Preparation and physicochemical analysis of some Ethiopian traditional alcoholic beverages

Ethiopian traditional alcoholic beverages namely tella, tej and areki are very common drinks in the country. Ten (10) alcohol vending houses were considered in the study by considering two from each five sub-cities, purposely for ‘filtered’ tella sampling and five for the unfiltered tella, tej and areki samples. The alcoholic contents of filter-tella, tej and areki were measured and found in the range of 3.84 to 6.48, 8.94 to 13.16 and 33.95 to 39.9% v/v ethanol, respectively. Difference in pH values and ethanol levels among all samples was significant (p<0.05). Variations within samples of each vending houses, coefficient of variation (CV>10%) among all samples were significant, though the variation in pH of the alcohols studied were analyzed and found at drinking range or according to European Brewery Convention. Finally, sensory responses which were taken from the community (people drinking these alcohols), indicated that they are high in aroma (bitterness for tella than other drinks reported).


INTRODUCTION
In nearly all areas of the world, some types of alcoholic beverage native to their region are prepared and consumed (Steinkraus, 1986).Indigenous fermented alcoholic beverages from different parts of the world are described (Abegaz et al., 2003;Kabak and Dobson, 2011).In Ethiopia, some of the fermented beverages include tella, tej, borde and shamita which are very popular traditional drinks.The latter two, borde and shamita are mainly prepared in central and southern Ethiopia (Alemu et al., 1991;Ghebrekidan, 1992) whereas considering popularity, traditional alcoholic beverages namely, tella and 'katikala'(areki) is very common in northern part of Ethiopia.Currently, even bottled 'Gojam areki' from north Ethiopia is in the market by gathering from different rular vending houses.
Among fermented foods, alcoholic beverages have been widely consumed since prehistoric times by people around the world.Fermented products can play an important role, contributing to the livelihoods of rural and perturbing dwellers (Gadaga et al., 1999;Jeyaram et al., 2009).In developing countries, traditional fermentation serves many purposes.It can improve the taste of food, enhance the digestibility of a food, preserve food from degradation by noxious organisms, and increase nutritional values.Further, it is used for medical reasons, recreational purposes, in marriages, in religious and nonreligious ceremonies (Kohajdova and Karovicova, 2007;Anteneh et al., 2011), at festivals and social gatherings, at burial ceremonies and as food substitutes (Hall and Sharples, 2008).
Fermentation methods for traditional alcohols are inexpensive and adaptable at household level in traditional communities (Paredes-López and Harry, 1988).Its process involves chemical change in bringing organic substrates through the action of biochemical catalysts, called enzymes.In brewing industry: Starch substrate ↦ glucose ↦ ethanol + carbon dioxide + energy.*Corresponding author.E-mail: melakrobel@yahoo.com.Fax: (047) 1111450.
Consumption of alcohols from different brewing products posses several damaging effects such as, mental problems, job trouble, loss of control, impaired judgment in humans and irresponsible behaviors (Coleman and Cater, 2005;Bhargav et al., 2008;Sui et al., 2009).Depending on the dose and the regularity of its consumption, alcohol is a more problematic causing heart disease, cancer diabetes, acute respiratory failure or death (Guidot and Hart, 2005;Gun et al., 2006).There are considerable evidences in some African countries that produced alcoholic drinks are known to have toxic components (Reilly, 1976;Sanni, 1993).
Various works have been reported in fermented food analysis (Aloys and Angeline, 2009;Satish Kumar et al., 2012), particularly alcoholic beverages in different parts of Ethiopia including the data with regards to methanol, fuel oil and ethanol contents of tella, areki and tej (Urga et al., 1997;Bekele et al., 2001).The ethanol and methanol content were reported seemingly from 'unfiltered' tella of Ethiopia though not clearly indicated (Desta, 1977).In light of this, 'filtered' tella physic-chemical parameters like ethanol level, pH, turbidity, sensory evaluation and community perception has been seldom addressed in Ethiopia.Hence, this study aimed to analyze ethanol level, pH and turbidity of some traditional alcoholic drinks accustomed in Ethiopia which include tella, tej and areki.In the case of tella, both 'filtered' and 'unfilterd' products were considered for analysis.Moreover, sensory evaluation and community perception were taken into consideration with freshly homemade tella.

Sampling and sampling site
Ten (10) samples of 'filtered' tella, five samples of tej and areki vending houses were considered from different sub-cities of Jimma, namely: Ajjip, Qochi, Markato, Menahera and Matrik Sefer.Moreover, five 'unfiltered' tella samples were monitored starting from preparation and taken for analysis from each five sampling sites.All those vending houses were selected purposively, and tella samples were collected using polyethylene bottles for analysis.

Tella
Tella is one of the Ethiopian traditional beverages, which is prepared from different ingredients.It is brewed from various grains and different cereals which include; barely, corn, wheat and sorghum and also from teff and maize, although in some regions, millet and Rhamnus prinioid (Fite et al., 1991).
Pre-preparation steps were similar to that described by Sahle and Gashe (1991).The clay container (insera) was washed with Grawa (Vernonia amygdalina) and water several times and after that smoked with wood from weyra (Olea eurapaea subsp.Cuspidate) in order to find good fragrance or flavor and to be neat.During the preparation of tella, an average duration of six to eight days was required by the tella producers at winter season.The preparation of tella has four major phases.

Tej
Tej is a home processed, fermented alcoholic beverage; it is also commercially available honey wine.It is prepared from honey, sugar, water and leaves of Gesho (Rhamnus prepoides).Preparation procedure was similar to those reported by Bahiru et al. (2001).

Areki
Areki is a distilled alcoholic beverage.It is a colorless, traditional alcoholic beverage which is distilled from fermentation products prepared in almost the same way as tella except that fermentation mass in this case is more concentrated.

Chemicals and apparatus
Abbee Refractometer (ATAGO, USA) pH meter, density meter (Compaq Evo D500, USA) were used for the experimental work.Distilled water was utilized.All experimental process was performed according to standard procedure.

Experimental
The collected samples of tella ('filtered'-case) and 'unfiltered' tella monitored during the preparation process plus tej were primarily filtered with 150 µm sieve and kept in a refrigerator until experimental work.The density meter was adjusted to determine the desired parameters.

pH values of the samples
The pH of the samples was measured by dipping the electrode of a digital pH meter into the samples after a proper calibration of the meter with standard solution.

Determination of the refractive index
All the refractive indices was measured by using Abbee refractrometer on a water bath and thermostat.The function of the water bath and the thermostat is to keep the temperature of the system constant (20°C).Before and after measurement of the refractive index of each sample, the refracto-meter was calibrated with distilled water.

Determination of the specific gravity
The specific gravity of the samples was determined using a pycnometer (long neck pycnometer).The weights of an empty pycnometer, pycnometer with distilled water, and pycnometer with the samples were measured using a balance.

Determination of ethanol level of the samples
The ethanol level of tella, tej and areki was determined in the quality control laboratory of Bedele Brewery, Bedele.It is first filtered using a fluted filter paper.Then, the ethanol level determination involved measurement of refractive index and specific gravity.The temperature of the filtrate was then set at 20°C.The refractive index and the specific gravity of the samples were measured at 20°C temperature.The alcoholic content of the samples were calculated using Dave Miller (Miller, 1988) who estimates the alcohol by volume using a formula: Alcohol by volume = (initial gravity -final gravity) / 0.75.

Physicochemical properties of alcoholic beverages
Significant variations in pH values of the tella within the sampling sites and pH value ranged from 4.00 to 4.99 (Table 1).There were also significant variations in the alcohol content of tella samples observed where the values ranged from 3.98 to 6.48 (% v/v) and averaged 5.17 (%v/v).Wide variations in results were obtained and this might be attributed to different methods of preparation of the beverages at the domestic level and the constituent variations are also suggested in literatures (Vogel and Gobezie, 1983).As these fermentations are natural and, thus, uncontrolled, alcohol produced during the fermentation methods are spontaneous, and variabi-lity of the product is inevitable (Zvauya et al., 1997).
Statistical one-way ANOVA analysis indicated that at the 0.05 (p = 0.028) level, the means of the ethanol (% v/v) of 'filterd' and 'unfiltered' tella are significantly different (Tables 1 and 2).The Original gravity reported for 'unfilterd' tella was found in the range of EBC (European Beer Convention).
In Table 3, the pH value of tej and areki ranged from 3.56 to 4.45, and 4.30 to 4.51, respectively.Moreover, alcohol contents of tej and areki samples ranged from 8.94 to 13.16 and 33.95 to 39.90 with average values of 11.47 and 37.22 %v/v, respectively.There is a significant variation in the alcoholic content of tej and areki samples collected from different area as it is supported by Gizaw ( 2006) through the study conducted at different location.The alcohol contents of the sub-cities reported (Figure 1) for each alcoholic drink is as indicated: Tella case; matrik> merkato> menaheria> Qochi> Ajip.For Areki the order of alcoholic content is matrik> merkato> qochi> menaheria> ajip.For tej: the order in alcoholic content is like merkato> qochi> menaheria> ajip> matrik.
In Jimma town, the variation in ethanol contents of traditional alcoholic beverages like areki and tej might be due to differences in preparation and fermentation as it is reported by Bahiru et al. (2001) and Susan and Lewis (1993).Conditions such as temperature, aeration and actions of the microorganisms also obviously affect the level of the alcohol in the samples (Sahle and Gashe,  1991).The average pH values of tej and areki in this study show considerable variation for each sample as indicated in the results obtained.In comparing the mean alcohol contents of tej from other studies in Ethiopia, deviation was observed such that the result is more than that reported by Desta (1977), but similar to that reported by Gizaw (2006).

Sensory evaluation of tella
A panel of ten people afterwards called judges who have had experiences in drinking alcohols were selected from the community on the basis of interest and availability.They were initially trained in descriptive analysis of the mouth feel attributes of tella.Most of the judges provide a sensory evaluation reflection of bitterness in the 'unfiltered' tella samples prepared under the supervision of the researcher.But for the cases of 'filtered' tella collected from five study sites, the judges dictated that most of the samples >70% have medium sourness by stating that they feel sweet taste and sour homogenized.Some of the mouth feels such as bitterness, sweet, sour, soapy and aromatic used by these judges were reported by Langstaff and Lewis (1993) though they used a term softness instead of soapy or CO 2 (Kebede et al., 2002).The judges emphasized that the reason for bitterness might be the higher use of gesho in the preparation.In view of this, it seems evident (Motarjemi and Nout, 1996) that the raw materials utilized for the production of the beverages as well as the type of yeast during fermentation conditions played the major role in defining the mouth feel parameters.In sensory evaluation, tella were found to be strongly affected by the method of preparation, which in turn played an important role in the perception of the people in the ingredient at the initial.
The judges were also interviewed on the perception of the community on alcoholic beverages in general about tella, areki and tej and responded as follows: there are assumptions that tej is to be consumed by peasants living near the town or by the aged people in the town.All the judges agreed that on the perceptions or importance, they they accepted because they contribute to medicine, it makes them to get fatter in short periods, and there is eye-watering as length of consumption period increased.Other serious cases those judges suggest when asked to provide their last words, was about the secrets things done to increase the alcoholic content of tella in the community which is adding cement and the use of certain plants.Market value or the business of venders is not as expected due this related secret perceptions and trigsjudges prediction.

Conclusion
The study indicates that the alcoholic content (% v/v) of traditional alcoholic drinks (tella, tej and areki) in Jimma town varied considerably by the type of alcoholic drink considered.Similarly, there was a significant variation in pH values of the three alcoholic drinks (tella, Tej and Areki) though it was on drink range.Not only the variation in alcoholic drinks but also ethanol level were reported with significant variation from each experimental site studied.The alcoholic content variability in local alcoholic beverages could be attributed to the spontaneous fermentation differences that the producers build.

Figure 1 .
Figure 1.Alcoholic content versus study site variation of alcoholic drinks.

Table 2 .
Ethanol level (%v/v) and original gravity measurements in each sample of 'unfiltered' tella.

Table 3 .
Experimental results of pH and ethanol level of Ethiopian traditional alcoholic drinks, tej and areki.