Changes in Homogalacturonan Metabolism in Banana Peel during Fruit Development and Ripening

Though numerous studies have focused on the cell wall disassembly of bananas during the ripening process, the modification of homogalacturonan (HG) during fruit development remains exclusive. To better understand the role of HGs in controlling banana fruit growth and ripening, RNA-Seq, qPCR, immunofluorescence labeling, and biochemical methods were employed to reveal their dynamic changes in banana peels during these processes. Most HG-modifying genes in banana peels showed a decline in expression during fruit development. Four polygalacturonase and three pectin acetylesterases showing higher expression levels at later developmental stages than earlier ones might be related to fruit expansion. Six out of the 10 top genes in the Core Enrichment Gene Set were HG degradation genes, and all were upregulated after softening, paralleled to the significant increase in HG degradation enzyme activities, decline in peel firmness, and the epitope levels of 2F4, CCRC-M38, JIM7, and LM18 antibodies. Most differentially expressed alpha-1,4-galacturonosyltransferases were upregulated by ethylene treatment, suggesting active HG biosynthesis during the fruit softening process. The epitope level of the CCRC-M38 antibody was positively correlated to the firmness of banana peel during fruit development and ripening. These results have provided new insights into the role of cell wall HGs in fruit development and ripening.

Effect of Aloe Vera Gel Coating on the Quality of Banana Fruit During Storage

The major goal of this study was to investigate the effect of Aloe vera gel coating on the changes in the quality of bananas at room temperature (26–30oC). To evaluate the influence of different concentrations of gel, a set of experiments was designed that included solutions of Aloe vera gel diluted 1:2, 1:3, and 1:4 (v/v) with distilled water and uncoated bananas as controls. Changes in physicochemical properties were analyzed during the preservation time such as weight loss, reducing sugar, total soluble solids, acidity, sensory testing, and color parameters (L*, a*, b*). Microbiological analysis was evaluated in the last storage period. In general, bananas treated with Aloe vera gel can reduce the weight loss and improve the fruit color and sensory value of the product.

Physico-chemical changes in “Xiem” banana cultivar (cultivated in Vietnam) during ripening and storage at different temperatures

There are changes in chemical and physical characteristics involved in the ripening of bananas. This study evaluated the changes in physico-chemical and nutritional characteristics of the "Xiêm" banana cultivar at the harvesting (unripe fruit) and ripe stages (ripe fruit). As the pulp to peel ratio and titrable acidity increased, the firmness decreased with an increase in ripening time. A significant increase in total polyphenol content and decrease in beta-carotene and vitamin C content was observed at climacteric peak during ripening. During ripening, the banana peel colour changed from green to yellow, the pulp softened, the flavour develops, and the moisture is lost. "Xiem" banana variety was fully mature after 7 and 22 days of storage at 28-30oC and 13-15oC, respectively. The correlation between various stages of ripeness and these properties were determined and the correlation coefficients were calculated. A very high coefficient of determination (r2 >0.937) was recorded between physical properties (pulp firmness/peel colour) and chemical properties (starch/sugar) of banana fruit with the stage of ripeness.

ESTIMATION OF POTASSIUM CONTENT OF DIFFERENT VARIETIES OF BANANA FRUIT IN AN INDIAN DELTA IS THERE A CLINICAL RELEVANCE

Banana fruit is one of the commonly taken foods in many parts of the world. The fruit is known for its high potassium content. We wished to study the potassium content of eleven types of ripe banana fruit available in the cauvery delta region of South India. We measured two values in each of the eleven types of banana fruit. We found the mean varied from 460.75mg/100gm in the Rasthali variety to 921.75 in the karpura valli variety. The potassium binding capacity of the soil and the fertilizers pumped may influence the values. The literature which presently describes the values between 200 to 400mg/100g cautions the use of bananas in patients taking antihypertensive medications like enalapril and in patients with renal dysfunction. Our study which shows the values to be double the described ones, will throw light on additional caution in such cases. We admit that there was no soil study in this work which can influence the potassium content. Before any dietetic advice on the intake of potassium, the bananas of the concerned geographical area and such high potassium values should be taken into account. When the needs to cater the patients of potassium arise in uncomplicated hypertension, the varieties karpuravalli and peyampalam can be considered.

Changes of Morphology, Chemical Compositions, and the Biosynthesis Regulations of Cuticle in Response to Chilling Injury of Banana Fruit During Storage

The plant cuticle covers almost all the outermost surface of aerial plant organs, which play a primary function in limiting water loss and responding to the environmental interactions. Banana fruit is susceptible to thermal changes with chilling injury below 13°C and green ripening over 25°C. Herein, the changes of surface morphology, chemical compositions of cuticle, and the relative expression of cuticle biosynthesis genes in banana fruit under low-temperature storage were investigated. Banana fruit exhibited chilling injury rapidly with browned peel appearance stored at 4°C for 6 days. The surface altered apparently from the clear plateau with micro-crystals to smooth appearance. As compared to normal ones, the overall coverage of the main cuticle pattern of waxes and cutin monomers increased about 22% and 35%, respectively, in browned banana stored under low temperature at 6 days. Fatty acids (C16–C18) and ω-OH, mid-chain-epoxy fatty acids (C18) dominated cutin monomers. The monomers of fatty acids, the low abundant ω, mid-chain-diOH fatty acids, and 2-hydroxy fatty acids increased remarkably under low temperature. The cuticular waxes were dominated by fatty acids (> C19), n-alkanes, and triterpenoids; and the fatty acids and aldehydes were shifted to increase accompanied by the chilling injury. Furthermore, RNA-seq highlighted 111 cuticle-related genes involved in fatty acid elongation, biosynthesis of very-long-chain (VLC) aliphatics, triterpenoids, and cutin monomers, and lipid-transfer proteins were significantly differentially regulated by low temperature in banana. Results obtained indicate that the cuticle covering on the fruit surface was also involved to respond to the chilling injury of banana fruit after harvest. These findings provide useful insights to link the cuticle on the basis of morphology, chemical composition changes, and their biosynthesis regulations in response to the thermal stress of fruit during storage.