Effect of different ripening stages on walnut kernel quality: antioxidant activities, lipid characterization and antibacterial properties.

Packing tissue between and around the kernel halves just turning brown (PTB) is a phenological indicator of kernel ripening at harvest in walnuts. The effect of three ripening stages (Pre-PTB, PTB and Post-PTB) on kernel quality characteristics, mineral composition, lipid characterization, sensory analysis, antioxidant and antibacterial activity were investigated in fresh kernels of indigenous numbered walnut selection of Kashmir valley "SKAU-02". Proximate composition, physical properties and sensory analysis of walnut kernels showed better results for Pre-PTB and PTB while higher mineral content was seen for kernels at Post-PTB stage in comparison to other stages of ripening. Kernels showed significantly higher levels of Omega-3 PUFA (C18:3n3) and low n6/n3 ratio when harvested at Pre-PTB and PTB stages. The highest phenolic content and antioxidant activity was observed at the first stage of ripening and a steady decrease was observed at later stages. TBARS values increased as ripening advanced but did not show any significant difference in malonaldehyde formation during early ripening stages whereas it showed marked increase in walnut kernels at post-PTB stage. Walnut extracts inhibited growth of Gram-positive bacteria (B. cereus, B. subtilis, and S. aureus) with respective MICs of 1, 1 and 5 mg/mL and gram negative bacteria (E. coli, P. and K. pneumonia) with MIC of 100 mg/mL. Zone of inhibition obtained against all the bacterial strains from walnut kernel extracts increased with increase in the stage of ripening. It is concluded that Pre-PTB harvest stage with higher antioxidant activities, better fatty acid profile and consumer acceptability could be preferred harvesting stage for obtaining functionally superior walnut kernels.

Structural, thermal, functional, antioxidant & antimicrobial properties of ß-d-glucan extracted from baker's yeast (Saccharomyces cereviseae)-Effect of γ-irradiation.

This study was carried out to evaluate the effect of γ-irradiation (0, 5, 10, 20, 30 & 50kGy) on the structural, functional, antioxidant and antimicrobial properties of yeast ß-d-glucan. The samples were characterized by ATR-FTIR, gel permeation chromatography (GPC) and the thermal properties were studied using DSC. There was a decrease in the average molecular weight of ß-d-glucan as the irradiation dose increased. The functional properties of irradiated yeast ß-d-glucan were largely influenced by the action of gamma radiation like swelling power and viscosity decreases with increase in the irradiation dose while as fat binding capacity, emulsifying properties, foaming properties and bile acid binding capacity shows an increasing trend. All the antioxidant properties carried out using six different assays increased significantly (p≤0.05) in a dose dependent manner. The antibacterial activity of yeast ß-d-glucan also showed an increasing trend with increase in the irradiation dose from 5 to 50kDa.

Mushroom varieties found in the Himalayan regions of India: Antioxidant, antimicrobial, and antiproliferative activities.

This study evaluates the antioxidant, antimicrobial, and antiproliferative activities of mushroom varieties (Agaricus bisporus, Pleurotus ostreatus, and Coprinus atramentarius) found in the Himalayan regions of Jammu and Kashmir, India. All three mushroom varieties exhibited antioxidant activity. A. bisporus showed the highest diphenyl-2-picrylhydrazyl inhibition activity (87.88±5.6%), C. atramentarius showed the highest reducing power (0.49±0.01) and metal chelating ability (48.57± 0.38%), and P. ostreatus contained the highest phenolic (5.25±0.14 mg gallic acid equivalent per gram) and flavonoid content (64.39±0.73 µg rutin equivalent per gram). C. atramentarius showed maximum antibacterial activity against all the pathogenic strains and the highest zone of inhibition was against S. typhi (7.45±0.5 mm). P. ostreatus exhibited the highest cell proliferation inhibition against Colo-205 and MCF-7 cancer cell lines. The structural analysis by Fourier transform infrared spectroscopy indicated the presence of ß-configuration in carbohydrates, phenolic compounds, and protein, which impart nutraceutical properties to mushrooms.