Detection of gamma radiation processed onion during storage using propidium iodide based fluorescence microscopy.

The determination of absorbed dose in gamma radiation processed onion (treated with 20-100 Gy for sprout inhibition) during storage is an important regulatory requirement to control unfair practices. To address this problem, a microscopy based method was developed using propidium iodide (PI) staining of onion adaxial epidermis. A proportional radiation dose dependent increase in nuclei count was observed during ambient (26 ± 2 °C) and low (2 ± 1 °C) temperature storage. The method was validated and dose of radiation could be determined accurately in stored onions using blind tests. During mechanism studies, boron-dipyrromethene (BODIPY) dye staining and malondialdehyde (MDA) estimation showed dose dependent increase in peroxidation of membrane lipids. The fluorescein diacetate (FDA) stained onion adaxial epidermis showed decrease in fluorescence indicating lowering of physiological activity. Enzyme peroxidase (POD), phenylalanine ammonia lyase (PAL) activities and phytochemicals (phenolics, flavonoids, ascorbic acid and pyruvic acid) did not change significantly with increasing dose of gamma radiation.

Methylation of guar gum for improving mechanical and barrier properties of biodegradable packaging films.

Improving functional properties of biopolymers for use as environment friendly packaging is an area of current interest. Biodegradable films with improved barrier and mechanical properties were prepared from methylated guar gum. Methylation resulted in structural modification of guar gum (GG) promoting greater crystallization thereby enhancing thermal stability towards decomposition. Reduction in radius of gyration (Rg), weight average molecular weight (Mw), and an increase in polydispersity index (PDI) were also observed due to methylation. Methylated guar gum (MGG) films exhibited 40% lower water vapor transmission rate (WVTR) as compared to control purified guar gum (PGG) films. Films prepared by partial replacement of PGG with MGG (10, 25, 50, 75 and 100% w/w) showed gradual improvement in percent elongation. The study gives an insight on the role of methylation in enhancing barrier and mechanical properties of GG based biodegradable films for possible application in food packaging.

Enhancing antioxidant activity, microbial and sensory quality of mango (Mangifera indica L.) juice by γ-irradiation and its in vitro radioprotective potential.

Gamma irradiation is an effective method currently being used for microbial decontamination and insect disinfestations of foods. In the present study, mango (Mangifera indica L.) juice was irradiated at doses of 0, 1.0, 3.0 and 5.0 kGy and microbial load, total polyphenols, flavonoids, ascorbic acid content, antioxidant activities, colour and sensory properties were evaluated immediately after irradiation and also during storage. Microbiological assay of the fresh and stored mango juice showed better quality after γ-irradiation. The total polyphenols and flavonoids were significantly (p < 0.05) increased while the ascorbic acid content decreased with the irradiation doses applied. As a result of γ-irradiation, a significant increment in gallic, syringic and chlorogenic acids and a significant reduction in ferulic and synapic acids were noted when analyzed by HPLC. In vitro antioxidant potentials were measured using DPPH, FRAP and NO scavenging assays; the results showed significant enhancement in the activities after irradiation, that correlated well with the increase in phenolic and flavonoid content. γ-irradiation improved the colour of mango juice without any adverse changes in the sensory qualities. Significant in vitro plasmid DNA protection was observed in the presence of mango juice against radiation induced damage, even at the dose of 5 kGy. This study confirmed the potential of γ-irradiation as a method for microbial decontamination and improving the quality of the mango juice without compromising on the sensory attributes.

Evaluation of antioxidant activity and characterization of phenolic constituents of Phyllanthus amarus root.

The antioxidant property of the 70% aqueous ethanol extract of Phyllanthus amarus roots and its ether-soluble, ethyl acetate-soluble, and aqueous fractions were investigated by various in vitro assays. The root extracts showed higher DPPH, hydroxyl, superoxide, and nitric oxide radical scavenging and reducing power activity. Among all the samples, the ethyl acetate-soluble fraction demonstrated highest radical scavenging activity and total phenolics content. Twenty-eight different phenolic compounds were identified by LCMS/MS analysis of the ethyl acetate-soluble fraction. The majority of the compounds were found to exist as their glycosides, and many of these were gallic acid derivatives. Free epicatechin and gallic acid were also identified in the ethyl acetate-soluble fraction. The present investigation suggested that P. amarus root is a potent antioxidant and can be used for the prevention of diseases related to oxidative stress.

Stability of lipid constituents in radiation processed fenugreek seeds and turmeric: role of phenolic antioxidants.

Impact of radiation processing on the lipid profile of fenugreek and turmeric was investigated. Oleic and linoleic acid were the dominant fatty acids with an appreciable amount of linolenic acid in both cases. Gamma-irradiation did not bring about any significant changes in the fatty acid profile of these spices despite a high content of unsaturation. The ability of aqueous methanolic extract of both spices with high phenolic content to prevent lipid peroxidation suggests a possible role of phenolic constituents in preventing lipid radiolysis. Among the phenolics identified, kaempferol-3-O-alpha-L-rhamnoside, kaempferol 3,7-O-alpha-L-dirhamnoside, quercetin 3,7-O-alpha-L-dirhamnoside, and 3-O-alpha-L-rhamnosyl quercetin are reported here to occur in fenugreek for the first time. The role of phenolic antioxidants in preventing lipid oxidation in the above spices is discussed.