Characterization of sol-gel transitions of food hydrocolloids with near infra-red spectroscopy

Near infra-red spectroscopy (NIR, 600-1100 nm) was used to characterize sol-gel transitions of food hydrocolloids including whey protein (WP), high acyl (HA) and low acyl (LA) gellan gums. Whey protein (20% w/w), LA and HA gellan (1% w/v) aqueous solutions with selected calcium concentrations (0-40 mM) were used. Principal components analysis (PCA) and principal component regression (PCR) were performed to analyze spectral data of gel dispersions at a series of controlled temperatures (20-95 °C). Gelling temperatures of gellan dispersions were determined directly based upon the PCA results without requiring for reference values. The gelling temperatures determined with the NIR method were similar to those obtained by dynamic rheological tests and dielectric property test. The PCR models showed a good predictability for temperatures of gellan dispersions with selected calcium concentrations during cooling or heating process. This study indicates that the NIR method has a great potential to detect structural change, and to monitor time and temperature dependant behaviour of food hydrocolloids during sol-gel transition period.     

Rheological characterization of dispersions and emulsions used in the preparation of microcapsules obtained by interfacial polymerization containing <Emphasis Type="Italic">Lactobacillus</Emphasis> sp.

The main objectives of this work were the rheological characterization of dispersions and emulsions used in the microcapsules preparation and the microcapsules obtain from gum arabic (A), gellan gum (G) and mesquite seed gum (M) to keep lactic bacteria (Lactobacillus sp.) viable using the interfacial polymerization technique (IP). Dispersions of A, G and M were prepared to obtain microcapsules, as well as binary mixtures of gum arabic and gellan gum (AG), gum arabic and mesquite seed gum (AM) and gellan gum and mesquite seed gum (GM); these dispersions exhibited a shear thinning non-Newtonian behavior. The emulsions were prepared using sunflower oil as the oily phase in a 1:1, 1:3 and 1:5 ratio with the disperse phase; the oily phase was added with Span 85 (surfactant) at 1, 2 and 3% concentrations; the emulsions A (1:5 and 3% Span 85) and GM (1:5 and 2% Span 85) showed higher viscosity and stability. Microcapsules were obtained using 0.05 mol L⁻¹ glutaraldehyde (crosslinking agent) with a reaction time of 3 min. The mean diameter of the microcapsules obtained was 30.17, 16.86 and 10.34 μm according to the AG, AM and GM mixtures, respectively. In the AG and AM dispersions, the microcapsules diameters became larger as the viscosity increased. The microorganism microencapsulates using gum arabic, gellan gum, and mesquite seed gum, was possible. The highest viability (46.7%) of Lactobacillus sp. was obtained with the GM mixture.     

Gelation mechanism and network structure of mixed solution of low- and high-acyl gellan studied by dynamic viscoelasticity, CD and NMR measurements

The gelation mechanism and the change of the network structure during cooling of the mixed solution of high-acyl (HA) and low-acyl (LA) gellan (containing 0.5% HA gellan and 0.5% LA gellan; hereafter called “mixed solution”) were elucidated on the basis of the results of dynamic viscoelasticity, circular dichroism (CD), and NMR measurements, which provide information about the network formation, the structural change due to random coil-double helix (C–H) transition, and the chain mobility of gellan, respectively. It was demonstrated that HA gellan chains in the mixed solution underwent C–H transition individually to form a network structure at the transition temperature for 1% HA gellan solution (75 °C), where storage modulus G′ and loss modulus G″ were steeply increased and the chain mobility of the HA gellan was restricted. The structural change of the HA gellan chains proceeded gradually with further cooling. At 25 °C, which is the C–H transition temperature for 1% LA gellan solution, LA gellan chains in the mixed solution formed a double helix, where G′ and G″ were slightly increased and the chain mobility of LA gellan was restricted. The results suggest that the double helix formation involves only the same kind of gellan chains even in the mixed solution, and that LA gellan chains decrease the mobility and promote the double helix formation of HA gellan chains, and vice versa.     

Thermal Degradation Kinetics of Chlorophyll in Pureed Coriander Leaves

Coriander leaves are widely used in cooking throughout the world. Thermal degradation kinetics of chlorophyll a, b, and total chlorophyll in coriander leaf puree was investigated at varying levels of pH (4.5–8.5) and processing temperature (80–145°C). Coriander puree at pH 4.5 was processed at 80° to 100°C, whereas that at pH 5.5 to 8.5 was processed at 105° to 145°C. Chlorophyll degradation followed first-order reaction kinetics. Good agreement was found between estimated and experimental chlorophyll retention in all cases (R ² > 0.80). Activation energies ranged from 6.57 to 96.00 kJ/mol. Reaction rate and activation energy data indicated that chlorophylls were more stable at alkaline pH. Transition state theory was applied to estimate the enthalpy, entropy, and Gibbs free energy of activation. Enthalpy of activation (ΔH ^#) ranged from 3.46 to 91.99 kJ/mol, whereas entropy of activation (ΔS^#) ranged from −0.265 to −0.047 kJ/(mol K). The overall free energy change was 107.55 kJ/mol. Results indicated that, the compensation effect did not exist for chlorophyll degradation in coriander puree during thermal processing.     

Mass Transfer Coefficients for the Drying of Pumpkin (Cucurbita moschata) and Dried Product Quality

The aim of this work was to determine the mass transfer properties of pumpkin (Cucurbita moschata) exposed to air drying. The drying temperatures tested ranged between 30°C and 70°C, and the kinetic behavior was studied in this temperature band. The samples were analyzed in terms of moisture content, acidity, proteins, lipids, and crude fiber, both in the fresh state and after drying. From the chemical analyses made, it was possible to conclude that drying induces some reductions in acidity, lipids, fibers, and proteins. As to the influence of the drying temperature on the process, it was observed that a temperature rise from 30°C to 70°C led to a 70% saving in drying time. The results obtained by fitting the experimental data to the kinetic models tested allowed concluding that the best model for the present case is Henderson–Pabis, and the worst is Vega–Lemus. Furthermore, in this work, it was possible to determine the values of the diffusion coefficient at an infinite temperature, D _e⁰, and activation energy for moisture diffusion, E _d, which were, respectively, 0.0039 m²/s and 32.26 kJ/mol. Similarly, the values of the Arrhenius constant and the activation energy for convective mass transfer, respectively, h _m⁰ and E _c, were also calculated, the first being 3.798 × 10⁸ m/s and the latter 86.25 kJ/mol. These results indicate that the activation energy for convective mass transfer is higher than that for mass diffusion.     

Determination of Rheological Behavior,Emulsion Stability,Color, and Sensory of Sesame Pastes (Tahin) Blended with Pine Honey

In this research, rheological properties of blends of pine honey (3%, 6%, and 9%) with sesame pastes (tahin) produced from hulled roasted sesame seeds, called simply tahin, and from unhulled roasted sesame seeds, so-called Bozkir tahin, were determined at temperatures ranging from 10°C to 60°C and at speeds ranging from 0.5 to 100 rpm. Tahin and Bozkir tahin blends with pine honey were found to exhibit non-Newtonian, pseudoplastic behavior at all temperatures. Apparent viscosities versus speed data were successfully fitted to the power law model. The flow behavior index, n, varied in the range of 0.4226–0.6228 for the tahin–pine honey blends, and in the range of 0.4661 to −0.7266 for the Bozkir tahin–pine honey blends. The consistency index, K, was in the range of 9.34–36.42 Pa·sⁿ for tahin–honey blends, and in the range of 9.92–37.53 Pa·sⁿ for Bozkir tahin–honey blends. The consistency index (K) increased with increasing honey levels in both tahin types. According to statistical analysis, the exponential model was a better model to describe the effect of the soluble solids on the viscosity of tahin samples represented by the pine honey percentage. The emulsion stability of both tahin types improved with the addition of pine honey. It was also correlated with activation energy (E _a), Arrhenius constant, some sensory properties such as spreadibility, firmness and overall acceptance, and color parameters such as the C and h. Temperature sensitivity of the consistency index was assessed by applying an Arrhenius type equation, and E _a value appeared in the range of 7.61–10.05 kJ/mol for tahin–honey blends and in the range of 9.02–10.50 kJ/mol for Bozkir tahin–honey blends.     

Supercritical fluid extrusion: Die design and physicochemical properties of milk protein extrudates

Extrusion processing has been used to modify the functional properties of proteins. The protein-protein interactions, surface hydrophobicity, and rheological properties of milk protein concentrate extruded using dies of different geometries (circular, annular and slit) were quantified. With the same extrusion treatment history prior to the die, extrudates generated using dies with higher wall shear (slit 1.4 × 10⁴ s⁻¹ > annular 1.1 × 10⁴ s⁻¹ > circular 2.9 × 10³ s⁻¹) showed greater protein extractability, higher index of surface hydrophobicity, and enhanced water solubility index indicating significant breakdown of protein aggregates. Higher viscoelastic moduli (G' and G") and apparent viscosity were observed for slit die extrudate dispersions. However, low flow behavior indices (0.04–0.23(−)) and a high viscous activation energy (43 kJ/mol) of slit die extrudate dispersions implied their shear and temperature sensitivity, respectively. Thus, extrudate functionality can be optimized by selection of the appropriate die design.     

Steady and dynamic shear rheological properties of sweet potato flour dispersions

Korean sweet potato flour dispersions at different concentrations (6, 7, 8, 9, and 10%) were evaluated for their steady and dynamic shear rheological properties. The steady shear rheological properties showed that sweet potato flour dispersions at 25 °C showed a shear-thinning fluid (n=0.31–0.41) exhibiting a yield stress. The magnitudes of Casson yield stress (σ_oc), consistency index (K) and apparent viscosity (η_a,100) increased with an increase in concentration. Within the temperature range of 25–70 °C, the apparent viscosity obeyed the Arrhenius temperature relationship with high determination coefficient (R ²=0.97–0.99) with activation energies (Ea) ranging 0.015–0.024 KJ/mol. Both power law and exponential type models were used to establish the relationship between concentration and apparent viscosity (η_a). Magnitudes of G′ and G″ increased with an increase in concentration. G′ values were higher than G″ over the most of the frequency range (0.63–63 rad/s), being frequency dependent. The sweet potato flour dispersions did not closely follow the Cox–Merz rule at concentrations lower than 10%.     

Mathematical Modeling and Experimental Study on Thin-Layer Vacuum Drying of Ginger (Zingiber Officinale R.) Slices

The vacuum-drying characteristics of ginger (Zingiber officinale R.) slices were investigated. Drying experiments were carried out at a constant chamber pressure of 8 kPa, and at four different drying temperatures (40 °C, 50 °C, 60 °C, and 65 °C).The effects of drying temperature on the drying rate and moisture ratio of the ginger samples were evaluated. Efficient model for describing the vacuum-drying process was chosen by fitting five commonly used drying models and a suggested polynomial was fitted to the experimental data. The effective moisture diffusivity and activation energy were calculated using an infinite series solution of Fick’s diffusion equation. The results showed that increasing drying temperature accelerated the vacuum-drying process. All drying experiments had only falling rate period. The goodness of fit tests indicated that the proposed two-term exponential model gave the best fit to experimental results among the five tested drying models. The average effective diffusivity values varied from 1.859 × 10⁻⁸ to 4.777 × 10⁻⁸ m²/s over the temperature range. The temperature dependence of the effective moisture diffusivity for the vacuum drying of the ginger samples was satisfactorily described by an Arrhenius-type relationship with activation energy value of 35.675 kJ/mol within 40–65 °C temperature range.     

高酰基结冷胶的溶胶和凝胶特性研究及结构初步分析

采用黏度计和质构仪对高酰基结冷胶的溶胶和凝胶性质进行研究。结果表明：高酰基结冷胶在质量浓度为 0.05～0.1g/100mL 时,表观黏度随质量浓度增加而增加,并呈现假塑性流体特性;在质量浓度为0.2～0.5g/100mL时形成凝胶,凝胶强度受胶体及 Ca2+ 质量浓度的影响明显,同时高酰基结冷胶比例增加,高低复配胶体的凝胶强度减小。并利用红外光谱扫描和核磁共振技术对高酰基结冷胶结构进行初步分析。     

Effect of temperature on rheological characteristics of molasses: Modeling of apparent viscosity using Adaptive Neuro - Fuzzy Inference System (ANFIS)

In this study, the effect of temperature on the rheological characteristics of apricot and date molasses was studied separately. Rheological characteristics of both molasses were evaluated in the shear rate range of 0.1-100 s⁻¹ at different temperatures (10-40 °C). Power law model was used for the calculation of flow behavior index and consistency coefficients of molasses. Consistency coefficients of apricot and date molasses were in the range of 5.408-39.905 Pa sⁿ and 0.910-2.852 Pa sⁿ, respectively. Molasses samples showed a non-Newtonian flow behavior. The effect of temperature on apparent viscosity was described by Arrhenius equation and calculated activation energy at the shear rate of 54.2 s⁻¹ was 41.42 and 38.19 kJ/mol for apricot and date molasses, respectively. An efficient predictive model for apparent viscosity values of molasses was constructed using Adaptive Neuro - Fuzzy Inference System (ANFIS) and this model showed satisfactory prediction with high coefficient of determination (0.979-0.999) and low root mean squared error (0.12-0.46).     

Characteristics of Convective Drying of Pepino Fruit (Solanum muricatum Ait.): Application of Weibull Distribution

The aim of this research was to study the behaviour of the drying kinetics of pepino fruit (Solanum muricatum Ait.) at five temperatures (50, 60, 70, 80 and 90 °C). In addition, desorption isotherms were determined at 20, 40 and 60 °C over a water activity range from 0.10 to 0.90. The Guggenheim, Anderson and de Boer model was suitable to depict the desorption data. A monolayer moisture content from 0.10 to 0.14 g water g⁻¹ d.m. was reported. The equations of Newton, Henderson–Pabis, Modified Page, Wang–Singh, Modified Henderson–Pabis, Logarithmic as well as standardised Weibull were tested for modelling drying kinetics. Besides, Fick’s second law model was used to calculate the water diffusion coefficient which increased with temperature from 2.55 to 7.29 × 10⁻¹⁰ m² s⁻¹, with estimated activation energy of 27.11 kJ mol⁻¹. The goodness of fit of the models was evaluated using sum squared error and chi-square statistical tests. The comparison of the experimental moisture values with respect to the calculated values showed that the standardised Weibull model presented the best goodness of fit, showing that this equation is very accurate for simulating drying kinetics for further optimisation of drying times.     

Characterization of gelation time and texture of gelatin and gelatin–polysaccharide mixed gels

The effects of cooling rate, holding temperature, pH and polysaccharide concentration on gelation characteristics of gelatin and gelatin–polysaccharide mixtures were investigated using a mechanical rheometer which monitored the evolution of G′ and G″. At low holding temperatures of 0 and 4 °C, elastic gelatin gels were formed whereas a higher holding temperature of 10 °C produced less elastic gels. At slow cooling rates of 1 and 2 °C/min, gelling was observed during the cooling phase in which the temperature was decreased from room temperature to the holding temperature. On the other hand, at higher cooling rates of 4 and 8 °C/min, no gelation was observed during the cooling phase. Good gelling behavior similar to that of commercial Strawberry Jell-O^® Gelatin Dessert was observed for mixtures of 1.5 and 15 g sucrose in 100 ml 0.01 M citrate buffer containing 0.0029–0.0066 g low-acyl gellan. Also, these mixed gels were stronger than Strawberry Jell-O^® Gelatin Desserts as evidenced by higher G′ and gel strength values. At a very low gellan content of 0.0029 g, increasing pH from 4.2 to 4.4 led to a decrease in the temperature at the onset of gelation, G′ at the end of cooling, holding and melting as well as an increase in gel strength. The gelation time was found to decrease to about 40 min for gelatin/sucrose dispersions in the presence of 0.0029 g gellan at pH 4.2 whereas the corresponding time at pH 4.4 was higher (79 min). In general, the gelation time of gelatin/sucrose dispersions decreased by a factor of 2 to 3 in the presence of low-acyl gellan. The addition of low-acyl gellan resulted in an increase in the gelation rate constant from 157.4 to 291 Pa. There was an optimum low-acyl gellan content for minimum gelation time, this optimum being pH dependent. Addition of guar gum also led to a decrease in gelation time to 73 min with a corresponding increase in the gelation rate constant to 211 Pa/min though these values were not sensitive to guar gum content in the range of 0.008–0.05 g. The melting temperature of gelatin/sucrose/gellan as well as gelatin/sucrose/guar mixtures did not differ significantly from that of pure gelatin or Strawberry Jell-O^® Gelatin Desserts. At pH 4.2, the melting rate constant was highest at a low-acyl gellan content of 0.0029 g whereas the rate constant was insensitive to low-acyl gellan content at pH 4.4. Addition of guar did not seem to affect the melting temperature or the melting rate constant.     

Steady and Dynamic Shear Rheology of Rice Starch‐Galactomannan Mixtures

Rheological properties of rice starch‐galactomannan mixtures (5%, w/w) at different concentrations (0, 0.2, 0.4, 0.6 and 0.8%, w/w) of guar gum and locust bean gum (LBG) were investigated in steady and dynamic shear. Rice starch‐galactomannan mixtures showed high shear‐thinning flow behaviors with high Casson yield stress. Consistency index (K), apparent viscosity (η_a,100) and yield stress (σ_oc) increased with the increase in gum concentration. Over the temperature range of 20–65°C, the effect of temperature on apparent viscosity (η_a,100) was described by the Arrhenius equation. The activation energy values (E_a = 4.82–9.48 kJ/mol) of rice starch‐galactomannan mixtures (0.2–0.8% gum concentration) were much lower than that (E_a = 12.8 kJ/mol) of rice starch dispersion with no added gum. E_a values of rice starch‐LBG mixtures were lower in comparison to rice starch‐guar gum mixtures. Storage (G′) and loss (G′′) moduli of rice starch‐galactomannan mixtures increased with the increase in frequency (ω), while complex viscosity (η*) decreased. The magnitudes of G′ and G′′ increased with the increase in gum concentration. Dynamic rheological data of ln (G′, G′′) versus ln frequency (ω) of rice starch‐galactomannan mixtures have positive slopes with G′ greater than G′′ over most of the frequency range, indicating that their dynamic rheological behavior seems to be a weak gel‐like behavior.     

Inactivation of peroxidase and polyphenol oxidase in red beet (Beta vulgaris L.) extract with continuous high pressure carbon dioxide

The inactivation of peroxidase (POD) and polyphenol oxidase (PPO) in red beet extract (RBE) with continuous high pressure carbon dioxide (HPCD) was investigated. HPCD treatment at 7.5 MPa (55 °C, 30 min) resulted in a reduction of their activities by approximately 73% and 93%, respectively. Compared with thermal treatment, continuous HPCD treatment reduced the decimal reduction time (D) of POD and PPO from 555.6 min to 55.9 min and 161.3 min to 32.1 min, respectively. The inactivation process could be described by first-order kinetics (r² > 0.70, p < 0.05); D values declined when temperature increased and continuous HPCD at 7.5 MPa and 55 °C resulted in the highest reaction rate constant (k value; smallest D value). The activation energy of the inactivation was reduced by HPCD treatment from 92.5 kJ/mol to 69.8 kJ/mol and 57.1 kJ/mol to 49.5 kJ/mol for POD and PPO, respectively. Continuous HPCD treatment had little effect on the antioxidant capacities of RBE samples.     

Rheological investigation of alginate chain interactions induced by concentrating calcium cations

Chain interactions of sodium alginate during its gelation were investigated by a new gelation method which was based on a Ca²⁺-concentrating gelling process (CCGP) produced by water evaporation of an alginate solution containing CaCl₂. For two commercially available sodium alginate samples (low viscosity (LA) and medium viscosity (MA)) having different molecular weight distributions but the same G/M blocks, the critical Ca²⁺ concentrations for their gelation were found to be 4.6 (for LA) and 4.5 (for MA) μmol/mL after evaporating water from 1% of alginate solutions containing 4 μmol/mL of CaCl₂. The CCGP gelation method for alginate under the above conditions were confirmed by rheological measurements and the observed highly ordered and uniform mesh structure of the CCGP-formed alginate gels shown in cryo-SEM images. Combinations of LA and MA at different ratios (0:4, 1:3, 2:2, 3:1, 4:0 on weight basis) were studied using the CCGP gelation method to further the understanding of the alginate chain interactions during gelation. Different LA/MA mixtures exhibited different rheological properties in either non-gelled or gelled systems, indicating that the molecular weight distributions of the sodium alginates influence the alginate chain interactions mediated by Ca²⁺. Thus, an appropriate combination of LA and MA is required for a strong alginate interchain interaction during CCGP, and alginate products with desirable characteristics can be produced by manipulating the mixing ratios of sodium alginates having different molecular weight distributions even at the same total composition and distribution of G/M blocks.     

Rheology-structure properties of waxy maize starch–gellan mixtures

Dynamic oscillatory shear and confocal laser scanning microscopy were used, respectively, to study the viscoelastic properties and ultrastructure of mixtures of unmodified waxy maize starch (3%) and gellan (0.005–0.05%), pasted at 75 and 90 °C. The two temperatures resulted in different rheological properties and ultrastructure. At 75 °C swollen and partially disrupted granules were observed, while at 90 °C the dominant feature was the presence of granule remnants. Addition of gellan produced mixtures with different elastic properties depending on the extent of granular disruption and gellan concentration in the mixture. Below 0.02% gellan, swollen and disrupted starch granules were surrounded by compact, yet slightly interconnected, gellan networks resulting in enhanced blends at both temperatures. Above such gellan concentration no enhancement was observed and gellan dominated the viscoelastic behavior of the mixtures because of the existence of more evenly distributed networks with swollen or disrupted starch granules exerting a weakening effect on the resulting structure.     

Pasting Properties of Non‐waxy Rice Starch‐Hydrocolloid Mixtures

The swelling and pasting properties of non‐waxy rice starch‐hydrocolloid mixtures were investigated using commercial and laboratory‐generated hydrocolloids. The swelling power of the rice starch‐hydrocolloid mixtures was generally depressed at low concentration of hydrocolloids (0–0.05%), but increased directly with increasing hydrocolloid concentrations (0.05–0.1%). In gellan gum dispersion, the swelling power at 100°C was higher than that of control. The rice starch‐hydrocolloids mixtures showed shear‐thinning flow behavior (n = 0.26–0.49). Hydrocolloids except the exopolysaccharide from S. chungbukensis (EPS‐CB) increased apparent viscosity and consistency index (K) of rice starch dispersions, but decreased the n value. Hydrocolloids enhanced the trough and final viscosity of rice starch dispersions but EPS‐CB reduced the viscosity of rice starch pastes. Hydrocolloids lowered peak viscosity but addition of guar gum resulted in high peak viscosity, apparent viscosity, and consistency index of rice starch dispersions. Total setback viscosity appeared to be not affected by hydrocolloids at low concentration (0.05%). The hot and cold paste of the starch‐gellan gum mixture exhibited the highest viscosity values in the Brookfield viscometer.     

Rheological Properties of Rice Starch Dispersions in Dimethyl Sulfoxide

The steady and dynamic shear rheological properties of rice starches dispersed in dimethyl sulfoxide (DMSO) solution (90% DMSO‐10% water) were evaluated at various concentrations (7, 8, 9 and 10%, w/w). Rice starch dispersions in DMSO solution at 25°C showed a shear‐thinning flow behavior (n=0.44–0.60) and their consistency index (K) and apparent viscosity (η_a,100) increased with the increase in concentration. The apparent viscosity over the temperature range of 25–70°C obeyed the Arrhenius temperature relationship, indicating that the magnitudes of activation energy (E_a) were in the range of 11.7–12.7 kJ/mol. The Carreau model provided better fit on the shear rate‐apparent viscosity data than the Cross model. Dynamic frequency sweep test showed that both storage modulus (G′) and loss modulus (G′′) of rice starch dispersions increased with the increase in concentration. G′′ showed a higher dependence on frequency (ω) compared to G′ due to the higher G′′ slopes. All rice starch dispersions showed the plateau of G′ at high frequencies. Intrinsic viscosity of rice starch dispersions in DMSO was 104.1 mL/g.     

Effect of Freezing on Textural Kinetics in Snacks During Frying

Kinetics of texture development during frying of snacks subjected to different initial conditions such as frozen, frozen–thawed, and unfrozen was investigated. The temperature dependency of the changes in the form of reaction constants was explained by Arrhenius equation. The increase in hardness and decrease in cohesiveness followed first-order reaction kinetics (R ² = 0.94–0.99) in all the samples. Frozen samples showed induction (phase I) and development/degradation (phase II) periods for textural parameters during frying. The activation energies for hardness were 33.81, 25.63, 19.09, and 20.13 kJ/mole for frozen (phase I and II), frozen–thawed, and unfrozen samples, respectively with the R ² = 0.96–0.99. Frozen samples showed high activation energies for textural parameters during frying as compared to the frozen–thawed and unfrozen samples. The increase in chewiness was found to follow the kinetics of zero-order reaction for all the samples. Temperature and time were found to have a significant effect (P < 0.01) on the changes in textural profile during frying.