Search

To improve the sensory quality of Moroccan red press wines, press wines were separately submitted to micro-oxygenation and three fining agents (gelatin, Polyvinylpolypyrrolidone (PVPP) based formulation and pea protein) treatments at the winery Chateau Roslane, Morocco. The results showed that each treatment has a distinct behavior in relation with interactions and precipitation monomeric fiavan-3-ol and fractions apparent and total condensed tannins. The fining agent corresponding to the vegetable protein has a greater affinity with the fraction of oligomeric condensed tannins with apparent aDP: 3.2. However, gelatin and PVPP based fining agent have an affinity with the catechin and epicatechin as well as with the fraction of polymeric tannins (apparent aDP: 6.6). For the structural parameters of proanthocyanidins, no significant differences were found out in global aDP and percentage of prodelphinidin between the different treatments. The global percentage of galloylation appeared slightly affected, while the global percentage of oxidized proanthocyanidins increased (9%) significantly (P < 0,05) for micro oxygenation treatment, unlike the fining agent has basic vegetable protein has decreased 36% the percentage of oxidation. For the Saliva Precipitation Index (SPI) and sensory analysis, the greatest reduction of SPI, bitterness and astringency was observed for both basic PVPP and vegetable protein fining agents.

In the present study, composite egg white/gelatin hydrogels were produced and their porosity was increased through the subsequent removal of gelatin by leaching into water. The composite gel with 0.5% gelatin showed a higher degree of swelling than did the control gelatin-free sample after 60 min of immersion in an aqueous medium which was ascribed to the formation of capillary channels due to gelatin leaching. The composite gel containing 0.3% gelatin showed the highest water-holding capacity and firmness indices among all samples. Gel porosity decreased with increasing gelatin content. However, after gelatin depletion, higher concentrations of gelatin yielded hydrogels with higher porosity, as confirmed by scanning electron microscopy. Based on Fourier transform infra-red spectroscopy, it was concluded that the count of hydrogen bonds decreased after gelatin depletion. X-ray diffraction analysis indicated that intermolecular interaction between gelatin and egg white proteins had taken place in the amorphous phase.

Gelatin is used to make hard capsules and has to meet strict dissolution specifications to guarantee homogeneous drug delivery. The aging of gelatin induces a decrease of its dissolution rate due to the formation of intra- and intermolecular cross-links. Cross-link formation has shown to be dependent on the environmental conditions of production, such as temperature and humidity, and therefore on the geographic origin of production. Gelatin structure consists of an amorphous phase (coil structure) and a crystal phase (triple-helixes) and is very sensitive to environmental changes. The present work aims at understanding the role and effects of structural changes during aging on gelatin dissolution, taking into account the origin of production. The molecular structure of pig skin gelatins from three different production sites of the same company were studied by differential scanning calorimetry, synchrotron circular dichroism and 1H nuclear magnetic resonance. It turned out that aging induced the melting of triple-helixes, an increase of random coils and, probably, β-turn conformations. The gelatin structure varied with the origin of production and thus affected the dissolution rate. Gelatins with non-compliant dissolution rates exhibited a higher amount of amorphous phase after aging than compliant gelatins. Although it was not possible to formulate any certain interpretation of the synchrotron circular dichroism results regarding gelatin dissolution, this technique is able to differentiate compliant dissolutions from non-compliant ones, even before gelatin aging.

The gelatin is an animal protein that comes from collagen skin or bone. It is used in pharmaceutical industry to make hard capsules. The variations of environmental conditions of production applied to the collagen and therefore gelatin may have an impact on its chemical composition and, as a consequence, on the capsules properties (1). Indeed, previous studies revealed that the gelatin tends to form cross-links between its amino acids in high temperature and humidity conditions or in the presence of chemical compounds as aldehydes (sugars, lipids, oxidations) (2). To understand the impact of the processing on the chemical composition of the gelatin, pig skins gelatin produced under different environmental conditions were analyzed in High-Resolution Magic Angle Spinning NMR (HRMAS). 1D proton NMR spectra were acquired and analyzed using PCA (Principal Components Analysis). The environmental conditions of production were discriminated and the spectral zones contributing to separate them showed differences on the amino acids composition and their structural arrangement. However, the abundance of amino acids masked the possible presence of other molecules. In our conditions, the HRMAS, alone, did not allow identifying all the molecules as the cross-links, sugars or lipids, but suggested the formation of Desmosine-type cross-link under one environmental condition of production.

Pig skins gelatin results of the collagen solubilization. Gelatin is used, amongst other applications, in the pharmaceutical industry to make hard capsules. Raw gelatin, on delivery, contains about 8-12% of water [1] and is a partially-crystalline polymer being composed of an amorphous phase (coil structure with primary chains) and a crystal phase [2]. The latter consists of partially reformed triple-helices of collagen. The shelf life of hard capsules is evaluated through gelatin USP dissolution test after aging under high temperature and high humidity conditions. After aging, the dissolution rate of gelatin is variable: either unchanged or reduced. The decrease of gelatin dissolution rate is partially due to intra- and intermolecular crosslinks formation in the amorphous phase which stabilize that structure [3]. Water in gelatin plays a role of plasticizer in the amorphous phase and is either free or bound to the polymer chains. The state of water in gelatin has been studied but no relation with aging or dissolution rate has been established. The aim of the present study was to understand how aging affects the gelatin structure and its water mobility, and in addition, to identify structural differences according to gelatin dissolution rate. Thus, sixty pig skin gelatins with correct and non-correct dissolution rate were analyzed using Differential Scanning Calorimetry (DSC). Proton Nuclear Magnetic Resonance (1H-NMR) spectroscopy was used on a subgroup of twelve gelatin films to measure the spin-spin relaxation time (T2). For both methods, samples were taken before and after aging. Aging decreased the amount and the stability to heating of crystals phase and increased the amorphous phase. The water mobility was increased which can be explained by the denaturation of crystals releasing the trapped water from the triple-helices [4]. After aging, the gelatins which failed the dissolution test showed a higher amount of amorphous phase but the water mobility was not modified. These results showed that the structure plays a major role in the gelatin dissolution rate. In order to support this major role of structural characteristics of gelatin, the conformation of the single chains and multiple helices will be assessed using circular dichroism.

The innovative use of gelatin as a temperature sensor based on capacitance was studied at a temperature range normally used for meat cooking (20–80 °C). Interdigital electrodes coated by gelatin solution and two sensors of different thicknesses (38 and 125 µm) were studied between 300 MHz and 900 MHz. At 38 µm, the capacitance was adequately measured, but for 125 µm the slope capacitance versus temperature curve decreased before 900 MHz due to the electrothermal breakdown between 60 °C and 80 °C. Thus, for 125 µm, the capacitance was studied applying 600 MHz. Sensitivity at 38 µm at 868 MHz (0.045 pF/°C) was lower than 125 µm at 600 MHz (0.14 pF/°C), influencing the results in the simulation (temperature range versus time) of meat cooking; at 125 µm, the sensitivity was greater, mainly during chilling steps. The potential of gelatin as a temperature sensor was demonstrated, and a balance between thickness and frequency should be considered to increase the sensitivity.

Gelatin, extracted from the collagen of animal’s skins or bone, is used, amongst other applications, in the pharmaceutical industry to make hard capsules. Dried gelatin contains about 10-12 % water and is a partiallycrystalline polymer being composed of an amorphous phase (coil structure with primary chains) and a crystal phase. The latter consists of triple-helical fragments that are remnants of the triple-helices naturally found in collagen. Dried gelatin, placed under high temperature and high humidity conditions, a step called aging in industry, tends to loose water solubility in time. This is due to intra- and intermolecular crosslinks formation which modify and stabilize the structure. Aging is always applied to gelatin to test the shelf life of hard capsules. A wide range of variable environmental conditions (pH and time, temperature, humidity …) are observed in the production process and the storage of gelatin. Our goal was to understand how aging and the production sites affect the dried gelatin’s internal structure and if structural differences were involved in the dissolution variability. For that purpose, sixty pig skin gelatins from different origins of production with different dissolution characteristics (pass or fail the USP dissolution test) were analysed using Differential Scanning Calorimetry (DSC) as a function of aging. Significant differences in glass transition temperatures, melting temperatures and the enthalpies of melting were observed according to the origin of production of the samples (different factories). The results showed that the amount of crystals and their stability to heating decreased with aging while the amorphous phase increased. Gelatins from different production sites display different amounts of crystals and a differential stability of both amorphous and crystalline phases. After aging, the gelatins which failed the dissolution test showed a higher amount of amorphous phase. On the basis of these results, schemes of the gelatin structure were proposed.

Modelling is essentially a way of representing processes or phenomena to explain the observed data and to predict behavior under different conditions. Very few data is available about small solutes diffusion in cheese and in particular how cheese matrix composition or microstructure can affect this diffusion (Floury et al., 2010). Nisin(positively charged bacteriocin, 3354 Da) has been chosen as a model of small solutes. Up to now, nisin diffusion has been studied only in agarose gel and packaging films.

Proton magnetic resonance was used to characterize the dynamics of water in gelatin. Both sol and gel states were investigated. Transverse relaxation rates (R-2) were dependent on the proton frequency measurement. (R-2) measured with the Carr-Purcell-Meiboom-Gill pulse sequence was dependent on pulse spacing. These observations were interpreted in terms of chemical exchanges between water protons and those of the macromolecules in the sol state, whereas in the gel state the contribution of diffusion through microheterogeneities in the sample seems to provide an additional transverse relaxation mechanism.