Production of novel dairy products using actinidin and high pressure as enzyme activity regulator

Milk clotting for the production of novel dairy products, alternative or complementary to cheese and yogurt type products can be achieved using plant sulfhydryl proteases. The objective was to apply the protease actinidin, from Actinidia chinensis, as the milk clotting agent, and High pressure (HP) technology to control excessive proteolysis. The effect of the dairy substrate and the process parameters on the coagulation rate and the texture and sensory properties of the end product, were studied. Selected values of design parameters were 25% total solids, 6.49 adjusted pH, 0.35 U activity of the clotting agent actinidin, 40 ºC process temperature and 2 h time. The selected pressure-temperature conditions, 600 MPa at 40 ºC, were applied to stop the potentially detrimental further proteolytic action of the enzyme. Results indicated that use of actinidin for milk clotting and HP to stop the enzyme activity in the final product, leads to a “fresh cheese” type dairy product.Industrial relevance: Alternative clotting methods for novel dairy products, complementary to cheese and yogurt type products, are of interest to the industry. Plant proteases can be a viable approach, provided that excessive proteolysis after structure formation is regulated. High hydrostatic pressure can be used for controlling proteolytic activity in the final products without affecting their texture and sensory characteristics.     

Detachment strength of human osteoblasts cultured on hydroxyapatite with various surface roughness. Contribution of integrin subunits

Hydroxyapatite (HA) has been widely used as a bone substitute in dental, maxillofacial and orthopaedic surgery and as osteoconductive bone substitute or precoating of pedicle screws and cages in spine surgery. The aim of the present study was to investigate the osteoblastic adhesion strength on HA substrata with different surface topography and biochemistry (pre-adsorption of fibronectin) after blocking of specific integrin subunits with monoclonal antibodies. Stoichiometric HA was prepared by precipitation followed by ageing and characterized by SEM, EDX, powder XRD, Raman spectroscopy, TGA, and specific surface area analysis. Human bone marrow derived osteoblasts were cultured on HA disc-shaped substrata which were sintered and polished resulting in two surface roughness grades. For attachment evaluation, cells were incubated with monoclonal antibodies and seeded for 2 h on the substrata. Cell detachment strength was determined using a rotating disc device. Cell detachment strength was surface roughness, fibronectin preadsorption and intergin subunit sensitive.     

Modeling Microbial Spoilage and Quality of Gilthead Seabream Fillets: Combined Effect of Osmotic Pretreatment,Modified Atmosphere Packaging,and Nisin on Shelf Life

ABSTRACT: The objective of the study was the kinetic modeling of the effect of storage temperature on the quality and shelf life of chilled fish, modified atmosphere-packed (MAP), and osmotically pretreated with the addition of nisin as antimicrobial agent. Fresh gilthead seabream (Sparus aurata) fillets were osmotically treated with 50% high dextrose equivalent maltodextrin (DE 47) plus 5% NaCl. Water loss, solid gain, salt content, and water activity were monitored throughout treatment and treatment conditions were selected for the shelf life study. Untreated and osmotically pretreated slices with and without nisin (2 × 10⁴ IU/100 g osmotic solution), packed in air or modified atmosphere (50% CO₂–50% air), and stored at controlled isothermal conditions (0, 5, 10, and 15 °C) were studied. Quality assessment and modeling were based on growth of several microbial indices, total volatile nitrogen, trimethylamine nitrogen, lipid oxidation (TBARS), and sensory scoring. Temperature dependence of quality loss rates was modeled by the Arrhenius equation, validated under dynamic conditions. Pretreated samples showed improved quality stability during subsequent refrigerated storage, in terms of microbial growth, chemical changes, and organoleptic degradation. Osmotic pretreatment with the addition of nisin in combination with MAP was the most effective treatment resulting in significant shelf life extension of gilthead seabream fillets (48 days compared to 10 days for the control at 0 °C).     

Evaluation of four isolation techniques for honey aroma compounds

The analysis of the volatile fraction of honey provides useful information for the determination of the botanical and geographical origin. However, the results obtained vary greatly upon the extraction procedure employed. Four different isolation techniques were compared, that is hydrodistillation (HD), micro‐simultaneous steam distillation–solvent extraction (MSDE), ultrasound‐assisted extraction (USE) and solid‐phase microextraction (SPME). From the data obtained, USE and SPME seem to be more suitable for the isolation of potent marker compounds. HD and MSDE have main drawbacks because of the drastic conditions used that lead to the formation of artefacts and the degradation of sensitive compounds. These drawbacks are avoided when employing USE and SPME. Copyright © 2004 Society of Chemical Industry     

Enthalpy-entropy compensation in water sorption by various wood species

Tsuga heterophylla ), Douglas fir (Pseudotsuga menziesii), western red cedar (Thuja plicata), sitka spruce (Picea sitchensis), and lodgepole pine (Pinus contorta). Enthalpy and entropy show a strong negative relation to the moisture content, the absolute desorption values always being higher than the adsorption ones, but with no clear trend between and within the species. Furthermore, it is shown that the linear plot of compensation between enthalpy and entropy correlates well for water sorption in wood; that water adsorption or desorption are irreversible, and that both are enthalpy-driven mechanisms.

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Tsuga heterophyll , Pseudotsuga menziesi, Thuja plicata, Picea sitchensis), und Pinus contorta. Enthalpie und Entropie steigen mit fallender Feuchte. Die Desorptionswerte sind immer etwas h?her als die Adsorptionswerte. Zwischen den Holzarten gab es keine signifikanten Unterschiede. Die lineare Kompensation zwischen Enhalpie und Entropie korrelliert gut mit der Sorption. Absorption und Desorption sind irreversible, Enthalpie-getriebene Prozesse.

     

Non-periodic Molecular Dynamics simulations of coarse grained lipid bilayer in water

We present a multiscale algorithm that couples coarse grained molecular dynamics (CGMD) with continuum solver. The coupling requires the imposition of non-periodic boundary conditions on the coarse grained Molecular Dynamics which, when not properly enforced, may result in spurious fluctuations of the material properties of the system represented by CGMD. In this paper we extend a control algorithm originally developed for atomistic simulations [3], to conduct simulations involving coarse grained water molecules without periodic boundary conditions. We demonstrate the applicability of our method in simulating more complex systems by performing a non-periodic Molecular Dynamics simulation of a DPPC lipid in liquid coarse grained water.     

Botanical discrimination and classification of honey samples applying gas chromatography/mass spectrometry fingerprinting of headspace volatile compounds

A validated method for the discrimination and classification of honey samples performing GC/MS fingerprinting of headspace volatile compounds was developed. Combined mass spectra of honey samples originated from different plants and geographical regions of Greece were subjected to orthogonal partial least squares-discriminant analysis™ (OPLS™-DA), soft independent modelling of class analogy (SIMCA), and OPLS™-hierarchical cluster analysis (OPLS™-HCA). Analyses revealed an excellent separation between honey samples according to their botanical origin with the percentage of misclassification to be as low as 1.3% applying OPLS™-HCA. Fragments (m/z) responsible for the observed separation were assigned to phenolic, terpenoid, and aliphatic compounds present in the headspace of unifloral honeys. On the other hand, a variable classification for citrus and thyme honeys according to their geographical origin could be achieved. Results suggested that the developed methodology is robust and reliable for the botanical classification of honey samples, and the study of differences in their chemical composition.     

The effect of heparin hydrogel embedding on glutaraldehyde fixed bovine pericardial tissues: Mechanical behavior and anticalcification potential

Heart valve diseases remain common in industrialized countries. Bioprosthetic heart valves, introduced as free of anticoagulation therapy alternatives to mechanical substitutes. Still they suffer from long term failure due to calcification. Different treatment methods introduced to inhibit calcification, have so far been limited in success. Glycosaminoglycans (GAGs) possess properties including high negative charge, anticoagulation and anti-inflammatory activity that make them a potential solution for calcification problem. In this study, heparin hydrogel was prepared and characterized both chemically and mechanically. After that, heparin hydrogel embedded bovine pericardial tissues, fixed with glutaraldehyde, were produced and tested for their mechanical behavior and anticalcifcation potential in vitro using the constant composition model. In the calcification experiments, tissues were divided into three groups: a) Controls without treatment, b) Hydrogel treated tissues and c) Tissues with raw heparin dissolved in the calcification solution. The results showed that embedding of tissue with hydrogel had no stiffening effect on its mechanical behavior. Calcification assessment showed a significant efficacy on inhibition of calcium phosphate deposition of hydrogel treated (second group) in comparison to untreated tissues (control, first group). Calcification inhibition potential was very similar in both the second and raw heparin (third group). Histological data confirmed the obtained results, suggesting that heparin treatment is a promising anticalcification agent.

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A convex optimization approach to signal reconstruction over switching networks

In this paper we consider signal reconstruction over communication network channels that can be modeled as input switching systems. Such systems can be associated with a variety of applications including control and estimation over networks. In particular, we formulate the signal reconstruction problem as a prototypical model matching problem where the various mappings involved belong to a class of input switching systems. The design interest is placed on minimizing the worst case or stochastic average performance of this model matching system over all possible switchings with an H₂ norm as the performance criterion. This minimization is performed over all stable receivers R in the class of input switching systems. For the particular setup at hand, and in the case of matched switching, two convergent sequences to the optimal solution from above and below respectively are formulated in terms of quadratic programs. An approximate solution with any a priori given precision is possible by finite truncation. Also, it is shown that in the cases of arbitrary, partially matched or unmatched switching, the optimal receiver R need not depend on the switching sequence and that it can be obtained as a linear time-invariant solution to an associated H₂ norm optimization.