Sensory Analysis of Full Immersion Coffee: Cold Brew Is More Floral, and Less Bitter, Sour, and Rubbery Than Hot Brew

Contribution of mozambioside roasting products to coffee's bitter taste

Roasting degrades the coffee compound mozambioside (1) into several products, including 17-O-β-D-glucosyl-11-hydroxycafestol-2-one (2), 11-O-β-D-glucosyl-16-desoxycafestol-2-one (3), 11-O-β-D-glucosyl-(S)-16-desoxy-17-oxocafestol-2-one (4), 11-O-β-D-glucosyl-15,16-dehydrocafestol-2-one (5), 11-O-β-D-glucosyl-(R)-16-desoxy-17-oxocafestol-2-one (6), bengalensol (7), and 11-hydroxycafestol-2-one (8). A UHPLC-MS/MS method was established to quantify 1-8 and monitor their formation during authentic coffee roasting. Concentrations of 1 and the dominant roasting products 4, 5, and 7 ranged from 21.0 to 170.4 nmol/g in coffee powders, with ∼41-128 % extracted into the brew. Human bitter taste thresholds of 1, 2, and 4-8 were determined. The major roasting products exhibited lower thresholds (27-80 μM) than 1 (132 μM). Genotyping of panelists revealed a correlation between sensitivity for mozambioside-derivatives and the presence of intact TAS2R43 gene loci. The combination of 1-8 in coffee concentrations elicited a bitter taste recognized in 80 % of the panelists, suggesting this compound class contributes to coffee's taste profile.

Effects of ultrafiltration membrane processing on the metabolic and sensory profiles of coffee extracts

In the coffee industry, the use of natural coffee extracts with differentiated attributes is desirable to drive new product development. This study evaluates the impact of ultrafiltration membrane processing on the sensory, metabolic, and physicochemical attributes of four commercially available coffee extracts: cold brew, lightly roasted, freeze concentrated and evaporated standard. The sensory analysis revealed an increase in acidity in the permeate across all extracts, with the most significant profile changes observed in the lightly roasted evaporated and evaporated extracts, accompanied by an enhancement of fruity and floral attributes. Furthermore, the permeate showed reduced total dissolved solids, while the caffeine concentration increased. Metabolomic analysis highlighted key coffee-related metabolites like cinnamic and coumaric acids, explaining observed variations due to their passage through the membrane. Our findings emphasize the potential of permeate as a coffee-based ingredient for ready-to-drink products development, providing a unique coffee experience with organoleptic profiles distinct from traditional beverages.

Sensory analysis of the flavor profile of full immersion hot, room temperature, and cold brewed coffee over time

With the growing popularity of cold brewed coffee comes a need for brewing efficiency while preserving the desirable flavor profile. Despite the wide use of full immersion brewing techniques, the effect of brew time on the dynamic sensory profiles of full immersion brewed coffee remains underexplored. Here, we investigated the relationship between coffee sensory quality and extraction dynamics, measured as Total Dissolved Solids (TDS) and Extraction (E) of full immersion brewed coffee at various roast levels, and brewing temperatures (4 °C, 22 °C and 92 °C), over brew time using a generic descriptive analysis method. Specifically, different brew time points were selected for different temperatures based on five targeted coffee extraction stages. Furthermore, the unique experimental design also explored a sensory-driven engineering research process. Roast level had the greatest impact on the sensory profile of the coffees, followed by brewing temperature, but brew time, especially the longer brew times as TDS plateaued, had subtler impacts than expected. Twenty-five of 28 sensory attributes were significantly different among the 30 coffee samples, indicating a single source green coffee blend can produce a wide range of complex sensory profiles using different combinations of roast level, temperature, and brew time. Specifically, the intensity of sweetness was negatively correlated with TDS, and 19 other attribute intensities were positively correlated with TDS. Interestingly, we found that certain long time cold brews had similar sensory profiles to those of some short time hot brews, suggesting the sensory profiles of certain hot brews and cold brews could possibly be matched through controlled preparation. Overall, our study demonstrated an approach of integrating food engineering and sensory analysis for product development, and our findings provide valuable insights into the extraction dynamics and sensory quality of full immersion brewed coffee and opens new brewing avenues for the coffee industry.

Profiling flavor characteristics of cold brew coffee with GC-MS, electronic nose and tongue: effect of roasting degrees and freeze-drying

BACKGROUND

Roasting is an important process in the formation of coffee flavor characteristics, which determines the quality of coffee and consumer acceptance. However, the influence of roasting degree on the flavor characteristics of cold brew coffee has not been fully described.

RESULTS

In the present study, the flavor characteristics of cold brew coffee with different roasting degrees were compared in detail by using chromatographic and electronic sensory approaches, and the flavor changes induced by freeze-drying were investigated. Pyrazine and heterocyclic compounds were the main aroma compounds in coffee, and gradually dominated with the increase of roasting. Pyridine was consistently present in cold brew coffees of different roasting degrees and showed significant gradient of quantity accumulation. Aroma compounds such as pyrazine, linalool and furfuryl acetate were the main contributors to coffee roasting, floral and fruity flavor. Freeze-drying preserved the fruity and floral aromas of medium-roasted cold brew coffee, whereas reducing the bitterness, astringency and acidity properties that are off-putting to consumers.

CONCLUSION

The higher consumer acceptance and enjoyment in medium roast cold brew coffee may be related to its stronger floral and fruity aroma. The aroma profile qualities of freeze-drying processed medium roasted cold brewed coffee were more dominant and more suitable for freeze-drying processing than medium dark roasting. Application of freeze-drying for cold brew coffee will promote the convenience of drinking. The present study provides valuable technical guidance in improving the flavor and quality of cold brew coffee, and also promotes its commercialization process. © 2024 Society of Chemical Industry.

Coffee and stress management: How does coffee affect the stress response?

This chapter explores the complex relationship between coffee drinking and stress management, highlighting the advantages and disadvantages of this widely consumed beverage. The chapter explores the physiological, psychological, and social effects of coffee on stress response and resilience through a thorough analysis of recent studies. It highlights the negative consequences of excessive intake on cardiovascular, gastrointestinal, and mental health while also discussing how moderate coffee consumption may lower stress levels, improve coping skills, and promote relaxation. Considerations for vulnerable populations, interactions with medications and supplements, and sustainability concerns in coffee production and consumption are also addressed. By identifying missing gaps in our understanding of coffee and stress management, the chapter underscores the need for future research to elucidate underlying mechanisms and promote mindful consumption practices. Ultimately, by embracing a holistic approach that considers individual health, environmental sustainability, and social responsibility, we can harness the potential of coffee to support resilience, well-being, and sustainability for individuals and communities worldwide.

Identification of mozambioside roasting products and their bitter taste receptor activation

Arabica coffee contains the bitter-tasting diterpene glycoside mozambioside, which degrades during coffee roasting, leading to yet unknown structurally related degradation products with possibly similar bitter-receptor-activating properties. The study aimed at the generation, isolation, and structure elucidation of individual pyrolysis products of mozambioside and characterization of bitter receptor activation by in vitro analysis in HEK 293T-Gα16gust44 cells. The new compounds 17-O-β-d-glucosyl-11-hydroxycafestol-2-on, 11-O-β-d-glucosyl-16-desoxycafestol-2-on, 11-O-β-d-glucosyl-(S)-16-desoxy-17-oxocafestol-2-on, 11-O-β-d-glucosyl-15,16-dehydrocafestol-2-on, and 11-O-β-d-glucosyl-(R)-16-desoxy-17-oxocafestol-2-on were isolated from pyrolyzed mozambioside by HPLC and identified by NMR and UHPLC-ToF-MS. Roasting products 11-O-β-d-glucosyl-(S)-16-desoxy-17-oxocafestol-2-on, 11-O-β-d-glucosyl-15,16-dehydrocafestol-2-on, and 11-O-β-d-glucosyl-(R)-16-desoxy-17-oxocafestol-2-on had lower bitter receptor activation thresholds compared to mozambioside. Molecular docking simulations revealed the binding modes of the compounds 11-O-β-d-glucosyl-15,16-dehydrocafestol-2-on and 11-O-β-d-glucosyl-(R)-16-desoxy-17-oxocafestol-2-on and their aglycone 11-hydroxycafestol-2-on in the two cognate receptors TAS2R43 and TAS2R46. The newly discovered roasting products 17-O-β-d-glucosyl-11-hydroxycafestol-2-on, 11-O-β-d-glucosyl-(S)-16-desoxy-17-oxocafestol-2-on, 11-O-β-d-glucosyl-15,16-dehydrocafestol-2-on, and 11-O-β-d-glucosyl-(R)-16-desoxy-17-oxocafestol-2-on were detected in authentic roast coffee brew by UHPLC-ToF-MS and could contribute to coffee's bitter taste impression.

Coffee brewing sonoreactor for reducing the time of cold brew from several hours to minutes while maintaining sensory attributes

This research designed and developed an ultrasonic reactor for a fast and on demand production of cold brew coffee, remarkably reducing the brewing time from 24 h to less than 3 min. The technology was engineered by utilizing resonance to induce ultrasonic waves around the walls of the brewing basket of an espresso machine. The sound transmission system comprised a transducer, a horn and a brewing basket. This arrangement transformed the coffee basket into an effective sonoreactor that injected sound waves at multiple points through its walls, thereby generating multiple regions for acoustic cavitation within the reactor. Furthermore, acoustic streaming induced greater mixing and enhanced mass transfer during brewing. The design was accomplished by modeling the transmission of sound, and acoustic cavitation. Brew characterization and chemical composition analysis was performed, considering factors such as pH, acidity, color, and the composition of caffeine, fatty acids, and volatiles. The efficiency of the extraction increased by decreasing the basket loading percentage (BLP). For instance, sonicating at 100 W doubled the extraction yield and caffeine concentration, from 15.05 % to 33.44 % at BLP = 33 %, and from 0.91 mg/mL to 1.84 mg/mL at BLP = 67 %, respectively. The total fatty acids increased from 1.16 mg/mL to 9.20 mg/mL, representing an eightfold increase, at BLP = 33 %. Finally, a sensory analysis was conducted to evaluate appearance, aroma, texture, flavor, and aftertaste, which demonstrated that coffee brewed for 1 and 3 min in the sonoreactor exhibited almost undistinguishable properties compared to a standard 24 h brewing without ultrasound.

Proof of Concept for Cell Culture-Based Coffee

The global coffee production is facing serious challenges including land use, climate change, and sustainability while demand is rising. Cellular agriculture is a promising alternative to produce plant-based commodities such as coffee, which are conventionally produced by farming. In this study, the complex process of drying and roasting was adapted for bioreactor-grown coffee cells to generate a coffee-like aroma and flavor. The brews resulting from different roasting regimes were characterized with chemical and sensory evaluation-based approaches and compared to conventional coffee. Roasting clearly influenced the aroma profile. In contrast to conventional coffee, the dominant odor and flavor attributes were burned sugar-like and smoky but less roasted. The intensities of bitterness and sourness were similar to those of conventional coffee. The present results demonstrate a proof of concept for a cellular agriculture approach as an alternative coffee production platform and guide future optimization work.

Evaluation of Physicochemical Characteristics and Sensory Properties of Cold Brew Coffees Prepared Using Ultrahigh Pressure under Different Extraction Conditions

Although cold brew coffee is becoming increasingly popular among consumers, the long coffee extraction time is not conducive to the further development of the market. This study explored the feasibility of ultrahigh pressure (UHP) to shorten the time required for preparing cold brew coffee. The effects of pressure and holding time on the physicochemical characteristics and sensory evaluation of UHP-assisted cold brew coffee were also determined. The extraction yield; total dissolved solid, total phenol, and melanoid content; antioxidant capacity; and trigonelline and chlorogenic acid contents of UHP-assisted cold brew coffee increased as the pressure increased. The extraction yield and the total dissolved solid, total phenol, total sugar, and chlorogenic acid and trigonelline contents were higher when the holding time was longer. The HS-SPME-GC/MS analysis demonstrated that the furan, aldehyde, and pyrazine contents in coffee increased as the pressure and holding time increased. The pressure did not significantly impact the concentrations of volatile components of esters and ketones in coffee samples. However, the increase in holding time significantly increased the ester and ketone contents. The sensory evaluation results revealed that as pressure rose, the intensities of nutty, fruity, floral, caramel, and sourness flavors increased, whereas bitterness and sweetness decreased. Longer holding time increased nutty, caramel, sour, bitter, sweet, and aftertaste flavors. Principal component analysis (PCA) results indicated that holding time is a more crucial factor affecting the physiochemical indices and flavor characteristics of coffee. UHP can shorten the preparation time of cold brew coffee. Pressure and holding time significantly affected the physiochemical indices and volatile components of UHP-assisted cold brew coffee. UHP-assisted cold brew coffee had lower bitterness, higher sweetness, and a softer taste than conventional cold brew coffee.

The Potential of Spent Coffee Grounds in Functional Food Development

Coffee is a popular and widely consumed beverage worldwide, with epidemiological studies showing reduced risk of cardiovascular disease, cancers and non-alcoholic fatty liver disease. However, few studies have investigated the health effects of the post-brewing coffee product, spent coffee grounds (SCG), from either hot- or cold-brew coffee. SCG from hot-brew coffee improved metabolic parameters in rats with diet-induced metabolic syndrome and improved gut microbiome in these rats and in humans; further, SCG reduced energy consumption in humans. SCG contains similar bioactive compounds as the beverage including caffeine, chlorogenic acids, trigonelline, polyphenols and melanoidins, with established health benefits and safety for human consumption. Further, SCG utilisation could reduce the estimated 6-8 million tonnes of waste each year worldwide from production of coffee as a beverage. In this article, we explore SCG as a major by-product of coffee production and consumption, together with the potential economic impacts of health and non-health applications of SCG. The known bioactive compounds present in hot- and cold-brew coffee and SCG show potential effects in cardiovascular disease, cancer, liver disease and metabolic disorders. Based on these potential health benefits of SCG, it is expected that foods including SCG may moderate chronic human disease while reducing the environmental impact of waste otherwise dumped in landfill.

Comparative Profiling of Hot and Cold Brew Coffee Flavor Using Chromatographic and Sensory Approaches

Coffee brewing is a complex process from roasted coffee bean to beverage, playing an important role in coffee flavor quality. In this study, the effects of hot and cold brewing on the flavor profile of coffee were comprehensively investigated on the basis of chromatographic and sensory approaches. By applying gas chromatography–mass spectrometry and odor activity value calculation, most pyrazines showed higher contribution to the aroma profile of cold brew coffee over hot brew coffee. Using liquid chromatography, 18 differential non-volatiles were identified, most of which possessed lower levels in cold brew coffee than hot brew coffee. The sensory evaluation found higher fruitiness and lower bitterness and astringent notes in cold brew coffee than hot brew coffee, which was attributed by linalool, furfural acetate, and quercetin-3-O-(6″-O-p-coumaroyl) galactoside. This work suggested coffee brewing significantly affected its flavor profile and sensory properties.