Mechanical and microstructure studies on the modification of CA film by blending with PS

DriedMusa paradiciaca (banana) stem and veins of the leaves, which were hitherto discarded as a waste, were collected and used as starting material for the preparation of cellulose and cellulose acetate. This cellulose acetate was mixed with polystyrene to form blend of cellulose acetate-polystyrene in order to provide enhanced stability and extended utility to the end products. The films of these composites or their individual partners were made separately and studied for their mechanical properties, chemical modification and morphological changes. We report here that banana stem is good source of cellulose and that cellulose completely undergoes modification upon esterification.     

芭蕉的α-葡萄糖苷酶抑制活性

利用体外α-葡萄糖苷酶抑制模型对芭蕉花与根提取物进行活性评价,并与阳性对照Acarbose比较,发现芭蕉花与根提取物均能抑制α-葡萄糖苷酶活性。除芭蕉花的乙酸乙酯和正丁醇提取物外,其他提取物活性均远大于阳性对照Acarbose(IC50=1103.01μg·mL-1)。其中,芭蕉根和花的石油醚提取物的活性最高(IC50=32.03μg·mL-1和49.37μg·mL-1)。不同部位比较,芭蕉根的α-葡萄糖苷酶抑制活性好于花;同一部位不同溶剂的提取物比较,石油醚提取物α-葡萄糖苷酶抑制活性高于乙酸乙酯和正丁醇提取物。     

In vitro antioxidant activity of different cultivars of banana flower (Musa paradicicus L.) extracts available in India

Abstract: Six different cultivars of banana flowers (Musa paradicicus) (Kathali, Bichi, Shingapuri, Kacha, Champa, and Kalabou) were analyzed for the content of polyphenol expressed as gallic acid equivalent and flavonoid expressed as quercetein equivalent, and the in vitro total antioxidative activities of the flower extracts were compared with standard and expressed as trolox equivalent. The reducing power, 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) and 2,2‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonic acid) radical cation (ABTS?⁺) scavenging activities, inhibition of lipid peroxidation in a linoleic acid emulsion system, and liposome peroxidation system were measured and compared with respective standard antioxidants. Iron‐mediated Fenton reaction was carried out to evaluate the protective effect of the extract of banana flower (Kacha cultivar) against H₂O₂‐induced DNA damage. The Kacha variety contains the maximum amount of polyphenol (11.94 ± 0.03 mg of gallic acid equivalent/g of dry weight) and flavonoid (0.174 ± 0.001 g of quercetin equivalent/g of polyphenol). It also has the highest total antioxidant capacity, DPPH radical scavenging activity, and ABTS?⁺ radical scavenging activity with a least EC₅₀ value of 0.051 mg/mL. Hepatic cell damage in iron‐mediated Fenton reaction caused by free radicals is reduced by the banana flower extract. On the basis of the results obtained, the banana flowers are found to be a potential source of natural antioxidants. This is the first report on the antioxidant properties of the extracts from banana flowers. The study suggests that the flowers of M. paradicicus that are found in India and consumed as vegetable can provide valuable functional ingredients that help in the prevention of oxidative stress.     

Phosphoric acid activation of recalcitrant biomass originated in ethanol production from banana plants

Biomass samples have been studied as activated carbon precursors. Two, denoted as recalcitrant biomass, are ethanol production wastes, one from acid hydrolysis of starch-rich banana (Musa acuminate) fruit and one from enzymatic hydrolysis of banana pseudostem (lignocellulosic material) and a third one is raw banana tree pseudostem. The samples were characterized by proximate, ultimate, forage, morphological and structural analyses. They all have volatile matter contents above 50% but present some remarkable differences. The sample coming from the acid hydrolysis has too high ash content (mostly calcium sulfate) and low cellulose and lignin contents that prevents its use as an activated carbon precursor. Contrarily, the other two samples have lower ash contents, higher carbon percentages and higher cellulose and lignin contents. The activation with phosphoric acid at 450 °C has been investigated. The results are quite reproducible, showing good porosity developments and a strong dependence on the precursor, the H₃PO₄ concentration and the H₃PO₄/sample weight ratio used. The activated carbons have quite high apparent surface area, porosity and yield. Interestingly, the phosphoric acid activated carbons prepared in this work have quite well developed mesoporosity which is especially useful for some applications (e.g. for gasoline evaporative control). Our preliminary comparative study, carried out with a well known commercial activated carbon used to control automobile hydrocarbons emissions, has shown that these activated carbons perform very well, being their performance a function of their mesoporosity development. Their oxygenated surface complexes (assessed from TPD experiments) are considerably high.     

Effect of pre‐ripening chilling temperatures on ripening,shelf life and quality of bananas treated with 1‐methylcyclopropene

Ethylene production, shelf life and fruit quality of Cavendish bananas (cv. Williams), held at different pre‐ripening storage temperatures (5 °C, 10 °C or 15 °C) prior to ethylene and/or 1‐methylcyclopropene (1‐MCP) application, were determined and compared. Levels of ethylene production during ripening were highest for control fruit that had been stored at 5 °C followed by 10 °C and then 15 °C. 1‐MCP treatment (at 300 nL L^?1) had no effect on ethylene production of fruit that had been stored at 10 °C by day 10 of storage, but ethylene production was significantly higher for fruit that had been stored at 15 °C and lower for those stored at 5 °C before 1‐MCP treatment. 1‐MCP also increased shelf life to a greater extent when applied to fruit that had been stored at 10 °C or 15 °C. Even though 1‐MCP had no significant effect on under peel chilling injury, it increased discolouration significantly, regardless of storage temperature. Firmness of 1‐MCP‐treated fruit decreased significantly compared to the control when fruit were held at 5 °C or 15 °C prior to ripening (and 1‐MCP application) but had no effect on fruit stored at 10 °C before ripening. These results indicate that pre‐ripening storage temperature affects ripening, shelf life and quality in both ethylene and 1‐MCP‐treated bananas.     

POLYPHENOL OXIDASE ACTIVITY IN BANANA CHIPS DURING OSMOTIC DEHYDRATION

ABSTRACT

Various treatments were used to determine polyphenol oxidase activity changes during osmotic dehydration of banana slices. A temperature of 35 °C and 5.0 pH were used as the most adequate conditions for polyphenol oxidase activity determination when 4-methyl catechol was used as a substrate. Enzyme activity change was determined in the central and edge region of fruit. The central part of the banana slice showed 2.4 times higher activity than in the edge region. A difference in the kinetics of enzyme activity decrease also occurred during four hours of drying. When the drying was carried out at 70 °C, the enzyme was completely inactivated after 60-90 minutes of specific osmotic treatments. After four hours of osmotic drying at 50 and 60 °C, polyphenol oxidase activity was still present; the residual activity varied from 1.3 to 15 %.