Effects of adding Rubus fruits on the antioxidant properties, physicochemical indexes and aroma of craft beer

Rubus fruits are primarily berries of the raspberry genus (Rubus spp.). These fruits can contain the bioactive substances, such as polyphenols, flavonoids, and anthocyanins. Their capacity of for strong antioxidants can greatly contribute to their high nutritional value and rich content of antioxidant compounds. As such, the Rubus fruits can be expected to incorporate be incorporated into the craft beer for the high quality. The study aims to specifically investigate the effects of Rubus fruits on the antioxidant activity, physicochemical properties, and aroma profile of craft beer. Two types of Rubus fruits were taken as the R. chingii Hu at 0.3% (w/w) and R. fruticosus L. at 10% (w/w). Several analytical techniques were then employed to evaluate the impact of Rubus fruit addition. The antioxidant activity of the beer samples was also assessed using three widely-accepted assays: 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging, 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS cation radical scavenging rate) free radical scavenging, and iron ion reducing power. The results demonstrated that the antioxidant properties were significantly enhanced in beers after the Rubus fruits addition, compared with the control group. Specifically, the DPPH, ABTS cation radical scavenging, and the iron ion reducing power increased by approximately 1.53, 5.33, and 1.79 times, compared with the control. The addition of Rubus fruits was greatly contributed to a substantial increase in the antioxidant capacity, thus improving The health benefits and oxidative stability of the beer. A further analysis was focused mainly on the total polyphenol and anthocyanin contents. These compounds also played a crucial role in the beer’s functional and sensory properties. The total content of polyphenol increased by 0.04 mg gallic acid equivalent per liter (mg /L), while the concentration of anthocyanin rose by 11.30 mg/L, compared with the control group. The Rubus fruits were enriched the bioactive composition of the beer, together with its color stability. The reason was that the anthocyanins were responsible for the red and purple hues, which were typically associated with the berry-rich products. A systematic analysis was also conducted to investigate the influence of Rubus fruit addition on the beer's aroma using gas chromatography-mass spectrometry (GC-MS). The Rubus fruits were incorporated to significantly increase both the concentration and variety of volatile aroma compounds. The presence of fruit-derived esters, alcohols, and terpenes was contributed to the beer’s overall complexity and aromatic intensity. Notably, the Rubus fruits were introduced the fruity, floral, and slightly woody notes, thus enriching the sensory experience of the craft beer. Sensory evaluation was performed to assess the consumer acceptability and preference for the modified craft beer. The various attributes were evaluated, including the aroma, taste, mouthfeel, and overall balance. The most favorable taste profile of craft beer was found in the R. chingii Hu fruits mixed with fresh blackberryblackberries. The beer’s malt and hop flavors were complemented with the a pleasant fruity aroma, moderate sweetness, and a well-balanced acidity. The improved mouthfeel and lingering aftertaste were further contributed to the beer's sensory appeal, leading to the preferred choice. Rubus fruits were incorporated to exert a positive impact on the quality and sensory attributes of craft beer. The antioxidant activity, polyphenol content, and aroma complexity were enhanced to serve the potential of Rubus fruits as a valuable ingredient for brewing applications. Furthermore, the Rubus fruits were extended into the functional beverages, thereby promoting their commercial utilization in the brewing industry. Beyond beer quality, the Rubus fruits addition can also contribute to the various brewing techniques and product innovation. The sustainable use of fruit resources can be well aligned with the favoring trends of the natural and health-enhancing ingredients in alcoholic beverages. Overall, the finding can lay a solid theoretical foundation to developfor developing the fruit-infused craft beers. New avenues are ever ever-opening for the future studies on brewing processes and additional fruit varieties in beer formulations.