Carbohydrates of the Coffee Bean. II. Isolation and Characterization of a Mannan 1

140

130

In commercial coffee species (Coffea arabica and Coffea canephora), fruit development is a lengthy process, characterized by tissue changes and evolutions. For example, soon after fecundation and up to mid development, the fruit is mainly constituted of the pericarp and perisperm tissue. Thereafter, the perisperm gradually disappears and is progressively replaced by the endosperm (true seed). Initially present in a "liquid" state, the endosperm hardens as it ripens during the maturation phase, as a result of accumulation of storage proteins, sucrose and complex polysaccharides representing the main reserves of the seed. The last step of maturation is characterized by the dehydration of the endosperm and the color change of the pericarp. Important quantitative and qualitative changes accompany fruit growth, highlighting the importance of its study to better understand the final characteristics of coffee beans. Following a description of the coffee fruit tissues, this review presents some data concerning biochemical, enzymatic and gene expression variations observed during the coffee fruit development. The latter will also be analyzed in the light of recent data (electronic expression profiles) arising from the Brazilian Coffee Genome Project. Key words: Coffea spp, bean development, cell cycle, endosperm, EST, gene expression, pericarp, perisperm.Cytology, biochemistry and molecular changes during coffee fruit development: Em espécies comerciais de café (Coffea arabica e Coffea canephora), o desenvolvimento do fruto de café é um processo longo, caracterizado por mudanças e evoluções nos tecidos. Por exemplo, logo após a fecundação e até a metade do desenvolvimento, o fruto é principalmente constituído pelo pericarpo e perisperma. Em seguida, o perisperma gradualmente desaparece e é progressivamente substituído pelo endosperma (semente verdadeira). Inicialmente o endosperma apresenta-se no estado "líquido", o endosperma endurece durante a fase de maturação, como resultado do acúmulo gradual de proteínas de reserva, sacarose e polissacarídeos complexos representando as principais reservas da semente. O último passo da maturação é caracterizado pela desidratação do endosperma e pela mudança de cor do pericarpo. Importantes alterações quantitativas e qualitativas acompanham o crescimento do fruto, ilustrando a importância do seu estudo para melhor compreender as características finais das sementes de café. Seguindo a descrição dos tecidos do fruto de café, esta revisão apresenta alguns dados relativos às variações bioquímicas, enzimáticas e de expressão gênica durante o desenvolvimento do fruto. A expressão de genes será também analisada em função de dados recentes (perfil de expressão eletrônica) oriundos do Projeto Genoma Brasileiro Café. Palavras-chave: Coffea spp, ciclo celular, desenvolvimento da semente, endosperma, EST, expressão gênica, pericarpo, perisperma. INTRODUCTIONThe Coffea genus contains around 100 species (Charrier and Berthaud, 1985). Within these species, C. arabica (Arabica) and C. canephora (Rob...

Section: Perispermmentioning

confidence: 99%

Cytology, biochemistry and molecular changes during coffee fruit development

Castro

Marraccini

2006

140

130

“…The part of the endosperm in front of the radicle tip is referred to as endosperm cap or micropylar endosperm and around the rest of the embryo is the lateral endosperm (da Silva et al, 2004) (figure 1). The endosperm tissue has a high content of polysaccharides (Wolfrom et al, 1961). The cell walls are composed of cellulose and hemicelluloses, mainly insoluble mannans (Huxley, 1964;Wolfrom and Patin, 1964).…”

Section: The Coffee Seedmentioning

confidence: 99%

Coffee seed physiology

Eira

Silva

Castro

et al. 2006

100

Considerable advances in our understanding of coffee seed physiology have been made in recent years. However, despite intense research efforts, there are many aspects that remain unclear. This paper gives an overview of the current understanding of the more important features concerning coffee seed physiology, and provides information on recent findings on seed development, germination, storage and longevity.

“…The literature reports wide-ranging degrees of substitution from 47:1 (Wolfrom and Patin, 1961), 130:1 (Bradbury and Halliday, 1990), 30:1 (Fischer et al, 2001a), 1:7 and 1:40 (Redgwell et al, 2003) and 3:1 and 9:1 (Oosterveld et al, 2004). It is likely that the mannan molecules in coffee consist of a heterogeneous mixture of substituted and unsubstituted polymers but definitive data on the exact nature of this mixture is not available.…”

Section: Galactomannansmentioning

confidence: 99%

Coffee carbohydrates

Redgwell

Fischer

2006

This review summarises recent advances in the chemistry, physiology and molecular properties of coffee carbohydrates with a particular focus on the cell wall polysaccharides. The results of detailed chemical studies have demonstrated novel structural features of both the galactomannans and the arabinogalactan polysaccharides of the green and roasted coffee bean. For the first time immunological probes based on monoclonal antibodies for specific polysaccharide epitopes were used to reveal the patterns of distribution of the galactomannans, arabinogalactans and pectic polysaccharides in the coffee bean cell wall. Finally, the results of physiological and molecular studies are presented which emphasise the growing awareness of the potential role the metabolic status of the green bean may play in final coffee beverage quality. Key words: Coffea, cell wall, beverage quality, seed. Carboidratos do café:Este artigo sumariza os mais recentes desenvolvimentos nas áreas de química, fisiologia e propriedades moleculares dos carboidratos do café, com um particular interesse nos polisacarídeos presentes nas paredes celulares. Os resultados dos estudos químicos detalhados demonstraram novas características estruturais tanto nos galactomananos como nos polissacarídeos dos arabinogalactanos do grão de café verde ou torrado. Pela primeira vez, estudos imunológicos baseados em anticorpos monoclonais foram usados para revelar a distribuição dos galactomananos, dos arabinogalactanos e dos polissacarídeos pectídicos na parede celular do grão de café. Finalmente, os resultados dos estudos fisiológicos e moleculares são apresentados de maneira a sublinhar a influência do status metabólico do grão verde do café na qualidade final da bebida. Palavras-chave: Coffea, parede celular, qualidade da bebida, semente.