Roasting Kinetics and Chemical Composition Changes of Robusta Coffee Beans During Hot Air and Superheated Steam Roasting

Abstract

As it is known that Robusta coffee beans exhibit more bitterness, less acidity, and lacks sweetness with unbalance flavor as compared to their Arabica counterpart, a means to improve the quality of Robusta coffee beans is desirable. As a step that contributes to the coffee quality, it is interesting to determine if an alternative roasting technique could lead to the desired improved quality. Here, roasting kinetics and changes in pH and composition of Robusta coffee beans undergoing hot air and superheated steam (SHS) roasting at 190 to 250°C were investigated. SHS roasting led to higher rates of bed temperature increase, moisture loss and decrease in lightness (L * value) of the beans. Evolutions of the moisture content and L * value of the beans could be well described by the adopted kinetic equations. pH, caffeine, sugars, and organic acids contents of the beans were significantly affected by the temperature and degree of roasting. Interestingly, beans roasted in SHS had lower pH, higher sucrose, glucose, and arabinose contents. Their fructose and acetic acid contents were nevertheless lower, indicating that the beans probably exhibited higher sweetness and citrus-like acidity, but lower unfavorable vinegar-like acidity.Practical Application: This study illustrates the possibility to improve the quality of Robusta coffee beans via a physical process. Use of superheated steam roasting at appropriate condition can enhance some desirable characters of Robusta beans; such beans indeed exhibit more resemblance to the more sought-after Arabica beans. This should be of much value to a roasting house and blender in such a way that a higher proportion of Robusta beans can be used in a commercial blend of coffee beans.

Organic Selenium as Antioxidant Additive in Mitigating Acrylamide in Coffee Beans Roasted via Conventional and Superheated Steam

“…These results suggest that chemical pretreatment is more effective than physical treatment in mitigating acrylamide in coffee, attributing to the removal of associated precursors. The lack of oxygen condition is the most important characteristic of the superheated steam roaster, because the air in the system is replaced by superheated steam, thus, the sample heated under environment lack of oxygen is not oxidized [ 9 , 28 ]. It has been reported that the coffee beans roasted under superheated steam had lower pH and higher sugar content [ 9 , 29 ].…”

“…Roasting of coffee beans at high temperatures involves a series of reactions including caramelization, Maillard reaction, Strecker degradation, and pyrolytic reaction responsible for the development of desirable organoleptic characteristics and antioxidant capacity of coffee [ 9 , 10 ]. Maillard reaction products (MRP) formed during roasting are important flavor and color components in roasted coffee, chiefly Melanoidins, strong antioxidants that account for ~29% of coffee brew dry matter [ 6 ].…”

“…However, the impact on the sensorial and nutritional properties of coffee are among the limitations of the intervention studies. Superheated steam roasting demonstrated improvement in sensorial quality, increase antioxidant capacity, and reduce lipid oxidation of roasted coffee beans due to the generation of oxygen absent environment at higher bed temperature [ 9 , 28 , 29 ]. Nevertheless, no information is available on the effect of superheated steam roasting on the fate of acrylamide in coffee.…”

Conventional and microwave-assisted extraction for bioactive compounds from dried coffee cherry peel by-products and antioxidant activity of the aqueous extracts

“…A diode array detector (Agilent, Germany) was set at 254 nm while the flow rate was 1 mL/min at room temperature with a sample volume of 20 µL. The mobile phase was methanol and 1% acetic acid in a 30:70 ratio [15]. The isocratic mode was used for mobile phase elution.…”

Physical Characteristics of Analog Coffee from Kepok Banana Skin (Musa paradisiaca) Fermented with Lactobacillus plantarum

“…During fermentation with L. plantarum there will be degradation of various macromolecular compounds into micromolecules including the production of flavor precursors [9]. During roasting various flavor precursor compounds will turn into compounds that cause the aroma, flavor, and color to change [10]. The longer roasting causes the analog color of the coffee to be darker and significantly different.…”