A new type of supramolecular assembly consisting of crown ether complex cation and a polyoxometalate anion: Synthesis and crystal structure of [Na(C20H24O6)(CH3CN)2]2[Mo6O19] · 4CH3CN

A novel supramolecular assembly consisting of sodium-dibenzo-18-crown-6(DB18C6) complex cation [Na(C₂₀H₂₄O₆)(CH₃CN)₂]²⁺ and isopolyanion [Mo₆O₁₉]²⁻ has been demonstrated in the 3D structure of [Na(C₂₀H₂₄O₆)(CH₃CN)₂]₂[Mo₆O₁₉] · 4CH₃CN (1). Weak intermolecular forces (C–HO hydrogen bonds) between isopolyanion and crown ether play a significant role in the construction of supramolecular framework in the crystal structure of 1. Compound 1 has been characterized in the solid state by single crystal X-ray diffraction, IR, CHN analysis, and TGA.     

Storage behaviour of minimally processed pumpkin (Cucurbita maxima) under modified atmosphere packaging conditions

 Minimally processed vegetables in fresh, ready-to-cook form are gaining the confidence of both the trader and the consumer. This has led to a need to develop technology for increasing shelf life while maintaining the microbial, nutritional and sensory quality of minimally processed vegetables. This investigation was carried out on pumpkin in minimally processed form, packed in different polymeric film bags of varying permeabilities, creating an active equilibrium modified atmosphere within the package for the extention of storage life. It was observed that minimally processed pumpkin, which has a high respiratory rate at room temperature (155.7 mg CO₂/kg/h) could be stored for a period of 25 days at 5±2  °C under modified atmosphere packaging conditions with a minimum physiological loss in weight of 0.06% and marginally low changes in biochemical constituents, such as vitamin C, total soluble solids, moisture, carotenoids and titrable acidity, enabling the retention of near-fresh quality. The microbial loads of mesophilic aerobes and coliforms, which were log 5.5 and log 4.3 were less than threshold level. There was no growth of yeasts and moulds or mesophilic spore formers at the end of the storage period. Received: 24 January 2000 / Revised version: 4 April 2000