Effect of dry‐salt processing on the textural properties and cell wall polysaccharides of cv. Thasos black olives

BACKGROUND: Thasos is an olive variety cultivated mainly in Greece used to produce ‘naturally black dry‐salted olives’. This process consists in placing the olives in disposed layers with coarse sodium chloride. The loss of water and other solutes gradually debitters and wrinkles the fruits. In this study, the effect of dry‐salt processing on the texture and cell wall polysaccharide composition was investigated. RESULTS: This type of processing affected primarily the mechanical properties of the olive flesh. In processed olives, this tissue was approximately 4.5 times stronger and also more deformable up to failure and stiffer than that from the raw olives. The dry‐salt processing had its strongest effect on pectic polysaccharides. This included the increment of solubilization of arabinose‐rich polymers in aqueous solutions, and thus their partial loss to the soak medium during dry‐salting. Contrarily, galacturonic acid‐rich polymers were further retained in the processed olives, probably by their stabilization within the cell walls by reduction of the electrostatic repulsion between the acidic groups of these polysaccharides due to sodium ions. CONCLUSION: The texture improvement of olive flesh by dry‐salt processing seems to be correlated with the reorganization of the galacturonic acid‐rich pectic polysaccharides into the cell wall of the fruit. Copyright © 2008 Society of Chemical Industry     

Differential effect of organic cultivation on the levels of phenolics,peroxidase and capsidiol in sweet peppers

BACKGROUND: Coincident with the changes in agricultural practices from conventional to organic, changes in the nutrient composition of fresh fruits and vegetables have been identified. The levels of peroxidase, total phenolics content, and capsidiol activity in organic as compared with conventional sweet pepper fruit were examined in this study. In order to avoid interferences of environmental factors on the studied parameters, the sweet peppers were grown (organically and conventionally) in a greenhouse under the same soil and climate conditions. RESULTS: Peroxidase was partially purified using the Triton X‐114 method and both organic and conventional peppers had the same isoenzymatic form. However, peroxidase activity in organic sweet peppers was higher than in conventional ones, in both maturity stages studied. The level of total phenolics compunds was also higher in organic than in conventional sweet peppers. With respect to the capsidiol activity, expressed as inhibition of fungus growth, it was not affected by the cultivation method at the green mature stage. However, at the red mature stage, organic sweet peppers showed higher capsidiol activity than those grown under the conventional system. CONCLUSION: Sweet peppers grown under organic culture have a maturity‐related response, with high levels of phenolic compounds, and peroxidase and capsidiol activity that contribute to disease resistance in organic farming. Copyright © 2007 Society of Chemical Industry     

Determination of preservatives in meat products by flow injection analysis (FIA)

Various preservatives are added to meat products to extend shelf-life and enhance food safety; thus, their determination is essential for legislative purposes and consumer health. Analytical methodologies based on flow injection analysis (FIA) offer attractive advantages compared with other procedures, such as versatility, precision, low cost, speed and ease of automation. This review considers the status of published FIA methodologies for the determination of preservatives in meat products. The techniques are described regarding their application to different preservatives (nitrates and nitrites, sulfites, sorbates, benzoates and p-hydroxybenzoate esters), with emphasis on extraction, separation, detection and quantification procedures in meat matrices.     

Furan and Methylfurans in Foods: An Update on Occurrence,Mitigation, and Risk Assessment

The acceptance of many foods is related to traditional cooking practices, which create taste and texture and are important to digestibility, preservation, and the reduction of foodborne illnesses. A wide range of compounds are formed during the cooking of foods, a number of these have been shown to lead to adverse effects in classical toxicological models and are known as food processing contaminants (FPC). It is essential that the presence and effects of such compounds alone and in combination within the diet are understood such that proportionate risk management measures can be developed, while taking a holistic view across the whole value chain. Furan and alkylfurans (principally 2‐ and 3‐methylfuran) are highly volatile FPC, which are formed in a wide range of foods at low amounts. The focus of research to‐date has been on those foods, which have been identified to be most consequential in terms of being sources of exposure, namely jarred and canned foods for infants and young children (meals and drinks) and coffee (roast and ground, soluble). This report presents (i) new industry data on the occurrence of furan and methylfurans in selected food categories following previous coffee studies, (ii) the most salient parameters that impact furan formation, and (iii) aspects of importance for the risk assessment.     

Alternative Methods to SO2 for Microbiological Stabilization of Wine

The use of sulfur dioxide (SO₂) as wine additive is able to ensure both antioxidant protection and microbiological stability. In spite of these undeniable advantages, in the last two decades the presence of SO₂ in wine has raised concerns about potential adverse clinical effects in sensitive individuals. The winemaking industry has followed the general trend towards the reduction of SO₂ concentrations in food, by expressing at the same time the need for alternative control methods allowing reduction or even elimination of SO_2. In the light of this, research has been strongly oriented toward the study of alternatives to the use of SO₂ in wine. Most of the studies have focused on methods able to replace the antimicrobial activity of SO₂. This review article gives a comprehensive overview of the current state‐of‐the‐art about the chemical additives and the innovative physical techniques that have been proposed for this purpose. After a focus on the chemistry and properties of SO₂ in wine_, as well as on wine spoilage and on the conventional methods used for the microbiological stabilization of wine, recent advances on alternative methods proposed to replace the antimicrobial activity of SO₂ in winemaking are presented and discussed. Even though many of the alternatives to SO₂ showed good efficacy, nowadays no other physical technique or additive can deliver the efficacy and broad spectrum of action as SO₂ (both antioxidant and antimicrobial), therefore the alternative methods should be considered a complement to SO₂ in low‐sulfite winemaking, rather than being seen as its substitutes.     

Modeling of biodiesel production: Performance comparison of Box-Behnken,face central composite and full factorial design

The performances of the response surface methodology (RSM) in connection with the Box-Behnken, face central composite or full factorial design (BBD, FCCD or FFD, respectively) were compared for the use in modeling of the NaOH-catalyzed sunflower oil ethanolysis. The influence of temperature, catalyst loading, and ethanol-to-oil molar ratio (EOMR) on fatty acid ethyl esters (FAEE) content was evaluated. All three multivariate strategies were efficient in the statistical modeling and optimization of the influential process variables but BBD and FCCD realization involved less number of experiments, generating smaller costs, requiring less work and consuming shorter time than the corresponding FFD. All three designs resulted in the same optimal catalyst loading (1.25% of oil) and EOMR (12:1). The reduced two-factorinteraction (2FI) models based on the BBD and FCCD defined a range of optimal reaction temperature (25℃-75℃) and 25℃, respectively while the same model based on the 3³ FFD appointed 75℃. The predicted FAEE content of about 97%-98.0% was close to the experimentally obtained FAEE content of about 97.0%-97.6% under the optimal reaction conditions. Therefore, the simpler BBD or FCCD might successfully be applied for statistical modeling of biodiesel production processes instead of the more extensive, more laborious and more expensive FFD.     

Effect of hydrolyzed collagen on thermal,mechanical and biological properties of poly(lactic acid) bionanocomposites

Iranian Polymer Journal - Bionanocomposites based on poly(lactic acid) (PLA), plasticized with commercial tributyl o-acetyl citrate (ATBC) and containing hydrolyzed collagen (HC) up to...     

Stability Is Not Everything: The Case of the Cyclisation of a Thrombin-Binding Aptamer

With the aim of developing a new approach to obtain improved aptamers, a cyclic thrombin-binding aptamer (TBA) analogue (cycTBA) has been prepared by exploiting a copper(I)-assisted azide–alkyne cycloaddition. The markedly increased serum resistance and exceptional thermal stability of the G-quadruplex versus TBA were associated with halved thrombin inhibition, which suggested that some flexibility in the TBA structure was necessary for protein recognition.