A Short Investigation of the Luminescence Properties of Talc

This report presents results of a short study of the thermoluminescence TL properties of talc. Talc is a magnesium silicate mineral utilised widely in industrial and pharmaceutical applications. It occurs in well defined geological situations with several known formation processes, and is extracted by quarrying and mining. The use in foods and dietary supplements is mainly as a filler. The work was initiated to address questions as to the possible impact of talc on application of EN1788 methods to detect irradiated foods. Authentic samples were obtained from extraction and processing facilities in France and Italy. Supplementary samples from Sardinia, China, Mexico and Australia were obtained indirectly. Irradiated pharmaceutical grade talc was obtained from a UK commercial source for comparison. All samples were characterised by TL analysis after initial preparation, and also following irradiation to a 200 Gy dose. The dose response and behaviour under storage at ambient and elevated temperatures and in a light box, were investigated for two samples in detail. Exploratory kinetic analysis was performed to provide first order estimates of trap parameters. All samples of talc exhibited measurable TL response in the 0-500°C region, with at least four recognisable TL peaks present in response to radiation. Sensitivities vary by some 3 or more orders of magnitude from sample to sample, accompanied by less pronounced changes in glow shape following radiation. The dose response increases progressively in the 100-6400 Gy range investigated. At higher dose levels the response is non-linear with the onset of saturation occurring in the kGy region for the majority of signals. Radiation induced signals from all four peaks were stable at ambient temperatures over the duration of the study. Samples stored at 50°C showed some thermal erosion of the low temperature signals. This observation together with analysis of the distribution of natural TL and the kinetic analyses confirms that lower temperature signals have comparable stability with other silicates, and that higher temperature signals are the dominant components of geologically induced signals. The stability requirements to explain natural signals in terms of simple production mechanisms have been defined. Exploratory kinetic analysis confirms that there are multi-trap contributions to the main TL peaks, but provides broad support for a simple explanation of the natural TL. The TL response following high dose irradiation can be distinguished from geological signals by 1-2 orders of magnitude in low temperature peaks. There may be scope for further investigation of phototransfer effects, but these would clearly be overtaken by bleaching in prolonged exposures to light. Thermal processing of pharmaceutical grades of talc reduces residual low temperature signals by some 1-2 orders of magnitude leading to product with negligible low temperature natural signals. TL could in principle be used to verify the effectiveness of such thermal treatment, and potentially to authenticate commercial products. It can also quite clearly be used to identify irradiated talc, providing the amount of prior exposure to light is limited. In samples containing talc in extreme dilution with other unirradiated products, there might be ambiguity in interpretation of glow curves with minor low temperature peaks dominated by high temperature signals. Care would be needed in interpreting EN1788 results of this sort

Investigation of Statistical and Imaging Methods for Luminescence Detection of Irradiated Ingredients

This project investigated two potential approaches to improving the reliability of lumines-cence methods for detecting minor irradiated ingredients in foods. Whereas in the 1980’s there were no validated methods for laboratory detection of irradiated foods, work conducted in the UK and elsewhere by the mid 1990’s had resulted in the development of a series of physical, chemical and biological methods capable of detecting a range of irradiated food classes. Of these the luminescence methods embodied in EN1788 (Thermoluminescence) and EN13751 (Photostimulated luminescence) standards have been applied to detection of a vari-ety of products including herbs and spices, and seafood. In common with the other EN stan-dard methods almost all validation work had been originally conducted using pure irradiated or unirradiated ingredients. Yet application experience had shown the presence of mixed products containing both irradiated and unirradiated ingredients. A short study was commis-sioned by MAFF to investigate the impact of blending on standard EN1788 methods, and on the provisional draft EN13751 (the standard having been published in the meantime) method. This showed the impact of dilution of irradiated material between 10% and 0.1% concentra-tions on detection rates, which unsurprisingly are reduced by extreme dilution. UK labelling regulation, both before and after adoption of the European Directive on Food Irradiation, call for labelling of all irradiated ingredients regardless of concentration or origin within the final product. This study was therefore motivated by the recognition of the long term need for im-proved methods to improve reliability at low concentrations. Two complementary approaches were investigated. The project first examined whether TL data collected using the EN1788 method could be enhanced using advanced statistical proce-dures. Data sets from the SURRC TL archive, and from project CSA4790 were used both to define the characteristics of irradiated and unirradiated end members, and to assess classifica-tion methods using the controlled blending experimental data sets of CSA 4790. Multivariate analyses, based on principal components analysis and discriminant analysis of glow curve data; kinetic deconvolution approaches coupled to PCA and DA, and neural analyses were investigated and compared with detection rates achieved using expert visual classification. To complement this experiments were undertaken to explore the potential of using focussed laser stimulation to produce spatially resolved measurements from mineral grains separated from foods. Two systems were evaluated based on IR and visible band lasers. Work was under-taken to explore sample presentation and to assess the ability of this approach to distinguish mixtures of irradiated and unirradiated grains. The statistical work was successful in developing three approaches which could be used for objective identification of irradiated materials. Pure irradiated and unirradiated data sets from 150 sample pairs were obtained having searched the SUERC archive of more than 3500 lu-minescence analyses. These were used to set up multivariate analyses based on the ap-proaches outlined above. Performance in recognising irradiated ingredients using these meth-ods was then assessed with data drawn from the MAFF blending investigation, comprising 160 permutations of irradiated and unirradiated herbs and spices at 10%, 1% and 0.1% con-centrations. It was possible to achieve good detection rates with alatistical approaches, the best approaches inigated being the use of glow curve deconvolution coupwith li discrimination, and the use of neural appros. The absolute performance achieved matched that opert visual clfication utilising the revised EN1788 criterwhich were adopted within the international standauring course of this project. The use of ad-vancedtistical methods, while not adding performance, can pde objective support to visual classifications. During performance assessment it was aloted that theformance of all methods wasficiently close to infer that detections rates are most dependent on the statistical presence or absence of irradiated grains within the extracted samples used for TL analysis. This raises practical suggestions for improving detection rates at low concentrations based on the use of larger samples and more specific mineral separation approaches. These may be worth investigating further. Laser scanning approaches were also investigated using highly focussed laser beams to stimulated luminescence sequentially from different parts of separated mineral samples. Work was conducted using a system which had been developed in earlier work at SUERC, and then followed by additional investigation using an improved instrument built during the project. Initial work confirmed the feasibility of using laser scanning approaches to obtain spatially resolved luminescence data at or near the dimensions of individual mineral grains. Practical obstacles included the recognition that laser scattering from surfaces coated with mineral grains introduced an element of cross-talk between different parts of the sample, and difficulties in accurate re-positioning of the sample using the first generation prototype in-strument. Work was conducted to investigate a series of different sample presentation media to improve the former, and to incorporate high precision mechanical and optoelectronic means of re-positioning samples between initial measurements, external irradiation, and sub-sequent re-measurement. Both IR and visible band semiconductor lasers were investigated with successful production of single grain images. The short and medium term reliability of the lasers used was acceptable. The lasers used both however eventually failed, which sug-gests that long term lifetime may be an issue for further work. Of the two lasers the IR laser in particular gave a good signal to background ratio for discriminating between irradiated and unirradiated grains. Quantitative analysis of the grain resolved images confirms the potential of this approach in identifying minor irradiated components. The overall conclusions of the work are that both statistical approaches and imaging instru-ments are able to enhance current methods. The observation that visual classification can match the performance even of deconvolution or neural approaches suggests that future effort should be directed more towards improvement of grain statistics in conventional measure-ments, and in further development and investigation of imaging approaches. In these ways it can anticipated that the performance of standard luminescence methods for detecting dilute mixtures of irradiated and unirradiated food ingredients could be significantly improved. To do so would further enhance work conducted by FSA and other bodies to ensure that regula-tions governing the use of irradiation in food processing and the labelling of imported foods are followed

'I don't think I ever had food poisoning' : A practice-based approach to understanding foodborne disease that originates in the home

© 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).Food stored, prepared, cooked and eaten at home contributes to foodborne disease which, globally, presents a significant public health burden. The aim of the study reported here was to investigate, analyse and interpret domestic kitchen practices in order to provide fresh insight about how the domestic setting might influence food safety. Using current theories of practice meant the research, which drew on qualitative and ethnographic methods, could investigate people and material things in the domestic kitchen setting whilst taking account of people's actions, values, experiences and beliefs. Data from 20 UK households revealed the extent to which kitchens are used for a range of nonfood related activities and the ways that foodwork extends beyond the boundaries of the kitchen. The youngest children, the oldest adults and the family pets all had agency in the kitchen, which has implications for preventing foodborne disease. What was observed, filmed and photographed was not a single practice but a series of entangled encounters and actions embedded and repeated, often inconsistently, by the individuals involved. Households derived logics and principles about foodwork that represented rules of thumb about 'how things are done' that included using the senses and experiential knowledge when judging whether food is safe to eat. Overall, food safety was subsumed within the practice of 'being' a household and living everyday life in the kitchen. Current theories of practice are an effective way of understanding foodborne disease and offer a novel approach to exploring food safety in the home.Peer reviewedFinal Published versio

The emergence of international food safety standards and guidelines: understanding the current landscape through a historical approach

Following the Second World War, the Food and Agriculture Organization (FAO) and the World Health Organization (WHO) teamed up to construct an International Codex Alimentarius (or 'food code') which emerged in 1963. The Codex Committee on Food Hygiene (CCFH) was charged with the task of developing microbial hygiene standards, although it found itself embroiled in debate with the WHO over the nature these standards should take. The WHO was increasingly relying upon the input of biometricians and especially the International Commission on Microbial Specifications for Foods (ICMSF) which had developed statistical sampling plans for determining the microbial counts in the final end products. The CCFH, however, was initially more focused on a qualitative approach which looked at the entire food production system and developed codes of practice as well as more descriptive end-product specifications which the WHO argued were 'not scientifically correct'. Drawing upon historical archival material (correspondence and reports) from the WHO and FAO, this article examines this debate over microbial hygiene standards and suggests that there are many lessons from history which could shed light upon current debates and efforts in international food safety management systems and approaches

A Preliminary Investigation of the Impact of Blending on Luminescence Detection of Irradiated Herbs and Spices

A preliminary investigation has been undertaken to study the impact of blending irradiated and unirradiated products on luminescence detection of irradiated herbs and spices. Samples of six products (oregano, basil, sage, paprika, ginger and cinnamon) were prepared combining irradiated material at three different concentration levels - 10%, 1% and 0.1% with unirradiated product under controlled conditions. The luminescence sensitivities of both the irradiated and unirradiated products were varied systematically, producing 9 sensitivity combinations at each of the three concentration levels. Samples were selected following an analysis of the sensitivity distributions of both PSL and TL from archival data sets at SURRC. Retained samples were combined under controlled conditions from materials believed to be unirradiated on the basis of previous PSL and TL analyses. Portions of these samples were irradiated to a 10 kGy gamma dose, and then recombined to produce the blended samples. Thus a total of 162 blended samples was produced for analysis. All samples were subjected to PSL screening measurements, and to TL analysis following standardised and validated procedures. The PSL analysis followed the EU standard method, which has been used in earlier MAFF supported interlaboratory trials. TL analyses were conducted relative to EN1788 and MAFF V27 protocols. PSL screening results showed that all samples could be identified in either intermediate or positive bands in 10% concentration; the proportion detected falling to 68% of samples containing 1% irradiated material, and 33% of samples containing 0.1% concentrations. Signal strengths were generally higher for high sensitivity materials, as expected, although the low concentration blends showed high variations. TL analyses were evaluated relative to both the 1998 revised EN1788 criteria, currently undergoing consultation prior to adoption, and the 1996 criteria which form the current EN standard. The 1998 criteria, in keeping with MAFF V27 place emphasis on peak shapes, and recognise the possibility that glow ratios can be adversely affected by blending. When this is done 96% of samples with 10% irradiated material could be detected. Falling to 75% with 1% irradiated material, and 54% with 0.1% concentrations. These figures compare favourably with those based on strict interpretation of the current (1996) EN1788 criteria where only 84%, 35% and 15% of these blends would have been identified as irradiated at the three respective concentration levels. These overall results confirm the importance of using peak shape as a primary classification tool, where blended materials are encountered. However when taken to critical limits this can introduce subjective elements to classification. Glow 1 peak shapes could be shown to comprise mixtures of two signal components – the higher temperature forms associated with residual geological luminescence in the silicate assemblages used for analysis, and the lower temperature components associated with the irradiated fractions. The data sets broadly confirm the expected behaviour of these components as a function of the sensitivities and concentrations of the irradiated components and the unirradiated matrices. Overall it can be seen that standard methods are able to detect a significant portion of irradiated blends at concentrations above 1-10%. Below these concentrations there is a significant probability of non-detection, particularly for low sensitivity components

A novel online food recall checklist for use in an undergraduate student population : a comparison with diet diaries

Peer reviewedPublisher PD

Exploring the Influence of Family on Adolescents’ Seafood Consumption Choices

Seafood in the adolescent diet has many benefits, yet a number of adolescents do not consume the recommended levels. Despite this the consumption of seafood by younger consumers has received scant attention in the extant literature. Previous studies on adolescents’ food-related behaviour tend to focus on general choice mechanisms or perceptions of food and mainly relate to fruit and vegetable intake. The present study seeks to address this gap through investigating the impact of family upon the consumption of seafood by younger consumers through exploring adolescents’ attitudes and behaviour in regard to eating seafood. Utilising an exploratory qualitative methodology, seven focus groups of adolescents aged 13–19 years were conducted at two schools in South-West England. Discussions covered a range of issues related to adolescent seafood consumption. The use of thematic content analysis found that the family, and parents in particular, exert high levels of influence over adolescents’ consumption of seafood both at home and when dining out. The parent who does the shopping and cooking has the greatest role. Sibling preferences and dietary choices also influence whether seafood is served in the home. Of value to researchers and management are the insights gleaned into the influences on adolescents’ attitudes toward and behaviour in regard to eating seafood. In particular encouraging seafood consumption will rely upon interventions aimed at both parents and children and need to take into account adolescents’ diet and lifestyle preferences, while also acknowledging the influence of peers and the school food environment

Experiments on torrefied wood pellet: study by gasification and characterization for waste biomass to energy applications

Samples of torrefied wood pellet produced by low-temperature microwave pyrolysis were tested through a series of experiments relevant to present and near future waste to energy conversion technologies. Operational performance was assessed using a modern small-scale downdraft gasifier. Owing to the pellet's shape and surface hardness, excellent flow characteristics were observed. The torrefied pellet had a high energy density, and although a beneficial property, this highlighted the present inflexibility of downdraft gasifiers in respect of feedstock tolerance due to the inability to contain very high temperatures inside the reactor during operation. Analyses indicated that the torrefaction process had not significantly altered inherent kinetic properties to a great extent; however, both activation energy and pre-exponential factor were slightly higher than virgin biomass from which the pellet was derived. Thermogravimetric analysis-derived reaction kinetics (CO2 gasification), bomb calorimetry, proximate and ultimate analyses, and the Bond Work Index grindability test provided a more comprehensive characterization of the torrefied pellet's suitability as a fuel for gasification and also other combustion applications. It exhibited significant improvements in grindability energy demand and particle size control compared to other non-treated and thermally treated biomass pellets, along with a high calorific value, and excellent resistance to water

Iodine status in pre-school children prior to mandatory iodine fortification in Australia

The iodine status of children between the ages of 5 and 15 years has been routinely assessed in many countries, but few studies have examined iodine status in pre-school children. We conducted a cross-sectional study of pre-school children living in Adelaide, South Australia, between 2005 and 2007. Children 1–5 years old were identified using a unique sampling strategy to ensure that the study population was representative. A 3-day weighed diet record, a blood sample and a urine sample were obtained from each child. The median urinary iodine concentration (UIC) of the children (n = 279) was 129 µg L⁻¹, indicating iodine sufficiency (normal range: 100–199 µg L⁻¹), but 35% of the children had a UIC < 100 µg L−1. The median thyroglobulin concentration of children (n = 217) was 24 µg L⁻¹ and thyroglobulin concentration declined with increasing age (P = 0.024). The mean daily iodine intake was 76 µg. The intake of iodine was lower than expected and highlights difficulties in accurately assessing iodine intakes. Further studies are needed to monitor dietary changes and iodine status in this age group since the implementation of mandatory fortification of bread with iodised salt in Australia in 2009.Sheila Skeaff, Ying Zhao, Robert Gibson, Maria Makrides, Shao Jia Zho

Comparison of the biotypes of Yersinia enterocolitica isolated from pigs, cattle and sheep at slaughter and from humans with yersiniosis in Great Britain during 1999-2000

Aims: To investigate the relationship between livestock carriage of Yersinia enterocolitica and human disease. The biotypes/serotypes of strains recovered from the faeces of pigs, cattle and sheep at slaughter during a national survey in Great Britain in 1999-2000, were compared with those of strains isolated from human cases of yersiniosis during the same period. Methods and Results: The faecal carriage of Y. enterocolitica by cattle, sheep and pigs at slaughter was 6.3, 10.7 and 26.1%, respectively. Yersinia enterocolitica biotype (BT) 1a was the most frequently isolated biotype from livestock (58%) and was the predominant biotype (53%) isolated from human cases over the same period. The main recognized pathogenic Y. enterocolitica biotype isolated from livestock was BT3 (O:5,27) (35% of sheep, 22% of pigs and 4% of cattle) but this biotype was not detected in any of the human isolates investigated. The major pathogenic biotypes of strains isolated from humans were BT3 (O:9) (24%) and BT4 (O:3) (19%) whereas of the veterinary isolates investigated, only pigs (11%) carried BT3 (O:9) strains. Conclusions: Because of significant overlaps in phenotypes of the veterinary and human strains it is not possible to comment on the correlation between host and pathogenicity, especially of biotype 1a. Significance and Impact of the Study: The data suggest that further investigations using methods with greater discriminatory power are required. However the data also suggests that pigs may be the primary reservoir for human pathogenic Y. enterocolitica infection