Post-harvest effects on beverage quality and physiological performance of coffee beans

Abstract

During coffee drying, different temperatures applied to the beans with varied humidity content levels can interfere in the membranes integrity, germination, organic acid and carbohydrate content resulting in coffees with distinct flavors. The quality control of the beans will be much more effective the earlier the alterations provoked in the postharvest are detected. This work has an objective to study alternative methods for the dehydration of the coffee beans using ultra-drying followed by slow drying and its impact on the sensorial quality, chemical composition and physiology. For that purpose, coffee lots were processed by the methods, dry (natural coffee) and wet (fully washed coffee); and sun-dried and machine-dried at a constant 60°C temperature and alternating 60/40°C. The sensory quality of the samples was assessed by the Specialty Coffee Association of America (SCAA) analysis protocol. The sugar, total titratable acidity and the phenolic compound content was also analyzed. The physiological alterations of the coffee beans were analyzed by germination tests, emergence speed index, electrical conductivity and potassium leaching. The temperature of the drying air significantly altered the sensorial quality of the coffee beans. The processing way associated to drying methods causes many physiological alterations with the highest damage observed in the natural coffees. For the first time, we are showing that drying with heated air at 60/40ºC is promising for the fully washed coffee beans, which are more tolerant to dehydration than the natural coffee beans. Conversely, the natural coffee beans were much more sensitive to drying regardless the temperature, with very low performance in the physiological analyses. The drying at the constant 60ºC temperature is inappropriate for the natural coffee as well as for the fully washed coffee beans. In addition, the physiological tests used were shown effective for the early evaluation of coffee beans quality.

Farm to Consumer: Factors Affecting the Organoleptic Characteristics of Coffee. II: Postharvest Processing Factors

“…On the other hand, Taveira et al. () documented the same results, elaborating that average sun‐drying rates on drying patios (temperature: 10 to 28 °C and RH: 34.5% to 61.2%) are 0.002 kg/kg H 2 O/hr for fully washed coffee and 0.002 kg/kg H 2 O/hr for natural coffee. In agreement with the results of Tsegaye, Mohammed, Shimber, Getachew, and Getachew (), Taveira and colleagues also claimed better cup quality conservation for slow drying (60/40 °C, details below) on patios with hot air rather than on flat‐ground surfaces.…”

The Harvest and Post-Harvest Management Practices’ Impact on Coffee Quality

“…The type of coffee processing methods (wet and dry) that are performed to obtain the green beans determined the flavour properties and created a typical quality difference [3,19]. Several reports also stated the final cup quality and chemical composition are also defined by the adopted method in wet processing [20][21][22]. The effect of different modified wet-processing methods on the final quality of coffee is evaluated and compared by Gonzalez-Rios et al [21].…”

“…The coffee beans that are obtained using dry-processing method are usually called unwashed (natural) coffee. In this processing method, to get the green coffee beans, the harvested cherry is dried in the sun or other mechanical drier and followed by separating the dried outer parts [22]. Sun drying is a lengthy process, and 95% of Arabica coffee from Brazil, Ethiopia, Haiti, Indonesia, Paraguay, India, and Ecuador are sun-dried [42].…”

“…Drying is the most critical step in this processing method because it affects the final quality of the coffee. The overdried fruits have brittle characteristics and produce many defective (broken) during hulling; however, on the other side, under-dried fruits are highly exposed to deteriorations because of fungus and bacteria growth [22]. Tadesse et al [44] reported that the number of imperfect beans with musty, earthy and greenish colour coffee defects frequently found in dry processed coffee.…”

Relevance of endo--mannanase enzyme in coffee seed deterioration process

“…Recent results have shown that changes that occur in coffee seeds during the postharvest operations influence the chemical composition and integrity of enzyme systems, affecting its physiological quality (Bytof et al, 2007;Saath et al, 2014;Taveira et al, 2015). Therefore, the aim of this study was to determine endo-β-mannanase enzyme activity on dry and soaked coffee seeds, evaluating the relationship between this activity and the effects of processing and drying of seeds in physiological quality.…”