Polysaccharide composition of raw and cooked chayote (Sechium edule Sw.) fruits and tuberous roots.

Chayote is a multipurpose table vegetable widely consumed in Latin America countries. Chayote fruits, leaves and tuberous roots contain complex carbohydrates as dietary fiber and starch, vitamins and minerals. The complex polysaccharides (cell walls and starch) were analyzed in the black and green varieties of chayote fruits as well as in green chayote tuberous root before and after a controlled cooking process to assess changes in their composition and structure. The monosaccharide composition and linkage analysis indicated pectins homogalacturonans and rhamnogalacturonan I backbones constitute about 15-20% of the wall mass, but are heavily substituted with, up to 60% neutral arabinans, galactans, arabinogalactans. The remainder is composed of xyloglucan, glucomannans and galactoglucomannans. Chayote cell-wall polysaccharides are highly stable under normal cooking conditions, as confirmed by the optical microscopy of wall structure. We found also that tuberous roots constitute a valuable additional source of quality starch and fiber.

Storage at low temperature differentially affects the colour and carotenoid composition of two cultivars of banana.

Different storage conditions can induce changes in the colour and carotenoid profiles and levels in some fruits. The goal of this work was to evaluate the influence of low temperature storage on the colour and carotenoid synthesis in two banana cultivars: Prata and Nanicão. For this purpose, the carotenoids from the banana pulp were determined by HPLC-DAD-MS/MS, and the colour of the banana skin was determined by a colorimeter method. Ten carotenoids were identified, of which the major carotenoids were all-trans-lutein, all-trans-α-carotene and all-trans-ß-carotene in both cultivars. The effect of the low temperatures was subjected to linear regression analysis. In cv. Prata, all-trans-α-carotene and all-trans-ß-carotene were significantly affected by low temperature (p<0.01), with negative estimated values (ß coefficients) indicating that during cold storage conditions, the concentrations of these carotenoids tended to decrease. In cv. Nanicão, no carotenoid was significantly affected by cold storage (p>0.05). The accumulation of carotenoids in this group may be because the metabolic pathways using these carotenoids were affected by storage at low temperatures. The colour of the fruits was not negatively affected by the low temperatures (p>0.05).

Black leaf streak disease affects starch metabolism in banana fruit.

Black leaf streak disease (BLSD), also known as black sigatoka, represents the main foliar disease in Brazilian banana plantations. In addition to photosynthetic leaf area losses and yield losses, this disease causes an alteration in the pre- and postharvest behavior of the fruit. The aim of this work was to investigate the starch metabolism of fruits during fruit ripening from plants infected with BLSD by evaluating carbohydrate content (i.e., starch, soluble sugars, oligosaccharides, amylose), phenolic compound content, phytohormones, enzymatic activities (i.e., starch phosphorylases, α- and ß-amylase), and starch granules. The results indicated that the starch metabolism in banana fruit ripening is affected by BLSD infection. Fruit from infested plots contained unusual amounts of soluble sugars in the green stage and smaller starch granules and showed a different pattern of superficial degradation. Enzymatic activities linked to starch degradation were also altered by the disease. Moreover, the levels of indole-acetic acid and phenolic compounds indicated an advanced fruit physiological age for fruits from infested plots.

Changes in total ascorbic acid and carotenoids in minimally processed irradiated Arugula (Eruca sativa Mill) stored under refrigeration

This work investigated the effects of irradiation (0, 1 and 2 kGy) on the content of bioactive compounds such as vitamin C and carotenoids with provitamin A activity in arugula during the storage at 571 1C for up to 13 and 16 days, respectively. The vitamin C content decreased in non-irradiated as well as irradiated (1 and 2 kGy) samples during the storage period. On the other hand, no significant change in the content of carotenoids with provitamin...(AU)

Analysis of ripening-related gene expression in papaya using an Arabidopsis-based microarray.

BACKGROUND: Papaya (Carica papaya L.) is a commercially important crop that produces climacteric fruits with a soft and sweet pulp that contain a wide range of health promoting phytochemicals. Despite its importance, little is known about transcriptional modifications during papaya fruit ripening and their control. In this study we report the analysis of ripe papaya transcriptome by using a cross-species (XSpecies) microarray technique based on the phylogenetic proximity between papaya and Arabidopsis thaliana. RESULTS: Papaya transcriptome analyses resulted in the identification of 414 ripening-related genes with some having their expression validated by qPCR. The transcription profile was compared with that from ripening tomato and grape. There were many similarities between papaya and tomato especially with respect to the expression of genes encoding proteins involved in primary metabolism, regulation of transcription, biotic and abiotic stress and cell wall metabolism. XSpecies microarray data indicated that transcription factors (TFs) of the MADS-box, NAC and AP2/ERF gene families were involved in the control of papaya ripening and revealed that cell wall-related gene expression in papaya had similarities to the expression profiles seen in Arabidopsis during hypocotyl development. CONCLUSION: The cross-species array experiment identified a ripening-related set of genes in papaya allowing the comparison of transcription control between papaya and other fruit bearing taxa during the ripening process.

2D-DIGE analysis of mango (Mangifera indica L.) fruit reveals major proteomic changes associated with ripening.

A comparative proteomic investigation between the pre-climacteric and climacteric mango fruits (cv. Keitt) was performed to identify protein species with variable abundance during ripening. Proteins were phenol-extracted from fruits, cyanine-dye-labeled, and separated on 2D gels at pH 4-7. Total spot count of about 373 proteins spots was detected in each gel and forty-seven were consistently different between pre-climacteric and climacteric fruits and were subjected to LC-MS/MS analysis. Functional classification revealed that protein species involved in carbon fixation and hormone biosynthesis decreased during ripening, whereas those related to catabolism and the stress-response, including oxidative stress and abiotic and pathogen defense factors, accumulated. In relation to fruit quality, protein species putatively involved in color development and pulp softening were also identified. This study on mango proteomics provides an overview of the biological processes that occur during ripening.

Chemical composition and nutritional value of unripe banana flour (Musa acuminata, var. Nanicão).

Banana flour obtained from unripe banana (Musa acuminata, var. Nanicão) under specific drying conditions was evaluated regarding its chemical composition and nutritional value. Results are expressed in dry weight (dw). The unripe banana flour (UBF) presented a high amount of total dietary fiber (DF) (56.24 g/100 g), which consisted of resistant starch (RS) (48.99 g/100 g), fructans (0.05 g/100 g) and DF without RS or fructans (7.2 g/100 g). The contents of available starch (AS) (27.78 g/100 g) and soluble sugars (1.81 g/100 g) were low. The main phytosterols found were campesterol (4.1 mg/100 g), stigmasterol (2.5 mg/100 g) and ß-sitosterol (6.2 mg/100 g). The total polyphenol content was 50.65 mg GAE/100 g. Antioxidant activity, by the FRAP and ORAC methods, was moderated, being 358.67 and 261.00 µmol of Trolox equivalent/100 g, respectively. The content of Zn, Ca and Fe and mineral dialyzability were low. The procedure used to obtain UBF resulted in the recovery of undamaged starch granules and in a low-energy product (597 kJ/100 g).

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.

Synthesis of fructooligosaccharides in banana 'prata' and its relation to invertase activity and sucrose accumulation.

Levels of sucrose and total fructooligosaccharides (FOS) were quantified in different phases of banana 'Prata' ripening during storage at ambient (approximately 19 degrees C) and low (approximately 10 degrees C) temperature. Total FOS levels were detected in the first days after harvest, whereas 1-kestose remained undetectable until the sucrose levels reached approximately 200 mg/g (dry weight) in both groups. Sucrose levels increased slowly but constantly at low temperature, but they elevated rapidly when the temperature was raised to 19 degrees C. Total FOS and sucrose levels were higher in bananas stored at low temperature than in the control group. In both samples, total FOS levels were higher than those of 1-kestose. The carbohydrate profiles obtained by HPLC and TLC suggest the presence of neokestose, 6-kestose, and bifurcose. The enzymes putatively involved in banana fructosyltransferase activity were also evaluated. Results obtained indicate that the banana enzyme responsible for the synthesis of FOS by transfructosylation is an invertase rather than a sucrose-sucrosyl transferase-like enzyme.

Molecular cloning and characterization of a ripening-induced polygalacturonase related to papaya fruit softening.

Pulp softening is one of the most remarkable changes during ripening of papaya (Carica papaya) fruit and it is a major cause for post-harvest losses. Although cell wall catabolism has a major influence on papaya fruit, quality information on the gene products involved in this process is limited. A full-length polygalacturonase cDNA (cpPG) was isolated from papaya pulp and used to study gene expression and enzyme activity during normal and ethylene-induced ripening and after exposure of the fruit to 1-MCP. Northern-blot analysis demonstrated that cpPG transcription was strongly induced during ripening and was highly ethylene-dependent. The accumulation of cpPG transcript was paralleled by enzyme activity, and inversely correlated to the pulp firmness. Preliminary in silico analysis of the cpPG genomic sequence revealed the occurrence of putative regulatory motifs in the promoter region that may help to explain the effects of plant hormones and non-abiotic stresses on papaya fruit firmness. This newly isolated cpPG is an important candidate for functional characterization and manipulation to control the process of pulp softening during papaya ripening.

Changes in cell wall composition associated to the softening of ripening papaya: evidence of extensive solubilization of large molecular mass galactouronides.

Papaya (Carica papaya) is a climacteric fruit that undergoes dramatic pulp softening. Fruits sampled at three different conditions (natural ripening or after exposition to ethylene or 1-methylcyclopropene) were used for the isolation of cell wall polymers to find changes in their degradation pattern. Polymers were separated according to their solubility in water, CDTA, and 4 M alkali, and their monosaccharide compositions were determined. Water-soluble polymers were further characterized, and their increased yields in control and ethylene-treated fruit, in contrast to those that were treated with 1-MCP, indicated a strong association between fruit softening and changes in the cell wall water-soluble polysaccharide fraction. The results indicate that the extensive softening in the pulp of ripening papayas is a consequence of solubilization of large molecular mass galacturonans from the pectin fraction of the cell wall. This process seems to be dependent on the levels of ethylene, and it is likely that the releasing of galacturonan chains results from an endo acting polygalacturonase.

Benzylglucosinolate, benzylisothiocyanate, and myrosinase activity in papaya fruit during development and ripening.

Papaya is a climacteric fruit that has high amounts of benzylglucosinolates (BG) and benzylisothiocyanates (BITC), but information regarding levels of BG or BITC during fruit development and ripening is limited. Because BG and BITC are compounds of importance from both a nutritional and a crop yield standpoint, the aim of this work was to access data on the distribution and changes of BG and BITC levels during fruit development and ripening. BG and BITC levels were quantified in peel, pulp, and seeds of papaya fruit. Volatile BITC was also verified in the internal cavity of the fruit during ripening. The influence of the ethylene in BG and BITC levels and mirosinase activity was tested by exposing mature green fruits to ethylene and 1-methylcyclopropene (1-MCP). The highest BG levels were detected in seeds, followed by the peel and pulp being decreased in all tissues during fruit development. Similarly, the levels of BITC were much higher in the seeds than the peel and pulp. The levels of BG for control and ethylene-treated fruit were very similar, increasing in the pulp and peel during late ripening but not changing significantly in seeds. On the other hand, fruit exposed to 1-MCP showed a decrease in BG amount in the pulp and accumulation in seed. The treatments did not result in clear differences regarding the amount of BITC in the pulp and peel of the fruit. According to the results, ethylene does not have a clear effect on BITC accumulation in ripening papaya fruit. The fact that BG levels in the pulp did not decrease during ripening, regardless of the treatment employed, and that papaya is consumed mainly as fresh fruit, speaks in favor of this fruit as a good dietary source for glucosinolate and isothiocyanates.

Mango starch degradation. II. The binding of alpha-amylase and beta-amylase to the starch granule.

During mango ripening, soluble sugars that account for mango sweetening are accumulated through carbon supplied by both photosynthesis and starch degradation. The cultivar Keitt has a characteristic dependence on sugar accumulation during starch degradation, which takes place during ripening, only a few days after detachment from the tree. Most knowledge about starch degradation is based on seeds and leaves currently used as models. However, information about the mango fruit is scarce. This work presents the evaluation of alpha- and beta-amylases in the starch granule surface during fruit development and ripening. Extractable proteins were assayed for amylase activity and detected by immunofluorescence microscopy and correlated to gene expression. The results suggest that both amylases are involved in starch degradation during mango ripening, probably under the dependence of another signal triggered by the detachment from the mother-plant.

Mango starch degradation. I. A microscopic view of the granule during ripening.

The starch content of unripe mango Keitt is around 7% (FW), and it is converted to soluble sugars during the ripening of the detached fruit. Despite the importance of starch-to-soluble sugar metabolism for mango quality, little literature is found on this subject and none concerning the physical aspects of starch degradation. This manuscript presents some changes in the physical aspects of the starch granule during ripening, as analyzed by light microscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM). According to the analysis, unripe Keitt-mango-starch being spherical in shape and measuring around 15 microm, has A-type X-ray diffraction pattern with a degree of crystallinity around 21% with slight changes after 8 days of ripening. AFM images of the surface of the granules showed ultra microstructures, which are in agreement with a blocklet-based organization of the granules. The AFM-contrast image of growing layers covering the granule showed fibril-like structures, having 20 nm in diameter, transversally connecting the layer to the granule. The appearance of the partially degraded granules and the pattern of degradation were similar to those observed as a result of amylase activity, suggesting a hydrolytic pathway for the degradation of starch from mango cultivar Keitt. These results provide clues to a better understanding of starch degradation in fruits.

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).

Papaya fruit ripening: response to ethylene and 1-methylcyclopropene (1-MCP).

Ripening affects the quality and nutritional contents of fleshy fruits, and papayas are climacteric fruits very susceptible to postharvest losses due to the fast softening caused by ethylene. This paper reports the changes in respiration, ethylene production, and pulp color and firmness, along with the contents of soluble sugars and major carotenoids, during ripening of 'Golden' papaya, an important Brazilian cultivar that has been exported to North American and European markets. The results obtained for nontreated and ethylene- or 1-MCP-treated papaya suggest that 1-MCP can decrease the quality of treated fruit and that even the use of ethylene for triggering or inducing homogeneous ripening can result in lower quality when compared to that of fruit allowed to ripe naturally.

Effects of ethylene and 1-methylcyclopropene (1-MCP) on gene expression and activity profile of alpha-1,4-glucan-phosphorylase during banana ripening.

Starch phosphorylases are enzymes that can use starch as substrate, and they are supposed to act in both in starch synthesis and degradation. This paper reports the effects of ethylene and 1-methylcyclopropene (1-MCP) on the degradation of starch and phosphorylase activity and gene expression. The results indicate that phosphorylase activity is induced during ripening and that it is associated with the onset of starch degradation. The regulation of banana phosphorylase activity is mainly dependent on gene expression, and the absence of ethylene perception by 1-MCP had a positive effect. However, this effect can be precluded by increased levels of ethylene, both autocatalytic and exogenous.

Activity, cloning, and expression of an isoamylase-type starch-debranching enzyme from banana fruit.

Unripe bananas have a high content of starch (almost 20%) that is metabolized during fruit ripening with a concomitant synthesis of soluble sugars. Since starch granules are composed of amylose and amylopectin, several enzymes have to be involved in its mobilization during banana ripening, with a necessary participation of one starch-debranching enzyme (DBE) to hydrolyze the alpha-1,6-branches of amylopectin. Banana DBE seems to be an isoamylase-type enzyme, as indicated by substrate specificity and the cloning of a 1575 bp cDNA, similar to the isoamylase sequences from potato, Arabdopsis, and maize. The assays for DBE indicated only minor changes in activity during ripening, and the results of the northern and western blots with antiserum against the recombinant banana isoamylase were in agreement with the steady-state level of activity, since no significant changes in gene expression were observed. The high activity on beta-limit dextrin and the similarity to the potato isoform 3 suggest that during banana ripening the hydrolysis of alpha-1,6-linkage of amylopectin results from the activity of a pre-existing isoamylase-type debranching enzyme in coordination with other amylolitic enzymes. To the best of our knowledge, this is the first evaluation of activity and expression of a DBE from a fruit.

Chemical composition and glycemic index of Brazilian pine (Araucaria angustifolia) seeds.

The seeds of Parana pine (Araucaria brasiliensis syn. Araucaria angustifolia), named pinhão, are consumed after cooking and posterior dehulling, or they are used to prepare a flour employed in regional dishes. Native people that live in the South of Brazil usually consume baked pinhão. As a result of cooking, the white seeds become brown on the surface due to the migration of some tinted compounds present in the seed coat. In this work, the proximate composition, minerals, flavonoids, and glycemic index (GI) of cooked and raw pinhão seeds were compared. No differences in moisture, lipids, soluble fiber, and total starch after boiling were found. However, the soluble sugars and P, Cu, and Mg contents decreased, probably as a consequence of leaching in the cooking water. Also, the boiling process modified the profile of the phenolic compounds in the seeds. No flavonols were detected in raw pinhão seeds. The internal seed coat had a quercetin content five times higher than that of the external seed coat; also, quercetin migrated into the seed during cooking. The internal seed coat had a high content of total phenolics, and seeds cooked in normal conditions (with the seed coat) showed a total phenolics content five times higher than that of seeds cooked without the seed coat. Cooking was then extremely favorable to pinhão seeds bioactive compounds content. The carbohydrate availability was evaluated in a short-term assay in humans by the GI. The GI of pinhão seeds cooked with the coat (67%) was similar to that of the seeds cooked without a coat (62%) and lower than bread, showing that cooking does not interfere with starch availability. The low glycemic response can be partly due to its high content of resistant starch (9% of the total starch).

Influence of cultivar on quality parameters and chemical composition of strawberry fruits grown in Brazil.

Six strawberry cultivars grown on the same commercial plantation in Brazil were evaluated for their chemical composition and quality attributes at the ripe stage. The profiles of the main soluble sugars, ascorbic acid, and anthocyanins were also obtained during the developmental stages. Results showed significant differences among cultivars in all of the investigated parameters. Cv. Campineiro showed an average value for texture of 0.63 N, half the value found for cv. Oso Grande. Anthocyanin content ranged from 13 (cv. Campineiro) to 55 (cv. Mazi) mg/100 g. Total ascorbic acid found for cv. Campineiro (85 mg/100 g) was twice the amount found in cv. Dover (40 mg/100 g). Fructose was the predominant soluble sugar in almost all cultivars. The proportion among the main soluble sugars (fructose, sucrose, and glucose) was similar for Oso Grande and Toyonoka cultivars. The flavonol content (quercetin plus kaempferol derivatives) ranged from 2.7 to 7.1 mg/100 g, with a mean value of 6.1 mg/100 g, whereas free ellagic acid ranged from 0.9 to 1.9 and total phenolics varied from 159 to 289 (mean 221) mg/100 g.