Proton spin–spin relaxation time of peel and flesh of navel orange varieties exposed to freezing temperature

Proton spin–spin relaxation times (T₂) of peel (albedo and flavedo) and juice sacs (flesh segments) of navel oranges were measured at 10 MHz using a Bruker Minispec PC 110 NMR spectrometer. The oranges were subjected to chilling (5 °C) and freezing (−7 °C) temperatures for 20 h and warmed to room temperature before peeling for T₂ measurements. The exposure to chilling or freezing temperature did not affect the T₂ values of peel, but freezing caused an appreciable decrease (∼15%) in the T₂ values of flesh segments of the varieties of navel oranges studied. When the peel was exposed to −20 °C, the T₂ showed a drastic reduction suggesting that the peel did not freeze at −7 °C. The possible cause of reduction in the T₂ values when exposed to freezing temperature may be damage to the juice sac membrane and leakage of juice out of the sac. The difference in the T₂ values between juice sacs of freeze-affected and normal oranges can potentially be used for detection of freeze-damaged fruits. Copyright © 2005 Society of Chemical Industry     

Characterization of water distribution in xanthan-curdlan hydrogel complex using magnetic resonance imaging, nuclear magnetic resonance relaxometry, rheology, and scanning electron microscopy

Abstract: Xanthan‐curdlan hydrogel complex (XCHC) has been shown capable of retaining moisture up to 5 freeze‐thaw cycles (FTCs); however, moisture distribution in the complex in relation to the hydrogel composition and structure remains uncharacterized. In the present study, magnetic resonance imaging (MRI), nuclear magnetic resonance (NMR) relaxometry, rheology, and scanning electron microscopy (SEM) were used to examine the effect of water distribution and interaction with 2.0% aqueous solutions of xanthan, curdlan, and XCHC consisting of equal amounts of both polysaccharides. A gel structure with an indication of syneresis was clearly seen in the MR image of curdlan alone, whereas the distribution of protons throughout xanthan and XCHC samples remained homogeneous and showed no detectable syneresis. The three‐dimensional network, indicated by frequency sweeps, of curdlan was responsible for curdlan's gel structure. The frequency sweep and slope of the storage modulus (G′) of XCHC was significantly closer to curdlan with higher elasticity and less dependency upon angular frequency than xanthan alone. The reduction in XCHC dynamic moduli (G′ and G″) compared to curdlan could be attributed to the formation of wavy layers instead of a fully cured three‐dimensional structure. Addition of xanthan to curdlan restricted XCHC spin–spin relaxation time (T₂) to intermediate and slower exchange regimes, namely approximately 110 and 342 ms, respectively, promoting the polymer's interaction with water while inhibiting interpolymer interactions found in curdlan. A 3rd proton pool with the slowest T₂ seen in curdlan was not found in XCHC, correlating to the absence of syneresis. Practical Application: The combination of texture measurements and discrete noninvasive techniques was found capable of providing insightful understanding of water distribution in a gel system. These techniques may be applied to other hydrogel complexes. The XCHC system investigated has the potential to enhance freeze‐thaw stability in frozen food products by minimizing syneresis due to undesirable temperature fluctuations during distribution and consumer application.     

Extrusion cooking of barley flour and process parameter optimization by using response surface methodology

BACKGROUND: The nutritional profile of barley places it in a prime position for development of a new extruded–expanded snack food with health benefits. It was therefore the aim to investigate the effect of extrusion processing variables on system parameters (specific mechanical energy, die pressure and die melt temperature) and physical properties (expansion, bulk density, texture and color) of barley flour extrudates and to optimize processing conditions for production of extruded snack food from barley flour by response surface methodology. RESULTS: Barley flour with 219.7 g kg^?1 moisture content was extruded at different die temperatures (140–160 °C) and screw speeds (150–200 rpm) through a co‐rotating twin‐screw extruder. The system parameters as well as product responses were mainly dependent on temperature, whereas the screw speed imparted a lesser effect. Extrudates produced under extrusion conditions of 160 °C, 150 and 200 rpm and at 164 °C and 150 rpm had higher preference levels of appearance, taste, texture and overall acceptability than that of other selected extrudates for sensory analysis. The optimal conditions for minimum bulk density and desired textural characteristics and color of extrudates correspond to a temperature of 156 °C and screw speed of 166 rpm. CONCLUSION: The results suggested that use of barley flour in extruded snack products offers a desirable variation in diet and can take advantage of the nutritional quality of barley. Copyright © 2008 Society of Chemical Industry     

Compressibility and relaxation of fiber reinforcements during composite processing

In many reinforced composite manufacturing processes it is necessary to compact the fiber materials to obtain the desired fiber/resin ratio in the finished part. Detailed knowledge of applied surface force versus material fiber volume is particularly important in processes such as pultrusion, resin transfer molding, and compression molding. The force required to compact a stack of reinforcing material is strongly dependent on the type of fiber used and its material form. Complicated interactions are possible, particularly when mixtures of unidirectional, oriented cloth and random fiber mats are used. This paper will present results of an experimental and analytical investigation of the response of various dry reinforcing materials subjected to compressive forces applied normal to their principle plane. Experiments were conducted by applying up to 8.6 MPa normal force to thick stacks of E-glass, graphite cloth, mat and unidirectional material and combinations of two different fiber orientation. Pressure versus fiber volume data were generated for both individual materials and various combinations. Experimental results were compared to analytical predictions. Data showed that the force versus deformation is very strongly dependent on the details of the fiber form or forms being used. There is structural relaxation during fiber compression. Relaxation is very related to fiber orientation, span length, and fiber breakage during compaction. Relaxation behavior decreases with fiber alignment. Random mats and 0/90 cloth show much more relaxation than unidirectional fibers. Data of relaxation is very well fitted with a Maxwell-Wiechert viscoelastic model.     

Assessment of empirical algorithms for bathymetry extraction using Sentinel-2 data

Bathymetry estimated from optical satellite imagery has been increasingly implemented as an alternative to traditional bathymetric survey techniques. The availability of new sensors such as Sentinel-2 with improved spatial and temporal resolution, in comparison with previous optical sensors, offers innovative capabilities for bathymetry derivation. This study presents an assessment of the fit between satellite data and the underlying models in the most widely used empirical algorithms: the linear band model and the log-transformed band ratio model using Sentinel-2A data. Both models were tested in two study areas of the Irish coast with different morphological and environmental conditions. Results showed that the linear band model fitted better than the log-transformed band ratio model providing coefficient of determination values, R², between 0.83 and 0.88 (0 m–10 m) for the five images considered in the study. The closest fit was found in the depth range 2 m–6 m. Atmospheric correction, bottom type influence, and water column conditions proved to be key factors in the bathymetric derivation using these satellite datasets.     

Coronary artery fistula after cardiac transplantation

A cardiac transplant recipient with multiple coronary artery fistulae draining into the right ventricle is described. These fistulae presumably resulted from repeated endomyocardial biopsies. The diagnosis of coronary artery fistulae was made at the annual coronary arteriography. The magnitude of the shunt remained small over eight years of follow-up.     

Congenital cystic diseases of liver and extrahepatic bile ducts

The paper presents 30-year experience in treating 158 patients with congenital cystic diseases of the liver and bile ducts. Depending on the pattern of hepatobiliary lesions, the diagnostic value of techniques, such as ultrasound, computerized tomography, scintigraphy of the liver duodenoscopy with THCG was defined. Analyzing the late outcomes provided recommendations for the most optimal surgical management: cystic fenestration and tunneling in hepatic polycystosis, pericystectomy in solitary cysts of the liver, different varieties of bile draining operations in choledochal cysts and Caroli's disease.