This can be seen in both total acidity and antioxidant activity measurements. All cold brew coffee samples analyzed in this study were found to have lower titratable acid levels than their hot brew counterparts. Coffee is composed of dozens of low molecular mass compounds, including numerous carboxylic acids such as citric, malic, quinic, succinic, and gluconic acids 40 , While all of these acids are readily soluble in water, their ability to detach from the coffee matrix and diffuse through the intra- and intergranular pore spaces in room temperature water as is used in cold brew method is poorly understood.
For cold brew coffee, a strong correlation was found between total CQA concentration and total antioxidant activity, while a weak correlation was seen for hot brew coffee. The total CQA concentration failed to correlate with antioxidant activity in hot brew coffee likely because those hot water extracts had a more diverse and complex chemistry than the cold brew samples.
It can be assumed that many of the compounds absent from the cold brew coffees were acidic molecules, as the total acidity levels in the hot coffees were found to be greater. This research finds that water temperature during aqueous extraction influences the transport of acidic molecules from the coffee matrix into the water phase substantially enough to alter the total titratable acidity and antioxidant activity of the resulting coffee beverage.
This research reveals important fundamental differences between hot and cold brew coffee that may have implications for possible health impacts on drinkers.
It is often claimed by cold brew coffee enthusiasts that cold brew coffee has lower acidity than its hot brew counterparts, and thus may be a better alternative for those who suffer from gastrointestinal symptoms. This study suggests that the hot brew method tends to extract additional non-deprotonated acids in comparison to the cold brew method. These acids may be responsible for the higher antioxidant activities observed in hot brew coffee samples. Additionally, the chemical composition of hot brew coffee may be more diverse and complex than that of cold brew coffee.
Additional research is needed to fully understand any possible differences in the health effects of coffee as a function of brewing temperature and time. The lower antioxidant capacity in cold brew coffees may decrease the chemoprotective benefits known to be associated with hot brew coffees. To better understand the relationship between brewing temperature and chemical complexity of the resulting coffee, compound-specific analysis of the extracts is needed. There are several classes of compounds present in coffee extracts that may be the cause of the differences seen in hot and cold brew coffee in this study.
One possible class of compounds that may influence pH and antioxidant activity levels are melanoidins. Previous studies have reported extensively on the chemical composition of coffee 34 , 35 , 36 , 37 , 42 , 56 , Future work to identify and quantify compounds present in hot and cold brew coffee would help to better elucidate the chemical differences between the two beverages.
Further work could also be done to characterize the antioxidant activity of specific compounds and classes of compounds to better understand the role of brewing temperature on total antioxidant character of the resulting coffee beverages. Pre-ground, light roast Brazilian, Colombian, Ethiopian, Mexican, and Myanmar coffees were purchased from commercial vendors.
Coffee samples from two regions of Ethiopia labeled as Ardi and Yirgz by the vendor were analyzed separately. Standard stock solutions of 2.
Standardized 0. Filtered municipal tap water was used to brew the coffees. A sample of The coffee samples were then filtered using the Hario V60 paper filter before analysis.
Hot brew extraction was conducted using the same coffee-to-water ratio as was used in the cold brew method. The water was heated to boiling, then added to coffee grounds in a traditional French press carafe. It is noted that the samples at the time of filtering were different between hot and cold brew experiments.
The experiments were designed to simulate typical brewing environments for consumption. Thus, the filtering process was not temperature controlled. Both cold brew and hot brew samples were freshly prepared for each experiment. Standard solutions and coffee extracts were analyzed using an adapted methodology reported in GL Sciences Technical Note No.
The flow rate was 1. Quantitation of the other CQA isomers was accomplished using the area of 5-CQA standard combined with the respective molar extinction coefficients of other two isomers as reported previously 33 , 34 , Total antioxidant activity of hot and cold brew coffees was determined using an ABTS radical cation decolorization assay modified from Re et al. The resulting solution was analyzed by UV-Vis following the procedure for the Trolox standards.
The total antioxidant capacity of each coffee sample was calculated as mmol Trolox equivalent per liter of brewed coffee. The output of the statistical analysis is included in the supplementary information. All data generated or analyzed during this study are included in this published article and its Supplementary Information files. Berry, D. Competition heats up in the cold brew category.
Skip to main content. Bioactive micronutrients in coffee: recent analytical approaches for characterization and quantification. Caffeine intake and the risk of first-trimester spontaneous abortion. In fact, caffeine consumption at a dose of mg resulted in a significant thermogenic effect despite the fact that subjects in that particular investigation had a habitual caffeine intake of mg per day [ 24 ]. Association of coffee and caffeine intake with the risk of Parkinson disease. Miscarriage : The results of observational studies that have examined the relationship between maternal coffee or caffeine intake and the risk of miscarriage spontaneous abortion have been conflicting.
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