

Humuluslupulus L (hop) plants and four selected Nigerian plants namely
Azadirachtaindica(neem), Garcinia kola (bitter cola), Gongronemalatifolium(heckel) and
Vernoniaamygdalina (bitter leaf) as substitutes for hops in beer brewing were
characterized in terms ofmethanolic and aqueousextracts using Gas Chromatography -
Mass Spectrometer (GC-MS-Q2010 plus, Shimadzu, Japan). The brewing qualities (isoalpha
acid and essential oil contents)of the extracts were investigated using standard
methods. Statistical analysis was carried out on the result of brewing qualities tests by the
application of one way analysis of variance (ANOVA). The GCMS results showed that
these plants contained metabolites comparable to those of hops, although some
metabolites[dehydro-cohumulunic acid; 4,4-dimethyl-2-buten-4-olide; 1,2-dimethylcyclopropane
carboxylic acid; lupulone; 2,5-dimethyl-2-hexanol; 4,4,5,5-tetramethylbicyclo
hexyl-6-ene-2,3-dione; octadecanoic acid, oxiranyl methyl ester and 1,2-
benzenedicarboxylic, bis(-2-ethyl hexyl) ester] present in hops were absent in the Nigerian
plants. Isomerized hop, hop leaf, G. kola and V. amygdalinacontained a total number of 14,
11, 12 and 9 metabolites respectively while A. indcaand G. latifolium each contained a
total number of 10 metabolites.The brewing qualities investigated showed that iso-alpha
acid ranged from 8.78-12.53ppm and essential oil ranged between 5.44-10.12g/100g. This
study revealed that the brewing qualities of all the extracts did not differ significantly.
Hence, extracts from tested Nigerian plants present potential substitutes for hops in the
Nigerian brewing industry without significant alteration to the brewing qualities.
Consequently, academic activity in the area of mixtures/blends of extract of plant species
which mimic hop taste is strongly recommended.