Shade improves coffee quality in a suboptimal coffeezone

Shade improves coffee quality in a sub-optimal coffee-zone of Costa Rica

Abstract Quality is an important attribute of coffee. Therefore it is important to understand the effect of overstory trees not only on the environment and long-term coffee production, but also on the quality of coffee grown underneath the trees. This study compared coffee quality of Coffea arabica L. vars. Caturra and Catimor 5175 under different levels of shade in a low-elevation, sub-optimal environment for coffee in Costa Rica（哥斯达黎加）. Fruit weight and bean size increased significantly when shade intensity was increased from 0% to more than 80% under unpruned Erythrina poeppigiana. While large beans (diameter > 6. 7 mm) accounted for 49 and 43% of the coffee from unshaded Caturra and Catimor, respectively, these proportions increased to 69 and 72% under dense（ 密集的） permanent shade. This suggested a stronger shade benefit for Catimor than for Caturra.

The conversion percentages from fresh-weight coffee fruits to dry-weight green coffee for export were not affected by the treatments. A blind tasting experiment showed consistent shade-induced improvements in appearance of green and roasted coffee as well as in acidity and body of the brew for both varieties. The effect of shade on aroma（芳香；气味） of the brew was neutral for Caturra and slightly negative for Catimor. It is hypothesized（假定） that, in the sub-optimal (lowaltitude) coffee-zone studied, shade promotes slower and more balanced filling and uniform ripening of berries, thus yielding a better-quality product than unshaded coffee plants. Shade experiments along environmental gradients should help to validate this conjecture and its relative importance in different coffee-zones.

Materials and methods 1. Research site a commercial coffee plantation of ‘Cafetalera Lindo S. A. ’ in Turrialba, Costa Rica at 9° 55¢ N, 83° 41¢ W and 700 m above sea level. The average yearly temperature was 21 °C and the annual rainfall 2600 mm, without a marked dry season. 2. Plant attributes and management

3. Sampling and sampleprocessing ⑴Coffee fruit weight was measured as the fresh weight (g) of 100 randomly selected ripe fruits (W 100) from each plot, taken from the collection baskets on 10 sampling dates (roughly at twoweek intervals, spanning the whole harvest period) for the harvest 94/95 and on three sampling dates in 95/96. ⑵In 24 hours，the samples were oven-dried at 40 to 50 °C until reaching 10– 12% humidity.

⑶ the beans were passed through a series of sieves with round perforations of 17, 16 and 15 sixtyforths of an inch in diameter (standard method to evaluate coffee bean size distribution; equivalent to 6. 7, 6. 4 and 6. 0 mm, respectively). ⑷The weight fractions retained on each sieve were recorded and converted to weight percentages of the total sample. （5）the standard procedure for detecting offflavors and defects (G. Astua, pers. comm. 1997) homogeneity of roasting, physical shape and defects were valued on a scale of 0 to a maximum of 10 for well-formed beans of homogeneous size and color, free of physical deformations or discoloration.

⑺The coffee brew quality was assessed using aroma (by smelling the freshly brewed cup), body (syn. with mouthfeel or viscosity sensu Clifford (1985)), acidity and cleanness of the coffee in the mouth. Under cleanness of taste, off-flavors were described. Aroma, body and acidity were given values on a scale of 0 (worst) to 10 (best quality). Results 1. Fruit weight

Figure 1. Fresh weight of 100 ripe fruits of two coffee varieties grown under increasing shade levels provided by black shade cloth (50%) or Erythrina poeppigiana (pollarded = small patchy shade; open = closed canopy with selective pruning of every second branch; dense = high closed canopy of unpruned trees) in a low-elevation coffee area (El Cañal, Turrialba, Costa Rica; 1994/95/96; 700 masl, 2600 mm). Within varieties, means with the same letter do not differ significantly (n = 26, P = 0. 05). 2. Bean size

Figure 2. Size distribution of green beans of Coffea arabica var. Caturra (above) and Catimor (below) under increasing shade from Erythrina poeppigiana (pollarded = small patchy shade; open = closed canopy with selective pruning of every second branch; dense = high closed canopy of unpruned trees) in a low-elevation coffee area (El Cañal, Turrialba, Costa Rica; 700 masl, 2600 mm). Under higher shade levels, the percentage of large beans (diameter > 17/64 ths of an inch; equivalent to 6. 7 mm) increased significantly.

The size distribution of green beans (‘café oro’) showed, for both coffee varieties, a significant and consistent increase in bean size with increasing shade levels under E. poeppigiana (Figure 2; significant at P = 0. 1 and P = 0. 01 for c 2 -test for Caturra and Catimor, respectively) The comparison between the shadecloth and pollarded treatments for Caturra indicated a higher proportion of large beans for the pollarded treatment (Figure 2).

3. Visual appearance and organoleptic attributes Figure 3. Quality attributes of green and roasted beans of two varieties of Coffea arabica grown without shade and with dense shade (> 80% shade) of Erythrina poeppigiana in a low-elevation coffee area (El Cañal, Turrialba, Costa Rica; 700 masl, 2600 mm). Beans were harvested at full maturity in Sept/Oct 1997. The scales use a relative index with a maximum of 10. Significance between unshaded and shaded given as ***P = 0. 01, **P = 0. 05 and *P = 0. 1.

both varieties benefitted consistently from shade (Figure 3). For Catimor, shade improved the appearance of green (P = 0. 01) and roasted (P = 0. 1) beans. Shade also improved both taste parameters (body and acidity), although only the difference for body was significant. In contrast, the index of aroma was significantly lower for shaded Catimor (Figure 3).

Conclusions The study suggests a substantial improvement of coffee quality through shading in a suboptimal and hightemperature environment where coffee plants are stressed. The main benefits from shading were: 1) higher weights of fresh fruits; 2) larger beans; 3) higher ratings for visual appearance of green and roasted beans; 4) higher ratings for acidity (Catimor only) and body; and 5) absence of offflavors.