Reduction In Intrinsic Viscosity Research Articles

Investigation of Hydroxyl Radical Yield in an Impact-Jet Hydraulic Cavitator

Hydroxyl radical (·OH) is a key component that leads to the cleavage of the glycosidic bond in the process of chitosan (CS) degradation by hydrodynamic cavitation (HC). In this paper, methylene blue (MB) was selected as the trapping agent of ·OH and the yield of ·OH in an impact-jet hydraulic cavitator was investigated. The results showed that the cavitation intensity and the number of passes (N) were the two main factors affecting the yield of ·OH. A smaller cavitation number (Cv) or a larger N indicated that more ·OH can be produced. Based on the dimensionless number correlation method, the yield of ·OH was correlated with Cv, N, Euler number (Eu), Reynolds number (Re), and a dimensionless parameter (γ), and a prediction model of ·OH yield was established. The relative deviations between the experimental and calculated values of the ·OH yield were basically within 10% by the prediction model. On the basis of the prediction model, the yield of ·OH produced in the process of CS degradation by HC was obtained. The results showed that the predicted yield of ·OH was significantly correlated with the intrinsic viscosity reduction rate of CS. It was suggested that the prediction model of ·OH yield based on the MB solution can be used to calculate the ·OH yield during the degradation of low concentration CS by HC.

Alkalization of Kraft Pulps from Pine and Eucalyptus and Its Effect on Enzymatic Saccharification and Viscosity Control of Cellulose.

Bleached kraft pulps from eucalyptus and pine were subjected to cold caustic extraction (CCE) with NaOH (5, 10, 17.5, and 35%) for hemicelluloses removal and to increase cellulose accessibility. The effect of these changes was evaluated in enzymatic saccharification with the multicomponent Cellic CTec3 enzyme cocktail, and in viscosity reduction of pulps with the monocomponent Trichoderma reesei endoglucanase (EG). After CCE with 10% NaOH (CCE10) and 17.5% NaOH (CCE17.5), hemicellulose content lower than 1% was achieved in eucalyptus and pine pulps, respectively. At these concentrations, cellulose I started to be converted into cellulose II. NaOH concentrations higher than 17.5% decreased the intrinsic viscosity (from 730 to 420 mL/g in eucalyptus and from 510 to 410 mL/g in pine). Cellulose crystallinity was reduced from 60% to 44% in eucalyptus and from 71% to 44% in pine, as the NaOH concentration increased. Enzymatic multicomponent saccharification showed higher glucose yields in all CCE-treated eucalyptus samples (up to 93%) while only CCE17.5 and CCE35 pine pulps achieved 90% after 40 h of incubation. Untreated bleached pulps of both species presented saccharification yields lower than 70%. When monocomponent EG was used to treat the same pulps, depending on enzyme charge and incubation time, a wide range of intrinsic viscosity reduction was obtained (up to 74%). Results showed that eucalyptus pulps are more accessible and easier to hydrolyze by enzymes than pine pulps and that the conversion of cellulose I to cellulose II hydrate only has the effect of increasing saccharification of CCE pine samples. Viscosity reduction of CCE pulps and EG treated pulps were obtained in a wide range indicating that pulps presented characteristics suitable for cellulose derivatives production.

Effects of konjac glucomannan with different molecular weights on gut microflora with antibiotic perturbance in in vitro fecal fermentation

This study investigated the effect of konjac glucomannan (KGM) of different molecular weight on fecal microflora against antibiotic disturbance. KGM (~1.8 × 107 Da) was partially hydrolysed with trifluoroacetic acid (TFA) for 10 and 60 min to KGM1 (~2.1 × 104 Da) and KGM2 (7413 Da), respectively. The acid treatment caused significant reduction of intrinsic viscosity, average molecular weight (MW) and particle size of KGM, but brought limited change to the molecular structure. Low-MW KGM2 showed the most significant effect on fecal microflora in the presence of two common antibiotics (ampicillin and clindamycin), by increasing the relative abundance of Bifidobacteriaceae while decreasing the proportion of Enterobacteriaceae. Additionally, both the native and acid-treated KGM counteracted the adverse influence of antibiotics on the production of short chain fatty acids. The results have demonstrated the effect of KGM on gut microbiota with antibiotic disturbance.

Field test on the biodegradation of poly(butylene adipate-co-terephthalate) based mulch films in soil

The use of plastic much films has been fundamental to promoting food production in many regions of the world. However, concern is growing about the progressive accumulation of plastic residues in soil after crop harvest and its subsequent impact on soil health and potential to enter the food chain. Although biodegradable films have been developed to prevent these problems, it is still unclear whether they are environmentally benign. Here we evaluated the physical and chemical breakdown of four commercial poly(butylene adipate-co-terephthalate) based biodegradable mulch films (BMF1, BMF2, BMF3 and BMF4) in an agricultural soil over a 26-month period. Based on visual examination, degradation followed the series BMF4 > BMF1, BMF2 > BMF3. Importantly, microplastic residues (fragments <5 mm) still remained in the soil of all 4 plastic types after 2 years, suggesting that they are likely to accumulate over time if used on an annual basis. Viscosimetry, Fourier transform infrared (FTIR) spectroscopy and Thermogravimetric Analysis (TGA) were used to characterise the breakdown process. Our results indicated that the degradation of the mulch film after burial in agricultural soil may be linked to the nature of the polymer but also to its manufacturing formulation. Although the peak changes of polyester in the infrared spectrum were not distinct, the plastic films showed other signs of degradation including a reduction in intrinsic viscosity after burial in soil. The different degradation rates of BMF1 and BMF2 at the molecular level may be due to the different CaCO3 contents. In conclusion, under field conditions, we show that slight variations in the formulations of commercial biodegradable mulch films leads to very different persistence rates in soil. Further, we conclude that their slow rate of degradation will ultimately lead to their progressive accumulation in soil if used repeatedly.

A high-molecular weight exopolysaccharide from the Cs-HK1 fungus: Ultrasonic degradation, characterization and in vitro fecal fermentation

This work was to examine the impact of power ultrasound (US) on the molecular properties of a high-molecular weight (MW) exopolysaccharide (EPS) from the Cs-HK1 medicinal fungus and the utilization, and prebiotic function of the US-treated EPS fractions in human fecal microflora in vitro. The US treatment caused notable reduction of intrinsic viscosity, average MW and aggregate size of EPS in water but no significant changes in the molecular structure. The US-treated EPS fractions were consumed more rapidly by the fecal microflora, resulting in a higher total level of short chain fatty acids. They also affected the relative abundance in the microflora more beneficially than the original EPS. The results suggest that power US is effective for modifying and improving the prebiotic properties of high-MW polysaccharides.

Effect of temperature and selected sugars on dilute solution properties of two hairless canary seed starches compared with wheat starch

In this paper, influence of temperature (25, 35, 45 and 55°C) and sugars (sucrose and lactose) at different concentrations (0, 5, 10 and 15%) on some molecular parameters of starches from two canary seed varieties (C05041 and CDC Maria) in the dilute regime were investigated in comparison to wheat starch (WS). The results indicated that the intrinsic viscosity ([η]) values of C05041, CDC Maria and WS samples were 1.42, 1.46 and 1.70dl/g at 25°C, respectively. Intrinsic viscosity of selected starches decreased with an increase in temperature, but the effect of high temperatures were somewhat unnoticeable. By increasing the sugar concentration, intrinsic viscosity of each starch solution significantly decreased in comparison with the value determined for sugar free solution. Lactose had more pronounced effect on the intrinsic viscosity reduction of CDC Maria starch and WS at 25°C and 35°C compared with sucrose (P<0.05). But at 55°C, the effect of increasing sucrose on decreasing of [η] of CDC Maria and WS samples were more considerable. The shape factor of starch samples at 25°C were spherical, but increasing temperature from 25°C to 55°C, CSSs and WS samples took an ellipsoidal shape.The interaction between starches and solvent/cosolutes is the predominant factors determining their functional properties in food systems. One of the aspects can help to understand the characteristic of biopolymers such as starches is determination of their dilute solution properties as a function of common additives which are used in food systems. As a matter of fact, dilute solution properties can help to understand the potential applications of biopolymers in food and non-food application. Attentively, dilute solution properties would give some priceless information about molecular properties, biopolymer behavior and its interaction with copolymers. For instance, intrinsic viscosity provides deep insight into fundamental properties of the solute and its interaction with the solvent and/or cosolutes, conformation of flexible chains. There are many studies which investigated the effect of different parameters such as temperature, salts and sugars on dilute solution properties of hydrocolloids, especially gums. Regrettably, few researches scrutinized the influence of various cosolutes on dilute solution properties of starch. Then in this paper, we studied the dilute solution properties of starches from two canary seed varieties (C05041 and CDC Maria), as a new potential source of starch, (CSSs), in comparison to wheat starch at different experimental conditions (temperatures and sugars at different concentrations) in order to shed light on its behavior in real system in comparison to wheat starch. Because of the unique properties of wheat starch, comparison of canary seed starch with wheat starch in dilute regime can help to having better vision of this new starch source. Overall, the intrinsic viscosity, coil dimensions (Rcoil and Vcoil), swollen specific volume, shape function, and hydration parameter of selected starches were determined affected by temperature and sugars concentration treatments. The importance of these results will be cleared when taking into account the influence of crucial additives generally used in food systems, for instance, different sugars and/or frequent processing parameters such as temperature on rheological and functional properties.

Waxy flour degradation – Impact of screw geometry and specific mechanical energy in a co-rotating twin screw extruder

Dextrinization of starch using extrusion processing is crucial to the quality of direct expanded products. To determine the extent of dextrinization, flour samples were extracted from a twin-screw extruder that had been brought to a sudden stop and molecular weights were determined by intrinsic viscosity. The screw profile and moisture feed content had the most significant impact on molecular weight reduction, reducing intrinsic viscosity from 1.75 to 0.70dL/g at the most. The breakdown, as shown by a reduction in intrinsic viscosity, had a strong negative correlation (r=−0.96) with specific mechanical energy. However, the extruder die did not have a measurable impact on the molecular weight reduction of waxy flour. Size exclusion chromatography confirmed intrinsic viscosity measurements were associated with reduction of the size of amylopectin molecules to approximately 1/10 the original molecular weight while native gliadin was nearly eliminated from the waxy flour following the extrusion treatments.

Effect of solution plasma process with bubbling gas on physicochemical properties of chitosan

In the present work, solution plasma process (SPP) with bubbling gas was used to prepare oligochitosan. The effect of SPP irradiation with bubbling gas on the degradation of chitosan was evaluated by the intrinsic viscosity reduction rate and the degradation kinetic. The formation of OH radical was studied. Changes of the physicochemical properties of chitosan were measured by scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis, as well as ultraviolet-visible, Fourier-transform infrared, and 13C nuclear magnetic resonance spectroscopy. The results indicated an obvious decrease in the intrinsic viscosity reduction rate after SPP irradiation with bubbling gas, and that the rate with bubbling was higher than that without. The main chemical structure of chitosan remained intact after irradiation, but changes in the morphology, crystallinity, and thermal stability of oligochitosan were observed. In particular, the crystallinity and thermal stability tended to decrease. The present study indicated that SPP can be effectively used for the degradation of chitosan.

Influence of some inorganic salts on the intrinsic viscosity of poly(acrylic acid) in aqueous solutions

In this work, the effect of temperature, concentration of sodium sulfate and potassium sulfate on the intrinsic viscosity of poly(acrylic acid) were investigated. Our data shows excellent conformance with the Wolf equation. The addition of salt screens the electrostatic repulsions between charges along the backbone of the polyelectrolyte chain. Consequently the intrinsic viscosity of PAA was decreased by increasing concentration of salt. Also the results reveal that the reduction of intrinsic viscosity of PAA in the presence of sodium sulfate is more than those of potassium sulfate. Potassium cation shows a screen effect less than sodium cation. Therefore the intrinsic viscosity of PAA in the presence of potassium sulfate is more than those of sodium sulfate. The flow activation energy was evaluated by Arrhenius equation. The flow activation energy data was correlated to polymer concentration with a meaningful equation. The UV–Vis spectra of poly(acrylic acid) shows that the absorption intensity of PAA was decreased with addition of sodium sulfate or potassium sulfate. The structure of the extended polymer chains reformed to random-coil conformation in the presence of salt, thus the value of electric multipole moment decreased. Consequently the absorption intensity of PAA was decreased with addition of sodium sulfate or potassium sulfate.

Whey protein–pectin soluble complexes for beverage applications

There is a strong interest in the consumption of beverages containing whey proteins due to implications in health outcomes such as increased satiety and metabolic regulation. However, low thermal stability limits the conditions under which whey protein beverages can be formulated. Studies have shown that at a narrow pH range near the protein isoelectric points, whey proteins and polysaccharides self assemble into soluble complexes (SCs) that exhibit unique functionality. This study investigated the formation and thermal stability of SCs under conditions relevant to beverage applications. Complexes were formed at pH 5 using whey protein isolate (WPI; 1–6% w/w) and high-methoxyl pectin (HMP; 0.125–0.75% w/w) and then heat-set at 85 °C for 25 min. Hydrodynamic properties, particle size distribution, ζ–potential, and dispersion viscosity were evaluated before and after heat-setting. Mean particle diameter ranged from 300 to 715 nm for unheated SCs, and 230 nm to 1 μm for heat-set SCs. Heat-setting SCs led to a significant (p < 0.05) reduction in intrinsic viscosity from 93.6 mL/g to 79.5 mL/g, suggesting conformational changes that favor a smaller hydrodynamic size. Dispersions of SCs exhibited decreased apparent viscosity, consistent with the lower intrinsic viscosity and smaller particle size. Heat-set SCs (4% WPI, 0.5% HMP) remained as sub-micron particles (d = 303–829 nm) after pH adjustment (pH 4–7) and thermal processing (142 °C for 6 s), indicating that WPI and HMP can be heat-set into complexes with enhanced colloidal stability in beverage applications.

Intensification of depolymerization of polyacrylic acid solution using different approaches based on ultrasound and solar irradiation with intensification studies

Depolymerization of polyacrylic acid (PAA) as sodium salt has been investigated using ultrasonic and solar irradiations with process intensification studies based on combination with hydrogen peroxide (H2O2) and ozone (O3). Effect of solar intensity, ozone flow and ultrasonic power dissipation on the extent of viscosity reduction has been investigated for individual treatment approaches. The combined approaches such as US+solar, solar+O3, solar+H2O2, US+H2O2 and US+O3 have been subsequently investigated under optimum conditions and established to be more efficient as compared to individual approaches. Approach based on US (60W)+solar+H2O2 (0.01%) resulted in the maximum extent of viscosity reduction as 98.97% in 35min whereas operation of solar+H2O2 (0.01%), US (60W), H2O2 (0.3%) and solar irradiation resulted in about 98.08%, 90.13%, 8.91% and 90.77% intrinsic viscosity reduction in 60min respectively. Approach of US (60W)+solar+ozone (400mg/h flow rate) resulted in extent of viscosity reduction as 99.47% in 35min whereas only ozone (400mg/h flow rate), ozone (400mg/h flow rate)+US (60W) and ozone (400mg/h flow rate)+solar resulted in 69.04%, 98.97% and 98.51% reduction in 60min, 55min and 55min respectively. The chemical identity of the treated polymer using combined approaches was also characterized using FTIR (Fourier transform infrared) spectra and it was established that no significant structural changes were obtained during the treatment. Overall, it can be said that the combination technique based on US and solar irradiations in the presence of hydrogen peroxide is the best approach for the depolymerization of PAA solution.

A novel approach for intensification of enzymatic depolymerization of carboxymethyl cellulose using ultrasonic and ultraviolet irradiations

The present work investigates the application of ultrasonic (US) and ultraviolet (UV) irradiations operated individually or in combination for intensification of enzymatic depolymerization of aqueous solution of carboxymethyl cellulose (CMC) present as sodium salt. The effect of different operating parameters such as reaction temperature, enzyme loading, UV and US power dissipation on the extent of depolymerization have been studied. The effectiveness of treatment approach has been analyzed on the basis of kinetic rate constant, limiting intrinsic viscosity and the time required for the desired extent of intrinsic viscosity reduction. The kinetic rate constant has been found to increase with an increase in the temperature and cellulase loading. The extent of depolymerization increased from 20% to 58.5% with an increase in the operating power of UV from 8W to 32W (irradiation time as 180min) whereas the increase was from 74% to 87% for an increase in ultrasonic power from 60W to 120W (irradiation time of 120min). In the presence of US (60W)+UV (16W)+enzyme (0.05%), the maximum extent of depolymerization of CMC has been observed as 99% with treatment time of 18min. The effect of ultrasonic irradiation on viscosity reduction was established to be more pronounced than the ultraviolet irradiations. The obtained results from FTIR spectra clearly established that no changes in the chemical structure were observed for the treated CMC using combined ultrasound, ultraviolet irradiations with enzyme and native CMC. The work has conclusively established, for the first time, that the combination of ultraviolet and ultrasonic irradiation in presence of cellulase enzyme gives maximum viscosity reduction in CMC polysaccharides as compared to individual approaches.

Intensified depolymerization of aqueous polyacrylamide solution using combined processes based on hydrodynamic cavitation, ozone, ultraviolet light and hydrogen peroxide

The present work deals with intensification of depolymerization of polyacrylamide (PAM) solution using hydrodynamic cavitation (HC) reactors based on a combination with hydrogen peroxide (H2O2), ozone (O3) and ultraviolet (UV) irradiation. Effect of inlet pressure in hydrodynamic cavitation reactor and power dissipation in the case of UV irradiation on the extent of viscosity reduction has been investigated. The combined approaches such as HC+UV, HC+O3, HC+H2O2, UV+H2O2 and UV+O3 have been subsequently investigated and found to be more efficient as compared to individual approaches. For the approach based on HC+UV+H2O2, the extent of viscosity reduction under the optimized conditions of HC (3bar inlet pressure)+UV (8W power)+H2O2 (0.2% loading) was 97.27% in 180min whereas individual operations of HC (3bar inlet pressure) and UV (8W power) resulted in about 35.38% and 40.83% intrinsic viscosity reduction in 180min respectively. In the case of HC (3bar inlet pressure)+UV (8W power)+ozone (400mg/h flow rate) approach, the extent of viscosity reduction was 89.06% whereas individual processes of only ozone (400mg/h flow rate), ozone (400mg/h flow rate)+HC (3bar inlet pressure) and ozone (400mg/h flow rate)+UV (8W power) resulted in lower extent of viscosity reduction as 50.34%, 60.65% and 75.31% respectively. The chemical structure of the treated PAM by all approaches was also characterized using FTIR (Fourier transform infrared) spectra and it was established that no significant chemical structure changes were obtained during the treatment. Overall, it can be said that the combination of HC+UV+H2O2 is an efficient approach for the depolymerization of PAM solution.

Merging of Zwitterionic ROP and Photoactivated Thiol–Yne Coupling for the Synthesis of Polyether Single-Chain Nanoparticles

Preparation of polyether single-chain nanoparticles (SCNPs) has remained as an elusive issue in spite of the significant interest in the synthesis of polyether derivatives with complex architectures (i.e., star-shaped, cyclic, multicyclic, and supramolecular structures). In this work, we report the facile access to polyether SCNPs by combining zwitterionic ring-opening polymerization (ZROP) and thiol–yne coupling (TYC) techniques. Linear copolymers of tetrahydrofuran (THF) and glycidyl propargyl ether (GPgE), P(GPgE-co-THF), and terpolymers of THF, GPgE, and glycidyl phenyl ether (GPE), P(THF-GPgE-GPE), having naked alkyne functional groups (10–21 mol %) were synthesized through ZROP at high content of THF in the feed. Only P(THF-GPgE-GPE) terpolymers were found to give polyether SCNPs upon photoactivated TYC reaction by working at appropriate dilution conditions (0.5 mg/mL) and using 3,6-dioxa-1,8-octane-dithiol as homobifunctional cross-linker. The different monomer sequence distribution in the copolymers when compared to that in the terpolymers was the responsible for this behavior, as revealed by in situ polymerization 13C nuclear magnetic resonance measurements. A significant reduction in intrinsic viscosity was observed upon SCNP formation. Analysis of hydrodynamic data from size exclusion chromatography with triple detection in terms of Mark–Houwink–Sakurada plots revealed that the degree of compaction increases upon increasing the alkyne content in the SCNP precursor. Polyether SCNPs were found to be noncrystalline rubbery materials at room temperature.

Intensification of degradation of guar gum: Comparison of approaches based on ozone, ultraviolet and ultrasonic irradiations

The application of ultraviolet irradiation (UV) for degradation of guar gum (GG) has been investigated with intensification using addition of hydrogen peroxide (H2O2) and potassium persulfate (KPS). Effect of UV power intensity and initiator concentration on the extent of degradation has been established. The efficacy of UV based approach has been compared with ultrasound (US) and ozone (O3) based processes on the basis of kinetic rate constant, final limiting viscosity and required treatment time. The combined approaches such as US+UV, US+O3 and UV+O3 have also been investigated. For the approach based on UV irradiation, addition of H2O2 and KPS increased the extent of degradation significantly. The combined approaches of US+O3 and UV+O3 have been found efficient as compared to individual approaches. Use of UV+H2O2 (0.1% loading) resulted in about 99.1% degradation in 20min whereas UV+KPS (0.1% loading), US+O3 (100mg/h) and UV+O3 (100mg/h) resulted in about 98.3%, 99.1% and 98.3% reduction in intrinsic viscosity in 90min, 30min and 35min respectively. In scale-up studies (7L capacity), maximum extent of degradation as 98.2% was achieved in 150min using US bath+UV+H2O2 (0.03% loading). The structure of the treated guar gum by all approaches was also characterized by FTIR and it was established that no significant chemical structure changes were obtained due to the treatment.

Ultrasonic effects on the degradation kinetics, preliminary characterization and antioxidant activities of polysaccharides from Phellinus linteus mycelia

In this study, a high-molecular-weight polysaccharide PL-N isolated from the alkaline extract of Phellinus linteus mycelia was degraded by ultrasound. Results showed that ultrasound treatment at different ultrasonic intensities decreased the intrinsic viscosity and molecular weight of PL-N, as well as narrowed the molecular weight distribution. A larger reduction in intrinsic viscosity and molecular weight was caused by a higher ultrasonic intensity. The degradation kinetics model was fitted to (1/Mt−1/M0)=k·t, and the reaction rate constant (k) increased with increasing ultrasonic intensity. Ultrasound degradation did not change the primary structure of PL-N, and scanning electron microscopy analysis indicated that the morphology of the original PL-N was different from that of degraded PL-N fractions. Antioxidant activity assays in vitro indicated that the degraded PL-N fraction with low molecular weight had stronger hydroxyl radical scavenging capacity and higher TEAC and FRAP values.

Ultrasound assisted enzymatic depolymerization of aqueous guar gum solution

The present work investigates the effectiveness of application of low intensity ultrasonic irradiation for the intensification of enzymatic depolymerization of aqueous guar gum solution. The extent of depolymerization of guar gum has been analyzed in terms of intrinsic viscosity reduction. The effect of ultrasonic irradiation on the kinetic and thermodynamic parameters related to the enzyme activity as well as the intrinsic viscosity reduction of guar gum using enzymatic approach has been evaluated. The kinetic rate constant has been found to increase with an increase in the temperature and cellulase loading. It has been observed that application of ultrasound not only enhances the extent of depolymerization but also reduces the time of depolymerization as compared to conventional enzymatic degradation technique. In the presence of cellulase enzyme, the maximum extent of depolymerization of guar gum has been observed at 60W of ultrasonic rated power and ultrasonic treatment time of 30min. The effect of ultrasound on the kinetic and thermodynamic parameters as well as the molecular structure of cellulase enzyme was evaluated with the help of the chemical reaction kinetics model and fluorescence spectroscopy. Application of ultrasound resulted in a reduction in the thermodynamic parameters of activation energy (Ea), enthalpy (ΔH), entropy (ΔS) and free energy (ΔG) by 47%, 50%, 65% and 1.97%, respectively. The changes in the chemical structure of guar gum treated using ultrasound assisted enzymatic approach in comparison to the native guar gum were also characterized by FTIR. The results revealed that enzymatic depolymerization of guar gum resulted in a polysaccharide with low degree of polymerization, viscosity and consistency index without any change in the core chemical structure which could make it useful for incorporation in food products.

Intensification of depolymerization of aqueous guar gum using hydrodynamic cavitation

Depolymerization of aqueous guar gum using hydrodynamic cavitation has been investigated for the first time, with a detailed understanding into the effect of initial concentration of polymer, inlet pressure, geometry of cavitating device, operating temperature and addition of potassium persulfate (KPS). The extent of depolymerization has been analyzed in terms of reduction in intrinsic viscosity using Ubbelohde glass capillary viscometer. It has been observed that lower initial concentration, higher inlet pressure, slit venturi as cavitating device and addition of KPS result in higher extent of depolymerization. Use of hydrodynamic cavitation alone under optimized conditions resulted in about 70% reduction in intrinsic viscosity whereas addition of KPS under optimum loading enhanced the extent of reduction to 96%. Kinetic analysis established that the kinetic rate constant increased with an increase in the temperature and concentration of KPS. FTIR analysis demonstrated that there were no structural changes and the chemical identity was retained. Hydrodynamic cavitation has been demonstrated to be more energy efficient and applicable at larger scale of operation as compared to ultrasound based operation.

Depolymerization of guar gum solution using different approaches based on ultrasound and microwave irradiations

The present work investigates the application of ultrasound and microwave operated individually or in combination for depolymerization of aqueous solution of guar gum. In addition, intensification aspects due to the use of an initiator, potassium persulfate (KPS), has been investigated. The extent of depolymerization has been analyzed in terms of the reduction in intrinsic viscosity. Also, the effectiveness of treatment approach has been analyzed on the basis of kinetic rate constant, limiting intrinsic viscosity and the time required for the desired extent of viscosity reduction. The kinetic rate constant has been found to increase with an increase in the temperature and KPS loading. For the individual operation involving irradiations, the rate was found to be higher in the case of ultrasound as compared to the microwave irradiations. In the case of sequential approach, microwave followed by ultrasound was more effective as compared to the approach of ultrasound followed by microwave. The obtained results clearly established that ultrasound in combination with KPS was the most effective approach for depolymerization. The work has also enabled to understand the effective role of KPS and operating temperature in intensifying the viscosity reduction of guar gum polysaccharides.

Degradation of chitosan by swirling cavitation

In the present work, degradation of chitosan by swirling cavitation was investigated. In swirling cavitation, the cavitating device of the turbine was used to generate cavitation. The effects of initial concentration, temperature, pressure, and treatment time on the degradation of chitosan were investigated initially. It was found that the degradation efficiency increased with increasing temperature, treatment time and pressure, and decreasing solution concentration. In addition, the optimum conditions were determined on the basis of orthogonal tests as follows: solution concentration 1 g·L− 1, pressure 0.4 MPa, treatment time 3 h and temperature 60 °C, the intrinsic viscosity reduction rate of chitosan was 83.65% under the optimum conditions. The structures of initial and degraded chitosan were characterized with Fourier-Transform infrared spectra (FT-IR). The present work establishes that swirling cavitation can be effectively used for the degradation of chitosan. Industrial relevance of medicine, food, chemical industry, cosmetic, water treatment, metal extraction and recycling, biochemical and biomedical engineering and many other fields.