The daily habit of drinking coffee has evolved beyond a routine into a
functional and meaningful aspect of modern dietary life. In particular, coffee
processing methods directly influence the composition and quality of its
components, necessitating...
The daily habit of drinking coffee has evolved beyond a routine into a
functional and meaningful aspect of modern dietary life. In particular, coffee
processing methods directly influence the composition and quality of its
components, necessitating scientific exploration of novel processing techniques.
This study applied repeated steaming and drying techniques to green coffee
beans and analyzed the physicochemical quality characteristics to explore the
potential for enhancing both functionality and safety. The findings aim to
provide scientific evidence for developing health-oriented coffee products and
diversifying coffee processing methods.
As the number of steaming and drying cycles increased, the moisture content
of green coffee beans gradually decreased. Crude ash content increased in
roasted beans, while crude lipid content significantly decreased after the third
cycle. Crude protein content showed a significant increase with more cycles,
whereas carbohydrate content significantly varied depending on the origin.
Chromaticity analysis revealed that the L values decreased with more
processing, a values increased at 3 and 6 cycles but decreased at 9, and b
values increased at 3 cycles and then declined. Both total sugar content and
pH showed a decreasing trend as the number of cycles increased.
Organic acid analysis identified six compounds—malic acid, fumaric acid,
lactic acid, formic acid, acetic acid, and 5-HMF. Malic acid was found in all
samples; fumaric and formic acids were present only in the 6 and 9 cycle
samples. Lactic acid was detected only in the control and 9 cycle samples,
acetic acid in all but the control, and 5-HMF exclusively in the BC-9 cycle
sample, indicating significant compositional changes according to treatment
intensity.
The contents of caffeine, chlorogenic acid, and trigonelline decreased sharply
with repeated treatments. Total polyphenol content increased with more cycles,
whereas flavonoid content, known to be heat-sensitive, significantly decreased.
Antioxidant activity measured via DPPH radical scavenging also decreased with
additional cycles.
GC/MS-based setabolite profiling analysis revealed significant changes in
compound composition across five categories: sugars and sugar alcohols, lipids
and derivatives, functional lipids and bioactive compounds, organic and phenolic
acids, and functional amino acids and inorganic compounds. This suggests that
repeated steaming and drying processes can alter the functional profile of green
coffee beans.
A Sensory evaluation of brewed coffee processed through repeated steaming
and drying (3, 6, and 9 cycles) revealed significant differences among
treatments. Although the EY-9 extract showed relatively balanced flavor, - 167
acidity, and body, all samples displayed diminished coffee-like sweetness and
depth, accompanied by enhanced tea- or herbal-like notes, indicating limitations
of steaming-drying alone in improving consumer preference.
For comparison, BC, GA and EY beans roasted under standardized conditions
(Agtron 45) were evaluated by 40 panelists. EY received the highest overall
scores, followed by GA and BC demonstrating clear varietal differences even
under identical roasting conditions.
These findings confirm distinct changes in the composition and sensory
characteristics of coffee beans depending on the processing method. However,
as this study is based on specific varieties and processing conditions, further
research involving diverse cultivars and comprehensive sensory evaluation is
necessary.
This study holds significance in its application of the traditional Korean
"Gujeunggupo" (nine-time steaming and nine-time sun-drying) method to green
coffee beans, offering insight into novel flavor development and processing
techniques. It presents foundational data for future innovations in functional,
traditional, and sensory-focused coffee products.