Henri S. Tapp

Chemical engineering applications of electrical process tomography

Electrical tomographic imaging has been applied to a broad range of chemical engineering processes, including: bubble columns, fluidised beds, pneumatic transport, liquid mixing, cyclonic separation, pressure filtration, liquid pipe-flow, polymerisation, emergency depressurisation, and paste extrusion. Two imaging approaches are described, electrical capacitance tomography (ECT) and electrical impedance tomography (EIT). To date, these have primarily been used as low-cost research tools for studying process dynamics, although they potentially may also act as sensors permitting on-line monitoring and control. Various aspects of design, operation and data processing are described, along with a review of applications in the literature.

Mid-infrared spectroscopy for food analysis: recent new applications and relevant developments in sample presentation methods

Abstract This article deals with recent developments in the use of mid-infrared (MIR) spectroscopy for the analysis of foods. It has become apparent that MIR can be used to address a wide range of issues and provide solutions for rapid analysis and on-line control. In parallel with the new applications to food, which include new qualitative and quantitative applications and discriminant (classification) methods, there have been several technical advances in other fields that are set to impact on the food sector. New applications of transmission methods are described, which have been particularly successful for the analysis of oils and fats. Despite new advances in other sampling techniques, transmission methods have been quite widely employed. Diffuse reflectance has also been used with some considerable success, with new accessory designs and applications in food authentication using chemometric methods. However, the largest number of new applications and technical developments have used attenuated total reflectance (ATR). Novel ATR cells have been designed for high-temperature, high-pressure and a range of on-line applications. ATR has been used for a wide range of analytical application. The analysis of sugars in various systems has been particularly well studied. The authors predict that the use of MIR spectroscopy is likely to continue to increase and develop in the near future.

Nutritional factors and gender influence age-related DNA methylation in the human rectal mucosa.

Aberrant methylation of CpG islands (CGI) occurs in many genes expressed in colonic epithelial cells, and may contribute to the dysregulation of signalling pathways associated with carcinogenesis. This cross‐sectional study assessed the relative importance of age, nutritional exposures and other environmental factors in the development of CGI methylation. Rectal biopsies were obtained from 185 individuals (84 male, 101 female) shown to be free of colorectal disease, and for whom measurements of age, body size, nutritional status and blood cell counts were available. We used quantitative DNA methylation analysis combined with multivariate modelling to investigate the relationships between nutritional, anthropometric and metabolic factors and the CGI methylation of 11 genes, together with LINE‐1 as an index of global DNA methylation. Age was a consistent predictor of CGI methylation for 9/11 genes but significant positive associations with folate status and negative associations with vitamin D and selenium status were also identified for several genes. There was evidence for positive associations with blood monocyte levels and anthropometric factors for some genes. In general, CGI methylation was higher in males than in females and differential effects of age and other factors on methylation in males and females were identified. In conclusion, levels of age‐related CGI methylation in the healthy human rectal mucosa are influenced by gender, the availability of folate, vitamin D and selenium, and perhaps by factors related to systemic inflammation.

Impact of steam explosion on biogas production from rape straw in relation to changes in chemical composition.

An 81day trial compared the cumulative production of methane from rape straw pre-treated by steam explosion at 15 levels of severity. The final methane yields were similar. The temporal variation in production rate exhibited two peaks: maximum production occurred in the first peak at around 21days with heights that increased with severity; the height of the second peak reduced with severity and peaked between 32 and 36days. Changes in the straw composition were investigated using mid-infrared spectroscopy. These were also strongly related to the degree of severity, allowing good predictive models to be built of severity and subsequently the rate of methane production. The main spectral changes showed the degradation of cellulose and xylose-containing hemicelluloses and production of furfural-like components commonly associated with biomass pre-treatments. Only small changes to lignin were associated with increased methane generation suggesting a structural rather than chemical role in this process.

Effect of environmental stress during grain filling on the soluble proteome of wheat (Triticum aestivum) dough liquor

The influence of genotype and environment on a soluble wheat dough liquor proteome was studied for four cultivars grown under field conditions and under hot/dry and cool/wet regimes by two-dimensional electrophoresis followed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry or quadrupole time-of-flight mass spectrometry. Although the four cultivars had similar patterns, differences in the relative abundances of some components were observed. Similarly, some differences were observed between the control samples and the samples grown under cool/wet and hot/dry conditions. These included differences in the abundances of storage proteins belonging to the 7S globulin (vicilin-like) and alpha-globulin families and of protective proteins including members of the serpin, described as allergens, and chitinase families. A number of novel annotations were made as compared to previous work on the dough liquor of cv. Hereward, including two 19 kDa alpha-globulins, precursors of endochitinases A and C, and several polypeptides belonging to the 7S globulin (vicilin-like) family.

Application-specific optimization of regularization for electrical impedance tomography

Single-step reconstruction of electrical impedance tomograms can have speed advantages. Key to obtaining good information from the tomograms is the regularization method used in reconstruction. For high-speed continuous monitoring of a patient or industrial process, there are important issues to consider when selecting a suitable value for the regularization parameter. A case study of a bubble column is presented. This demonstrates automation of the interpretation of sequences of tomograms and the optimal choice of regularization parameter.

Evaluation of multiple variate selection methods from a biological perspective: a nutrigenomics case study.

Genomics-based technologies produce large amounts of data. To interpret the results and identify the most important variates related to phenotypes of interest, various multivariate regression and variate selection methods are used. Although inspected for statistical performance, the relevance of multivariate models in interpreting biological data sets often remains elusive. We compare various multivariate regression and variate selection methods applied to a nutrigenomics data set in terms of performance, utility and biological interpretability. The studied data set comprised hepatic transcriptome (10,072 predictor variates) and plasma protein concentrations [2 dependent variates: Leptin (LEP) and Tissue inhibitor of metalloproteinase 1 (TIMP-1)] collected during a high-fat diet study in ApoE3Leiden mice. The multivariate regression methods used were: partial least squares “PLS”; a genetic algorithm-based multiple linear regression, “GA-MLR”; two least-angle shrinkage methods, “LASSO” and “ELASTIC NET”; and a variant of PLS that uses covariance-based variate selection, “CovProc.” Two methods of ranking the genes for Gene Set Enrichment Analysis (GSEA) were also investigated: either by their correlation with the protein data or by the stability of the PLS regression coefficients. The regression methods performed similarly, with CovProc and GA performing the best and worst, respectively (R-squared values based on “double cross-validation” predictions of 0.762 and 0.451 for LEP; and 0.701 and 0.482 for TIMP-1). CovProc, LASSO and ELASTIC NET all produced parsimonious regression models and consistently identified small subsets of variates, with high commonality between the methods. Comparison of the gene ranking approaches found a high degree of agreement, with PLS-based ranking finding fewer significant gene sets. We recommend the use of CovProc for variate selection, in tandem with univariate methods, and the use of correlation-based ranking for GSEA-like pathway analysis methods.

Consumption of a diet rich in Brassica vegetables is associated with a reduced abundance of sulphate‐reducing bacteria: A randomised crossover study

Scope We examined whether a Brassica‐rich diet was associated with an increase in the relative abundance of intestinal lactobacilli and sulphate‐reducing bacteria (SRB), or alteration to the composition of the gut microbiota, in healthy adults. Methods and results A randomised crossover study was performed with ten healthy adults who were fed a high‐ and a low‐Brassica diet for 2‐wk periods, with a 2‐wk washout phase separating the diets. The high‐Brassica diet consisted of six 84 g portions of broccoli, six 84 g portions of cauliflower and six 300 g portions of a broccoli and sweet potato soup. The low‐Brassica diet consisted of one 84 g portion of broccoli and one 84 g portion of cauliflower. Faecal microbiota composition was measured in samples collected following 2‐wk Brassica‐free periods (consumption of all Brassica prohibited), and after each diet, whereby the only Brassica consumed was that supplied by the study team. No significant changes to the relative abundance of lactobacilli were observed (p = 0.8019). The increased consumption of Brassica was associated with a reduction in the relative abundance of SRB (p = 0.0215), and members of the Rikenellaceae, Ruminococcaceae, Mogibacteriaceae, Clostridium and unclassified Clostridiales (p < 0.01). Conclusion The increased consumption of Brassica vegetables was linked to a reduced relative abundance of SRB, and therefore may be potentially beneficial to gastrointestinal health.

Image improvement in soft-field tomography through the use of chemometrics

This paper reports a novel soft-field reconstruction method based on an experimental evaluation of the system, in our case an electrical capacitance tomograph. A least-squares estimate solution of the inverse problem is calculated using chemometrics, specifically by multiple linear regression. Example tomograms displaying three-phase discrimination are presented.

Acute Consumption of Flavan-3-ol-Enriched Dark Chocolate Affects Human Endogenous Metabolism

Flavan-3-ols and methylxanthines have potential beneficial effects on human health including reducing cardiovascular risk. We performed a randomized controlled crossover intervention trial to assess the acute effects of consumption of flavan-3-ol-enriched dark chocolate, compared with standard dark chocolate and white chocolate, on the human metabolome. We assessed the metabolome in urine and blood plasma samples collected before and at 2 and 6 h after consumption of chocolates in 42 healthy volunteers using a nontargeted metabolomics approach. Plasma samples were assessed and showed differentiation between time points with no further separation among the three chocolate treatments. Multivariate statistics applied to urine samples could readily separate the postprandial time points and distinguish between the treatments. Most of the markers responsible for the multivariate discrimination between the chocolates were of dietary origin. Interestingly, small but significant level changes were also observed for a subset of endogenous metabolites. 1H NMR revealed that flavan-3-ol-enriched dark chocolate and standard dark chocolate reduced urinary levels of creatinine, lactate, some amino acids, and related degradation products and increased the levels of pyruvate and 4-hydroxyphenylacetate, a phenolic compound of bacterial origin. This study demonstrates that an acute chocolate intervention can significantly affect human metabolism.