Plantain and banana starches: granule structural characteristics explain the differences in their starch degradation patterns.

Different banana cultivars were used to investigate the influences of starch granule structure and hydrolases on degradation. The highest degrees of starch degradation were observed in dessert bananas during ripening. Scanning electron microscopy images revealed smooth granule surface in the green stage in all cultivars, except for Mysore. The small and round granules were preferentially degraded in all of the cultivars. Terra demonstrated a higher degree of crystallinity and a short amylopectin chain length distribution, resulting in high starch content in the ripe stage. Amylose content and the crystallinity index were more strongly correlated than the distribution of amylopectin branch chain lengths in banana starches. α- and ß-amylase activities were found in both forms, soluble in the pulp and associated with the starch granule. Starch-phosphorylase was not found in Mysore. On the basis of the profile of α-amylase in vitro digestion and the structural characteristics, it could be concluded that the starch of plantains has an arrangement of granules more resistant to enzymes than the starch of dessert bananas.

Avaliação comparativa de características estruturais do amido e enzimas relacionadas à sua degradação em cultivares de banana como padrão distinto do modelo representado pela cultuvar Nanicão / Comparative evaluation of structural characteristics of starch and enzymes related to their degradation in banana cultivars as distinct from the standard model represented by cultuvar Nanicão

O acúmulo de açúcares solúveis observados em banana madura é resultado da ação de diversas enzimas que atuam sob o amido acumulado durante o seu desenvolvimento. Este processo pode ocorrer fora da planta e, em um período relativamente curto conhecido como amadurecimento. A rápida mobilização associado a escassez de trabalhos que enfoquem o processo de degradação de amido em Orgãos que armazenam amido temporariamente, como bananas, o objetivo desse estudo foi localizar cultivares que se comportem diferente do modelo Nanicão, que é objeto de estudo do laboratório ha muito tempo, sendo por isso, a cultivar mais conhecida e estudada. Bananas pertencentes a diferentes grupos genômicos foram selecionadas e analisadas, sendo elas: Nanicão (AAA), Terra (AAB), Mysore (AAB), Pacovan (AAB) e Figo (ABB). Quanto aos parâmetros de amadurecimento analisados, as cultivares Nanicão, Terra e Pacovan tiveram um comportamento climatérico típico. A sacarose foi o açúcar predominante em todas as cultivares seguida pela glicose e frutose que mantiveram uma proporção 1:1. A cultivar Nanicão teve maiores teores de açúcares solúveis seguida pela Figo, Pacovan, Terra e Mysore. Em extrato bruto de banana, os maiores valores de atividade da β-amilase foi verificada nos estágios finais do amadurecimento, enquanto que a da α-amilase foi, praticamente, constante durante o período analisado, com exceção da Figo. Para detectar a presença das amido-fosforilases foi realizado ensaio, em extrato bruto de banana, de eletroforese em condições não-desnaturantes (PAGE-nativo) e, duas bandas com atividade foram visualizadas nas cultivares, com exceção da Mysore. O inicio do processo de degradação de amido ocorreu anterior a produção autocatalitica de etileno e, as cultivares tiveram diferentes percentuais de degradagao de amido, sendo os maiores obtidos/na Pacovan seguida pela Mysore, Nanicão, Figo e Terra. Os grânulos de amido das cultivares Terra e Figo mostraram-se resistentes a...

The soluble sugars accumulation in mature banana is consequence of several enzymes action on accumulate starch obtained during its development process. The starch degradation can occur outside the plant in a relatively short time called ripening. Associate at the faster starch mobilization, few works are available focusing this process in organs that store starch temporarily like banana. The aim of this study was identified cultivars that show different pattern of starch degradation when compared with Nanicao model. Bananas of different genomic groups were selected and analyzed, Nanicao (AAA), Terra (AAB), Mysore (AAB), Pacovan (AAB) and Figo (ABB). The Nanicao, Terra and Pacovan cultivars had a typical climacteric behavior. Sucrose was the predominant sugar followed by glucose and fructose that maintained 1:1 ratio, in all cultivars. Nanicao had the higher levels of soluble sugars followed by Figo, Pacovan, Terra and Mysore. The onset of starch degradation seems to be independent of ethylene. The higher activities of β-amylase, in banana pulp, was obtained in the last ripening stages, while α-amylase activities was constant and low at Nanicao and Pacovan. Two bands with activities were visualized in native PAGE which corresponded to cytosolic and plastidial forms of starchphosphorylases, with exception of Mysore. All cultivars had different perceptual of starch degradation and the higher one was observed at Pacovan, followed by Mysore, Nanicao, Figo and Terra. Starches granules of Terra and Figo showed to be resistant to enzymatic hydrolysis. All cultivars had a and β-amylase activities associated to granule throughout the ripening process. Only Mysore showed αamylase activity associated to granule higher than β-amylase. No significant change along the ripening was observed in amylose content and amylopectin chain length distribution. The micrographs revealed that granule surface suffer changes along the ripening, exposing structures...

Identification of fructooligosaccharides in different banana cultivars.

Banana has been currently indicated as a good source of fructooligosaccharides (FOS), which are considered to be functional components of foods. However, significant differences in their amounts in bananas have been observed in the literature. This work aims to identify and quantify FOS during ripening in different banana cultivars belonging to the most common genomic groups cultivated in Brazil. Considering that these differences can be due to cultivar, stage of ripening, and the methodologies used for FOS analyses, sugar contents were analyzed by high performance anion exchange chromatography-pulsed amperometric detection (HPAEC-PAD) and gas chromatography-mass spectrometry (GC-MS). An initial screening of eight cultivars (Ouro, Nanicão, Prata, Maçã, Mysore, Pacovan, Terra, and Figo) in a full-ripe stage showed that 1-kestose, the first member of the FOS series (amounts between 297 and 1600 microg/g of DM), was accumulated in all of them. Nystose, the second member, was detected only in Prata cultivar. Five of the cultivars were analyzed during ripening, and a strong correlation could be established with a specific sucrose level ( approximately 200 mg/g of DM), which seems to trigger the synthesis of 1-kestose (the low amounts of FOS, below the functional recommended dose, indicates that banana cannot be considered a good source of FOS).