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Title: Investigation of Bitter Leaf (Vernonia amygdalina) Extract as a Potential Substitute for Imported Hops.
???metadata.dc.contributor.*???: Teshome Worku (Ass. Prof.)
Etefa, Gurmesa
Keywords: hop substitution;bitter leaf;optimization;bitterness level;Iso-alpha acid;alpha acid;resin
Issue Date: Jun-2017
Publisher: AAU
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 in 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 a bitter leaf to an appreciable level of 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 are adequate for beer brewing.
Appears in Collections:Thesis - Process Engineering

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