Abstract : The potential of four selected Nigerian plants namely Azadirachta indica (neem), Garcinia kola (bitter cola), Gongronema latifolium (heckel) and Vernonia amygdalina (bitter leaf) as substitutes for hops in beer brewing were evaluated in terms of methanolic extracts. Bitterness character of the extracts was investigated using UV-visible spectrophotometer. Phytochemical assays of the extracts were carried out using standard methods. Mineral contents of all the extracts were carried out using Atomic Absorption Spectrophotometer (AAS) after digestion with perchloric acid and concentrated nitric acid. These tropical plants were statistically ranked by the application of Analysis of Variance (ANOVA). The concentration of iso-alpha acid ranged from 7.95-12.53ppm. Phytochemical assay revealed that alkaloid content in all the extracts ranged between 3.2-4.8%; tannin ranged from 2.0-4.8% and saponin ranged from 0.80-5.20%. The AAS results showed that the concentration of metals investigated in all the samples were calcium (16.300–33.145ppm), sodium (92.019–101ppm), potassium (8.297–206.838ppm), magnesium (19.331-22.188ppm), lead (Not detected), manganese (0.426-38.628ppm), cobalt (0.00–0.002ppm), zinc (0.963-17.944ppm), mercury (0.00–1.127ppm) and iron (0.159-8.614ppm). It was established from ranking that the order of closeness of the vegetables investigated to isomerized hop extract was G. latifolium (0.919) > G. kola (0.819) > A. indica (0.712) > V. amygdalina (0.517) while that to hop leaf extract was V. amygdalina (0.964) > G. kola (0.679) > G. latifolium (0.433) > A. indica (0.288). Hence, the extracts from tested Nigerian plants could be used as suitable substitutes for hops in beer brewing. Extract of G. latifolium had the greatest potential as substitute for isomerized hop extract and that of V. amygdalina was the closest substitute for hop leaf extract.
Keyword : hops, extract, mineral, phytochemicals, iso-alpha acid, Nigerian plants, substitutes, bitterness.