The authors have declared that no competing interests exist.
Beer is typically brewed from four basic ingredients (water, a starch source, brewer’s yeast and flavoring agent such as hops). In Ethiopian case hops are coasty ingredient of beer which is imported with hard currency of the country. But this flavoring agent (hops) in beer production can also be substituted by locally available flavouring agent called gesho “Rhamuns Prinoide” leaf. In this study the effect of drying temperature and time on brewing components of gesho “Rhamuns Prinoide” leaf was examined using oven dryer. Brewing components of gesho “Rhamuns Prinoide” leaf were compared by taking the commercial hop brewing component as a standard. Drying temperature and time have a significant effect (P< 0.05) on major beer brewing components (Resin, Hop oil, Polyphenol, Mineral and Protein) of gesho leaf. Not only drying temperature and time but also the interaction effect has significant effect on these major brewing components of the leaf. The optimal drying temperature and time of gesho leaf was also determined to commercialize the gesho leaf powder or pellet as hop substitute in commercial beer brewers as flavouring
Beer is not the only widely consumed alcoholic beverage in the world but also the third most popular drink after water and tea. Beer is mainly brewed from four basic ingredients which are water, a starch source, brewer’s yeast, and a flavoring agent such as hops. Different types of beer are available in the market where this typicality comes from these ingredients, the additives used and the brewing processes. Beer is composed of a complex mixture of phenolic compounds extracted from the starch source and hop. Now a day’s special trend from micro breweries in the U.S.A. is the production of several range of extremely bitter beer created by the addition of extra hop during the brewing process.
The hop derived xanthohumol and the iso-alpha acid are primarily responsible for the perceived bitterness of beer. Most of the secondary metabolites are not only important for health benefits; it is also needed for beer flavor as well as stability. But some secondary metabolites of beer will make it quality loss during storage by the creation of haze (Piendl et al, 1989).
Beer contains nutrients such as carbohydrates, amino acids, minerals, and vitamins. In addition to nutrients beer also contains many of non-nutrient components including phenolic compounds.
The type and quality of beer brewed depends the following factors, the variety of barley, the malting process, temperature and pH of mashing, sparging, wort boiling, the variety of hops added during wort boiling, and fermentation process. It has been estimated that about 70–80% of beer polyphenols are malt-derived. Barley polyphenols are changed in the malting and brewing process. The phenols found in malt are less characterized when compared to the phenol derived from hops. The phenols extracted from malt during mashing and sparging known as polyphenol or tannins and it also react with proteins in the wort to form chill haze or permanent haze. In order to control these problem reduce sparge temperature below 77oc; reduce sparge time and the alkalinity of brewing liquor (De Keukeleire, 2000).
The hop is a perennial climbing plant; the aerial part dies off in the autumn but the rootstock stays in the soil, sometimes for many years. The plant needs a support up which to grow. In the wild, hops are found in hedgerows but for cultivation they are trained up strings attached to permanent wirework. Hops are used in beer production in small amount to impart its characteristic aroma and bitterness. Hops also contribute to the beer its antifungal and antibiotic properties so that the produced beer remains safe during storage (Verzele et al, 1991). The composition of the hops is extremely important for the quality of the beer produced from it and on dry weight basis the bitter substances (Resin) (18.5%), hop oil (0.5%), polyphenols (3.5%), protein (20.0%) and minerals (8.0%).The rest consists of cellulose and other materials which are unimportant for beer production. The most important components of hop for the production of beer are the bitter substances (resins) and essential oils or the hop oils (Kunze, 1996). During drying of hop the air speed and temperature should be carefully controlled so that volatile compounds which are heat sensitive will not be destroyed with increasing air temperature for prolonged time. But if the air speed is too low, the air will become saturated with moisture in the lower layers of the bed where lastly deposit moisture on the hops in the upper layer which finally causes discoloration of the hops (Verzele et al, 1991).
Gesho is a plant which grows up to six meters and it is cultivated in Ethiopia for its importance in the production of domestically fermented beverages like tella and teji. In Ethiopia the leaves and steams of gesho are crucial components in the production of traditional fermented beverages (Ashenafi M., 2006). Although gesheo leaf had been used as flavouring as well as antibiotic agent in traditional beverages, it had yet tried to commercialize it as hop substitute in commercial beer brewing industries. In doing so drying is the critical process in gesho leaf powder or pellet production. Because major brewing components of gesho leaf powder are volatile compounds which will be destroyed during drying by high temperature and moisture. Traditionally gesho leaf is dried simply using sunlight by spreading the leaf on the ground that had been already prepared for drying purpose where it negatively affect on its taste and flavor. In this study the optimal drying temperature and time had been investigated and hence it can potentially substitute the commercial hop imported as a flavouring agent in commercial beer brewing industries. So gesho leaf powder or pellet dried at the optimal drying condition had similar brewing components as that of the commercial hop imported by Dashen brewery Share Company.
The general objective of this study is: Determination of optimum drying conditions of gesho leaf powder as commercial hop substitute in modern beer brewing industries
To determine the optimum drying temperature of gesho leaf as hop substitute in commercial beer brewing industries
To determine the optimum drying time of gesho leaf as hop substitute in commercial beer brewing industries
To characterize the composition of dried gesho leaf for its major brewing components as hop substitute in commercial beer brewing industries
Gesho leaf which was physiologically matured collected from Amhara Agriculture ResearchInstitute (ARARI) at Adet Agriculture Research Center. The collected gesho leaf sample was cleaned manually to remove seed and other extraneous materials such as stalks and dusts before drying process conducted.
Drying of gesho leaf was conducted by drying oven to investigate the effect of drying factors (drying temperature and time) on the quality of gesho leaf powder as commercial hop substitute in commercial beer brewing industries. During conducting the experiment, the sample was dried at different temperature and time with five levels (40oc, 45oc, 50oc, 55oc and 60oc) and (1hr, 1.5hr, 2hr, 2.5hr and 3hr) to investigate the optimum drying parameters of drying process. Then dried gesho leaf was milled using laboratory grain miller at Amhara Agricultural Research Institute grain laboratory and packed with polyethylene using bag seller. Finally products were characterized for its important brewing components (polyphenol, bittering substance, hop oil, mineral and protein content).
The crucibles were washed and dried using drying oven for 1hr at 100oC, placed in the desiccators (with granular silica gel), cooled for 30 minute and weighed. 5.00g of the prepared samples were weighed and transferred into the dried and weighed crucibles. The crucible containing samples were dried in the oven at 110oc with one hour interval until constant weight of the crucible containing sample were weighed and recorded. At each interval of the drying step the sample were cooled in the desiccators to room temperature before weighing the sample. The amount of water present in a sample is considered to be equal to the loss of weight after drying the sample to constant weight at a temperature about the boiling point of water.
equation (1)
Where:
Mintial = Weight of sample before drying in the oven
Mfinal = Weight of the sample after drying in the oven
Protein was determined by the Kjeldahl method. All nitrogen is converted to ammonia by digestion with a mixture of concentrated sulphuric acid and concentrated orthophosphoric acid containing potassium sulphate as a boiling point raising agent and selenium as a catalyst. The ammonia released after alkalinization with sodium hydroxide is steam distilled into boric acid and titrated with sulphuric acid.
mg nitrogen in the sample = V*N*14---------------------equation (2)
g nitrogen sample/100g sample = mg of nitrogen*100/mg of the sample
equation (3)
Crude protein (%) = Total nitrogen (%) * F---------------equation (4)
Where:
V=Volume of sulfuric acid consumed to neutralize the test material (ml)
Vb=Volume of the acid consumed to neutralize the blank
F=Conversion factor of total nitrogen to crude protein (6.25)
14=Equivalent weight nitrogen
N= Normality of standard sulfuric acid
Ash was determined by incineration of known weights of the samples in a muffle furnace at 550oc until a white ash was obtained. Organic matter was burned off and the inorganic material remaining is cooled and weighed. Heating was carried out in stages, first to derive the water, then to char the product thoroughly and finally to ash at 550oc in a muffle furnace. The ashing dishes (made of porcelain) were placed into a muffle furnace for 30 min at 550oC. The dishes were removed and cooled in desiccators (with granular silica gel) for about 30 min at room temperature; each dish was weighed. 2.5g of powder sample was added into each dish. The dishes were placed on a hot plate under a fume-hood and the temperature was slowly increased until smoking ceases and the samples become thoroughly charred. The dishes were placed inside the muffle furnace at 550oC for 6 hr, and removed from the muffle and then placed in desiccators for 1hr to cool. The ash was clean and which in appearance. When cooled to room temperature, each dish plus ash was re-weighed. Weight of total ash was calculated by difference as:
equation (5)
Where:
Mash = Refers to weight of ash
Mwet= Refers to original weight of the sample
Polyphenol were determined by the modified vanillin assay method (Butter et al., 1982). 200 mg samples were weighed and then extracted with 10 ml absolute methanol for 20 minutes rotating screw cap culture tubes (130*100mm). The mixture then is centrifuged for 10minutes at 3000*G and the supernatant were used in the analysis. About 0.0 – 1.0 ml aliquot of catechin standard is dispended into two sets of culture tubes and each sample was brought to 1.0 ml by the addition of absolute methanol. Incubate the tubes in water bath. 5 ml of the working vanillin reagent was added at 1 min interval to one set of standards, and 5ml of the 4% HCl solution is added at 1 min interval to the second set of standards. After 20 min, the absorbance of sample solution and the standard solution were measured at 500 nm by using spectrophotometer. The absorbance of the blank is subtracted from the absorbance of the corresponding vanillin-contain sample. A standard curve has been constructed (Absorbance vs Catechin) and the linear portion of the curve will be extrapolated to produce the standard curve.
Finally, the polyphenol contents will be calculated. Values of tannins will be expressed in milligram of D-catechin equivalent per gram of sample.
Polyphenol in mg/100g = (absorbance density*weight of sample *100) -----equation (6)
equation (6.1)
Where:
Pw-Weight of polyphenol in gm
Ws-Weight of sample in gm (100gm)
Bitterness substance (Resin) content
For resin analysis 20g of the sample was dissolved in 100 ml of cold methanol in a conical bottom flask and the mixture was vigorously agitated by swirling the flask. Thereafter, the solution was filtered. The filtrate containing the resin was then dried and the total resin was calculated as a percentage of the original sample weight.
equation (7)
Where: Mdf and Mintial are weight of extract after dry and initial weight of the sample respectively
With regard to resin determination, 20 grams of each sample was dissolved in 20 ml of n-hexane thoroughly stirred and filtered using filter paper. Filtrate was dried to a constant weight at 50oc. The soft resin was calculated as the percentage of the original weight of sample dissolved in the n-hexane. Hard resin was determined by subtracting soft resin from total resin.
equation (8)
Where:
Mfinal = weight of the final dried sample
Mintial=Weight of the sample dissolved in the n-hexane
In hop oil content analysis, 10 gram of the sample was taken in 1000 ml round bottom flask and then 750 ml of distilled water was added. The mixture was agitated by swirling the flask. A Clevenger apparatus was mounted and fitted on to the round bottom flask and then connected to a tap water source. The set up was held tight with a retort stand and the mixture was placed on a suitable electric heating mantle. When the water boils, the steam rises through the stockings, thus extracting the essential oil. The delivery from the condenser was connected to the separating funnel to receive the mixture of steam and oil on condensation. After 120 min, the set up was switched-off and allowed to cool. The water-oil mixture was decanted to separate the oil from the water at the water oil interface. After drying in an electric oven the mass was recorded and calculated as a percentage from the original sample.
equation (9)
Where:
Mdf = weight of the sample after drying phenomenon
Mintial = Initial weight of the sample
Chemical and physical measurements were stastically analyzed by design expert-7 software. The comparison between sample treatments and the indices were done by using analysis of variance with a probability (P < 0.05). In this experimental work all physical and chemical measurements were performed in triplicates
As it is observed from the optimization table-one below, drying of gesho leaf at a temperature of 55oc for 2 hours has high desirability value (0.948) than the rest of the products processed at a given levels of factors (drying temperature and time). High desirability value which approaches to one indicates the best operating drying condition of the product to be processed in relation to the target components of the product in this case the brewing components of gesho leaf. On the contrary gesho leaf powder with low desirability value indicates inferior quality. So in gesho leaf drying, the best optimal drying temperature and time were 55oc for two hours. At optimal drying condition the brewing component of gesho leaf had equivalent values on dry wet basis with that of the commercial hop as it is stated in (Kunze, 1996).
From
No_ | Tern-'c | Tim-hr | moisture | protein | Polyph. | mineral | resin | hopoil | desirability |
1 | 55 | 2 | 10.125 | 18.055 | 3.53 | 8.055 | 18.015 | 0.965 | 0.948 |
2 | 50 | 2 | 14.34 | 18.015 | 3.565 | 7.985 | 18.02 | 1 | 0.94 |
3 | 50 | 2.5 | 12.06 | 18 | 3.455 | 7.98 | 17.88 | 0.965 | 0.932 |
4 | 50 | 3 | 10.34 | 17.98 | 3.42 | 7.975 | 17.94 | 0.8 | 0.923 |
5 | 40 | 1 | 17.435 | 18.085 | 3.82 | 8.02 | 18.03 | 0.985 | 0.909 |
6 | 60 | 3 | 18.64 | 18.06 | 3.885 | 8.06 | 17.685 | 0.525 | 0.862 |
7 | 45 | 2.5 | 16.34 | 17.885 | 3.665 | 8.115 | 18.035 | 1.305 | 0.852 |
8 | 60 | 1.5 | 12.055 | 18.05 | 3.86 | 8.06 | 17.03 | 0.485 | 0.843 |
9 | 50 | 1.5 | 20.34 | 18.025 | 3.97 | 7.96 | 18.03 | 0.87 | 0.836 |
10 | 55 | 1.5 | 13.36 | 17.885 | 3.565 | 8.025 | 18.43 | 1.005 | 0.827 |
11 | 40 | 2.5 | 19.57 | 18.08 | 4.9775 | 8.065 | 18.005 | 1.21 | 0.826 |
12 | 55 | 2.5 | 9.46 | 18.32 | 3.23 | 8.06 | 17.93 | 0.89 | 0.776 |
13 | 40 | 2 | 23.455 | 18.53 | 3.98 | 8.01 | 18.045 | 1.2 | 0.755 |
14 | 60 | 2 | 9.34 | 18.03 | 3.23 | 7.975 | 16.525 | 0.425 | 0.696 |
15 | 50 | 1 | 38.45 | 18.085 | 4.11 | 8.12 | 18.02 | 0.93 | 0.644 |
16 | 55 | 3 | 8.98 | 17.865 | 2.975 | 8.06 | 17.025 | 0.465 | 0.612 |
17 | 45 | 2 | 18.4 | 17.89 | 3.68 | 8.32 | 18.03 | 1.195 | 0.426 |
18 | 45 | 1.5 | 32.485 | 17.87 | 5.02 | 8.31 | 18.05 | 1.12 | 0.366 |
19 | 45 | 1 | 40.965 | 17.885 | 4.01 | 8.31 | 18.105 | 1.12 | 0.36 |
20 | 60 | 2.5 | 7.445 | 18.415 | 2.88 | 7.895 | 16.025 | 0.4 | 0.314 |
21 | 40 | 1.5 | 38.075 | 18.56 | 4.015 | 8.325 | 18.045 | 1.225 | 0.265 |
In
Considering
As it is shown in the
The amount of minerals in beer production shall be within the desired level if not it will totally disturb the overall brewing process through various interactions in the course of the process (kunze, 1996). In the
High moisture content negatively affects the quality of gesho leaf powder where the α-acids break dawn by the action oxygen as a result the bitterness substance will be lost which indicates inferior quality. It was clear that in
The optimal drying condition (drying temperature and time) for the production of gesho leaf powder or pellet as hop substitute in commercial beer brewing industry was found to be 55oc for two hours. At the optima drying condition the bitterness substances, the hop oil and polyphenol content of gesho leaf which are highly heat sensitive were found 18.025, 0.96% and 3.53% respectively while protein and mineral content which are less heat sensitive were 18.055% and 8.055% respectively. As a conclusion at the optimal drying condition gesho leaf can certainly substitute the imported commercial hop for commercial beer brewing industries in terms of beer brewing components. The finding also helps in saving foreign currency by import substitution of the commercial hop. Commercializing this flavouring agent as hop substitute improved the livelihood of farmer’s especially rural women where the cultivation was mainly held by women in Ethiopia. The finding also would reduce the coast of commercial beer brewing process so that it will increase the profitability of beer brewers.
Evaluation of optimally dried gesho leaf powder need further in commercial beer production by substituting the commercial need further study. The impact of soil type and growing environment on composition of brewing component of gesho leaf shall also need further investigation.