Characterisation of Dioscorea bulbifera native starch

A non conventional source of starch, bulbs of Dioscorea bulbifera, was evaluated. Giving a yield of 28.48 g/100 g on dry weight, chemical composition, physical, physico-chemical and morphological characteristics were assessed, as well as its rheological properties. Chemical analysis showed a amylose content of 29.37%. Micrographies showed that most of the starch granules were of irregular shape, similar to a pyramid with rounded vertices, and a smaller number were elongated with smooth surface. Dioscorea starch showed a gelatinization temperature of 70.8 degrees C and maximum viscosity at 88.6 degrees C of 435 Brabender units (BU). It presented a relatively stable consistency to the cooking process and a low tendency to retrogradation; which suggest the starch possible use in food products that need a fast viscosity and a gel with a stable consistency.     

A new experimental device to evaluate eye ulcers using a multispectral electrical impedance technique

We present a novel experimental technique to determine eye ulcers in animals using a spectral electrical impedance technique. We expect that this technique will be useful in dry eye syndrome. We used a sensor that is basically a platinum (Pt) microelectrode electrically insulated by glass from a cylindrical stainless steel counter-electrode. This sensor was applied to the naked eye of New Zealand rabbits (2.0-3.5 kg in weight). Whereas half of the eyes were normal (control), we applied to the remainder a few drops of 20% (v/v) alcohol to produce an ulcer in the eye. Using a multispectral electrical impedance system we measured ulcerated and control eyes and observed significant difference between normal and pathological samples. We also investigated the effects of different applied pressures and natural degradation of initially normal eyes as a function of time. We believe that this technique could be sufficiently sensitive and repetitive to help diagnose ocular surface diseases such as dry eye syndrome.     

Acrylonitrile butadiene nanocomposites containing different clays by latex compounding method

Considering elastomers nanocomposites, most of the works are focused on natural rubber, styrene butadiene rubber and rubber blends, while few of them deal with nitrile butadiene rubber (NBR). This article presents the reinforcing effect of two raw sodic montmorillonites (Mts) and one organoclay on NBR matrix prepared by the latex compounding method. Raw Mts increase the mechanical properties of neat matrices. A pseudoplastic behavior is observed with the incorporation of clays into the NBR latex, indicating interactions between polymer chains and clay sheets, in agreement with the results of zeta potential analysis. X‐ray diffraction evaluates changes in the interlayer distance of the clay, indicating the NBR intercalation phenomenon in all cases. Matrices with different clay proportions present variations in the mechanical properties, depending if the aggregation phenomenon is promoted. Morphological analysis of clays and nanocomposites as well as thermal analysis were performed. The variation in mechanical properties after an aging process was studied, evaluating the effects on the tensile strength, ultimate strain and 300% modulus. POLYM. ENG. SCI., 59:736–744, 2019. © 2018 Society of Plastics Engineers     

Chemometric studies for the characterization and differentiation of microorganisms using in situ derivatization and thermal desorption ion mobility spectrometry

Whole-cell bacteria were characterized and differentiated by thermal desorption ion mobility spectrometry and chemometric modeling. Principal component analysis was used to evaluate the differences in the ion mobility spectra of whole-cell bacteria and the fatty acid methyl esters (FAMEs) generated in situ after derivatization of the bacterial lipids. Alternating least squares served to extract bacterial peaks from the complex ion mobility spectra of intact microorganisms and, therefore, facilitated the characterization of bacterial strains, species, and Gram type. In situ thermal hydrolysis/methylation with tetramethylammonium hydroxide was necessary for the differentiation of Escherichia coli strains, which otherwise could not be distinguished by spectra acquired with the ITEMISER ion mobility spectrometer. The addition of the methylating agent had no effect on Gram-positive bacteria, and therefore, they could not be differentiated by genera. The classification of E. coli strains was possible by analysis of the IMS spectra from the FAMEs generated in situ. By using the fuzzy multivariate rule-building expert system and cross-validation, a correct classification rate of 96% (22 out of 23 spectra) was obtained. Chemometric modeling on bacterial ion mobility spectra coupled to thermal hydrolysis/methylation proved a simple, rapid (2 min/sample), inexpensive, and sensitive technique to characterize and differentiate intact microorganisms. The ITEMISER ion mobility spectrometer could detect as few as 4 x 10(6) cells/sample.     

Immunomagnetic isolation of enterohemorrhagic Escherichia coli O157:H7 from ground beef and identification by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and database searches

A rapid (25 min) and facile method was developed for the isolation and identification of the enterohemorrhagic Escherichia coli (serotype O157:H7) in ground beef. The isolation method employed microscopic magnetic beads coated with antibodies covalently bonded to the surface that were specific to antigens of serotype O157. This selective preconcentration step was necessary because direct matrix-assisted laser desorption/ionization (MALDI) MS analysis of bacteria was not amenable, serving to isolate the bacteria from meat components and other nontarget bacteria. The immunomagnetic separation increased the sensitivity of the method and permitted the detection of bacteria in meat. MALDI time-of-flight MS furnished bacterial mass spectra that were useful for organism identification. Molecular weight database searches using the Expert Protein Analysis System proved useful for confirmation of the organism's identity. Bacterial biomarkers from direct MALDI analysis of pure bacterial suspensions were consistently present in bacterial suspensions of buffer/tryptic soy broth (positive controls) and meat extract samples. The detection limits were 2 x 10(6) cells/mL for the experimental approach used herein. Cross-reactivity studies performed on three nontarget bacterial strains revealed that the immunomagnetic beads are specific only to E. coli strain serotype O157:H7, and there is no cross-reactivity with the other relatively innocuous strains studied.     

Detection of methamphetamine in the presence of nicotine using in situ chemical derivatization and ion mobility spectrometry

The detection of methamphetamine in the presence of nicotine has been successfully accomplished using in situ chemical derivatization with propyl chloroformate as the derivatization reagent and ion mobility spectrometry (IMS). The rapid detection of methamphetamine is important for forensic scientists in order to establish a chain of evidence and link criminals to the crime scene. Nicotine is pervasive in clandestine drug laboratories from cigarette smoke residue. It has been demonstrated that nicotine obscures the methamphetamine peaks in ion mobility spectrometers due to their similar charge affinities and ion mobilities, which makes their detection a challenging task. As a consequence, false positive or negative responses may arise. In situ chemical derivatization poses as a sensitive, accurate, and reproducible alternative to remove the nicotine background when detecting nanogram amounts of methamphetamine. The derivatization agent was coated onto the sample disk, and the derivatization product corresponding to propyl methamphetamine carbamate was detected. In the present study, in situ chemical derivatization was demonstrated to be a feasible method to detect methamphetamine hydrochloride as the carbamate derivative, which was baseline-resolved from the nicotine peak. Alternating least squares (ALS) was used to model the datasets. A mixture containing both compounds revealed reduced mobilities of 1.61 cm(2)/V.s and 1.54 cm(2)/V.s for methamphetamine and nicotine, respectively. The reduced mobility of propyl methamphetamine carbamate was found at 1.35 cm(2)/V.s.     

Independent block identification in multivariate time series

In this‐30 work we propose a model selection criterion to estimate the points of independence of a random vector, producing a decomposition of the vector distribution function into independent blocks. The method, based on a general estimator of the distribution function, can be applied for discrete or continuous random vectors, and for i.i.d. data or dependent time series. We prove the consistency of the approach under general conditions on the estimator of the distribution function and we show that the consistency holds for i.i.d. data and discrete time series with mixing conditions. We also propose an efficient algorithm to approximate the estimator and show the performance of the method on simulated data. We apply the method in a real dataset to estimate the distribution of the flow over several locations on a river, observed at different time points.     

Biogenic amine content in Chilean Gauda cheese: physico‐chemical and microbiological factors that may influence this content

The presence of four biogenic amines in Chilean Gauda cheese was studied, and the effect of certain factors may influence the production of those amines. Histamine, tyramine, putrescine and cadaverine were quantified with high‐performance liquid chromatography (HPLC), in cheeses from the three major Chilean cheese manufacturers. Multiple regression analysis revealed that water activity, free amino acid content and the Enterobacteriaceae count all favoured production of biogenic amines. The total amount of biogenic amines in the samples studied was between 47.9 and 150.5 mg/kg of cheese, much lower than that associated with a possible consumer health risk (1000 mg/kg).     

Sensory and nutritional attributes of fibre-enriched pasta

The objective of this study was to evaluate the impact that the incorporation of resistant starch type II (RSII), resistant starch type IV (RSIV) and oat bran (OB) have on sensory and nutritional quality of pasta. RSII, RSIV and OB were incorporated into recipes in four proportions (w/w): 2.5, 5.0, 7.5, and 10.0 g/100 g. Resistant, digestible and total starch were measured in cooked pasta. An in vitro digestion and sensory analysis of pasta were performed in order to estimate glycemic index. Results showed that both, the type and amount of added fibre influence nutritional quality of pasta. Incorporation of RSII into pasta formulation generates an additional quantity of resistant starch content in cooked pasta. Differences in in vitro digestibility of pasta can be appreciated. RSIV presented the greatest effect on total starch hydrolysis. The lower glycemic index was obtained with addition of RSIV and RSII at 7.5 g/100 g and 10.0 g/100 g. Sensory analysis showed high scores for overall acceptability for Control, RSII and RSIV samples. Results suggest that by using insoluble fibre it is possible to enhance the nutritional quality of pasta, without affecting its sensory properties negatively.     

Blends of PP/PE co‐octene for modified atmosphere packaging applications

The aim of this work was to obtain films of polypropylene (PP)/polyethylene co‐octene (POE) blends and study the influence of their composition and mixing conditions on final morphology and ultimate properties (thermal, mechanical, oxygen and water vapour transmission rates). Scanning electron microscopy showed segregation of POE domains in the PP matrix. Thermal analysis indicated that the addition of POE modified neither the melting temperature nor the crystallinity of PP in the pressed films. It was found that permeabilities of films were mainly related to POE content rather than morphological features. For the maximum POE concentration used (40%), the oxygen permeability increased up to ∼100% from that of neat PP. A similar trend was found for water vapour permeability. Rigidity of blends dropped significantly with the addition of POE although their ductility slightly increased when compared to pure PP. No significant effect of blend preparation conditions on these properties was found. Mechanical and permeability characteristics of films make them very attractive to be used for MAP of fresh produce such as apple, blueberry and mushroom. Copyright © 2011 John Wiley & Sons, Ltd.