PhD, EngD and MSc by research theses (Cranfield Health)

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Open Access
Analytical methods for assessing paper degradation In transformers
(Cranfield University, 2006-05) Christofidis, Stavros; Setford, S.; Ritchie, Laurie; Aldred, David
Power transformers are essential equipments for distributing electricity. However, maintenance of these equipments is necessary to ensure long working life and to avoid catastrophic incidents. Insulation of the instrument is essential, and mainly consists of mineral oil and cellulosic paper. This research work investigates and examines in a series of different experiments the compounds produced from the degradation of the cellulosic paper, known as furanic compounds. Five furanic derivatives (5-HMF, 2-FAL, 2-ACF, 5-MEF and FOL) were examined, and it was established throughout this work that these furanic compounds degradate faster in aqueous solution, under a controlled environment, than in an organic, it is possible to produce from one furanic compound other derivatives, and finally each furanic compound distributes differently in an oil water environment, affecting the recovery of each individual. The knowledge obtained from this research work can be used for the development of the existing method of analysis of furanic compounds, and help to provide a better diagnosis of the insulation state of the transformer.
Open Access
The biochemistry and physiology of different hybrid and grafted eggplants in response to NaCL salinity in soil and hydroponic systems
(Cranfield University, 2013-12) Panagiotakis, Giorgos D.; Dragassaki, Magdalene; Aldred, David
The major problem of salinity n regions of intensive cultivations such as Ierapetra, has started to affect the crop production. This project was designed to study the effects of salinity on several biochemical and physiological parameters in two hybrids of eggplant as grafted and non-grafted. The two hybrids were the Solanum melongena L hybrid Habana and Solanum melongena L hybrid Vernina. The concentrations that were chosen (12.5 25, 50, 100, 150 and 200mM) represent a scale of salt concentration and were cultivated as self rooted plants in soil, hydroponically and hydroponically as grafted. Grafting also seems to play an important role for salinity tolerance. To corroborate the different parameters were used as indicators of salinity affection and quantified. Plant height and number of leaves were affected in all three experiments and for all plant types whether grafted or not. Similar were the results for the dry and fresh weight of stem leaves and fruits. For the physiological function of the plants factors such as chlorophyll fluorescence and photosynthetic rate were affected especially at higher concentrations of NaCL. The chlorophyll content in the leaves, which was also measured, was negatively affected in all hybrids. Biochemical measurements the K and Na concentrations in dry leaves and the enzyme activity of APX, GPX and SOD were also made. The K and Na ion concentrations were similar with other studies presenting a reduction of K and raise of Na as the concentration of salt was rising. Unfortunately the enzyme activity was not affected at the specific experiment so it was not able to find exactly how the salinity affects this factor. Overall the results of grafted plants were better than as self rooted and the Solano torvum plant used as rootstock is more tolerant than the Tomato Resistar also used as rootstock.
Open Access
Characterisation of stachybotrys chartarum from water damaged buildings
(Cranfield University, 2011) Frazer, Schale; Aldred, David
Fungal contaminated buildings and related adverse human health implications have long been a topical issue throughout the world and concern is mounting with regards to the presence of more toxigenic fungi found in buildings and the associated health risks. These risks are compounded when homes are affected by water damage as a result of water intrusion problems, in particular flooding. With the ever changing climate and unpredictable weather conditions the frequency of flash flooding has increased in recent years and is set to increase and subsequently more homes will inevitably be effected by mould contamination. The present study initially aimed to determine the types of fungi commonly detected in buildings in the United Kingdom with varied levels of water intrusion problems via a small survey using various sampling techniques and particularly aimed to determine the conditions by which growth of the toxigenic fungi Stachybotrys chartarum could occur. Penicillium, Cladosporium and Aspergillus species were the most commonly detected fungi in buildings with relatively moderate levels of water intrusion problems; Stacybotrys chartarum was only detected in building with more severe water intrusion problems. Cont/d.
Open Access
The development of a solid-phase fermentation system for the production of pharmaceutically useful secondary metabolites in fungi
(Cranfield University, 2000-05) Aldred, David; Magan, Naresh; Penn, J. (external supervisor); Martin, S. (external supervisor)
A Phoma species, producing a squalestatin (Si) was grown on agar media derived from wheat, oats, oil seed rape and malt extract over a range of water availability values corresponding to water activity (aa) levels of. 0.998,0.995,0.990,0.980 and 0.960. Growth of the organism was not significantly affected by aw, except at the lowest value, but production of SI was significantly enhanced at intermediate aW in the range 0.990 - 0.980. For example, at 25°C and 0.98 aw wheat extract produced a l Ox increase in titre compared to 0.998 aw at the same temperature. Wheat extract was shown to be the best substrate for SI production. For example, at 25°C and 0.98 aW, this substrate produced 2x, 5x and 8x increases in titres compared to oat, malt and oil seed rape extracts respectively. A range of raw and processed agricultural products, including those used as extracts with the Phoma species, as well as maize, rice, soya, wheat flakes, bulgar wheat, couscous and "shredded wheat", were selected as candidate materials for solid substrate fermentation (SSF). Moisture sorption isotherms were prepared for each of these so that aW could be accurately set in experimental work. Small scale fermentations (40 cm3 wet substrate volume) were carried out with these materials and the fungi Epicoccum nigrum, Sarophorum palmicola, Drechslera dematioidea and Corynespora cassiicola over the aw range 0.998 - 0.970. Studies with E. nigrum in particular produced a range of unique metabolites at low aw, and other metabolites where titres were increased by as much as 20x compared to high aW conditions. The optimum aw level for metabolite production in this fungus appeared to be in the range 0.990-0.980. Ultimately, E. nigrum was chosen as the model fungus and bulgar wheat as the model substrate, with 3 key target metabolites being followed (metabolites 1,2 and 3). A series of scale-up studies (40 cm3-3 litres wet volume) were carried out utilising the model system. These studies typically produced reasonable levels of metabolites, but were subject to problematic water and heat accumulation, and bacterial contamination. These were identified as critical parameters. A system was ultimately developed around a Bioengineering AG submerged liquid fermenter, modified for use with solid substrates, and incorporating forced aeration and mechanical agitation. This apparatus gave encouraging levels of metabolites, producing most of these rapidly and uniformly, and showed good critical parameter control. The overall scale-up achieved in the final fermenter studies was 75x, in terms of wet substrate volume. Increased titres were achieved for all three target metabolites compared to small-scale studies with the same substrate. These increases were approx. 17x for metabolite 1, approx. 3x for metabolite 3, while metabolite 2 was absent from small scale studies at the relevant aW level.
Open Access
Dynamics and control of ochratoxigenic strains of Penicillium Verrucosum and Aspergillus Ochraceus in the stored grain ecosystem
(Cranfield University, 2004-04) Cairns-Fuller, Victoria; Magan, Naresh; Aldred, David
This study investigated the effect of interacting environmental factors on the ecophysiology of Penicillium verrucosum and Aspergillus ochraceus and ochratoxin A (OTA) production and potential for controlling growth and OTA production using essential oils and resveratrol on wheat grain. Two dimensional temporal profiles of growth and OTA production were constructed for the first time and showed that the water activity (aw) ranges required for growth and OTA production were different in vitro and on wheat grain. Growth occurred over a wider aw range than OTA production for P. verrucosum and A. ochraceus respectively regardless of the temperature tested. For example, P. verrucosum grew at 0.80-0.995 aw on wheat grain however OTA production occurred between 0.85-0.995 aw. A. ochraceus grew at 0.80-0.995 aw on wheat grain however OTA production occurred between 0.85-0.995 aw. Optimum OTA production was at intermediate aw ranges (0.93-0.98 aw) and increased with incubation period. Interestingly at sub-optimal aw there was a' stimulation in OTA production by A. ochraceus at 15-25 oC on wheat grain. Cont/d..
Open Access
Ecophysiology and production of the biocontrol agent Phlebiopsis gigantea
(Cranfield University, 2007) Swanwick , Susanne; Magan, Naresh; Aldred, David
Heterobasidion annosum, the causative agent of the disease “root and butt rot” in conifers, is ubiquitous in the environment and causes severe financial losses to the forestry industry throughout the temperate zone. The normal route of infection is as basidiospores that land on the freshly cut stump surface during thinning operations, the colonisation of the stump providing sufficient inoculum for the fungal hyphae to invade healthy roots of adjoining trees. The most successful disease control measures involve depriving the pathogen the opportunity to become established in the food source of the fresh cut stump. Frequently killing the surface of the stump with a chemical treatment does this, but there is also some success with a biocontrol method. When the antagonist Phlebiopsis gigantea, a saprophyte, is inoculated onto the stump surface it rapidly invades the tissue thus preventing the pathogen access to the resource. Environmental studies have been carried out to assess the fitness of different isolates of the antagonist relative to the pathogen. Competitiveness was affected by environmental factors; water availability, osmotic/matric potentials, temperature, nutrition, and substrate. These indicate that the antagonist is not able to suppress the pathogen under all conditions. Generally, in wet warm conditions the antagonist is dominant, ID 10:2 antagonist:pathogen, but in drier, cooler conditions the pathogen is dominant, ID 2:10 on MEA. Interactions in situ on wood discs showed the pathogen was restricted to 0-2% of the treated portion and 2-10% of the un-treated surface at 25 ºC, but at 4 ºC it colonised 2-24% of the former and 34-57% the latter. Consideration needs to be given to possible field conditions at the time of application to maximise the establishment of the antagonist. Studies have been carried out to examine potential for liquid or solid substrate fermentation systems for optimising production of P.gigantea. Liquid culture studies were variable regardless of available nutrients and ecophysiological stresses imposed, producing a maximum of 6.5 log10 CFU ml -1 . However, temporal studies on solid substrate based on Pinus sylvestris sawdust gave 8 Log10 viable oidia g -1 in the best moisture content treatments. Scale up, to 200g substrate produced similar CFUs, however increasing to 400 g showed a reduction in viable oidia, due to lack of moisture equiibration. Analyses of the endogenous reserves to identify specific quality characteristics were inconclusive. Mycelial pellets and submerged conidia produced in fermentation had increased levels of glycerol and erythritol as aw was lowered, however this was not replicated by oidia produced in solid substrate fermentation. Preservation studies, in a fluidised bed reactor showed, the survival of PG21 spores at up to 60 ºC for 20 min. Studies were carried out to analyse volatile fingerprints of antagonist and pathogen isolates using an AlphaM.O.S. electronic nose. Volatile fingerprints showed clear grouping of antagonist and pathogen isolates, as distinct from each other. With some isolates, the fingerprints of interactions were co-incidental with the antagonist. It is suggested that this novel technique could be used as a rapid screening method for potential BCAs.
Open Access
Effect of heavy metal stress in plant metabolism of solanaceous plant species with emphasis on nitrogen assimilation
(Cranfield University, 2011-02) Christofaki, Maria Ioannou; Loulakakis, Konstantinos; Primikirios, Nikolaos; Aldred, David
Several plant species are able to accumulate and withstand large quantities of heavy metals in their tissues without dramatic alterations in their growth usually observed in plants. Such metal accumulating plants are tested and used for remediation of contaminated soils and waters. Although the literature provides extensive information on the effect of heavy metals in growth and development of several metal-accumulating and non accumulating plants, nitrogen metabolism and the regulation of related enzymes have not been widely studied. In an effort to better understand the responses of plants species under heavy metal stress, a comparative study was held between two solanaceous species, Nicotiana tabacum and Nicotiana glauca, plants with promising properties for phytoremediation. Plants of the two species were grown in the presence of different concentrations of the heavy metals zinc (Zn), nickel (Ni) and cadmium (Cd) in the following experimental systems in the greenhouse: in pots containing artificial substrate for 6 weeks and hydroponically for 8 days. In order to get a global picture for the heavy metal –induced variations concerned the examined species, the accumulation and distribution of metals in various plants tissues (lower and upper leaves, lower and upper shoots, roots) was determined. Also, several morphological parameters related with plants growth, physiological related with light and dark reactions of photosynthesis and water balance, biochemical related with nitrogenous compounds metabolism and the enzymes involved in ammonia assimilation, were followed. The presence of the referenced metals in the culture medium induced alterations, in all the parameters examined. In particular, strong positive correlations exhibited between the accumulation of Zn, Ni and Cd in the examined tissues and the supplied metals concnentrations. Our data revealed different accumulation patterns for each examined metal at tissue and species level. Furthermore, both growth and physiological parameters were negatively affected at least by the higher concentration of the three metals tested. However, differential responses were observed between N. tabacum and N. glauca, where the latter seemed to be more sensitive at the higher concentration of the metals, especially for Ni and Cd, showing heavier symptoms. In addition, proline accumulation was positively affected over the range of the three metals concentrations. Alterationsinduced in quantitive and qualitive profile of soluble proteins corresponding to Zn, Ni and Cd treatments. Furthermore, the concentration of Zn, Ni and Cd differentially affected the specific activities and the protein levels of ammonia assimilating enzymes glutamine synthetase (GS), glutamate synthase (Fd-GOGAT) and glutamate dehydrogenase (GDH).
Open Access
Effect of Milsana concentration in metabolism of solanum lycopersicum plants grown under salinity stress
(Cranfield University, 2013) Christoulaki, Maria Eirini; Loulakakis, Konstantinos; Aldred, David
Salinity is a major abiotic factor that causes serious problems in agriculture around the world which leads to reduced crop production. Scientists all over the world are looking for natural, environment friendly compounds against biotic and abiotic factors. Milsana, a formulated plant extract from Reynoutria sachalinensis, is widely used to elicit plant defences against biotic stress. In addition Milsana has been found to act by enhancing the flavonoid metabolic pathway. Considering the about the effect of Milsana concentration on tomato plants under physiological conditions and under NaCl stress was examined. The experimental approach included the study of the effect of various concentrations of Milsana (0/5%, 1.0% and 2.0%) on untreated plants and plants under salinity stress (70mM and 140mM NaCl). Plant height, fruit quality, antioxidant and photosynthetic capacity were used to determine the response of tomato plants to Milsana, NaCl stress, and their combination. The effect of Milsana was tested in two different sets of experiments, one carried out in growth chambers under controlled conditions and the other carried out in a greenhouse. Milsana led to enhanced growth, when applied to non saline stressed plants. Furthermore the negative effect of NaC1 on photosynthesis, ROS homeostasis, and fruit quality traits was counteracted by the application of Milsana.
Open Access
Exploitation of Bioactive Constituents of Olive Leaves, Grape Pomace, Olive Mills Waste Water and their Application in Phytoprotection
(Cranfield University, 2009-10) Mavrakis, Titos Nikolaou; Aldred, David; Ververidis, Filippos N.
Pure plants extracts or/and essential oils show antifungal and antibacterial activity against a wide range of fungi and bacteria. Recently there has been increasing interest in the effects of natural compounds against important plant pathogens (fungi and bacteria). Although the antimicrobial activity of oleuropein, grape pomace (GPE) and olive mills waste water (OMWW) extracts have been studied widely, little research has been done on the in vitro and in vivo evaluation of these extracts efficiency against important plant diseases and postharvest treatments. The overall objectives of this study were firstly to extract and isolate from olive leaves (oleuropein), olive mills waste water and from grape pomace (winery by-products) natural compounds in order to be used for in vitro and in vivo experiments. In particular, all three natural extracts were found to restrain in vitro growth of a series of important bacterial and fungal pathogens, such as: Botrytis cinerea, the cause of grey mold disease, Alternaria alternata, causing leaf spots and moulds on several plant species, Fusarium oxysporum fsp melonis, causing Fusarium wilt of melon, a Rhizopus species (a genus causing fruit and vegetable decays), the crucifer pathogen Colletotrichum higginsianum, causing anthracnose leaf spot disease on several Brassica and Raphanus species and Phytophthora parasitica var. nicotianae, the causal agent of the black shank disease of tobacco. Bacterial strains including Clavibacter michiganensis spp. michiganensis, the cause of bacterial canker of tomato, Ralstonia solanacearum causing bacterial wilt in solanaceous plants, Pseudomonas syringae pv. tomato, the cause of bacterial speck on tomato and Arabidopsis and Xanthomonas campestris pv. vesicatoria causing the bacterial spot disease of pepper and tomato were tested. Oleuropein (semipure and pure) showed remarkable antibacterial activity. The minimal inhibitory concentration (MIC), at least of oleuropein was lower than 0.1%. MICs values for GPE and OMWW extract ranged from 0.1% to 0.2%. Moreover, these natural extracts were shown to inhibit and/or restrain spore germination of fungi in solid media, however grape pomace extract, was sufficiently effective to inhibit spore germination and germ tube of C. higginsianum and B. cinerea. Furthermore in vivo antibacterial activity of pure oleuropein and OMWW extract was assessed in greenhouse experiments, on Xanthomonas campestris pv. vesicatoria, the cause of bacterial spot of pepper plants and Pseudomonas syringae pv. tomato, the cause of bacterial speck of tomato plants, respectively. It seems that 0.1% pure oleuropein (98%) and 0.1% OMWW extract had a protective effect against bacterial spot and bacterial speck respectively, which is more obvious when oleuropein application started before infection. Besides endophytic growth of Phytophthora parasitica var. nicotianae, causal agent of the black shank disease of tobacco, on tobacco leaves by measuring its radial growth inside the infected tissue, was assessed. 0.1% GPE showed the most significant inhibition in all tobacco leaves treatments. The potential of postharvest treatment of table grapes with the grape pomace extract (GPE) to restrain grey mould (Botrytis cinerea) disease incidence and development was estimated. 5% GPE treatments produced the strongest inhibitory effect against B. cinerea incidence on grape berries and the time after treatment influenced the numbers of decayed berries. Finally the use of pure oleuropein as antibacterial in vase solution for cut flowers (carnation) was evaluated. Oleuropein showed strong antibacterial activity as vase solution and carnations vase life was more than doubled by using oleuropein 200ppm and 400ppm, compared with control (water).
Open Access
Extending the vase life of mixed flower bouquets
(Cranfield University, 2012-12) Suntipabvivattana, Niramon; Aldred, David; Magan, Naresh
The popularity of mixed flowers bouquets has increased in the cut flower industry. The longevity of mixed flowers bouquets is limited by the individual life of each flower in the bunch. Various factors have been studied for their effect on the individual life of each flower in mixed flowers bouquets. The results indicate that the differences in vase life of each flower in mixed bouquets may come from the influence of their phenotype. In cut rose flowers, there were various contents of fructose, glucose, sucrose and myo-inositol in all cultivars. However, levels of sugars contents were not related to the long-lived cultivars. For cut lily flowers, the contents of fructose, glucose and sucrose were measured in the primary and the secondary bud of ‘Tiber’ lilies. Differences in the contents of fructose, glucose and sucrose between the primary and secondary bud, did not relate to the longevity of individual bud life. However, this experiment found increases in sucrose contents in both positions before the time of opening. This increase in sucrose may relate to the role of the carbohydrate energy source for bud opening. Bacteria found in this study seemed to be largely specific to different flower types. Also, species of bacteria found in the vase water of mixed flowers were less than in that of single varieties. Difference in species of bacteria may be due to differences between plants, and the conditions they exert in the vase water. In general bacterial numbers were high at the beginning of all the experiments, indicating a strong inoculum effect from stems, although there was no straightforward relationship between stem numbers and inoculum size, in all cases. Experiments of single varieties were studied using ‘Tiber’ lily, ‘Akito’ rose and ‘Valentino’ rose. The results indicated that the addition of stems did not result in higher numbers of bacteria, but vase life was reduced, especially for the roses. The effect of number of stems in mixed flowers was investigated in distilled water and liquid flower food. The result of the addition of stems was to reduce the vase life of both ‘Tiber’ lily and ‘Akito’ rose. However, the effect of more stems of ‘Akito’ roses had a greater effect on vase life, fresh weight and water uptake than in ‘Tiber’ lilies. This indicated that ‘Akito’ roses had a greater response to high bacteria populations than lilies. The role of chemical exudates on flowers was not clear in the present study as they only had an effect during the early part of the vase life. The vase lives of ‘Tiber’ lilies and ‘Akito’ roses in all treatments were not significantly different. Perhaps treatment effects caused by the presence of chemical exudates may have been ‘masked’ by the presence of micro-organisms. The screening of 12 essential oils (West Indian bay, cinnamon leaf, clove bud, clove leaf, Chinese ginger, lemongrass, mandarin, rosemary, sage, spearmint, sweet fennel, and thyme) showed that thyme oil and lemongrass oil are effective against more bacterial species over other essential oils. The comparison of the minimal bactericide concentration (MBC) of thyme oil and lemongrass oil showed that the average MBC for thyme oil was lower than that of lemongrass. However, the thyme oil failed to extend the vase life of ‘Tiber’ lily and ‘Akito’ rose. Thyme oil was effective against bacteria for a very short time and could not extend vase life, especially that of the ‘Akito’ rose. Overall, thyme oil treatment appeared to reduce vase life. The efficacy of nine weak organic acids was studied in vivo for their effect on six bacterial species. Bacterial samples were inoculated on trypticase soya agar (TSA) pH 4 and 7. At pH 7, the TSA was prepared by using distilled water. All six bacteria species grew well under these conditions. The results of weak organic acids studied at pH 7 showed that Trans-cinnamic acid was the only weak organic acid that could act against some bacteria. At pH 4, only L8 (Bacillus spp.) could grow, and Trans- cinnamic acid was effective against this bacteria. The initial result of testing Trans- cinnamic acid against bacteria offered some promise for it to be applied successfully to the vase water of cut flowers, in combination with buffer systems.
Open Access
Legionella control in water systems using copper and silver ion generation systems
(Cranfield University, 2012-01-31) Bedford, Birgitta; Aldred, David; Magan, Naresh
Legionella can cause human disease which can be fatal. Routine monitoring for Legionella in water systems is not recommended by UK authorities. Evidence of the efficacy of control modalities against Legionella in these water systems is, therefore, not available. Although studies have been conducted with copper and silver ionization on its efficacy against Legionella and on its value in reducing hospital-acquired legionellosis, little evidence of its efficacy is available from routine monitoring data. This study demonstrates the efficacy of copper and silver ionization against Legionella in water systems of 10 hospitals from data obtained from routine monitoring for Legionella, copper and silver. The inefficiencies of maintaining temperatures above 50ºC at hot outlets and below 20ºC at cold outlets, as recommended by UK authorities for controlling Legionella in water systems, is also demonstrated from the data obtained from routine monitoring for Legionella and temperatures. The futility of maintaining hot temperatures above 50ºC and then to reduce them to temperatures that do not present a risk of scalding is also demonstrated from the data obtained. This efficacy of copper and silver ionization and inefficiency of maintaining temperatures at 50ºC against Legionella was demonstrated as well in novel model rigs, built to simulate a typical water system of a small hospital, by data obtained from Legionella, copper, and silver analysis, and temperature recordings. The differences in biofilm formation and Legionella growth on the surfaces of copper, polyethylene, and synthetic rubber, which are commonly used plumbing materials, were also examined in the model rigs as well as with a Robbins device. These studies indicated that copper is not as biocidal as previously reported in other studies, and gave similar results to polyethylene, which previously been shown to promote biofilm development. Synthetic rubber, however, showed to promote biofilm production and should not be used as a plumbing material.
Open Access
Microbiological and chemical characterization of traditional cheese made from milk produced by the Algarvian goat breed
(Cranfield University, 2010-12) Ratao, Isabel Maria Carneiro; Aldred, David; Dionísio, Lídia
This study was concerned with a chemical and microbiological characterisation of cheese made using milk from Algarvian goat breed. Seasonal variation of the microbiota and the gross chemical composition of the raw and boiled milk and cheese during the lactation period were studied. The cardoon microbiota and the variation of microbiota during ripening were studied also. The lactic acid bacteria (LAB) were isolated, identified to genus level and their technological properties such as bacteriocin production, acidifying capacity, proteolysis and lipolysis were studied. The results showed that boiling milk does not represent a cause of variation in its gross composition and almost all the gross components of the milk and cheese register no variation during the studied period, except for fat, which increased until the middle of the lactation period and decreased after that. In cardoon, the microorganisms that are able to produce spores are the most important, thus analysis of yeasts and moulds was carried out which allowed the arrangement of the tested samples into three groups. Most of the identified moulds from the cardoon samples are from the genus Aspergillus. During the study period, differences in the microbiota of the raw milk were not observed, with Lactococcus and Lactobacillus being the prevalent groups. All the tested microorganisms increased approximately by two orders of magnitude from milk to cheese. Lactobacillus was the predominant group during the maturation period. Total coliforms tended to diminish in the early stages of ripening. Isolates from Lactobacillus and Pediococcus genera showed fast acidification capacity, which could be an indicator of good potential for their use as starter bacteria. Some Lactobacillus produced bacteriocin which can contribute to the removal of other bacteria. Aerococcus, Leuconostoc and Lactobacillus presented high proteolytic activity, which mean they could be used as adjunct cultures to improve proteolysis. Only one isolate (Pediococcus) showed lipolytic activity. In conclusion, by their technological characteristics some isolates could be selected as starter cultures, however, further research of their pathogenesis is necessary before using them in pilot plant production.
Open Access
Monitoring the succession of bacterial communities during storage of raw meat
(Cranfield University, 2010) Doulgeraki, Agapi I.; Aldred, David; Magan, Naresh; Nychas, George-John E.
Fresh meat is exposed to various factors which cause microbiological contamination during handling, processing, packaging and storage. Furthermore, the storage conditions applied may affect the microbial association of the product and consequently the spoilage process. Therefore, the purpose and importance of this study was to identify areas that should be addressed to monitor the succession of bacterial communities during storage of raw meat. The improvement of the microbiological quality and safety of meat was also studied. Cont/d.
Open Access
Pathogen responses in foods : underestimated ecophysiological factors
(Cranfield University, 2009-01) Dourou, Dimitra; Aldred, David; Nychas, George-John E.
Accurate prediction of the fate of microbial foodborne pathogens in foods is of great concern for anyone involved in the food chain. Factors that may influence microbial responses in foods and food environments, such as food structure and composition, microbial interactions and mode of growth were identified and assessed in the present study. The fate of Listeria monocytogenes, Salmonella Typhimurium and Escherichia coli O157:H7 was monitored both in and on teewurst, a raw spreadable sausage, at different storage temperatures. Regardless of the storage temperature and inoculation type, pathogen numbers decreased during storage. The increase of endogenous lactic acid bacteria and the concomitant reduction of pH mostly accounted for this reduction. The inactivation of all three pathogens inoculated into batter or onto slices varied considerably among trials possibly due to variations in the initial batch-to-batch levels of lactic acid microflora and the associated microbial interactions. The effect of structure, composition and microbial interactions on the growth kinetics of L. monocytogenes was evaluated in different growth substrates, including broth, agar, sterile meat blocks, naturally contaminated meat blocks and minced meat. The growth responses of L. monocytogenes were significantly different in the different growth media and food products tested. These differences were more pronounced at low temperatures. The validation of a model based on data from broth against the observed growth of the pathogen in the rest of the tested media showed that broth models may result in significant prediction errors. The potential for mono- or multi-strain cultures of Escherichia coli O157:H7 to attach and form biofilm in combinations of food-contact surfaces, growth substrates and storage temperatures was examined. The susceptibility of biofilms to sanitizers was also evaluated. Attachment and biofilm formation was strain dependent. The presence of food residues (liquid or solid) facilitated the attachment/transfer of E. coli O157:H7 on food-contact surfaces. At moderately cold temperatures culture broth was more conducive to subsequent growth. At chill temperatures the presence of natural microflora in liquid residues enhanced further attachment of the pathogen. Biofilms were less susceptible to sanitation treatments as compared to planktonic cells. Biofilm cells surviving sanitation were able to survive and present slight increases at refrigeration and abuse temperatures, respectively, in cross-contaminated ground meat. Acylated homoserine lactones (AHLs) and autoinducer-2 (AI-2) signalling molecules in the cell-free supernatants of Pseudomonas aeruginosa, Yersinia enterocolitica-like, Serratia proteamaculans and a mixture of two Yersinia enterocolitica strains were found to affect the growth kinetics of two Salmonella Enteritidis and S. Typhimurium strains, respectively. P. aeruginosa synthesized quorum sensing signals that accelerated the metabolic activity of Salmonella strains. All other quorated bacteria tested had a negative effect on both initiation of growth and metabolic activity. The effect seems to be strain and QS signal dependent.
Open Access
Response of four greenhouse pepper hybrids to NaCl salinity
(Cranfield University, 2011-01) Argyropoulou, Konstantina Efstathiou; Magdalene, Dragassaki; Aldred, David
The decline in availability of fresh water in the region of Ierapetra, Crete, Greece has resulted in the increased use of saline water for irrigation of greenhouse crops. The aim of this work is to study the responses of four greenhouse pepper hybrids, that are widely used in this region ( Capsicum annuum L., Drago, Sammy, Kappy and Gracia ), to NaCl salinity during in hydroponic culture ( perlite ) and culture in soil of young plants and during in vitro germination and seedling growth. Salinity treatments were imposed by adding NaCl either to the irrigation solution, or the substrate of the in vitro culture, at concentrations of 0, 12.5, 25, 50, 100, 150, 200 mM. High concentrations of NaCl affected the growth of the plants in hydroponic culture and in soil culture and the growth of seedlings in vitro in all four hybrids. Growth parameters such as height, number of leaves, fruits and flowers per plant and plant weight were significantly reduced in all hybrids. The percentage germination in the in vitro culture of the seeds was 100% for all hybrids on all NaCl concentrations. The photosynthetic rate (Po), the stomatal conductance, the intercellular CO2 concentration and the transpiration were significantly affected at high concentrations of NaCl in Drago and in Sammy. The Fv/Fm values of the leaves, which are related to the chlorophyll fluorescence, were significantly reduced at 100-200 mM NaCl, more in Kappy and Gracia and less in Drago and Kappy. The chlorophyll content in the leaves was negatively affected in all hybrids. NaCl caused a decrease in the soluble proteins in all hybrids. The decrease was significant in Drago, Kappy and Gracia in the greenhouse experiment while in vitro the protein content was less affected by the increasing concentrations of NaCl. Soil salinity positively affected the activity of GDH at 100 mM to 200 mM NaCl more in Kappy and Gracia and less in Sammy and Drago. In the vitro experiments there was a small increase in the higher concentrations of salt in all hybrids. The presence of NaCl affected the antioxidant enzyme GPX in Sammy Kappy and Gracia, SOD in Drago and POD in Kappy while APX was not affected. In general Sammy was the least affected by NaCl followed by Kappy , Drago, and Gracia.
Open Access
Study of phenolic content and antioxidant activity of Greek red and white wines by means of classical methods and FTIR
(Cranfield University, 2015) Strataridaki, Argiro E.; Aldred, David; Lydakis, Dimitrios
Phenolic and antioxidant contents of wines are very important in terms of both flavour attributes and health benefits. Changes occur during ageing of wine in containers (e.g. wooden barrels) in relation to their antioxidant activity and phenolic content. Vilana, Dafni, Kotsifali and Mandilari single variety Cretan wines, were vinificated to determine their antioxidant activity and phenolic content Wines were aged in different containers after two vinifications. Changes in the above characteristics were determined every three months for a twelve month period. Stainless steel with and without oenosticks containers, American oak, French oak, Acacia and Chestnut barrels were used for wine ageing. As far as phenolic and antioxidant contents are concerned, ageing of wine in chestnut barrels, Kotsifali and Mandilari (red wines) and in Acacia barrels for Vilana and Dafni (white wines), gave the best results, achieving the highest phenolic content and antioxidant activity after 12 months of ageing. The phenolic fingerprints of Vilana, Dafni, Kotsifali and Mandilari wines were determined for the first time. The phenolic fingerprint of wines has been recently used for the authentication and discrimination of red wines. In this study, attempt has also been made to use the phenolic fingerprint of white wines, for authentication. Differences were observed in Kotsifali and Mandilari (red wines) and in Vilana and Dafni (white wines) directly after vinification, allowing their discrimination. Also the changes in their phenolic fingerprints were monitored during ageing in different containers for a 12 month period. The effect of hydroxytyrosol and oleuropein on wine spoilage induced by acetic acid bacteria was also determined. Hydroxytyrosol was better than oleuropein in controlling the increase of volatile acidity, causing wine spoilage. Wines treated with 0.5mg/l hydroxytyrosol showed control of volatile acid production, and may be a promising alternative to sulphites in wine production in the future. Finally, extracts obtained from olive oil mills and winery by-products were used in Vilana vinification instead of sulphites and antioxidant activity and phenolic content of the wines determined.

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Browsing PhD, EngD and MSc by research theses (Cranfield Health) by Author "Aldred, David"

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