The physicochemical properties of Ethiopian commercial beers are described in the Table 2. The value of AE was ranged from 1.74 to 2.51oP and generally found in the order of B5 > B2> B4 > B1 > B3. The highest AE value may be related to the presence of unfermented sugars (oligosaccharides) by yeasts, while the least AE value was due to fermentation of lower molecular weight sugars present in the wort like glucose, fructose and maltose basically come from the malt. Similarly, B5 showed the highest RE value, followed by B2, B4, B1 and B3. Among the investigated beers, B2 displayed the highest OE value (11.28 0P), while B4 was the least (10.74 0P), this attributed to the quality and amount of malt used; and the nature of brewing process used for beer production .
The maximum value of ADF and RDF were observed in B3, whereas the least amount were found in beer sample B5 and B4, respectively (Table 2). The highest RDF indicates that the extract originally present in the wort was converted in to ethanol and CO2 in better degree than the one which contained least RDF value .
The alcoholic (ethanol) content was found in the range of 4.58 to 4.88 (%, v/v), the highest alcoholic content was found in B2 and the least one was in B4. The results of this investigation are consistent with researches carried out by Pai et al. , Mitic et al. . The difference in alcoholic content among all beer samples may be attributed to the difference in brewing temperature, yeast cell count, aeration, composition of wort (i.e. amount of original extract, pH, dissolved oxygen, metals, etc) . Many studies demonstrated that the alcoholic content of most beers were found in the range of 3%–6% (v/v) .
The pH of the beer samples ranged from 4.20 to 4.38. B4 was the most acidic among all the beer samples, while B1 was the least acidic. The variation attributed to the difference in raw material used, water and the amount of acid added in the mashing step. The pH of a beer strongly influences physiological parameters such color, odour, taste, biological and chemical stability of beer. The pH range of beers identified in this study are consistent with previous reports .
On the other hand, the haziness of this study followed the order B3 > B1 > B4> B2 > B5, this attributed to residual starch, oxalate from calcium deficient worts, carbohydrate and protein from autolysed yeast, lubricants from can lids, and dead bacteria from malt . Concerning bitterness, B2 had the highest bitter with a value of 27.68 IBU, while B4 had the least bitter with a value of 14.76 IBU. This difference is due to variation in the type and amount of hope added in the brewing process. The physicochemical properties Ethiopian commercial beers that was studied here are in agreement with other reports [13, 17, 18].
Total polyphenols content
Phenolic compounds play critical roles in both ﬂavour and colloidal stability of beer . The total phenolic contents of beer depend on the raw materials for brewing mainly malt and hop; and the type of beer produced . Studies showed that beers with high phenolic content showed better quality, more stable sensory properties and longer shelf life than beers with low phenolic content [14, 19].
As shown in Table 3, the total phenolic content signiﬁcantly varied with the type of beer, which ranged from 190.24 to 219.8 mg/L, of which B1 contained highest amount of total phenolic content and B3 the least total phenolic content (190.24±5.63 mg/L). The result indicated that significant differences were observed (p < 0.05) on total phenolic content in all analyzed beer samples except between B3 and B4 (p > 0.05). The amount of TPC variation comes from the difference in raw material used mainly from malt and hope and the nature of beer production process [20, 21]. The results obtained in this study were in agreement with reported values [1, 5, 6, 20].
So, the difference in amount of total polyphenols can cause difference on their antioxidant activities, flavour, color and sensory properties and also may contribute to maintain the endogenous redox balance in humans .
The values of antioxidant activity for the analyzed beers was expressed as percent of inhibition (Table 3). Among the beers, B1 had significantly (p<0.05) highest percent of inhibition (84.16 %), whereas B3 had the least percent of inhibition with a value of 72.7%. Like with the total polyphenol content, the antioxidant activity of Ethiopian commercial can be ranked as follows: B1 > B5 > B2 > B4 > B3, attributed to the difference in the amount of raw materials and brewing process. A beer which had greater DPPH radical scavenging activity could have enhanced flavour stability because beer staling can occur as a result of the formation of trans-2-nonenal and other saturated and unsaturated aldehydes as a result of oxidation . The antioxidant activity of Ethiopian beers are found to be in agreement with studies reported in literature [1, 13, 17, 21].
As shown in Table 4, the total phenolic content of beers showed positive correlations with the antioxidant capacities of the beers analyzed. This indicating that total phenolic content could be used as an indicator in evaluating the antioxidant capacity of beers which may preliminarily applied as natural sources of antioxidant functional beverages .
Levels of metals
The efficiency of the analytical method that used to determine the levels of each metal in commercial beers was validated through linearity, recovery, precision and limit of detection. The validated data of the methods are presented in Table 5. The correlation coefficients of the calibration curves of the analyzed metals were found above 0.9979.
The recovery test was performed for the analysis of metals in beer samples through spiking experiments, in which known volumes of standard solutions of elements of interest were added in to beer samples. The spiked samples were digested following the same procedures as utilized for digesting the beer samples. As shown in Table 5, the percentage recovery were 99.2±5.4%, 90.9±8.9%, 95.2±10.5%, 96.5±8.7 and 104.3±9.1% for Cd, Cr, Cu, Ni and Pb, respectively. The recovery results indicated that the method was applicable for determining the levels of metals in beer samples.
The limit of detection (LOD) was obtained from three times its standard deviation of the blank signals divided by the slope of the calibration equation, whereas limit of quantification (LOQ) was calculated by multiplying LOD by a factor of three  and the values for LOD and LOQ of all studied elements are given in Table 5.
As shown in Table 6, Cd was only detected in B2, B3 and B4, whereas in B1 and B5 it was under the limit of detection of the method applied.
The trend of Cr concentration (mg/L) in beers was B3 (0.47±0.002) > B5 (0.23±0.004) > B4 (0.05±0.001) > B2 (0.035±0.002) > B1 (0.023±0.001). Cr levels in beers have been reported in the range of 0.0256-0.4417 mg/L  and 0.17–0.34 mg/L , which suggest that the values obtained in this study are within range reported in literatures.
Copper content of beers ranged between 0.020 and 0.041 mg/L. B4 had the highest level (0.041 ± mg/L) of Cu, while B1 had the smallest level (0.020 ± mg/L) of Cu. This is within ranges of beer studies by Voica et al.  and Izah et al.  who reported a range of 0.0259-0.736 mg/L and 0.04–0.08 mg/L, respectively.
The overall concentration of Ni ranged from 0.026 to 0.064 mg/L, the highest being from B4 and the lowest from B3. However, Ni metal were found to below detection limit in B1 and B2. Of all the studied beers, B2 and B4 were contained highest values of Ni. These results were in agreement with reported by Voica et al. . Lead metal was detected only in B3, B4 and B5. However, Pb was found below of detectable limit in B1 and B2. These results are comparable with the results reported by Voica et al. and Izah et al. [24, 25].
In general, Cu was found to be highest in B1, B3 and B5, while Ni was the highest among other metals in B2 and B4. However, lead was the least detected.