Abstract
Manufacturing beer with a high biological value requires identifying new methods for increasing the health-enhancing compounds level. The aim of this study was to increase the biological value of beer by adding antioxidant-rich eggplant (Solanum melongena L.) peel extract (EPE). The total phenolic content (TPC), total flavonoid content (TFC), and total monomeric anthocyanin content (TMA) were determined. Moreover, the antioxidant activity was evaluated by different radical scavenging assays. The addition of different levels of EPE resulted in a significant increase of TPC and TFC of beer samples from 0.426 to 0.631 mg GAE/mL, and from 0.065 to 0.171 mg CE/mL, respectively. The EPE-supplemented beer samples developed a reddish color because of the presence of anthocyanin pigments. The TMA content of beer varied from 0.011 to 0.083 mg D3G/mL with the level of added EPE. The HPLC analysis indicated that the anthocyanins prevailing in the eggplant peels were delphinidin-3-rutinoside, delphininidin-3-glucoside and delphinidin-3-rutinoside-5-glucoside. The radical scavenging assays indicated a linear increase of the antioxidant activity following EPE addition, without altering the physicochemical parameters of the beer. These results are promising for using the EPE as a functional ingredient for beer production.
Highlights
Beer is one of the most appreciated alcoholic beverages worldwide, and has a higher nutritional value than other alcoholic beverages [1]
According to Zhao et al [6], about 80% of the phenolic compounds present in beer wort are derived from barley malt, and 20% come from hop, all of which are recognized as having important antioxidant
The phytochemical characterization of EPE was performed by an evaluation of the total monomeric anthocyanin content (TMA), total flavonoid content (TFC), total phenolic content (TPC), and antioxidant activity (Table 1)
Summary
Beer is one of the most appreciated alcoholic beverages worldwide, and has a higher nutritional value than other alcoholic beverages [1]. Because of the natural bioactive compounds found in beer, moderate consumption might provide several benefits for human health, such as a protective cardiovascular effect, control of cholesterol metabolism, blood clotting, and glucose metabolism [2,3]. The major antioxidants present in beer include the phenolic compounds and Maillard reaction products [5] Among these antioxidants, phenolic compounds play a significant role in malting and brewing, due to their ability to delay or prevent oxidation processes [6]. The phenolic compounds identified in beer are mainly represented by phenolic acids, flavonoids, tannins, and amino phenolic compounds [7] These antioxidants originate from raw materials, such as barley and hop [8]. According to Zhao et al [6], about 80% of the phenolic compounds present in beer wort are derived from barley malt, and 20% come from hop, all of which are recognized as having important antioxidant
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