ABSTRAKPenelitian ini bertujuan untuk mengkaji hubungan antara suhu dan lama pengukusan terhadap penurunan kandungan kafein dan asam klorogenat serta menentukan energi aktivasi (Ea) dengan pendekatan persamaan Arrhenius. Biji kopi Robusta masing-masing seberat 750 g dikukus dalam autoklaf (sistem tertutup) pada suhu 100, 110, dan 120 °C masing-masing selama 1, 2, 3, 4, 5, 6, dan 7 jam. Penelitian dilakukan dengan 3 kali ulangan. Analisis kafein dan asam klorogenat dilakukan menggunakan HPLC. Pengukusan biji kopi pada suhu 100, 110, dan 120 °C, menghasilkan penurunan kandungan kafein dan asam klorogenat tertinggi pada pengukusan selama 7 jam. Penurunan kandungan kafein selama 7 jam pada suhu pengukusan 100, 110, dan 120 °C berturut-turut 13%, 18%, dan 25%. Kandungan asam klorogenat mengalami penurunan 37%, 50%, dan 59% berturut-turut pada suhu 100, 110, dan 120 °C. Pada semua suhu yang diuji, penurunan kafein dan asam klorogenat mengikuti reaksi orde satu. Penurunan kafein mengikuti persamaan y = -0,019x + 0,862, y = -0,023x + 0,820, dan y = -0,033x + 0,759, sedangkan untuk asam klorogenat mengikuti persamaan y = -0,071x + 1,421, y = -0,089x + 1,271, dan y = -0,120x + 1,201. Besarnya energi aktivasi penurunan kafein dan asam klorogenat berturut turut adalah 33.543,66 kJ/molK dan 31.934,91 kJ/Mok. Kata kunci: Energi aktivasi; kafein; asam klorogenat ABSTRACTThis study was aimed to examine the correlation between temperature and duration of steaming on caffeine and chlorogenic acid reduction as well as to determine energy activation (Ea) according to Arrhenius equation. About 750 g of Robusta coffee was steamed by autoclaving at 100, 110, 120 °C for 1, 2, 3, 4, 5, 6 and 7 hours. The study was conducted in 3 replications. Analyses of caffeine and chlorogenic acid were performed using HPLC. Steaming coffee beans at 100, 110 and 120 °C resulted in the highest decrease of caffeine and chlorogenic acids content for 7 hours by 13%, 18% and 25% for caffeine; and by 37%, 50% and 59% for chlorogenic acids. At all temperatures investigated, decaffeination and chlorogenic acid reduction followed first order reaction. The decaffeination equation at 100 °C, 110 °C and 120 °C followed equation of y = -0.019x + 0.862, y = -0.023x + 0.820, and y = -0.033x + 0.759, respectively. Meanwhile, the chlorogenic acid reduction at 100 °C, 110 °C, and 120 °C followed equation of y = -0.071x + 1.421, y = -0.089x + 1.271, and y = -0.120x + 1.201. Activation energies of decaffeination and chlorogenic acid reduction were 33,543.66 kJ/mol K and 31,934.91 kJ/mol K, respectively. Keywords: Activation energy; caffeine; chlorogenic acids PENDAHULUAN Kopi merupakan salah satu minuman yang paling banyak dikonsumsi di seluruh dunia (Lara, 2010), termasuk juga di Indonesia. Minuman kopi disukai konsumen bukan sebagai sumber nutrisi melainkan sebagai minuman penyegar karena memiliki cita rasa dan aroma yang khas.Cita rasa ini disebabkan
The research aimed to study the effects of storage time of cacao fruit before fermentation, aeration rate and temperature of fermenter during fermentation on the color value of dry cocoa beans, including the value of L *, a *, b *, chroma, hue, and RGB, and their relationship using response surface methodology.. The results showed that storage time of cacao fruits before fermentation, aeration rate and temperature of the fermenter had an influence on the color values of L *, a *, b *, chroma, hue, and RGB of dried cocoa beans produced. The highest brightness prediction value of chroma color was ± 26 obtained in the treatment of the storage time of 9-day, aeration rate of 0.4 liters/minute, and fermenter temperature of 50 o C Meanwhile, the highest hue prediction value was 51.8 obtained in the treatment of storage time of 9 days, aeration rate of 0.3 liters / minute, and fermenter temperature of 50 o C. Furthermore, the RGB color of dried cocoa beans showed that the color range of R (red) and G (green) of cocoa beans after fermentation was higher when compared to cocoa beans without fermentation, while the value of color B (blue) had a different tendency showing that dried fermented cocoa beans had a lower blue range compared to unfermented cocoa beans.
A tray dryer using source of energy from biomass and solar was developed to dry sorghum crackers. In this dryer, solar dryer was combined with a heating system of drying air through pipes above the furnace while cooking sorghum stem's juice. This research investigated drying characteristics of sorghum crackers using the dryer in various drying air velocities. This drying air velocity was conducted at 0.0176; 0.0194 and 0.0272m 3 /s. The higher drying air velocity blown into the dryer through pipes above the furnace, the lower temperature of drying air. There is a little different of drying air and crackers temperature in each tray. Sorghum crackers were dried from 186.78% d.b. to approximately 13.88% d.b. The mechanism of drying consists of constant rate period and falling rate period. The constant value during constant rate period in each drying air velocity was 0.0109; 0.0102 and 0.0098%/s while during falling rate period velocity was 0.0085; 0.0089 and 0.0085%/s. The drying air velocity affected constant value during constant period significantly. These models were valid to predict moisture content during drying and describe the drying process in the dryer.
The application of starch films, such as food packaging materials, has been restricted due to poor mechanical and barrier properties. However, the addition of a reinforcing agent, cellulose nanofibers (CNF) and also thymol, into the films, may improve the properties of films. This work investigates the effects of incorporating different concentrations of thymol (3, 5, 7, and 10 wt.%) on physical, mechanical, water vapor barrier, and antibacterial properties of corn starch films, containing 1.5 wt.% CNF produced using the solvent casting method. The addition of thymol does not significantly affect the color and opacity of the films. It is found that the tensile strength and Young’s modulus of the films decreases from 10.6 to 6.3 MPa and from 436.9 to 209.8 MPa, respectively, and the elongation at break increased from 110.6% to 123.5% with the incorporation of 10 wt.% thymol into the films. Furthermore, the addition of thymol at higher concentrations (7 and 10 wt.%) improved the water vapor barrier of the films by approximately 60.0%, from 4.98 × 10—9 to 2.01 × 10—9 g/d.m.Pa. Starch/CNF/thymol bionanocomposite films are also found to exhibit antibacterial activity against Escherichia coli. In conclusion, the produced starch/CNF/thymol bionanocomposite films have the potential to be used as antibacterial food packaging materials.
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