Effect of calcium propionate on the microstructure and pectin methy‐ lesterase activity in the parenchyma of fresh‐cut Fuji apples

There is an increasing demand for fresh‐cut fruits. One of the main problems with these products is their short shelf life. The use of additives such as calcium propionate may increase their shelf life, because calcium preserves the structural integrity of the cells and propionate acts as food preservative. This work analyses the microstructure of Fuji apple parenchyma treated with calcium propionate immediately after treatment and after storage for 1 and 2 weeks at 4 °C by using light microscopy (LM) and low‐temperature scanning electron microscopy (cryo‐SEM). This work also studies the effects of treatment and storage time on the enzymatic activity of pectin methylesterase (PME) by measuring the amount of acid released per unit of time at pH 7 and at 63 °C. The results show that calcium propionate treatment has consolidating and structuring effects on the parenchyma and partially minimises the degrading effects of fresh‐cut apples. In addition, treatment with calcium propionate decreases the activity of the PME both in non‐stored apples and in those stored for 1 and 2 weeks probably due to the inhibiting effect of propionate. Copyright © 2006 Society of Chemical Industry     

Physical properties and antioxidant capacity of starch–sodium caseinate films containing lipids

Biodegradable films based on starch, sodium caseinate, glycerol and lipids (oleic acid and/or α-tocopherol) were obtained and evaluated in terms of microstructure, mechanical behaviour, barrier and optical properties and antioxidant capacity. The effect of film storage time on these properties was also analysed. The lipid incorporation provoked phase separation due to the different interaction between each polymer and lipids, although structural rearrangement of components during storage could be deduced from the change in mechanical behaviour. After storage, all films showed similar mechanical properties, but lipid containing films were more stretchable. Lipid addition did not induce a notable decreased in water vapour permeability of the films, but oxygen permeability highly increased when they contained oleic acid. All films were highly transparent, with very small differences among formulations, although their gloss values increased when lipids were added. The incorporation of α-tocopherol greatly increased the antioxidant capacity of the films which affected oxygen permeability.     

A simple DNA extraction method suitable for PCR detection of genetically modified maize

BACKGROUND: The polymerase chain reaction (PCR) is a powerful tool that is being increasingly used for detection of transgenic DNA. PCR requires only a minute quantity of template, but sensitive and accurate testing requires DNA of sufficient purity and free from inhibitors such as plant polysaccharides. Several standard protocols are available for this purpose, but they usually involve several steps, imply destruction of the maize kernel, or are time‐consuming. Our aim was to develop a fast and simple extraction method to isolate a raw DNA‐containing solution from maize tissues suitable for use as a template in a PCR‐based detection assay with specific oligonucleotides directed to the identification of event MON810. RESULTS: The NaOH‐based DNA extraction method we report here is time‐saving (5 min) and can be used to isolate DNA‐containing solutions from a small maize leaf portion (down to 1 mg) or from a single overnight‐germinated kernel. PCR performed with selected primers yielded reproducible detection of transgenic DNA. CONCLUSION: The main advantages of the procedure are the quick extraction step, the possibility of non‐destructive testing of maize kernels, and the robustness of the PCR‐based detection, a consequence of the selection of MON810‐matching oligonucleotides yielding intense and highly specific amplicons. Copyright © 2007 Society of Chemical Industry     

Protein breakdown during the preparation of frozen batter-coated squid rings

The objective of this paper was to study the main chemical and microstructural changes in squid proteins during processing as a frozen batter-coated product using different coatings. Protein bands of the squid and of the batters used for coating were studied using SDS-PAGE. It is concluded that it is not only the proteins of the layer of batter, which are directly exposed both to the frying oil and to freezing temperatures, that deteriorate during the preparation process, the protein fraction of the squid substrate, mainly the myofibrillar proteins, is also degraded. At a microstructural level, big voids are generated during freezing as a consequence of the packing of the fibres, although the size of these voids decreases after final frying. After this step of the process, the central sarcoplasm is still visible but has been altered by coagulation of the sarcoplasmic proteins and the sarcolemma is observed to be separate from the myofibrillar package.     

A new Fortran 90 program to compute regular and irregular associated Legendre functions

We present a modern Fortran 90 code to compute the regular and irregular associated Legendre functions for all x∈(−1,+1) (on the cut) and |x|>1 and integer degree (l) and order (m). The code applies either forward or backward recursion in (l) and (m) in the stable direction, starting with analytically known values for forward recursion and considering both a Wronskian based and a modified Miller's method for backward recursion. While some Fortran 77 codes existed for computing the functions off the cut, no Fortran 90 code was available for accurately computing the functions for all real values of x different from x=±1 where the irregular functions are not defined.

Program summary

Program title: Associated Legendre FunctionsCatalogue identifier: AEHE_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEHE_v1_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 6722No. of bytes in distributed program, including test data, etc.: 310 210Distribution format: tar.gzProgramming language: Fortran 90Computer: Linux systemsOperating system: LinuxRAM: bytesClassification: 4.7Nature of problem: Compute the regular and irregular associated Legendre functions for integer values of the degree and order and for all real arguments. The computation of the interaction of two electrons, 1/|r₁−r₂|, in prolate spheroidal coordinates is used as one example where these functions are required for all values of the argument and we are able to easily compare the series expansion in associated Legendre functions and the exact value.Solution method: The code evaluates the regular and irregular associated Legendre functions using forward recursion when |x|<1 starting the recursion with the analytically known values of the first two members of the sequence. For values of the argument |x|<1, the upward recursion over the degree for the regular functions is numerically stable. For the irregular functions, backward recursion must be applied and a suitable method of starting the recursion is required. The program has two options; a modified version of Miller's algorithm and the use of the Wronskian relation between the regular and irregular functions, which was the method considered in [1]. Both approaches require the computation of a continued fraction to begin the recursion. The Wronskian method (which can also be described as a modified Miller's method) is a convenient method of computations when both the regular and irregular functions are needed.Running time: The example tests provided take a few seconds to run.References:

• [1] 

  A. Gil, J. Segura, A code to evaluate prolate and oblate spheroidal harmonics, Comput. Phys. Commun. 108 (1998) 267–278.

     

Structure and stability of edible oleogels prepared with different unsaturated oils and hydrocolloids

Edible oleogels, with three oil types (olive, sunflower and flaxseed), hydroxypropylmethylcellulose (HPMC) and xanthan gum (XG), as structuring agents, were developed using the emulsion-template approach, and subsequent drying of the emulsions using conventional or vacuum drying. Our results showed that for both drying methods, well-structured oleogels were obtained using olive and sunflower oils for the preparation. These oleogels showed oil losses ˂10% after 35 days of storage. However, unstructured non-homogeneous oleogels were obtained when using flaxseed oil and conventional drying, while it was not feasible to develop flaxseed oleogel with vacuum drying. Oleogels showed interesting rheological properties, including a high oleogel strength with an elastic modulus of the order 10⁴–10⁵ Pa, weak dependence on frequency, and good thermostability. Moreover, high oxidative stability was obtained for olive oil oleogels, using both conventional and vacuum drying, and for sunflower oleogels using vacuum drying. Still, the initial oxidation rates of sunflower oleogels using conventional drying should be improved in future studies.     

Production of hematopoietic regulatory factors in cultures of adult and fetal mouse organs: measurement by specific bioassays

Factor-specific cell line bioassays were used to monitor the production in vitro by adult and fetal mouse organs of GM-CSF, G-CSF, M-CSF, Multi-CSF (IL-3), IL-6 and leukemia inhibitory factor (LIF). No tissue was observed to produce Multi-CSF. Highest producers of the other regulators were lung, muscle, thymus, heart and bone shaft and all tissues producing detectable growth factors produced all five with the same rank order of activity. Adult tissues produced more GM-CSF than G-CSF and less M-CSF than either, no differences being observed between male, female and pregnant female tissues. In contrast, the pregnant uterus produced high levels of M-CSF as did the fetal membranes and tissues with only low GM-CSF and no G-CSF production. Pre-irradiation did not alter the pattern of regulator production by adult tissues. The intravenous injection of endotoxin elevated serum levels of GM-CSF, G-CSF, M-CSF and IL-6 but the dominant rise was in G-CSF levels. The data indicating that multiple organs produce the regulators monitored in a common rank order suggest some overall linkage in their production with major differences between adult and fetal tissues.     

Gas barrier changes and morphological alterations induced by retorting in ethylene vinyl alcohol–based food packaging structures

Ethylene vinyl alcohol (EVOH)–based packaging structures were analyzed in terms of both barrier properties and morphological alterations after a retorting process and as functions of ethylene content. From the results, it was found that the samples do have a substantial decrease in oxygen barrier properties and that the kinetics of recovery strongly depends on the copolymer ethylene fraction. A morphological deterioration was also observed as a result of retorting, particularly for packaging structures composed of EVOH copolymers of low ethylene contents. However, the polymer morphology and barrier properties were restored after a dry thermal treatment of the retorted samples. Interestingly, preannealing of copolymers of low ethylene content rendered them more resistant to the retorting process by means of promoting both a more robust crystallinity and a lower water sorption capacity. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2192–2202, 2005     

Dielectric and mechanical-dynamical studies on poly(cyclohexyl methacrylate)

The relaxation processes in poly(cyclohexyl methacrylate) have been studied by transient and dynamic dielectric means as well as by viscoelastic techniques. The study embraces also the effect of the thermal treatment on the α and β relaxations. The α relaxation has been fitted into the empirical model of Havriliak and Negami, and the functional relation between the mean relaxation times and the temperature has been adjusted to the equation of Vogel. The β relaxation is strongly hindered, so it is scarcely perceivable. The secondary γ relaxation was studied mainly by dielectric means. Its apparent activation energy does not depend on the temperature and amounts to 11.2 ± 0.2 kcal mol^?1. It allows an application of the time-temperature superposition principle and its behaviour is thermorheologically simple. A δ relaxation with a temperature-independent apparent activation energy of 8.5 kcal mol^?1 has been obtained     

Testing Different Ensemble Configurations for Feature Selection

In recent years, ensemble learning has become a prolific area of study in pattern recognition, based on the assumption that using and combining different learning models in the same problem could lead to better performance results than using a single model. This idea of ensemble learning has traditionally been used for classification tasks, but has more recently been adapted to other machine learning tasks such as clustering and feature selection. We propose several feature selection ensemble configurations based on combining rankings of features from individual rankers according to the combination method and threshold value used. The performance of each proposed ensemble configuration was tested for synthetic datasets (to assess the adequacy of the selection), real classical datasets (with more samples than features), and DNA microarray datasets (with more features than samples). Five different classifiers were studied in order to test the suitability of the proposed ensemble configurations and assess the results.