Fruit Thinning and Shade Improve Bean Characteristics and Beverage

Journal of the Science of Food and Agriculture J Sci Food Agric 86:197–204 (2006) DOI: 10.1002/jsfa.2338 Fruit thinning and shade improve bean characteristics and beverage quality of coffee (Coffea arabica L.) under optimal conditions Philippe Vaast,1,2∗ Benoit Bertrand,2 Jean-Jacques Perriot,2 Bernard Guyot2 and Michel Genard´ 3 1Centro Agronomico´ Tropical de Investigacion´ y Ensenanza˜ (CATIE), Apdo 3, 7170 Turrialba, Costa Rica 2Centre de Cooperation´ Internationale en Recherche Agronomique pour le Developpement´ (CIRAD), 2477 Avenue du Val de Montferrand, BP 5035, F-34032 Montpellier, France 3Institut National de la Recherche Agronomique (INRA), Plantes et Systemes` de Cultures Horticoles, Domaine Saint-Paul Agroparc, F-84914 Avignon Cedex 9, France Abstract: Under two contrasting light regimes (full sun and 45% shade) and the optimal coffee-growing conditions of the central valley of Costa Rica, production pattern, bean characteristics and beverage quality were assessed over two production cycles on dwarf coffee (Coffea arabica L. cv. Costa Rica 95) trees with varying fruit loads (quarter, half and full loads) imposed by manual fruit thinning. Shade decreased coffee tree productivity by 18% but reduced alternate bearing. Shade positively affected bean size and composition as well as beverage quality by delaying berry flesh ripening by up to 1 month. Higher sucrose, chlorogenic acid and trigonelline contents in sun-grown beans pointed towards incomplete bean maturation and explained the higher bitterness and astringency of the coffee beverage. Higher fruit loads reduced bean size owing to carbohydrate competition among berries during bean filling. These results have important implications in terms of agricultural management (shade, fruit thinning, tree pruning) to help farmers increase coffee plantation sustainability, produce coffee beans of larger size and higher quality and ultimately improve their revenues, especially during times of world overproduction. 2005 Society of Chemical Industry Keywords: bearing pattern; bean biochemical content; berry maturation; coffee beverage quality; fruit load; shade INTRODUCTION Arabica coffee (Coffea arabica L.) is a cash crop Until recently the emphasis in coffee research has of major economic importance in Central American focused mainly on orchard management practices countries, which have a long-lasting reputation for to increase coffee productivity and on breeding pro- producing coffee of high quality. In this region, grammes to enhance resistance to pests and diseases. Arabica coffee was traditionally grown under shade in Owing to the current low market prices caused by complex agroforestry systems with up to three storeys world overproduction, there is a strong interest in of vegetation.7 In the late 1970s, however, the rapid producing and marketing coffee of higher quality to development of leaf rust disease (Hemileia vastatrix)led alleviate financial difficulties encountered by coffee to the planting of a new generation of resistant, dwarf farmers. Coffee quality is mainly assessed through the cultivars. Compared with traditional ones, these dwarf physical aspects of coffee beans such as bean colour, cultivars have a more compact canopy and shorter size, density and percentage of physical defects in branches, allowing higher planting densities under producing countries, whereas cup quality is the main their own dense shade and hence increased production criterion in consuming countries. Numerous factors per hectare.8 This has radically modified agricultural affect coffee quality,1 including soil water status,2 practices, especially pruning and fertilisation regimes, climatic conditions,3,4 maturity of coffee berries at and often resulted in the complete elimination of shade harvest and bean processing (fermentation, washing, trees. However, these full-sun and intensively managed drying, storage, roasting, beverage preparation), agri- coffee systems are not recommended in the absence cultural management (shade, pruning, fertilisation) of optimal ecological conditions. Furthermore, these and genetic properties of cultivars.5,6 systems are not only more economically risky but ∗ Correspondence to: Philippe Vaast, Centro Agronomico´ Tropical de Investigacion´ y Ensenanza˜ (CATIE), Apdo 3, 7170 Turrialba, Costa Rica E-mail: [email protected] Contract/grant sponsor: European Commission; contract/grant number: CASCA ICA4-CT-2001-10071 Contract/grant sponsor: Science and Cultural Cooperation Centre, French Embassy, Costa Rica (Received 23 March 2004; revised version received 7 December 2004; accepted 25 May 2005) Published online 10 October 2005 2005 Society of Chemical Industry. J Sci Food Agric 0022–5142/2005/$30.00 197 P Vaast et al. also less ecologically sustainable. The presence of 1/2, half of initial fruit load; 1/4, quarter of initial shade trees is known to improve soil organic fruit load) were imposed on the coffee trees, resulting matter content, alleviate high solar irradiance, buffer in six combinations of light levels and fruit loads detrimental diurnal changes in air temperature and with 16 replicates per combination. Fruit thinning was humidity9 and reduce nutrient leaching, especially performed manually a few days after flowering at the nitrate which contaminates aquifers.10 Additionally, beginning of the 1999 and 2000 production cycles. products derived from associated timber and fruit trees In 2001, fruit thinning was not undertaken, to test help farmers to diversify their income. Finally, shade the effects of previous fruit loads on tree productivity. trees play an important role in the region owing to the Furthermore, only coffee production was assessed for valuable impact of coffee agroforestry systems on the this third production cycle (2001). environment and natural resources (preservation of biodiversity, soil conservation, water quality, carbon Leaf area, leaf-to-fruit ratio, leaf temperature sequestration). Recent studies in Guatemala11 and and irradiance measurements Costa Rica12 have demonstrated that elevation and The area of individual leaves was measured with shade improved coffee quality owing to cooler climatic a LICOR 1800 area meter (LICOR, Lincoln, NE, conditions and probably a longer ripening period of USA). Measurements were performed on three coffee berries. In 1999 a collaborative research effort branches (branch positions 10, 17 and 25 as seen was developed in Central America to compensate low from the top of the coffee tree) positioned in the coffee market prices by promoting coffee agroforestry main producing zone of the canopy. From these systems to improve coffee farmers’ incomes through measurements at these three levels (U, upper; M, diversification (timber production), production and middle; L, low) in the canopy an average branch commercialisation of high-quality coffee and payment leaf area was computed, a total plant leaf area was of incentives for environmental services provided by estimated and leaf-to-fruit ratios were derived for each these ecologically sound coffee systems. Within this tree after counting the number of coffee berries. research framework, several scientific investigations To estimate light availability and temperature within have been undertaken to determine the importance the canopy, instantaneous measurements of PPFD and of factors such as microclimatic conditions, tree temperature were taken at leaf level in September 2000 productivity, berry position within the canopy, shade under clear sky conditions (ca 2000 µmol m2 s−1)using management and fertilisation regimes on coffee tree the quantum and temperature sensors of a DeltaT AP4 physiology and beverage quality. The present study porometer (DeltaT, Burwell, UK). Measurements focuses on the effects of tree productivity, manipulated were performed on the right leaf of leaf pairs 3, 6, 12, by fruit thinning, and light regime on the size and 15, 18, 21, 24 and 27 on the three selected branches, biochemical composition of coffee beans and their with leaf pair 3 being the closest to the tree trunk impact on beverage quality. inside the canopy and leaf pairs 18–27 the outermost ones. Values presented for each leaf position within a branch are means of the 16 spot readings, all taken MATERIALS AND METHODS between 10:00 and 12:00 (i.e. solar noon ±1h). Experimental location and design The study was carried out over three production Fruit parameters cycles, from March 1999 to February 2002, on Arabica Only fully ripe coffee berries, as determined by the coffee (C. arabica L.) trees of the dwarf cultivar ‘Costa bright red colour of their skin, were harvested from Rica 95’ planted under the optimal coffee-growing individual trees. Five to six harvests were necessary to conditions of the Coffee Research Centre (CICAFE), collect all the berries over a period of 3 months. The Heredia, Costa Rica at 1180 m elevation, with an fresh weight of berries was recorded at each harvest. annual average temperature of 20.5 ◦C, on an Andosol Coffee samples were prepared by the wet processing soil and with 2200 mm of annual rainfall. The plot was method (wet de-pulping, anaerobic fermentation for initiated in 1997 without shade. ‘Costa Rica 95’ has a 24 h, sun drying, de-husking) to obtain ready-to-be- maximum height, after four to five years, not exceeding roasted coffee beans (commonly named green coffee 2.5–3.0 m. Plant spacing was 2 m between rows and or green beans). For the production cycles of 1999 1 m within rows. Plants received 144 kg N, 24 kg P, and 2000, bean size was assessed

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