Beatriz Rosana Cordenunsi

Physico-chemical changes related to quality of five strawberry fruit cultivars during cool-storage

Abstract Several parameters related to strawberry quality, such as texture, anthocyanin content, titratable acidity, pH, total ascorbic acid, and total soluble sugars, were evaluated over a week of cool storage. The results indicated that low temperature used to increase strawberry shelf-life could also induce small changes in some of the quality parameters studied. However, the data revealed the importance of the cultivar in question since there were some contrasting responses among the cultivars. Also the initial values for some of the parameters were clearly different, indicating that the cultivar is the most important factor for determining post-harvest quality and extended shelf-life. Texture is an important parameter with regard to shelf-life but was not determined since the ‘Mazi’ cultivar had a high initial value for texture but no changes occurred over the storage period. However, it had the shortest shelf-life. Changes in anthocyanin content were highly dependent on the cultivar. Except for ‘Toyonoka,’ no marked changes were observed in titratable acids or pH. Ascorbic acid decreased by 50% in all cultivars. The profiles of soluble sugars were different among cultivars but, for all of them, sucrose disappeared on day 2 of storage.

Composition and Functional Properties of Banana Flour from Different Varieties

The chemical composition and some physico-chemical characteristics of the flour obtained from eight different banana varieties are presented. The flour was prepared by freeze-drying a homogenate of green banana pulp. Amylose, starch, dietary fiber, protein, ash, moisture and lipid contents were determined. Viscosity and gelatinization of starch were also investigated. Banana flour is rich in starch granules. Peak temperature of gelatinization varied from 68 to 76 °C according to the variety. All of them showed an increase in viscosity during cooling but the variety Ouro colatina showed more stability during shearing and cooling. Chemical composition of the flour also varied according to the variety. The range obtained were 61—76.5% starch, 19—23% amylose, 2.5—3.3% protein, 4—6% moisture, 0.3—0.8% lipids, 2.6—3.5% ashes, and 6—15.5% total fiber. Considering that the flour production is easier and faster than the isolation of the starch, it would be not only more practical but also less expensive to use the flour instead.

Banana sucrose-phosphate synthase gene expression during fruit ripening

Abstract. A 952-base pair polymerase-chain-reaction product of sucrose-phosphate synthase (SPS) (EC 2.3.1.14) from banana (Musa acuminata cv. Nanicão) fruit was cloned and used to study expression of the enzyme during development and ripening. The deduced amino acid sequence shows that banana SPS has a high homology with the leaf, tap-root and bean enzymes from other species. Enzyme activity, and mRNA and protein levels point to an increase in SPS expression during ripening. The accumulation of sucrose was correlated to starch degradation and happened 4 d after SPS mRNA and activity had reached their maxima. These results indicate that access to substrate and transcriptional activation with increase in SPS expression might be important regulatory events of sweetening during banana fruit ripening.

Inhibition of β-amylase activity, starch degradation and sucrose formation by indole-3-acetic acid during banana ripening

Abstract. In order to observe the effect of indole- 3-acetic acid (IAA) on carbohydrate metabolism, unripe banana (Musa acuminata AAA, cv. Nanicão) slices were infiltrated with the hormone and left to ripen under controlled conditions. The climacteric respiration burst was reduced by the action of IAA, and starch degradation and sucrose formation were delayed. Sucrose synthase (SuSy; EC 2.4.1.13) and sucrose-phosphate synthase (SPS; EC 2.4.1.14) activities and transcript levels were not affected, indicating that prevention of sucrose accumulation was not related to sucrose-metabolizing enzymes. Impairment of sucrose synthesis could be a consequence of lack of substrate, since starch degradation was inhibited. The increase in activity and transcript level of β-amylase was delayed, indicating that this enzyme could be important in starch-to-sucrose metabolism in bananas and that it might be, at least partially, controlled at the transcriptional level. This is the first report showing that IAA can delay starch degradation, possibly affecting the activity of hydrolytic enzymes such as β-amylase (EC 3.2.1.2).

The onset of starch degradation during banana ripening is concomitant to changes in the content of free and conjugated forms of indole-3-acetic acid

Summary Banana ( Musa acuminata AAA cv. Nanicao) slices were infiltrated with mannitol (control) and mannitol plus indole-3-acetic acid (IAA); then, some important ripening parameters like starch degradation, synthesis of ethylene and respiration were monitored. The contents of free-IAA and conjugated forms of IAA (ester and amide) were analyzed, by GC-MS-SIM, throughout the ripening in both banana slices and whole bananas. The starch degradation of IAA-treated slices was delayed for several days, but there was no difference between control and IAA-treated slices in the ethylene and respiration profiles. On day zero after infiltration, free-IAA levels were 500-fold higher in IAA-treated slices than in the control slices, but within 72 hours they declined to values 15-fold higher than those in the control group, with concomitant increase in IAA-ester. Similar to the banana slices, the onset of starch degradation occurred in whole bananas only when the free-IAA concentration was about 4 ng/g FW. The results herein suggest that IAA levels play a role during banana ripening in events like starch degradation with the consequence of banana sweetening.

Phenolics and Antioxidant Properties of Fruit Pulp and Cell Wall Fractions of Postharvest Banana (Musa acuminata Juss.) Cultivars

Banana fruits are important foods, but there have been very few studies evaluating the phenolics associated with their cell walls. In the present study, (+) catechin, gallocatechin, and (-) epicatechin, as well as condensed tannins, were detected in the soluble extract of the fruit pulp; neither soluble anthocyanidins nor anthocyanins were present. In the soluble cell wall fraction, two hydroxycinnamic acid derivatives were predominant, whereas in the insoluble cell wall fraction, the anthocyanidin delphinidin, which is reported in banana cell walls for the first time, was predominant. Cell wall fractions showed remarkable antioxidant capacity, especially after acid and enzymatic hydrolysis, which was correlated with the total phenolic content released after the hydrolysis of the water-insoluble polymer, but not for the posthydrolysis water-soluble polymer. The acid hydrolysis released various monosaccharides, whereas enzymatic hydrolysis released one peak of oligosaccharides. These results indicate that banana cell walls could be a suitable source of natural antioxidants and that they could be bioaccessible in the human gut.

Physico-chemical characterization and bioactive compounds of blackberry fruits (Rubus sp.) grown in Brazil

Five blackberry cultivars (Rubus sp.) were evaluated for antioxidant capacity, bioactive compounds and composition. Ascorbic acid levels, consisting of dehydro-ascorbic acid, ranged from 9.8 to 21.4 mg.100 g-1 fresh weight. Cyanidin (66 to 80% of total flavonoids), epicatechin, quercetin and traces of kaempferol were the main flavonoids found in all cultivars. The five cultivars presented high antioxidant capacity in the β-carotene/linoleic acid system, with inhibition similar to the synthetic antioxidant BHT, at a 50 µM concentration. Caingangue cultivar presented high vitamin C and total phenolics content, while Guarani had the highest cyanidin, total anthocyanin and total flavonoids levels and also the highest antioxidant capacity. These cultivars also presented good TSS/TA ratios. From the data, at a quantitative level, blackberry can be considered a good source of bioactive compounds, as well as potentially beneficial to human health.

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.

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.