Investigation of Bitter Leaf (Vernonia amygdalina) Extract as a Potential Substitute for Imported Hops.
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Date
2017-06
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Addis Ababa University
Abstract
Recently, considerable attention has been focused on the brewing industry that are helping
transform Ethiopia’s business landscapes with alcoholic beverage industries having a lion’s
share in terms of investment and market. However, the country`s requirement of hops are met
through import. Thus, the need to investigate some Ethiopian plants that could substitute hops in
beer brewing. In this paper work bitter leaf (Vernonia amygdalina) was investigated using a
reflux condenser extraction unit and appropriate solvent material to obtain the extract.
Thereafter, the extract was characterized in order to determine its suitability for use in brewing
by comparing it with those of standard commercial hops values. The optimization of process
parameters for the bitter leaf extract was investigated using GFD. The three parameters and
their ranges namely temperature (80-100oC), time (1-3hr), and particle size (0.25-1.0mm) were
chosen. The individual parameters effect as well as effect of interactions between the process
parameters on bitterness level and Iso alpha acid value was analyzed using various graphical
representations. The physicochemical analysis of the bitter leaf showed that the sample extract
had brewing properties or variables as follows: Iso-alpha acid (mg/l) ranged from 7.99-9.14,
alpha acid (mg/l) of 9.51, total resin (%) of 19.72, hard resin (%) of 5.7, soft resin (%) of 14.02,
protein content (%) of 27.73% and fat content (%) of 2.74. The Analytical Bitterness Unit (ABU)
was found to be adequate and ranged from 16.55-17.1. The AAS results showed that the
concentrations of metals of the samples investigated were Calcium (mg/100g) of 25.61±0.048,
Magnesium (mg/100g) of 4.92±0.04, Iron (mg/100g) of 9.1±0.07and Zinc (mg/100g) of
2.27±0.052. Based on the comparison, it was observed that the brewing qualities of hops are
present in bitter leaf to an appreciable level with variation in the protein and mineral contents.
Consequently, the results obtained showed that bitter leaf presents an acceptably high level of
their hop properties that is adequate for beer brewing.
Key words: hop substitution, bitter leaf, optimization, bitterness level, Iso-alpha acid, alpha acid,
resin.
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Keywords
hop substitution; bitter leaf; optimization; bitterness level; Iso-alpha acid; alpha acid; resin