Emanuela Gobbi

Electronic Nose for Microbiological Quality Control of Food Products

Electronic noses (ENs) have recently emerged as valuable candidates in various areas of food quality control and traceability, including microbial contamination diagnosis. In this paper, the EN technology for microbiological screening of food products is reviewed. Four paradigmatic and diverse case studies are presented: (a) Alicyclobacillus spp. spoilage of fruit juices, (b) early detection of microbial contamination in processed tomatoes, (c) screening of fungal and fumonisin contamination of maize grains, and (d) fungal contamination on green coffee beans. Despite many successful results, the high intrinsic variability of food samples together with persisting limits of the sensor technology still impairs ENs trustful applications at the industrial scale. Both advantages and drawbacks of sensor technology in food quality control are discussed. Finally, recent trends and future directions are illustrated.

Molecular characterization of a phytoplasma causing Phyllody in Clover and other herbaceous hosts in Northern Italy

Red clover (Trifolium pratense) and Ladino clover (Trifolium repens) plants showing phytoplasma-associated symptoms (yellowing/reddening, virescence and phyllody) have been recovered in Friuli-Venezia Giulia, Italy. Using AluI RFLP analysis of PCR amplified 16S rDNA we showed that the disease can be caused independently by two phylogenetically distinct phytoplasmas. One of them showed the very typical 16S rDNA RFLP pattern of the agent of Clover Phyllody in Canada (CCPh). The 16S rDNA of the other phytoplasma (Italian Clover Phyllody phytoplasma, ICPhp) has been PCR amplified, cloned and sequenced. The sequence revealed high similarity (>98%) with phytoplasmas belonging to the X disease cluster, which includes organisms not reported to cause phyllody on their hosts. The analysis by AluI RFLP of the PCR amplified pathogen 16S rDNA from other herbaceous plants (Crepis biennis, Taraxacum officinale, Leucanthemum vulgare) collected nearby with phytoplasma-associated symptoms showed similar patterns. Southern blot hybridization of their EcoRI digested total DNA revealed identical RFLP patterns, suggesting that the causative agent may be the same organism.

Nanostructured Metal Oxide Gas Sensors, a Survey of Applications Carried out at SENSOR Lab, Brescia (Italy) in the Security and Food Quality Fields

In this work we report on metal oxide (MOX) based gas sensors, presenting the work done at the SENSOR laboratory of the CNR-IDASC and University of Brescia, Italy since the 80s up to the latest results achieved in recent times. In particular we report the strategies followed at SENSOR during these 30 years to increase the performance of MOX sensors through the development of different preparation techniques, from Rheotaxial Growth Thermal Oxidation (RGTO) to nanowire technology to address sensitivity and stability, and the development of electronic nose systems and pattern recognition techniques to address selectivity. We will show the obtained achievement in the context of selected applications such as safety and security and food quality control.

Mitochondrial DNA of Cryphonectria parasitica lack of migration between vegetatively compatible strains.

To examine the extent of mtDNA migration between compatible strains of C. parasitica, we have isolated mtDNA from different strains of the fungus, partially characterized the mtDNA, and cloned a restriction fragment for use as a probe to facilitate detection of mtDNA movement. We concluded that the mtDNA does not move readily between compatible strains of the fungus, although dsRNA moves rapidly between the strains

Air analysis in the assessment of fumonisin contamination risk in maize

BACKGROUND In maize-growing areas where fumonisin contamination is endemic, there is an urgent need for novel methods to assess the quality of grain lots before their delivery to common drying and storage collection centres. Aerobiological samples of fungal spores released during harvest were analysed to establish a relationship between fumonisin contamination and the abundance of pathogen propagules collected in the combine harvester using a cyclone and membrane filters. Filter-captured propagules were analysed by direct plating, immunoenzymatic assay of specific Fusarium extracellular polysaccharides and real time polymerase chain reaction of the extracted DNA using fum1, a gene involved in the biosynthesis of fumonisin, as a target. RESULTS The results showed that time of harvest and environmental conditions strongly influenced the efficiency and performance of the collection system. The data obtained were informative in comparing individual samples collected under similar conditions. The immunoenzymatic assay provided the most reliable data, which improved the ability of a neural network to predict the fumonisin content of lots, when added to agronomic, environmental and phytosanitary data. CONCLUSION This is the first attempt to evaluate the Fusarium propagules dispersed during harvesting as a predictive means to assess maize quality. A method based on cyclone/filter capture and immunological detection has been shown to be feasible and to have the potential for the development of a continuous monitoring system, but the prediction capabilities in the present implementation were limited.

Electronic Nose and Its Application to Microbiological Food Spoilage Screening

Electronic Nose (EN) is a machine designed for detecting and discriminating complex odours using an array of broadly specific chemical sensors by mimicking the working mechanism and the main building blocks of biological olfaction. ENs are valuable candidates to be applied in various areas of food quality control, including microbial contamination diagnosis. In this chapter the EN technology is presented and its exploitation for microbiological screening of food products is reviewed. Two paradigmatic examples are presented. Both advantages and drawbacks of sensor technology in food quality control are discussed. Despite of many successful results, the high intrinsic variability of food samples together with persisting limits of the sensor technology still impair ENs trustful applications at the industrial scale thus further research efforts and technology improvements are required.

Mitochondrial plasmids of the pCp family are spread worldwide in Cryphonectria parasitica populations

A worldwide collection of strains of Cryphonectria parasitica was examined to draw a precise picture of the incidence and diversity of mitochondrial plasmids related to the plasmid pUG1. Amplification by specific PCR of 199 strains showed the presence of pUG1-like plasmids in 22% of the populations examined. The entire plasmid molecules were amplified by multiplex PCR and the products showed different RFLP patterns. The variability was mostly in a non-coding region of the molecule that has been sequenced in some representative strains, enabling the molecular evolution of the molecule to be elucidated. The data show that mitochondrial plasmids of C. parasitica comprise an almost homogeneous family (designated pCp) that can be divided into two clusters based on the presence/absence respectively of a 60 nucleotide region in North American and European plasmids.

Early detection of fungal contamination on green coffee by a MOX sensors based Electronic Nose

Fungal growth can occur on green coffee beans along all the distribution chain, eventually bringing on health hazards to consumers, because of the production of toxic metabolites (mycotoxins) [1]. Besides, the sensorial contamination due to volatiles by‐products of fungal metabolism could cause defects on coffee also after roasting. Therefore, it is necessary to devise strategies to detect and quantify fungal infection and toxin production at early stages of the food chain. One of the most promising techniques is the analysis of volatile compounds in the headspace gas surrounding the samples. The aim of this work was to verify the ability of the Electronic Nose (EN EOS835) to early detect the microbial contamination of Arabica green coffee. This EN is equipped with Metal Oxide Semiconductor sensor array. Gas chromatography coupled to mass spectrometry (GC‐MS) analysis of the static headspace of non‐contaminated Arabica green coffee samples was carried out to confirm the EN ability to provide satisfactory ...