Isabel H. Chacón-Figueroa

Spent coffee is rich in bioactive compounds, including chlorogenic acid, caffeic acid, and caffeine, which offer health benefits. However, digestive processes can degrade these compounds; therefore, microencapsulation within Saccharomyces cerevisiae yeast cells offers a novel method to stabilize these bioactive compounds during digestion. In fact, it is important to mention that this technique of microencapsulation in Saccharomyces cerevisiae has not been previously applied to spent coffee extract. As a result, in this study, spent coffee extract was microencapsulated in non-plasmolyzed (NPCs) and plasmolyzed (PCs) yeast cells using the spray drying method. The physicochemical properties of the extract and the microencapsulates were characterized, and the bioaccessibility of the bioactive compounds was evaluated with digestion in vitro. Encapsulation efficiency (EE) was 38.62% for NPCs and 55.78% for PCs, with loading capacities (LCs) of 126.36 and 242 g/kg, respectively (according to Equations (1) and (2)). The presence of antioxidant compounds, identified by HPLC in spent coffee, was confirmed in the microencapsulates using FTIR. In vitro digestion assays revealed higher bioaccessibility of bioactive compounds in the intestinal phase, greater than 90%, and increased antioxidant activity in beer made with plasmolyzed microcapsules (BPM). These results suggest that yeast microencapsulation effectively stabilizes the bioactive compounds of spent coffee extract, releasing them throughout the gastrointestinal tract in vitro, mainly in the intestinal phase. Thus, microencapsulated compounds could serve as functional additives with a good percentage of intestinal bioaccessibility.

Coffee bean bagasse is one of the main by-products generated by industrial coffee production. This by-product is rich in bioactive compounds such as caffeine, caffeic and chlorogenic acid, and other phenols. The aims of this work are to optimize the extraction conditions of phenolic compounds present in coffee bean bagasse and incorporate them into stout-style craft beers, as well as to determine their effect on the phenol content and antioxidant capacity. The optimal conditions for extraction were 30% ethanol, 30 °C temperature, 17.5 mL of solvent per gram of dry sample, and 30 min of sonication time. These conditions presented a total phenol content of 115.42 ± 1.04 mg GAE/g dry weight (DW), in addition to an antioxidant capacity of 39.64 ± 2.65 μMol TE/g DW in DPPH^• and 55.51 ± 6.66 μMol TE/g DW for FRAP. Caffeine, caffeic and chlorogenic acids, and other minor compounds were quantified using HPLC-DAD. The coffee bean bagasse extracts were added to the stout craft beer and increased the concentration of phenolic compounds and antioxidant capacity of the beer. This work is the first report of the use of this by-product added to beers.