Edible moisture barriers: how to assess of their potential and limits in food products shelf-life extension?

Control of moisture transfer inside composite food products or between food and its environment remains today a major challenge in food preservation. A wide rage of film-forming compounds is now available and facilitates tailoring moisture barriers with optimized functional properties. Despite these huge potentials, a realistic assessment of the film or coating efficacy is still critical. Due to nonlinear water sorption isotherms, water-dependent diffusivities, and variations of physical state, modelling transport phenomena through edible barriers is complex. Water vapor permeability can hardly be considered as an inherent property of films and only gives a relative indication of the barrier efficacy. The formal or mechanistic models reported in literature that describe the influence of testing conditions on the barrier properties of edible films are reviewed and discussed. Most of these models have been validated on a narrow range of conditions. Conversely, few original predictive models based on Fick's Second Law have been developed to assess shelf-life extension of food products including barriers. These models, assuming complex and realistic hypothesis, have been validated in various model foods. The development of nondestructive methods of moisture content measurement should speed up model validation and allow a better comprehension of moisture transfer through edible films.

Corn protein-based thermoplastic resins: effect of some polar and amphiphilic plasticizers.

Homogeneous blends of corn gluten meal (CGM) and "polar" plasticizers (water, glycerol) or "amphiphilic" plasticizers [octanoic and palmitic acids, dibutyl tartrate and phthalate, and diacetyl tartaric acid ester of mono-diglycerides (DATEM)] were obtained by a hot-mixing procedure. The glass transition temperature (T(g)) of the blends was measured by modulated differential scanning calorimetry and dynamic mechanical thermal analysis, as a function of plasticizer type and content (0-30%, dwb). The plasticizing efficiency (i.e., decrease of T(g)) at equal molar content was found to be proportional to the molecular weight and inversely proportional to the percent of hydrophilic groups of the plasticizer. The migration rate of the plasticizers in the polymer was related to their physicochemical characteristics. It was assumed that polar substances interacted with readily accessible polar amino acids, whereas amphiphilic ones interacted with nonpolar zones, which are buried and accessible with difficulty. The temperature at which a thermoplastic resin of plasticized CGM could be formed was closely connected to the T(g) of the blend.

Properties of chemically and physically treated wheat gluten films.

Chemical (vapors of formaldehyde), physical (temperature, UV and gamma radiation), and aging treatments were applied to wheat gluten films. Changes in film mechanical properties, water vapor permeability, solubility, and color coordinates were investigated. An aging of 360 h led to a 75 and 314% increase in tensile strength and Young's modulus, respectively, and a 36% decrease in elongation. Severe thermal (above 110 degrees C, 15 min) and formaldehyde treatments highly improved the mechanical resistance of the films. Under these conditions, up to 376 and 654% increase in tensile strength and Young's modulus and up to 66% decrease in elongation have been observed. Water solubility was only slightly modified, whereas water vapor permeability was not affected. Color coordinates of films heated above 95 degrees C changed to a great extent. An almost total insolubilization of proteins in sodium dodecyl sulfate occurred for heat- and formaldehyde-treated films, due to the modification of protein network leading to changes in properties of the films.

Protein insolubilization and thiol oxidation in sulfite-treated wheat gluten films during aging at various temperatures and relative humidities.

Gluten films were prepared by casting an acidic and ethanolic solution of gluten previously treated with sodium sulfite. The effects of sulfitolysis on proteins were investigated by SE-HPLC and thiol/disulfide content measurements. During sulfitolysis, insoluble glutenin macropolymer was converted into its constitutive subunits. About 10% of gluten disulfide bonds were cleaved, of which three-fourths originated from interchain disulfide bonds. Oxidation of thiol groups released during sulfitolysis was followed for various temperatures (T) and relative humidities. Oxidation was shown to be a second-order rate process occurring below the glass transition temperature (T(g)) and related to T - T(g). Thiol oxidation ensured the formation of interchain bonds between specific classes of gluten proteins according to an ordered process. Intrachain bonds were also formed and through thiol/disulfide-exchange reactions were finally converted to interchain bonds. Thus, fully oxidized gluten films had more insoluble glutenin macropolymers than native gluten.

Thermal behavior of native and hydrophobized wheat gluten, gliadin and glutenin-rich fractions by modulated DSC.

The glass transition temperature (T(g)) of hydrophobized and native wheat gluten and its protein fractions, with water mass fraction from 0 to 0.2, was studied using modulated differential scanning calorimetry. The T(g) values of unplasticized products were approximately 175 degrees C whatever the treatment (hydrophobization) or the fraction tested, except for the gliadin-rich fraction (162 degrees C). Experimental change in heat capacity at the glass transition (DeltaC(p)) ranged from 0.32 to 0. 50 J/g/ degrees C depending on the gluten fractions. The Gordon-Taylor fit of T(g) evolution as a function of water content showed that glutenin-rich fractions were more sensitive to water plasticization than the gliadin-rich fraction. The Kwei equation gave better fit to experimental data and demonstrated that the water plasticization of gluten and its fractions is influenced by secondary interactions. However, the application of the Couchman-Karasz equation without fitting predicts satisfactorily the plasticization of gluten proteins by water.

Thermal properties of corn gluten meal and its proteic components.

Thermal properties of corn gluten meal (CGM) and of its extracted proteic components (zein and glutelin) at 0% moisture content, is studied by dynamic mechanical thermal analysis (DMTA) and modulated differential scanning calorimetry (MDSC). The glass transition temperature (Tg) on first heating, is measured at 176 and 174 degrees C, respectively, for hot-air-dried and native CGM. For zein and glutelin isolated fractions, the measured Tg values are 164 and 209 degrees C, respectively. The calculated Tg from using Matveev's method (Matveev YI. Spec Publ R Soc Chem 1995;156;552) is in good agreement with experimental data for zein, a well defined protein. MDSC allows the measurement of change in heat capacity at Tg (deltaCp) with a single heating scan, avoiding sample alteration, and deltaCp values are 0.365 J/g per K for zein and 0.184 J/g per K for glutelin. The differences observed in Tg, relaxation temperatures, deltaCp and tan delta peak height are related to differences in the structure of the proteins, through the cross-linkages and hydrogen or van der Waals interactions. Experimental data from DMTA and MDSC, and the Couchman-Karasz thermodynamic approach indicate that CGM behaves as a miscible blend of its components, with high non-polar interactions between zein and glutelin proteins.

The introduction of a new MRI index to evaluate sagittal patellofemoral engagement.

INTRODUCTION: Patella alta is one of the primary factors of patellofemoral instability and its importance lies in the reduced engagement between patella and trochlea during the early degrees of flexion. The evaluation of patellar height is based on conventional x-rays, CT scan and, more recently, MRI. The objective of this multicentric prospective study is to describe a novel index to assess in the sagittal plane the functional engagement between patella and trochlea. MATERIALS AND METHODS: One hundred and thirty-five patients with objective patellar dislocation were prospectively enrolled between April 2010 and September 2011 and were compared with a second group of 45 controls. All patients underwent a standard MRI and a complete radiographic study. Sagittal engagement was measured as the ratio between the articular cartilage of the patella and the trochlear cartilage length measured on two different MRI slices. RESULTS: The mean Sagittal Patellofemoral Engagement (SPE) index was 0.43 ± 0.18 and ranged from 0.02 to 0.913 in the Objective Patellar Dislocation group versus 0.42 ± 0.11 range 0.22 to 0.55 in controls. In the Patellar Dislocation group the mean Caton-Deschamps index was 1.18 ± 0.21 (range 0.71 to 1.91). There were 58 patients with patella alta, in whom the mean SPE was 0.39 ± 0.18 (range 0.02 to 0.87). Sagittal engagement was significantly higher when compared with patients in the Patellar Dislocation group who had no patella alta (mean 0.46 ± 0.16, range 0.1-0.913). DISCUSSION: The present study introduces a new method to measure the SPE with the use of MRI. The evaluation of the functional engagement of the patella with the femoral trochlea in the sagittal plane can serve as a supplementary tool to the existing methods of evaluating patellar height, and may help to better identify the cases where inadequate engagement is recorded despite the absence of patella alta, so that the need for tibial tuberosity osteotomy may be re-assessed.

Axial MRI index of patellar engagement: a new method to assess patellar instability.

INTRODUCTION: The aim of this study was to define a new index to measure lateral patellar displacement (LPD) using nuclear magnetic resonance imaging (MRI), an axial index of engagement of the patella (AEI) obtained from two different axial MRI views then to validate its use in a prospective series of patients presenting an objective patellar instability (OPI). MATERIALS AND METHODS: One hundred and thirty-five patients with OPI and no history of surgery of the patella were included in a prospective study organized by the French Society of Arthroscopy performed between June 2010 and August 2012. All patients underwent axial and sagittal MRI. The AEI was obtained by projecting predefined patellar and trochlear landmarks (cartilaginous landmarks) on 2 different axial MRI views (one trochlear and one patellar). The results were compared with a series of controls (n=45). RESULTS: The preoperative AEI of the patella was 0.94 ± 0.09 for the control group and 0.84 ± 0.16 for OPI group (P=0.000016). The AEI could be obtained in 100% of the cases if it was measured on 2 MRI views while it could not be measured in 38.5% of the cases if the measurement was only obtained from one MRI view or whenever the widest part of the patella was not across from the femoral trochlea. The AEI did not significantly depend on dysplasia or the presence of a supratrochlear spur. The lowest AIE values were associated with trochlear dysplasia with a supratrochlear spur (P=0.0023) and a more prominent trochlea (P=0.0016). The AEI was correlated with patellar tilt (P<0.000001) and TT-TG on MRI (P<0.000001). DISCUSSION: AEI is a new index to measure LPD. It can be obtained in all cases because it is obtained from two different MRI views. The normal value is close to 1. It can be used to measure patellar instability on the axial plane in patients with OPI, especially in the most severe cases.

Painful medial knee compartment syndrome in over-45-year-olds. II--technical note: Biomechanical considerations: theoretic analysis of load distribution in the knee according to plane and to gait phase.

Varus deviation as defined by Thomine is the basis for understanding load distribution between the medial and lateral tibial plateau; it was originally defined in the frontal plane. Analysis in the sagittal and horizontal planes leads to a concept of varizing area. Varizing area sheds light on how, during gait, load predominates in the medial and posteromedial knee. It also accounts for the following two findings: (a) degenerative lesions are mainly medial, even when the mid-knee axis is normal; (b) degenerative lesions are mainly posterior.

Painful medial knee compartment syndrome in over-45 year-olds: I--medical or surgical management: a series of 174 patients.

INTRODUCTION: There is at present no consensus on the management of degenerative medial meniscus lesions in patients aged over 45 years without proven osteoarthritis, especially given that the causal relation between degenerative meniscal lesion and osteoarthritis remains controversial. A prospective multicenter non randomized study was therefore performed. The principal objective was to assess surgeons' practice in the management of degenerative medial meniscus lesions. The secondary objectives were to identify predictive and prognostic factors and to compare medical versus surgical attitudes so as to draw up an adapted treatment strategy. PATIENTS AND METHOD: One hundred and seventy-four patients were included between September 2008 and February 2010, and distributed between a surgical (n=104) and a medical group (n=70). Minimum follow-up was 6 months. Patient satisfaction and health-related quality of life on the SF-36 questionnaire were assessed at 6 months. RESULTS: No difference emerged between the surgical and medical groups. However, predictive factors for poor results were identified: overweight (p=0.005), cartilage lesions (p=0.035) and meniscus extrusion (p=0.006). DISCUSSION: Results clarified the relation between degenerative meniscus lesions and osteoarthritis, in terms of meniscal incompetence. Meniscal extrusion should be seen as an arthrogenic degenerative meniscus lesion. We recommend a management strategy based on terrain and imaging data (X-ray and MRI), with the aim of providing patient relief while conserving cartilage.

Recent innovations in edible and/or biodegradable packaging materials.

Certain newly discovered characteristics of natural biopolymers should make them a choice material to be used for different types of wrappings and films. Edible and/or biodegradable packagings produced from agricultural origin macromolecules provide a supplementary and sometimes essential means to control physiological, microbiological, and physicochemical changes in food products. This is accomplished (i) by controlling mass transfers between food product and ambient atmosphere or between components in heterogeneous food product, and (iii) by modifying and controlling food surface conditions (pH, level of specific functional agents, slow release of flavour compounds), it should be stressed that the material characteristics (polysaccharide, protein, or lipid, plasticized or not, chemically modified or not, used alone or in combination) and the fabrication procedures (casting of a film-forming solution, thermoforming) must be adapted to each specific food product and usage condition (relative humidity, temperature). Some potential uses of these materials (e.g. wrapping of various fabricated foods; protection of fruits and vegetables by control of maturation; protection of meat and fish; control of internal moisture transfer in pizzas), which are hinged on film properties (e.g. organoleptic, mechanical, gas and solute barrier) are described with examples.

[Intermediate moisture foods: polysaccharide and protein gels]. / Aliments a humidité intermédiaire: gels polysaccharidiques et protéiques.

The aim of this study was to prepare concentrated foods (20-40 p. 100 water), edible as such, chemically and microbiologically stable, nutritionally balanced, and which could be used as meal substitutes (travel, camping, snacks, etc.). With high methoxyl pectins, it was possible to obtain a pectic gel (pH 3,5), similar to a fruit jelly, but containing 20 p. 100 d.w. protein, and less sucrose. Water activity (Aw) was 0,75-0,78, for a 25 p. 100 water content, as a result of adding glucose syrup and sorbitol. After 4 months storage at 20 or 38 degrees C in aluminium pouches, no mold growth was detected (even following prior inoculation) nor practically any change in flavor, texture of Aw. With low methoxyl pectins, gel foods richer in water (35 p. 100), softer, less acid (pH 4,3) and containing even less sugars have been prepared (26 p. 100 d.w. protein, 35 p. 100 carbohydrates, 15 p. 100 lipids). Aw was lowered to 0,84 by adding humectants (sucrose, glycerol, sorbitol, citric acid, sodium citrate and chloride). Starch gels (40 p. 100 starch/d.w.), of pH less than 4,5, containing proteins and lipids, were flavored with vegetale powders. For 30 p. 100 water and with humectants, Aw was 0,84-0,88. The texture changes more or less favorably with time according to the nature of the starch used. Using the technology of processed cheeses, protein gels were made with either of the following characteristics: 1. A reduced Aw (0,86, for 38 p. 100 water) by adding humectants, but with a soft texture similar to that of a processed swiss cheese; 2. The same reduced Aw, with a starch content of 26 p. 100/d.w., and a harder texture, comparable to that of Emmenthal cheese.

Sentinel lymph node detection for breast cancer: which patients are best suited for the patent blue dye only method of identification?

BACKGROUND: The objectives of this study were, first, to define the preoperative criteria for using solely the blue dye method and, second, to decrease its operator dependence in predicting axillary lymph node status. METHODS: Two hundred fifty-three women consecutively identified with operable breast cancer underwent sentinel lymph node (SLN) detection by the patent blue dye method followed by completion axillary lymph node dissection. A standard pathological examination was performed for all SLN. Then, a pathological color quality assessment (PCQA), which checked for the presence of the blue dye, was performed on the paraffin blocks of the nonmetastatic SLN. Six preoperative identifiable variables likely to influence the detection rate were examined. RESULTS: The surgical detection (sd) rate was 84% (213 of 253) and the PCQA rate was 73% (185 of 253). Only breast size (sd, P = .0005; PCQA, P = .0007) and body mass index < or =30 (sd, P = .005; PCQA, P = .0007) were significant for SLN identification. Multivariate analysis revealed two independent factors influencing SLN identification: breast size (sd, P = .0001; PCQA, P = .002) and the timing of injection-injection prior to lumpectomy (sd, P = .04). CONCLUSIONS: The optimal patient features for identifying the SLN by the patent blue dye method are small or medium-sized breasts, low body fat, and that the procedure is carried out prior to tumor excision. The PCQA offers a useful second assessment of the surgically removed SLN, introducing an independent element of quality control.