Instantaneous Compliance Research Articles

Wakame replacement alters the metabolic profile of wheat noodles after in vitro digestion

The development of nutritional noodles of high quality has become a new hotspot of research in the area of food science. Since wakame is edible seaweed rich in dietary fiber and proteins and rarely found in ordinary noodle, this study investigated the release of metabolites, the texture quality, and the rheological properties of wakame noodle, as well as the mechanism by which extruded wakame flours can influence noodle texture and viscoelasticity through digestion. Basically, nuclear magnetic resonance spectra were applied to identify the 46 metabolites including amino acids, saccharides, fatty acids, and other metabolites. Both PCA and OPLS-DA model showed fit goodness and good predictivity, which were assessed the increasing release of most metabolites. Structural studies discussed the effects on the enhancement of interlinkage with gluten matrix and protein matrix, which were validated via the decreasing instantaneous compliance J0 (1.64 × 10-5 to 0.16 × 10-5 Pa−1). Wakame addition best matched the physiochemical properties of noodle, in terms of chewiness (99.10 vs 122.66 g.mm), gumminess (281.98 vs. 323.44 g), and gel strength (132.65 vs 173.95 kPa•s−1). Beyond the functional characteristics it contributes benefits like reduction of diet-related diabetes. As a consequence, the creation of personalized nutritious, healthy noodles will be an innovative route from a scientific viewpoint and an application standpoint.

Improving the texture and rheological qualities of a plant-based fishball analogue by using konjac glucomannan to enhance crosslinks with soy protein

Global fisheries pressure generates interest in sustainable seafood production and developing plant-based seafood. This study took fishball as an example of seafood products applying konjac glucomannan (KGM) in developing plant-based fishball (PFB) analogues mimicking the texture of fishball. Increasing KGM concentration (up to 8.0%) influenced texture and rheological properties of PFB progressively, where the hardness, chewiness, and gel strength of PFB were significantly enhanced. Decreased pH value (9.38 to 7.93) and increased α-helix, β-sheet, and helix/coil ratio (1.40 to 1.70%) validated a promotion of hydrogen bonds and ordered structures by KGM. The strengthened interaction strength and hydrogen bonds formed at -OH groups of KGM and amide linkage of soy protein could be responsible for textural improvement. A more compact and regular microstructure also validated a firmer texture in PFB with higher KGM levels. Besides, KGM (3.5–8.0%) significantly decreased instantaneous compliance J0 (101.3 × 10−6 to 58.1 × 10−6 Pa−1), indicating denser crosslinks and firmer structures. In conclusion, KGM improved the texture and viscoelasticity of PFB and had an excellent application value in developing plant-based seafood analogues.

Effect of Citrus Fiber on the Rheological Properties of Dough and Quality of the Gluten-Free Bread

The aim of the study was to evaluate the use of citrus fiber for the nutritional enrichment and technological improvement of gluten-free bread. A partial replacement of starch in bread formulation was analyzed in terms of the dough’s rheological properties and selected quality parameters of the bread. The results allowed to conclude that the presence of citrus fiber modifies the rheological properties of the dough, causing an increase in storage modulus (G′) and loss modulus (G″) values, as well as zero shear viscosity, accompanied with a decrease in instantaneous compliance (J0) and viscoelastic compliance (J1) to the applied stress, which reflects dough strengthening caused by significantly greater water binding and swelling properties characteristic of this ingredient. The introduction of the citrus fiber to bread formulations caused a significant decrease in bread volume and structure changes in crumb visible in the larger porosity and average pore size. The presence of citrus fiber affected texture, decreasing crumb hardness, springiness, cohesiveness and chewiness in comparison to the control. It could also be observed that the use of citrus fiber results in limited crumb hardening during storage, which indicates that this component could be an effective factor retarding the staling of the gluten-free bread based on starch and hydrocolloids.

Myosin Cross-Bridge Behaviour in Contracting Muscle-The T1 Curve of Huxley and Simmons (1971) Revisited.

The stiffness of the myosin cross-bridges is a key factor in analysing possible scenarios to explain myosin head changes during force generation in active muscles. The seminal study of Huxley and Simmons (1971: Nature 233: 533) suggested that most of the observed half-sarcomere instantaneous compliance (=1/stiffness) resides in the myosin heads. They showed with a so-called T1 plot that, after a very fast release, the half-sarcomere tension reduced to zero after a step size of about 60Å (later with improved experiments reduced to 40Å). However, later X-ray diffraction studies showed that myosin and actin filaments themselves stretch slightly under tension, which means that most (at least two-thirds) of the half sarcomere compliance comes from the filaments and not from cross-bridges. Here we have used a different approach, namely to model the compliances in a virtual half sarcomere structure in silico. We confirm that the T1 curve comes almost entirely from length changes in the myosin and actin filaments, because the calculated cross-bridge stiffness (probably greater than 0.4 pN/Å) is higher than previous studies have suggested. Our model demonstrates that the formulations produced by previous authors give very similar results to our model if the same starting parameters are used. However, we find that it is necessary to model the X-ray diffraction data as well as mechanics data to get a reliable estimate of the cross-bridge stiffness. In the light of the high cross-bridge stiffness found in the present study, we present a plausible modified scenario to describe aspects of the myosin cross-bridge cycle in active muscle. In particular, we suggest that, apart from the filament compliances, most of the cross-bridge contribution to the instantaneous T1 response may come from weakly-bound myosin heads, not myosin heads in strongly attached states. The strongly attached heads would still contribute to the T1 curve, but only in a very minor way, with a stiffness that we postulate could be around 0.1 pN/Å, a value which would generate a working stroke close to 100 Å from the hydrolysis of one ATP molecule. The new model can serve as a tool to calculate sarcomere elastic properties for any vertebrate striated muscle once various parameters have been determined (e.g., tension, T1 intercept, temperature, X-ray diffraction spacing results).

Evaluating the viscoelastic properties of soy protein isolate by creep–recovery behavior

The viscoelastic properties of soy protein isolate (SPI) were investigated by creep–recovery under creep time (75 s, 150 s, 300 s, and 600 s), shear stress (1 Pa, 6 Pa, 10 Pa, and 20 Pa), and creep temperature (25°C, 50°C, and 80°C). Creep compliance (JC) increased proportionally with creep time from 75 to 600 s and with stress from 1 to 20 Pa, it decreased proportionally with temperature from 25 to 80°C. Results showed that the flow behavior of SPI varied along with creep time, stress, and temperature. Creep compliance data were best-fitted to 4-element Burgers model (R2 > .94), the instantaneous compliance (J0), retardation compliance (J1), retardation time (r1), steady-state viscosity (η0), and recovery (%) have significant changes with creep time, stress, and temperature (p < .05). Adding maltodextrin (MD) accelerated the deformation of SPI. The flexibility and rigidity of SPI molecular chains was dependent on creep time, stress, and temperature. Practical applications In this research paper, we studied the viscoelasticity of SPI using the creep–recovery analysis. The chain flexibility, rigidity, and viscidity of SPI molecules were discussed at creep time, shear stress, and creep temperature. At the same time, the viscoelasticity of SPI adding of MD is also discussed. According to the experiment, this study provides new insights into the viscoelastic properties of SPI and builds a fundamental foundation for the comprehensive utilization of SPI in the food industry.

Effect of the viscoelastic properties of modified starch as a wall material on the surface morphology of microcapsules.

Since microcapsule technology has a good protective effect on unstable bioactive substances, many studies have focused on exploring the best technical conditions for forming microcapsules. Modified starch is a microcapsule wall material with good emulsifying and film-forming properties. The objective of this work was to study the creep-recovery behavior of modified starch pastes for various creep time, shear stress and temperature. Furthermore, the effect of creep-recovery behavior on the morphology of microcapsules made of the modified starch was investigated. The maximum creep compliance (Jmax ), instantaneous compliance (J0 ) and retardation compliance (J1 ) of modified starch increased proportionally with increasing creep time and shear stress but decreased with increasing temperature. The Newtonian viscosity (η0 ) increased with increasing creep time and temperature but decreased with increasing shear stress. The recovery rate of the modified starch pastes varied from 0.92 to 33.68% in the creep-recovery test conditions. Creep-recovery data could be well explained by a four-parameter Burgers model (R2 > 0.918). Modified starch pastes exhibited time-, stress- and temperature-dependent creep-recovery behavior. The Jmax values of modified starch pastes were low(<0.20 Pa-1 ) and the η0 values high (>3.5×103 Pa s) for all test conditions. The results revealed the modified starch pastes had a good rigid network structure to resist deformation but recovery was difficult once deformation occurred. Microcapsules produced using the modified starch exhibited a small deformation with regular spheres and some dents, consistent with the results of creep-recovery tests. © 2019 Society of Chemical Industry.

Effects of amino acids on gelatinization, pasting and rheological properties of modified potato starches

The effects of amino acids – cysteine (Cys), glutamic acid (Glu) and lysine (Lys) – on gelatinization, pasting and rheological properties of chemically modified starches including distarch phosphate (E 1412), acetylated distarch phosphate (E 1414) and acetylated distarch adipate (E 1422) were studied. The amino acids were added at 0.2 mol/kg of the starch dry weight. Glu contributed to an increase in gelatinization temperatures of the E 1412 and E 1422 starches, while the same effect, additionally accompanied by increase in gelatinization enthalpy, was found for Lys in the E 1414 and E 1422 systems. Addition of the amino acids decreased peak viscosity of the E 1412 and E 1422 pastes by 26.3–40.8% and 2.3–24.9%, respectively. Furthermore, the amino acids lowered final viscosity of these starches by 9.4–37.7% and 3.9–36.5%, respectively. Significant effects of Glu on pasting behaviour of E 1414 included reductions in both percentage breakdown and percentage setback in viscosity. Mechanical spectra showed that all the systems studied behaved as weak gels. The G′ and G″ values of the E 1412 and E 1422 gels with amino acids were lower than those determined for the respective control samples. The results of creep and recovery test revealed that a common effect of Lys in all the modified starch systems was an elevation of instantaneous compliance (J0) and reduction in retardation time (λret), whereas the effect of the other amino acids on rheological parameters were dependent on the type of starch.

Using the mixture design approach to predict the rheological properties of low-calorie dairy desserts containing gum tragacanth exuded by three Iranian Astragalus species.

In this study, the flow behavior and creep parameters of saffron desserts containing gum tragacanth combinations of three species were modeled by the mixture design approach. Flow behavior and creep-recovery experiments were performed and models were predicted for apparent viscosity, consistency index, flow index, instantaneous compliance, and viscoelastic compliance. Five representative samples regarding the range of apparent viscosity at the shear rate of 50s-1 were subjected to sensory evaluation. According to rheological measurements, the addition of GT species of A. gossypinus led to the production of a dessert with a strong structure. Then, two samples with the highest consistency index and the lowest creep parameters were compared with two commercial saffron desserts. The results revealed that the overall acceptance of the two selected samples [containing 4% (w/w) A. gossypinus or 2.66% (w/w) A. gossypinus and 1.33% (w/w) A. fluccosus] was similar to those of the two commercial samples.

Study of fracture resistance of a weldment with a propagating crack

The overall fracture resistance of a weldment with a propagating crack across the weld, HAZ and base material has been evaluated for a AISI type 316LN stainless steel (SS), based on coupled experimental-finite element analysis. Compact type (CT) specimens with initial crack tip in the weld, heat affected zone (HAZ) and base material have been tested to evaluate J-integral resistance curve (J-R curve) across the weldment. Towards evaluating the J-integral for a heterogeneous material, elastic component of J was determined using equivalent Young's modulus (Eeq) in terms of instantaneous compliance and crack depths. Simultaneously, finite element (FE) analyses have been carried out to estimate J-integrals for various contours across the weldment and for nodal singularities along interfaces, leading to a modified J-integral for overall weldment. The reasonable agreement among experimental J values from different regions with the modified J-integral values gives credence to this procedure to predict overall fracture resistance across the weldment over a heterogeneous microstructural gradient.

Effects of κ-carrageenan on the structure and rheological properties of fish gelatin

Fish gelatin (FG) and κ-carrageenan (KC) were mixed to simulate the physicochemical properties of porcine gelatin (PG). The effects of the mixing ratio between FG and KC on the interaction, structure, and rheological properties of FG were investigated. The maximum associative interaction occurred at the critical mixing ratio of KC:FG (w/w) at 4:96, where the median particle size (D50) of the FG-KC coacervates was 1168 ± 175 nm, and the zeta potential was −3.8 ± 0.8 mV. Interestingly, the rheological properties of the mixed gel (KC:FG at 4:96) matched those of PG, including the melting temperature (Tm), gelling temperature (Tg), dynamic consistency factor (Kf), and instantaneous compliance (J0). The relationship between structure and physicochemical properties was proposed as a schematic model. The associative interaction between FG and KC was critical for FG's modification and could be applied to improve FG's rheological properties towards PG.

Abstract 020: Regression of Atherosclerosis Through Manipulation of Vascular Macrophages; a Novel Gene-therapy Approach

Aggressive lipid lowering halts atherosclerotic plaque progression but does not lead to bulk plaque regression in humans. We have previously reported that gene transfection of the HDL protein apoAI into macrophages (MΦ-apoAI) decrease the rate of plaque development in atherosclerosis-prone mice. In this study, we hypothesized that MΦ-apoAI can promote regression of atherosclerosis synergistically with lipid-lowering. Atherogenic mice (LDLR -/- and LDLR -/- /MΦ-apoAI) were fed a high-fat diet to promote stage II/III atherosclerotic lesions (as baseline comparator), and then switched to an extreme lipid-lowering intervention (chow with MTTP inhibitor). After 3 weeks on the lipid-lowering diet, both groups showed reduced systemic and lesion inflammation, and reduced macrophage content on histology when compared to baseline. Upon lipid-lowering, vascular ultrasound showed that LDLR -/- /MΦ-apoAI mice has 21% improvement in aortic pulse transit time, and a 37.1% improvement in instantaneous aortic compliance (a surrogate marker for arterial elastic modulus), compared to LDLR -/- mice. Histologic evidence showed that LDLR -/- /MΦ-apoAI mice on lipid-lowering diet also had reduced lesion size (-24%), reduced macrophage content (-27.5%), increased M2/M1 ratio (+51%) and reduced necrotic core area (-28.6%), compared to LDLR -/- mice. Using transplantation of bone marrow cells from MΦ-apoAI mice into recipient mice with established lesions, we show that newly recruited cells are not major contributors to the regression afforded by MΦ-apoAI. Thus, to study the kinetics of pre-existing cells in the lesion during regression, we developed a contrast ultrasound-mediated gene delivery system to tag and trace lesion cells in LDLR -/- mice, which revealed that lesion macrophages expressing apoAI specifically migrate to mediastinal LN in a CCR7-dependent manner during regression. Expression of apoAI in pre-existing lesion macrophages, promotes regression of atherosclerosis beyond lipid-lowering alone, and increases CCR7-dependent egress of macrophages to adjacent lymph nodes. Ultrasound-mediated gene delivery can be a useful device to study the kinetics of cell in the artery wall and also represent a novel approach with application to human therapy.

Cardiogenic oscillations to detect intratidal derecruitment and overdistension in a porcine model of healthy and atelectatic lungs

Low positive end-expiratory pressure (PEEP) can result in alveolar derecruitment, and high PEEP or high tidal volume (VT) in lung overdistension. We investigated cardiogenic oscillations (COS) in the airway pressure signal to investigate whether these oscillations can assess unfavourable intratidal events. COS induce short instantaneous compliance increases within the pressure-volume curve, and consequently in the compliance-volume curve. We hypothesised that increases in COS-induced compliance reflect non-linear intratidal respiratory system mechanics. In mechanically ventilated anaesthetised pigs with healthy (n=13) or atelectatic (n=12) lungs, pressure-volume relationships and the ECG were acquired at a PEEP of 0, 5, 10, and 15cm H2O. During inspiration, the peak compliance of successive COS (CCOS) was compared with intratidal respiratory system compliance (CRS) within incremental volume steps up to the full VT of 12mlkg-1. We analysed whether CCOS variation corresponded with systolic arterial pressure variation. CCOS-volume curves showed characteristic intratidal patterns depending on the PEEP level and on atelectasis. Increasing CRS- or CCOS-volume patterns were associated with intratidal derecruitment with low PEEP, and decreasing patterns above 6mlkg-1 and high PEEP showed overdistension. CCOS was not associated with systolic arterial pressure variations. Heartbeat-induced oscillations within the course of the inspiratory pressure-volume curve reflect non-linear intratidal respiratory system mechanics. The analysis of these cardiogenic oscillations can be used to detect intratidal derecruitment and overdistension and, hence, to guide PEEP and VT settings that are optimal for respiratory system mechanics.

Characterization of intrinsic material properties of a model lipoproteic emulsion gel by oscillatory and creep compliance rheometry.

This research evaluates the effects of formulation and processing factors on the properties of a protein/fat-based food system. These properties may be related to sodium mobility and salty taste perception. This research provides information on strategies that can be used to control factors influencing the physical properties of protein/fat-based food systems targeting sodium reduction.

Comparative analysis of dough rheology and quality of bread baked from fortified and high-in-fiber flours

The research, evaluated the rheological properties of dough and final bread quality production, in function of time, made from wheat refined flour that was enriched with an oat dietary fiber in two dosages (WOF 6% and WOF 12%), spelt flour and two types of wholegrain flour: wholegrain (full milling) and wholemeal (one-step milling). The rheological measurements revealed that the highest instantaneous compliance (J0) was observed in the wholemeal sample and the lowest was in the WOF 6%. The lowest specific volume was observed in the wholegrain bread (0.82 cm3/g), while the highest was observed in the control white bread sample (1.60 cm3/g). The most rapid loss of moisture appeared in white bread. The moisture content was significantly influenced by the type of flour, day of storage and the interaction of these two variables (p ≤ 0.01). The hardest was the sample of wholegrain bread on the first and third day. The smallest pores were noticed in WOF 12% sample. In water extraction, white bread and WOF 12% were comparable and there were no significant differences between spelt bread and wholegrain bread. THE WOF 12% sample had the optimal ratio of health benefits and technological properties.

Viscoelastic properties of amaranth starch gels and pastes. Creep compliance modeling with Maxwell model

In this work, the morphological, thermal, and crystalline properties of starches isolated from two amaranth cultivars, Amaranthus cruentus (ACr) and Amaranthus caudatus (ACa); the viscoelastic properties of their pastes and gels, through oscillatory and creep‐recovery tests and the adjustment to the Maxwell mechanical model, were studied. Both starches presented type A crystalline patterns with high crystallinity degree (CD), 41.84% for ACr and 40.70% for ACa, associated to their low apparent amylose content (AAM) (1.06 g/100 g for ACr and 7.39 g/100 g for ACa). The ACr starch showed the highest values for temperature of gelatinization (Tg) (74.50°C) and ΔH (16.15 W/g). Amaranth gelatinized starches exhibited rheological behavior that corresponds to concentrated macromolecular solutions for ACr while ACa starches showed a gel‐type behavior. The ACa gels behaved as a viscoelastic solid with smaller values of instantaneous compliance (0.006 Pa−1 &lt; J0 &lt; 0.0002 Pa−1), retarded compliances (0.0005 Pa−1 &lt; J1 &lt; 0.000006 Pa−1; 0.0016 Pa−1 &lt; J2 &lt; 0.00008 Pa−1) and higher values of newtonian viscosities (33.4 × 105 Pa · s ≤ η0 ≤ 357.1 × 105Pa · s) than ACr, which facilitated their later structural recovery (75.8% ≤ final recovery ≤ 85.1%). The gels exhibited a small contribution of viscous flow's compliance (t/η0) brought about by the dashpot of the Maxwell's simple element, while in the ACr pastes, this element acquired importance. The Maxwell model of six‐parameters adjusted satisfactorily (R2 ≥ 0.986; RSS ≤ 3 × 10−4) the results of creep curves.

Creep Behavior of Wood Plasticized by Moisture and Temperature

Moisture in wood acting as a plasticizer will strongly affect the wood’s viscoelastic properties. However, achieving the desired moisture content (MC) at elevated temperatures during creep tests is difficult. The aim of this study is to accurately and systematically investigate the creep behavior of birch wood at high temperatures. Experiments were conducted using a dynamic mechanical analyzer with a relative humidity accessory coupled with polyvinylidene chloride (PVDC) film for wrapping samples. Creep behavior was examined at six MCs (0%, 6%, 12%, 18%, 24%, >30%) and 11 temperatures (5 to 105 °C). The MC of wood was strictly and accurately controlled during creep tests. Instantaneous compliance (IC) and creep compliance (CC) increased with the increase of both temperature and MC, with significant changes at higher temperatures and MCs. The effects on IC and CC were more pronounced when the subject was influenced by MC, with readings approximately three times and one time greater than those influenced by temperature, respectively. Dramatic increases in CC were found at certain temperatures and MC values. There was a complex interaction between temperature and MC on IC and CC.

Weighted multiparameter compliance efficiency method for effluent assessment

Developing, validating and implementing effective numerical indicators are crucial tasks in both broad and specific environmental management practices. This work aims to describe a method for generating numerical indicators for effluent assessment based on flow and weighting factors for each chemical species present in the discharge stream. The premises are: (1) optimal effluent has no detectable pollutants; (2) strict legal parameters should have a greater weighting factor than less strict ones; (3) the weighting factor should be derived directly from the regulation that the effluent must comply to; (4) a tendency to lower volumetric discharges is more efficient than constant volumetric discharges. By these premises, a method was developed and applied to five sets of effluent data and regulations for different purposes. First, it was used to compare one French, one American and two Brazilian discharge regulations. Then, it was used to verify the relationship between flow and compliance efficiency. Finally, it was used to compare different effluent streams that must comply with the same regulation. The advantages of the method are: (a) it allows a periodic assessment of a given effluent for its instantaneous compliance efficiency; (b) it enables a comparative assessment of the same effluent with respect to different regulations; (c) it is possible to compare different composition effluents for the compliance of the same regulation. Using the efficiency indicator presented in this study will enable environmental managers and researchers to objective compare effluent polluters and treatment technologies.

Mock Circulatory Loop Compliance Chamber Employing a Novel Real-Time Control Process

The use of compliance chambers in mock circulatory loop construction is the predominant means of simulating arterial compliance. Utilizing mock circulatory loops as bench test methods for cardiac assist technologies necessitates that they must be capable of reproducing the circulatory conditions that would exist physiologically. Of particular interest is the ability to determine instantaneous compliance of the system, and the ability to change the compliance in real-time. This capability enables continuous battery testing of conditions without stopping the flow to change the compliance chamber settings, and the simulation of dynamic changes in arterial compliance. The method tested involves the use of a compliance chamber utilizing a circular natural latex rubber membrane separating the fluid and air portions of the device. Change in system compliance is affected by the airspace pressure, which creates more reaction force at the membrane to the fluid pressure. A pressure sensor in the fluid portion of the chamber and a displacement sensor monitoring membrane center deflection allow for real-time inputs to the control algorithm. A predefined numerical model correlates the displacement sensor data to the volume displacement of the membrane. The control algorithm involves a tuned π loop maintaining the volume distention of the membrane via regulation of the air space pressure. The proportional integral (PI) controller tuning was achieved by creating a computational model of the compliance chamber using Simulink™ Simscape® toolboxes. These toolboxes were used to construct a model of the hydraulic, mechanical, and pneumatic elements in the physical design. Parameter Estimation™ tools and Design Optimization™ methods were employed to determine unknown physical parameters in the system, and tune the process controller used to maintain the compliance setting. It was found that the resulting control architecture was capable of maintaining compliance along a pressure-volume curve and allowed for changes to the compliance set point curve without stopping the pulsatile flow.

IMPACT OF CALCIUM ON VISCOELASTIC PROPERTIES OF FORTIFIED APPLE TISSUE

ABSTRACTThe objective of this study was to analyze the linear viscoelastic behavior of calcium impregnated apples by creep and sinusoidal tests and to correlate the changes in rheological parameters with some structure features. The effect of different Ca concentrations of impregnation solutions (0, 0.1 and 0.53%, w/w), system pressure (vacuum or atmospheric) and process time was studied. All samples showed a viscoelastic solid behavior with the storage modulus (G′) dominating the viscoelastic response. Treated apple samples with or without calcium showed a pronounced decrease in G′as compared with fresh tissue. Instantaneous compliance (J0), decay compliances (J1 and J2) and fluidity significantly increased after treatments, while retardation times were approximately constant. Impregnation at high calcium concentrations provoked severe folding of walls and/or a general inner disruption of cells with plasmolysis and membrane breakage in a different way according to the pressure applied and the treatment time, explaining the viscoelastic behavior. Changes in compliances and storage modulus values were significantly lower for apples treated under vacuum than when the treatment was performed at atmospheric pressure, suggesting that vacuum impregnation is an effective methodology to fortify apple tissue avoiding serious damage in viscoelastic properties and presumably in texture.PRACTICAL APPLICATIONIncorporation of physiologically active food components (PACs) into vegetable matrices to obtain functional foods opens new product opportunities for the food industry. Impregnation processes performed at atmospheric pressure or under vacuum conditions may be employed to incorporate PACs, among them calcium. Because of alterations in structure, these processes can strongly modify rheological properties and hence texture of fruits. The results of this research can help to select operative impregnation conditions that allow the incorporation of great calcium quantities in apple tissue minimizing changes in viscoelastic properties. This objective is of primordial interest when designing minimally processed “fortified apples” preserved by refrigeration and to be consumed as is.

Viscoelasticity, texture and ultrastructure of cut apple as affected by sequential anti-browning and ultraviolet-C light treatments

The aim of this work was to analyze the effect of UV-C radiation (fluence: 11.2 kJ/m 2), with or without an anti-browning pretreatment containing 1% (w/v) ascorbic acid plus 0.1% (w/v) calcium chloride, on the linear viscoelastic properties (oscillatory shear and creep/recovery), instrumental texture (TPA), sensory texture and ultrastructure (ESEM, TEM) of cut apple. Changes in structural features and viscoelastic parameters were mainly evidenced after refrigerated storage. All samples showed a viscoelastic solid behavior with the storage modulus ( G′) dominating the viscoelastic response. Overall, both dynamic moduli decreased, and instantaneous compliance ( J 0), decay compliances ( J 1 and J 2) and fluidity significantly increased after treatments and storage at 5 °C, while retardation times were in general constant. Fracture properties proved to be the most highly correlated with sensory texture. The test panel only significantly differentiated stored untreated apple from the other samples regarding fracturability and juiciness. Mechanical spectra and creep parameters showed ability to evidence ultrastructural differences (rupture of membranes, swelling of cells, alteration of cell walls) in the surface of cut apples subjected to the different treatments.