The Journal of Food Technology in Africa Vol. 9 No. 1, 2004, pp. 13-16
Potential African Substitutes for Hops in Tropical Beer Brewing
*Ajebesone P. E.1 and Aina J.O.2
1. Department of Food Science and Nutrition, E.N.S.A.I.
P. O. Box. 455, University of Ngaoundere, Cameroon.
Code Number: ft04002
The potential of four selected tropical vegetables, Grongonema latifolium (Utazi), Vernonia amigdalina (Bitter leaf), Azadirachta indica (Neem) and Garcinia cola (Bitter Kola) as substitutes for hops in tropical beer brewing were evaluated.
The vegetables were processed into powder by drying at 50°C for 24 hours (such that they maintained their original colour) and then cooled in dessicator before milling in a hammer mill. Proximate analysis showed that these vegetables had protein and crude fibre values comparable to those of commercial hops. Fat content values were however much higher than those for hops with Grongonema latifolium having the highest values of 19.10%. Garcinia cola with a total resin value of 8.24% and an essential oils value of (1.16ml/ 100g) had values which were significantly different from those of hops. The other three had values comparable to those for hops. Bitterness levels were high when the vegetables were extracted with organic solvents, than with distilled water. These values however decreased, the longer the storage period. Losses in bitterness were more when the vegetables were stored at ambient temperature than when they were stored at refrigeration or freezing temperatures. Losses in bitterness were more for water extracts than for organic solvent extracts.
Key words: Hops, Resins, Essential Oils, Bitterness level.
Hops the female flowers of the hop plant (Humulus lupulus) are grown in the temperate regions of the word, solely to meet the demands of the brewing Industry (Hough et al., 1982, Grant, 1977). Hops contribute to foam stability and also provide hop flavour, hop character and preservative properties to the beer (Laws, 1983). In most tropical countries, the hops are imported. With the expansion of the brewing industry in Africa, huge amounts of money are therefore being spend by developing countries for the importation of hops.
A lot of effort has been made in the brewing industry for the substitution of barley with some local cereals. The substitution of hops with local raw materials has not however received the same attention. Some pioneer work by Okafor and Anichie (1983), showed that leaves of the tropical vegetable, Grongonema latifolium (utazi), show great potential as substitute for hops.
They found out that this plant possessed some antiseptic properties against beer spoilage micro-organisms. The chemical properties of beer brewed using this plant did not differ much from that brewed with hops though their organoleptic differences were pronounced (Okafor and Anichie, 1983). Okafor and Anichie (1983) however did not characterise the vegetable as they only used it for brewing and sensory analysis.
This piece of work intends to characterise in addition to Grongonema latifolium, three other bitter vegetables used for food in the tropics. These are Vernoniq amygdalina (Bitter leaf), Azadirachta indica (Neem) and Garcinia cola (Bitter kola). Azadirachta indica is used in some parts of Africa for the treatment for malaria, while Garcinia cola is used in some areas for the treatment of stomach ache and gastritis. All four vegetables have one thing in common. They are bitter vegetables.
The principal objective of this study is therefore to compare these vegetables to commercial hops by:
MATERIALS AND METHODS
Procurement of raw Materials
(a) The Association of Official
Analytical Chemists (A.O.A.C.)
Processing of vegetables to powders
The resulting powders were then put into high density polythene bags of thickness 0.06 mm, heat sealed and then stored in air tight metal containers. The flow chart below represents the process.
Preparation of Vegetable Extracts
Bitterness level determination
Determination of the storage
stability of vegetables and hops
RESULTS AND DISCUSSION
Table 1 compares the proximate analysis values of the vegetables to those of commercial hops. Grongonema latifolium had the highest fat content, wish was about six times the value for commercial hops. This partially explains why beer brewed with Grongonema latifolium as reported by Okafor and Anichie (1983), had a poor foam head. Protein values for the vegetables were comparable to those of commercial hops. Total resin values for Grongonema latifolium, Vernonia amygdalina and Azidirachta indica compare well with those for hops.
However Table 2 shows all the vegetables having values for hard resins greater than that for hops. The hard resins are generally accepted as the oxidation products of the soft resins (Grant, 1977). These values suggest that the vegetables will oxidise or deteriorate faster than commercial hops.
The bittering levels of the vegetable extracts are presented in Table 3. The values clearly show that the vegetables differ in their degree or level of bitterness. Water extracts gave low bittering values, whilst organic fat solvent extracts gave much higher values. These values were comparable to those of hops. The enhanced bittering yields by organic extracts implies the removal of interfering fat and other lipid materials from the vegetable tissues. These results are consistent with the report of Ashurt (1971) that non-polar fat solvents are suitable extracts for the bittering constituents of hops.
The results clearly show that hops has a better storage stability than the vegetable extracts. Bittering stability varied with the vegetable, extractant, storage temperature and duration of storage. Grongonema latifolium showed the highest losses in bittering potential among the vegetables. Generally however, losses in bitterness were more for water extracts than for organic solvent extracts stored for the same length of time and at the same temperature. After twelve weeks of storage at ambient temperature, most organic solvent extracts still maintained over 70% of their original bitterness, while some water solvent extracts had lost as much as 50% of their bitterness.
Results also show that freezing and chilling storage led to lower losses in bittering potential than storage at ambient conditions. This is in agreement with the reports of Grant (1977) and Hough et al. (1982) which say that cold storage provided greater stability for hop bitterness than storage at elevated temperatures. Generally, bitterness levels decreased with the duration of storage.
Grongonema latifolium, Vernonia amygdalina, Garcinia cola and Azadirachta Indica all have great potential as substitutes for hops. Grongonema latifolium, Vernonia amygdalina and Azadirachta Indica because of their high bitterness levels, will impart considerable bitterness to beer while Garcinia cola with its high value in essential oils will impart flavour and aroma to beer.
The vegetables will maintain their bitterness for longer periods if they are stored at cold temperatures. Stability may also be increased further by pelletizing the powders of the vegetables and then vacuum packing. This will reduce their contact with oxygen and also the rate of oxidation.
Copyright 2004 - The Journal of Food Technology in Africa, Nairobi
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