Cold Brew Research Articles

Microbial Changes and Quality Properties of Commercial Cold Brew Coffee by Cold Drip Method During Storage Period

This study investigated the non-volatile and volatile compounds in samples of cold brew (CB) coffee, coffee from a coffee shop (CS), ready-to-drink (RTD) coffee, and brewed coffee from a coffee maker (CM). The volatile compounds were identified using headspace solid-phase microextraction with gas chromatography-mass spectrometry, and the samples were treated with high-performance liquid chromatography for the quantification of caffeine, chlorogenic acid, and trigonelline. The results indicate that RTD coffee had the lowest amounts of non-volatile compounds. A total of 36 volatile compounds were semi-quantified; the contents of most volatile compounds in CS and Folgers samples were higher than those in CB and CM samples. The contents of 25 volatile compounds in the CM sample were higher than those in the CB sample. The consumer and instrumental data show that the bitterness intensity was correlated with pyrazines, pyrroles, and guaiacols, whereas the coffeeID intensity was correlated with phenols. Semi-quantification and principal component analysis results show that the extraction method and temperature could influence the volatile compound profiles.

ABSTRACT The aim of this work was to analyze the influence of brewing temperature and coffee particle size on the evolution of physicochemical, bioactive, and antioxidant properties of Mexican cold brew coffee (CBC). The brewing process was carried out at two extraction temperatures (10 ± 0.5°C and 25 ± 0.5°C) and two particle sizes: medium (MG, 0.70–1.70 mm) and fine (FG, 0.43–0.71 mm). CBC brewing showed a complex relationship between brewing temperature and coffee grind particle size. The increase in brewing temperature enhanced the extraction rate. However, the particle size conditioned the extraction equilibrium time and final CBC properties. MG accelerated the brewing extraction rates to reach equilibrium in CBC properties (~7 h for 25ºC and ~12 h for 10ºC), while FG induced slower extraction rates and prolonged extraction times (above 12 h for both temperatures). However, FG produced CBC with higher bioactive compound content, darker color, and slightly less acidity than MG.

SummaryThis study examined effects of grind size (n = 3; 0.65, 1.15, 1.65 mm) and brew time (n = 3; 18, 24, 30 h) on the sensory traits, consumer likability and antioxidant activity of cold brew coffee (brewed at 4 °C). Total dissolved solids were measured to evaluate extraction efficiencies. The finest grind size demonstrated significantly greater antioxidant activity than the other samples, but grind size was not a significant factor for eighteen of the nineteen assessed sensory traits nor for hedonic assessments of appearance, flavour or overall likability. Notably, 24 h brew time samples showed consistently lower magnitudes of sensory traits, hedonic assessments and antioxidant activity than those brewed at 18 or 30 h. This effect was significant in predictive modelling and not explainable by magnitudes of dissolved solids (which increased with brew time). Findings demonstrate substantial nonlinear relationships between processing time and cold brew attributes.

Cold brew coffee has emerged as a new trend over the last decade. However, “cold brew” is an extraction style of ground roasted coffee with water at lower than body temperature (typically 8 °C or room temperature), rather than a beverage per se. Cold brew extraction poses several challenges, including the need for specific optimization depending on the multiple influences of coffee variety and processing, roast degree, grinding, dosage, water composition, turbulence, brew system (drip, immersion etc.), time and temperature, and their interactions. While cold brew is typically characterized by a floral sweetness, over-extraction may lead to abundant acidity and bitterness. To avoid this, an extraction degree of 70% was suggested using shorter time frames (i.e., 2 h at 15 °C with 80 g/L coffee for optimized medium roast profiles). Due to the lack of sterilizing temperatures during preparation, cold brew is significant in the coffee sector because hygiene and food safety requirements pose specific challenges. To avoid microbiological contamination and deterioration in quality, cold brew should be as freshly prepared as possible and shelf-life should be minimized.

Coffee shops, which are public spaces, provide experiences that consumers can provide in different ways. The purpose of this study is to reveal the consumption habits of consumers, who prefer X, Y, and Z generation, who prefer coffee shops. For this purpose, interviews were conducted with thirteen participants with semi-structured questions using the interview technique, which is one of the qualitative research methods. As a result of the interviews, findings were collected under five headings. These; The habits of the participants to choose coffee shops, brand preferences, service expectations, the physical elements they care about and the products they buy are determined. As a result of the findings, it is understood that the participants of the X generation go to less coffee shops than the other generations, the brands that meet the standard are more preferred, the X generation service to the table, the Z generation self-service and the Y generation prefer both service types. Generation X is more comfortable, Generation Y is more modern and Generation Z prefers more original environments. They prefer more traditional coffees such as X belt filter and Turkish coffee, coffees prepared with more innovative and modern methods such as Y generation V60, siphon, chemex and cold brew, and Z generation coffees prepared with different syrups, extracts, chocolates and creams.

Determining the impact of roasting degree, coffee to water ratio and brewing method on the sensory characteristics of cold brew Ugandan coffee

Abstract Black tea is considered as good source of bioactives like phenolics and antioxidants. In this study, cold brewing of black tea is coupled in combination with ultrasound‐assisted extraction (UAE) to maximize extraction efficiency of bioactives. Response surface methodology was designed to optimize the conditions for extraction using UAE for cold‐brewed black tea. A multiparameter face‐centered central composite design was used to predict the conditions (amplitude: 10–70%, solvent volume: 25–100 ml, and sonication time: 10–60 min). The results obtained indicated a second‐order polynomial model. The optimized conditions for maximum extraction of bioactive for cold brewing of black tea were found to be 69.9% amplitude, 25 ml solvent volume, and 30 min of sonication time. The experimental values from the optimal process were as follows: 72.2 mg gallic acid equivalent (GAE)/g, 6.77 mg GAE/g, 37.67%, 62.97% for total phenolic content (TPC), total tannin content, 2,2‐diphenyl‐1‐picrylhydrazyl, and 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid). The validation results agreed with the predicted models and showed an increase of 4 folds for TPC and 1.5 folds increase in antioxidant activity of cold‐brewed black tea. The displayed outcomes can remain as an extension for designing techniques for the accelerated extraction process for cold‐brewed black tea.Practical ApplicationThe application of cold brewing is limited due to the low extraction efficiency and longer extraction time. Ultrasound‐assisted extraction (UAE) improves the extraction of valuable nutrients with higher efficiency and shorter extraction time, helping the industry to produce larger amounts of cold‐brewed tea with lesser time. For other researchers, UAE‐treated cold‐brewed tea is a technique, which yields higher antioxidants and can be used as a method to study other cold‐brewed teas in the market.

An innovative ultrasensitive electrochemical aptamer-based sensor was developed for ochratoxin A (OTA) detection in cold brew coffee through revolutionary combination of nanofibers, electrochemicalmethod, and aptamer technologies. The assembly of the aptasensor was based on the activation of silanized cellulose nanofibrous membranes as a supporting matrix for methylene blue (MB) redox probe-labeled aptamer tethering. Cellulose nanofibrous membranes were regenerated by deacetylating electrospun cellulose acetate nanofibrous membranes with deacetylation efficacy of 97%, followed by silanization of the nanofiber surfaces by using (3-aminopropyl)triethoxysilane (APTES). A replacement of conventionally casted membranes by the nanofibrous membranes increased the active surface area on the working electrode of a screen-printed three-electrode sensor by more than two times, consequently enhancing the fabricated aptasensor performance. The developed aptasensor demonstrated high sensitivity and specificity toward OTA in a range 0.002-2ngmL-1, with a detection limit of 0.81pgmL-1. Moreover, the assembled aptamer-based sensor successfully detected OTA in cold brew coffee samples without any pretreatment. The aptasensor exhibited good reusability and stability over longstorage time. Graphical abstract.

Abstract Cold brew coffee is an increasingly popular beverage category with potentially distinct sensory attributes from traditional hot brewed coffees. A category survey of cold brew coffees was conducted with 44 commercial cold brew coffees. Ready‐to‐drink (RTD), cold brew at‐home (BAH), concentrates (CONC), and nitrogen infused cold brew coffees (NBC) were included. Descriptive analysis was performed by a highly trained panel. Selected representative coffees (n = 8) were then evaluated by temporal check all that apply (TCATA) with a trained panel to provide additional temporal differentiation and by consumers (n = 125) to determine consumer liking. Key differentiating attributes of cold brew coffees were mouthfeel attributes (viscosity, silkiness, astringency), basic tastes (sour, sour, bitter), and aromatics (overall aroma, smoky, ashy, nutty, beany, caramel/molasses, brothy) (p < .05). Beverages were also distinguished temporally based on category (RTD vs. BAH vs. NBC) (p < .05). Drivers of liking for all consumers were cocoa, spicy/resin, and caramel/molasses flavors and sweet taste. Drivers of dislike for all consumers were silky mouthfeel, beany, fruity, and woody/twig flavors and sour taste. The multimodal sensory perceptions generated by cold brew coffees and consumer perception of the cold brew coffees enhances understanding of this expanding beverage category.Practical applicationsThere are many ways to brew cold brew coffee and many sensory attributes present. The results of this study provide insight into different flavors imparted by different cold brew methods and insights for consumer preferences of different cold brew flavors.

Cold brew

Cold brewing of rooibos tea affects its sensory profile and physicochemical properties compared to regular hot, and boiled brewing

The role of roasting in cold brew coffee chemistry is poorly understood. The brewing temperature influences extraction processes and may have varying effects across the roast spectrum. To understand the relationship between brew temperature and roast temperature, hot and cold brew coffees were prepared from Arabica Columbian coffee beans roasted to light, medium, and dark levels. Chemical and physical parameters were measured to investigate the relationships among degree of roast, water temperature, and key characteristics of resulting coffees. Cold brew coffees showed differential extraction marked by decreased acidity, lower concentration of browned compounds, and fewer TDS indicating that cold water brewing extracts some compounds less effectively than hot water brewing. Compounds in coffee did exhibit sensitivity to degree of roast, with darker roasts resulting in decreased concentrations for both hot and cold brew coffees. Total antioxidant capacity (TAC) was only sensitive to degree of roast in cold brew coffees, while hot brew coffees had a constant TAC for all three roast levels. This indicates that the solid bean matrix and its chemical constituents interact with cold water differently than with hot water. Surface wetting, pore dynamics, and solubility all contribute to the extraction potential during brewing and are all functions of water temperature.

Chemists love drinking coffee—and studying it. The chemistry of hot-brewed coffee is a well-researched niche. With the rising popularity of cold brew, a team of scientists at Thomas Jefferson University were inspired to study the chemical differences between the two beverages. Niny Rao and a team of researchers brewed batches of light, medium, and dark roast coffees at both 100 °C and room temperature. Caffeine content was about the same in coffee brewed at both temperatures. Hot coffee measured higher in both total titratable acidity and total antioxidant content, with the differences becoming more pronounced the darker the roast. Rao hypothesizes that some antioxidants are soluble only at higher temperatures, preventing them from filtering through to the coffee when brewed at room temperature. To find which type of coffee is best for you, Rao suggests going by the data. “If you’re looking for something a little bit low acidity, I

Conservatively, tea is an aromatic beverage made from dried leaves of tea plant (Camellia sinensis). However, lemongrass (Cymbopogon citratus) and pandan leaves (Pandanus amarylifolius Roxb.) can also be processed as herbal tea to develop their functional properties. This current study aims to investigate the sensory profiles of the herbal tea as well as to determine the optimum techniques for hot, iced and hot+ice brewings. Spectrum Descriptive Analysis method was conducted by involving 12 trained panellists to develop sensory vocabularies. Meanwhile, the sensory optimization was conducted by Just about Right (JAR) method involving 106 consumer respondents. The Spectrum data shows that 4 out of 12 sensory attributes, including sweet, astringency, lemongrass flavor, and pandan flavor; were significantly affected by different brewing techniques (p-values <0.05). Through Penalty analysis on JAR data, it shows that sweet and pandan flavor were optimum for hot brewing. Meanwhile, the sweet and astringency were optimum for cold brewing. Under current set up, there is no optimum attributes was obtained for hot+ice brew technique. Considering their functional properties, the cold brewed herbal tea shows the most superior among the samples tested as it shows the highest total sugar content, total phenolic compound, and antioxidant activity (p-values<0.05).

The “natural coffee” produced through sun-drying has been a common coffee post-harvest processing practice and well-known to exhibit specific sensory characters. However, the sensory profile of coffee in a cup could be influenced by many other factors including the brewing techniques. The objective of this research was to study the effect of different manual brewing techniques i.e. Indonesian “tubruk” method, Vietnam drip, cold brew, and aero press to the sensory profile of two Indonesian “natural coffees” origin i.e. Robusta Gayo and Arabica Kerinci. Evaluation was performed on 33 sensory attributes using Sensory Descriptive Analysis method employing 10 trained student panellists. Data analysis was performed using Minitab 17 and the Unscrambler® X MVA software. The result showed that in total; as many as 21 attributes were rated by the panellist. The two samples showed different sensory profiles, particularly in some sensory attributes assessed. The different manual brewing techniques was also found to have significant impact (α = 0.05) on 17-18 sensory attributes, showing that each technique will be responsible for certain sensory characters perceived by coffee consumer.

The effects of extraction conditions on the acrylamide/furan content, antioxidant activity, and sensory properties of cold brew coffee were probed for samples prepared by steeping and dripping at various temperatures and for different times. Sensory properties were evaluated using a nine-point hedonic scale and an overall preference ranking test. Samples prepared by 3-h extraction featured the lowest acrylamide levels, while the lowest furan contents were observed for samples prepared by 24-h steeping and 12-h dripping. Among steeping-prepared samples, that extracted for 24h showed the highest total phenol content, although no significant differences were observed for extraction times above 12h, with a similar trend observed for ABTS free radical anion scavenging activity. Thus, the contents of bioactive and hazardous chemicals as well as sensory properties were found to be influenced by various extraction conditions.

Effects of geographical origin of Coffee Arabica beans (Brazil, Colombia and Peru), roasting degree, particle size and different brewing methods (French press, chemex and cold brew) on physicochemical and spectral properties of coffee samples were investigated in this study. Analyses of pH, total phenolic content (TPC) and total antioxidant activity (TA), UV and fluorescence spectroscopy measurements were performed. Principal component analysis (PCA) was used to obtain the most effective parameters on chemical changes. Results indicated that the increase of roasting degree caused decrements in the intensities of UV-spectra because of the degradation of trigonelline and chlorogenic acid molecules while counterpart trend was observed in the fluorescence spectra due to formation of fluorescence Maillard reaction products (MRP) during roasting. French press and cold brew methods caused similar TPC (1873.33-3818.33 and 2648.88-3824.44μg/mL gallic acid equivalent, respectively) and TA (0.18-0.32 and 0.16-0.27μmol/mL Trolox equivalent, respectively) values whereas chemex method showed different physicochemical properties (TPC: 1008.88-3543.88μg/mL gallic acid equivalent and TA: 0.08-0.26μmol/mL Trolox equivalent). Roasting degree and brewing method-compared to other parameters-were the most discriminating factors on the basis of UV spectra and fluorescence spectra of coffee brew samples, respectively. All roasting degrees could be distinguished with the rate of 71.42% on PC1 and 23.45% on PC2 of total variance according to UV-spectra while chemex and French press-cold brew methods could be differentiated with the rate of 97.24% on PC1 and 1.79% on PC2 of total variance based on fluorescence spectra on PCA score graphs.

The Effect of Caffeine on Health and Exercise Performance with a Cold Brew Coffee Approach: A Scoping Review

Elucidation of key odorants in Beninese Roselle (Hibiscus sabdariffa L.) infusions prepared by hot and cold brewing