Identification of volatiles generated by potato tubers (Solanum tuberosum CV : Maris Piper) infected by erwinia carotovora, bacillus polymyxa and arthrobacter sp

Bacteria were isolated from internal tissues of surface sterilized healthy tubers of Solanum tuberosum cv. Maris Piper (8 different isolates) and from tubers inoculated with Erwinia carotovora ssp. carotovora showing soft-rot symptoms (3 different isolates), and identified by fatty acid profiling. Bacillus polymyxa and an Arthrobacter sp. were isolated from both sources, E. carotovora only from the soft-rotted tubers. The volatile organic compounds (VOCs) generated by tubers inoculated with E. carotovora, B. polymyxa and the Arthrobacter sp. were identified. Inoculated tubers of cv. Maris Piper were incubated under controlled humidity (95% relative humidity) and temperature (10°C) to simulate typical storage conditions. B. polymyxa and Arthrobacter sp. did not cause symptoms, whilst E. carotovora caused limited soft-rot infections after 4 weeks at the low temperatures typically associated with potatoes in storage. The VOCs released to the headspace around these tubers were collected using an adsorbent system and analysed by Gas Chromatography-Mass Spectrometry (GC-MS). Twenty-two volatiles unique to E. carotovora infection of potato tubers were found,) including 10 alkanes, four alkenes, two aldehydes, one sulphide, one ketone, one alcohol, one aromatic, one acid and one heterocyclic compound. B. polymyxa generated three unique volatiles: N,N-dimethylformamide, 1-pentadecene and 1-hexadecane. Only one volatile, 2,3-dihydrofuran, was unique to the Arthrobacter infection. Production of volatile nitrogen species from E. carotovora-infected tubers increased with time, whereas none were detected in the headspace above uninfected tubers. Further analysis using a modified GC-MS method established that ammonia, trimethylamine and several volatile sulphides were evolved from tubers infected by E. carotovora. No specific volatile was useful as a marker associated with any of the three bacterial species but in the case of E. carotovora-infected potato tubers a significant increase in the volume of compounds evolved was clearly observed. The results are discussed in relation to the use of sensors to detect VOCs evolved from infected tubers in order to provide an early warning system for the control of soft rot in potato store

Simple Methods for the Extraction and Identification of Amine Malodurs from Spoiled Foodstuffs

Headspace GC-MS analysis was performed on potato tubers infected withErwinia carotovorabacteria and on Iberian cured ham infected withMicroccusandLactobacillusbacteria strains, which cause extensive losses in stored foodstuffs. Headspace samples of infected potatoes and ham were entrained passively on to a SPME fiber and dynamically onto Tenax GR and Chromosorb 103 thermal desorption tubes. Ammonia was identified as the major amine component in all cases. Other amines that accounted in total for less than 5% of the ammonia peak by total ion current were identified. The potato headspace contained triethylamine, while the ham headspace contained methylamine and dimethylamine, identified by SPME and by both thermal desorption tubes. The Chromosorb 103 also entrained trace amounts of ethyleneamine from the ham headspace. Simple Drager tube studies of the sample headspaces also confirmed the presence of volatile amines. © 1998 Academic Press

Development of a sensor system for the early detection of soft rot in stored potato tubers

A number of sensor types were fabricated and tested for their electrical resistance changes to compounds known to be evolved by potato tubers with soft rot caused by the bacterium Erwinia carotovora. On the basis of these tests, three sensors were selected for incorporation into a prototype device. The device was portable and could be used without computer control after threshold values and sensor settling criteria had been downloaded. The prototype was assessed for its discriminating power under simulated storage conditions. The device was capable of detecting one tuber with soft rot in 100 kg of sound tubers in a simulated storage crate. The device was also able to detect a tuber inoculated with E. carotovora, but without visible signs of soft rot, within 10 kg of sound tubers. The same system was able to follow the progression of the disease in a tuber stored amongst 10 kg of sound tubers when operated at 4 °C and 85% relative humidity (conditions typical of a refrigerated storage facility)

Adsorbed poly(ethyleneoxide)-poly(propyleneoxide) copolymers on synthetic surfaces: Spectroscopy and microscopy of polymer structures and effects on adhesion of skin-borne bacteria Adsorbed poly(ethyleneoxide)-poly(propyleneoxide) copolymers on synthetic surfaces: Spectroscopy and microscopy of polymer structures and effects on adhesion of skin-borne bacteria.

Poly (ethyleneoxide)-copoly(propyleneoxide) (PEO-PPO) polymer coatings were evaluated for their resistance to the attachment of the marker organism Serratia marcescens and the skin-borne bacteria Staphylococcus epidermidis. The copolymers were adsorbed onto poly(styrene) films chosen as simplified physicochemical models of skin surfaces-and their surface characteristics probed by contact angle goniometry, attenuated total reflectance-Fourier transform infrared (ATR-FTIR), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). These functional surfaces were then presented to microbial cultures, bacterial attachment was assessed by fluorescence microscopy and AFM, and the structures of the polymer films examined again spectroscopically. Surface characterization data suggest that the adsorbed copolymer was partially retained at the surface and resisted bacterial attachment for 24 h. Quantitative evaluation of cell attachment was carried out by scintillation counting of 14C-labeled microorganisms in conjunction with plate counts. The results show that a densely packed layer of PEO-PPO copolymer can reduce attachment of skin commensals by an order of magnitude, even when the coating is applied by a simple adsorptive process. The work supports the hypothesis that adhesion of microorganisms to biological substrates can be reduced if a pretreatment with an appropriate copolymer can be effected in viv