Abstract: Keribo is one of Ethiopian fermented products made by uncontrolled fermentation of roasted barley through chance inoculation of microbes from the environment. Scientific information on the fermentation process of Keribo is scanty. The main objectives of this study was, therefore, to document the traditional knowledge on the techniques of Keribo preparation, to identify the raw materials and equipment used for its production, to evaluate the yield and production cost of Keribo fermentation. Information on the production processes were collected from local brewers in Jimma town and four of its districts around Jimma town using open and closed ended questionnaires and through focus group discussion. The raw materials used for laboratory fermentation of Keribo were bought from local markets and processed following the traditional techniques. In this study, detailed information pertaining to the preparation processes and the raw materials used for its preparation was documented. Finally, flow chart of traditional Keribo fermentation process was developed. The mean pH and titratable acidity of Keribo samples were 3.84±0.35 and 12%, respectively. Keribo has short shelf life and the product turned unacceptable shortly after fermentation. This work is the first of its kind and hopefully serves as baseline data for further investigation of this traditional fermented product.
INTRODUCTION
Traditional methods and age-old techniques of food processing are still used in developing countries especially in rural communities. Household-level fermentation of Keribo is one such indigenous technology that has been developed by a range of ethnic groups from locally available equipments and raw materials. These communities need improved technology to advance fermentation processes for food safety and nutritional value. Keribo is an indigenous traditionally fermented beverage produced and consumed in different parts of the country, including Jimma zone. It is produced mainly from barley and sugar. Fermented Keribo constitutes a major part of the beverages being served on holidays, wedding ceremony and also as sources of income of many households in Jimma zone. However, more effective and scientific knowledge-based production could give increased income for those who are involved in the production. This product is most frequently used by religious groups who do not like alcoholic beverages. Being considered as a non- or low- alcoholic beverage, Keribo is popular among both adults and children. Keribo is a cereal based traditional fermented beverage produced on small-scale using locally available equipment and it has short shelf-life and consumed within short period of its production. Together with its safety, the fermentation processes and raw material profile of ‘Tella’ (Samuel and Berhanu, 1991), ‘Borde’ (Bacha et al., 1998) and ‘Shamita’ (Bacha et al., 1999) are well documents. However, a study on documentation of existing technology and raw materials of Keribo production is scarce. Therefore, the present study was conducted to investigate production processes, document the existing technology, proportions and treatments of ingredients and shelf-life of the ready-to consume product.
MATERIALS AND METHODS
Study area, sample size and data collection: Traditional ‘Keribo’ brewers in Jimma town and in four of the districts around Jimma town, Oromia Regional state, were included in the study. The four districts included Seka, Dedo, Yebu and Serbo. Selection of the districts was based on their closeness to Jimma town which are found at an average distance of 20 km from Jimma town. Two kebeles which are known for vending of ready-to-consume Keribo for income generation were selected based on availability of the product. After preliminary screening of respondents, a total of 95 'Keribo’ brewers were selected randomly for interview and 10 brewers were selected for sample collection. Information pertinent to ‘Keribo’ preparation techniques, the raw materials used and duration of fermentation were gathered through interview, focus group discussion, questionnaire and on-site video recording. Focus group discussion (Keim et al., 1999) was made with 10 of the focus groups 2 brewers from each study area).
The brewers were interviewed using their native language in the village and at the market places (Morgan, 1997).
The questionnaire used to gather issues related to traditional processing techniques, proportions of raw materials, economic importance and shelf life of Keribo. Moreover, the respondents were asked to explain major problems encountered during ‘Keribo’ production, distribution and consumption and to suggest possible solutions, if any. During interview and data collection, personal information like age, religion and education were recorded and the data from the survey were translated and analyzed for significances of mean differences. The study was conducted from November, 2009 to May, 2010.
Laboratory fermentation of Keribo: monitoring of processing parameters: The art of fermentation of traditional brewers is crucial for understanding every step used in the fermentation technology. Although the traditional brewers might not have scientific background, they could normally ensure a proper fermentation as a result of years of experience. Without knowledge of the art of traditional food fermentation, a scientist cannot provide a scientific explanation for the process and attempt to provide assistance in improvement of the technology. To this effect, Keribo was prepared by an experienced woman brewer from a mixture of ingredients following the traditional recipe in Microbiology Laboratory for appropriate documentation of steps and procedures and immediate analysis of the product under study for some physico-chemical parameters.
Based on information gathered during data collection, appropriate equipments and raw materials were purchased from local market in Jimma town. The main equipments and ingredients suggested for Keribo fermentation were plastic bucket, griddle of iron (‘Mitad’), dish, Sieve, barley, sugar and yeast (commercially available yeast).
Physico-chemical analysis: The pH of samples was determined by dipping an electrode of a digital pH meter (HANNA-211 meter, Portugal) into 10 ml aliquot sample drawn during laboratory fermentation. The pH meter was calibrated against standard buffer solutions at pH 4.0 and 7.0 (Merck). The total amount of lactic acid present in each of the sample drawn was determined by titration against a 0.1 N NaOH (Byaruhanga, 1998). The percent of lactic acid present in the sample was calculated using the formula:
Shelf-life evaluation: For determination of shelf-life of the final product, samples were drawn at 12 h interval until the products quality turns unacceptable to the consumer (too moldy and sour) for three days. The taste and flavor of the fermented Keribo were monitored and compared throughout the 3 days period of study.
Statistical analysis: Average values of the processing parameters, pH and TA were calculated and compared by analysis of variance (α = 0.05) using Duncan’s test.
RESULTS
Description of the production processes of Keribo: A total of 95 people gave information on raw materials used for detail Keribo preparation procedures. All respondents were women which consisted of house wives (56%), merchants (36%), teachers (7%) and health professionals (1%). Among these, the proportions of Muslim, Protestant and Orthodox followers were 52, 32 and 16%, respectively (Table 1). Most of the informants (79%) were Afan oromo speakers which is used as the local language and few of them (21%) were Amharic speakers. According to results of the preliminary survey, the production techniques and equipment used for Keribo fermentation were the same among all the families contacted in all study areas: all families used plastic bucket, griddle of iron (‘Mitad’), dish, Sieve, barley, sugar and yeast for the fermentation of Keribo.
| Table 1: | Socio-demographic characteristic of the study populations |
Proportion of Ingredients for Keribo preparation: Keribo preparation has been the art and duty of females. The local producers of Keribo relied on yeast assisted fermentation of barley and table sugar (Table 2). There was significant variation among respondents opinion concerning the proportion of the raw materials, barley and sugar, used for Keribo preparation (CV>10%), but no significant variation on the proportion of yeast to be used as starter (CV<10%).
After the brewer had decided on the extent of treatments, the type of cereal ingredient, the quantity of each ingredient was measured before mixing according to the traditional recipe of Keribo production.
For Keribo preparation, barley was first cleaned of broken kernels, chaff and extraneous materials. Then the deeply roasted barley is added to boiling water and continued boiling for 10-20 min at 65-70°C until the ungrounded grain seems to be dissolved. Finally it is allowed to cool and sieved.
To the filtrate, sugar and yeast were added, thereafter, the container is sealed (to create anaerobic conditions) and left to ferment overnight.
The final product can then be poured into bottle for sale or for consumption the next day but before consumption, some amount of sugar was added to the fermented product until it become sweet enough. The preparation process was easy to follow (Fig. 1) and it took one day to get it fully fermented under optimum temperature.
| Table 2: | Mean weight of ingredients used for Keribo preparation |
| Min: Minimum, Max: Maximum; SD: Standard deviation | |
| Fig. 1: | Flow chart of traditional Keribo fermentation process |
Malt was not used in Keribo fermentation and starch and sugar are the only principal fermentable carbohydrates. From this, it was possible to estimate the cost of production and potential profit.
Results of FGD and interview
Fermentation time: It was found that the traditional methods used
for the preparation of Keribo and fermentation period were similar in all households
surveyed in the study area. According to the respondents’ opinion, warmer/temperature/of
the fermentation environment, tightly sealed plastic container and yeast were
found to be the most important factors in determining the fermentation periods.
The average fermentation period required for the traditional Keribo to be ready
for serving was about 8 h. Optimum temperature and anaerobic environment in
tightly sealed plastic container increased the rate of fermentation.
Cost of production: It was observed that Keribo production is cost-effective; estimated cost of a liter of Keribo is 2.6 Birr. The current (2009/10) price of 1 kg of barley, 5 g yeast and 1 kg sugar is approximately 5.00, 1.00 and 15.00 Birr, respectively and when mixed with 10 L of water, it produces 10 L of Keribo.
Safety issues of Keribo production: Some of the advantages of traditional fermentation are that they are integrated into village life; commonly utilize locally produced raw materials, inexpensive and part of culture of local consumers. However, there is no scientific protocol for the production of traditionally fermented Keribo. Fermentation period is chosen according to the brewers’ judgment. The quantity of water and substrate to be used for its fermentation is not regulated or standardized. The potential health risks posed by the inhalation of carbon dioxide released during deep roasting of barley and the consumption of fermented Keribo are not known. There is no way to assure a consistently uncontaminated environment for the fermentation; the unpredictable processing environment, the hygiene of handlers, equipment and facilities are not evaluated. The lack of knowledge or information on the effect of heat treatment of ingredients and fermentation on the nutritional quality of the final product questions the nutritional value of the product.
Patterns of consumption: It was found that all the respondents have been using Keribo for household consumption, invite guests, or on special occasions during holidays and weeding ceremony. About 30% of the study population has used Keribo for income generation as well. It was considered as non- or low- alcoholic beverage and was popular among both adults and children as a drink and was consumed daily, especially during the dry seasons. The customers demand and Keribo production by vendors decrease during rainy seasons in all study areas. The consumers consumed the product only to quench their thirsty. It is considered to be ready for consumption when it begins to produce vigorous foam and bubble. Keribo is retailed at market places and at vendors’ house. According to the consumers and brewers view, decline in the active fermentation and failure in bubble production is a signal of quality deterioration and after which the product becomes sour and alcoholic. Both producers and consumers of Keribo also believed that the product has poor keeping quality with shelf-life of not more than 2 days. It should preferably be consumed within 8-10 h after fermentation without any refreshment with sugar. It becomes unacceptable by the consumer for consumption after 10 h. The brewers usually prefer to produce Keribo on small-scale and add sugar to refresh fermentation to avoid loss.
| Table 3: | pH and titratable acidity of some Keribo samples |
| TA: Titratable acidity, SD: Standard deviation, CV: Coefficient of variation | |
pH and titratable acidity of Keribo Samples: Keribo samples had mean pH of 3.84±0.4 and mean titratable acidity (TA) of 12%±3.20% (Table 3). There was no significant variation among Keribo samples in pH (CV<10%), however, there was significant variation in TA values (CV>10%).
Shelf-life evaluation: The fermented Keribo had a moldy flavor on 3rd days after it was ready for consumption. By the end of the 3 days, it was no longer consumable in terms of acid/alcohol with the final pH of 3.10, Titratable Acidity (TA) at 0.25, means too acidic and has moldy flavor. The color did not change from the original brown while the flavor had changed to a moldy flavor and sweet taste to a characteristic sour taste.
DISCUSSION
Keribo fermentation is socio-culturally bound to the people in southwestern parts of Ethiopia, especially with the religious groups who do not consume alcoholic drinks. The cereal ingredient used for Keribo preparation and the overall traditional processing techniques of its preparation were found quite similar in all the communities where it has been prepared and consumed.
As the production of Keribo requires no expensive facilities and made using locally available materials and ingredients, the commercialization of Keribo is potential area of investment. It is a traditional, non-alcoholic, dark brown colored fermented beverage, with some similarity to Boza of Bulgaria, Albania, Turkey and Romania (Blandino et al., 2003). Unlike Boza, however, Keribo has short shelf life; and has been commonly consumed in rural and urban areas of Jimma zone, southwestern of Ethiopia. It is produced by an over-night fermentation of cereal (barley) predominantly by activities of LAB like the fermentation of shamita (Bacha et al., 1999).
The processes involved in Keribo production are simpler than those related traditional Ethiopian fermented beverages such as ‘Tella’ (Samuel and Berhanu, 1991), ‘Shamita’ (Bacha, 1997) and ‘Borde’ (Bacha et al., 1998), although traditional Keribo brewers still rely upon locally available equipment. The sources of fuel are common to all these products: they all use rudimentary sources of energy which do not readily lend themselves to modernization of the process or development of local capacity. Firewood is traditionally used for cooking of the ingredients and alternative energy sources should be sought when the production technology is upgraded. The roasting of barley for Keribo preparation is the same as roasting of enkuro for borde and/or tella brewing.
Several researchers Damelin et al. (1995), Johansson et al. (1995) and Bacha (1997) have indicated that the microorganisms involved in the spontaneous fermentation of cereals during fermentation of traditional foods and/or beverages are essentially the micro-flora of the raw materials and equipment. Keribo brewers also believe that if yeast and table sugar is not used during fermentation, the fermentation plastic bucket (‘yewuha baldi’) is not satisfactory for fermentation until it has been used several times. This is an indication that microorganisms are being retained in the plastic bucket from the previous batch of fermentation. The vendors rarely use back-slopes from previous fermentation during Keribo preparation.
According to Rose (1977), the alcohol content in the early stages of fermentation of beverages is too low for an intoxicating effect. Since the duration of fermentation of Keribo is short (maximum of one day), significant amount of alcohol may probably not accumulate. Thus, the method of production may perhaps explain why Keribo was considered to be a non-alcoholic beverage by the consumers. Keribo brewers usually refresh an over fermented Keribo by adding sugar to the product.
The success of the fermentation of Keribo was found to depend on fermentation temperature as the case is for ting production (Moss et al. 1984) and anaerobic conditions.
The shelf life of fermented Keribo is not longer than 3 days, indicating that the product could not be kept beyond this period at room temperature. Gould (1992) observed that metabolic products and the bacteriocins produced by lactic acid and related bacteria are antagonistic to the activity of other microorganisms in a product although it could also contribute to loss of product acceptability at higher concentration.
CONCLUSION
The results of this study indicated that Keribo is a cereal based traditional fermented beverage produced on small-scale using locally available equipment and it has short shelf-life and consumed within short period of its production. It was found that people tend to consume more than they require because most households cannot afford cooling devices to extend the keeping quality of the Keribo which could result in further fermentation with final sour taste. Because of its low alcohol, the beverage has been consumed by both adults and children. This study documented information about ingredients and equipments used which could serve as useful and informative baseline data for further studies to scale-up this product.