Estimation of concentration-dependent diffusion coefficient in drying process from the space-averaged concentration versus time with experimental data
- Authors: Loulou, T. , Adhikari, Benu , Lecomte, D.
- Date: 2006
- Type: Text , Journal article
- Relation: Chemical Engineering Science Vol. 61, no. 22 (2006), p. 7185-7198
- Full Text: false
- Reviewed:
- Description: The estimation of a concentration-dependent diffusion coefficient in a drying process is known as an inverse coefficient problem. The solution is sought wherein the space-average concentration is known as function of time (mass loss monitoring). The problem is stated as the minimization of a functional and gradient-based algorithms are used to solve it. Many numerical and experimental examples that demonstrate the effectiveness of the proposed approach are presented. Thin slab drying was carried out in an isothermal drying chamber built in our laboratory. The diffusion coefficients of fructose obtained with the present method are compared with existing literature results. (c) 2006 Elsevier Ltd. All rights reserved.
Preparation of starch-based nanoparticles through high-pressure homogenization and miniemulsion cross-linking: Influence of various process parameters on particle size and stability
- Authors: Shi, Aimin , Li, Dong , Wang, Li Ming , Li, Bingzheng , Adhikari, Benu
- Date: 2010
- Type: Text , Journal article
- Relation: Carbohydrate Polymers Vol. 83, no. 4 (2010), p. 1604-1610
- Full Text: false
- Reviewed:
- Description: A new and convenient synthetic route using high-pressure homogenization combined with water-in-oil (w/o) miniemulsion cross-linking technique was used to prepare sodium trimetaphosphate (STMP)-cross-linked starch nanoparticles. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) revealed that starch nanoparticles had narrow size distribution, good dispersibility and spherical shape. Effect of process parameters (surfactant content, water/oil ratio, starch concentration, homogenization pressure and cycles) on the starch nanoparticle size in miniemulsion was evaluated. We show that there is an optimal surfactant concentration giving rise to smaller starch nanoparticles and better stability. Apart from the water/oil ratio and starch concentration, the homogenization pressure and cycles (passes) also significantly affect the size of starch nanoparticles (p < 0.05). The stability analysis of starch nanoparticles in water for 2 h to 2 days and in temperature ranges of 25-45 °C showed firm structure and good stability. These nanoparticles are expected to be exploited as drug carriers. © 2010 Elsevier Ltd. All rights reserved.
- Description: 2003008433
Spray drying of skim milk mixed with milk permeate : Effect on drying behavior, physicochemical properties, and storage stability of powder
- Authors: Shrestha, A. , Howes, Tony , Adhikari, Benu , Bhandari, Bhesh
- Date: 2008
- Type: Text , Journal article
- Relation: Drying Technology Vol. 26, no. 2 (2008), p. 239-247
- Full Text: false
- Reviewed:
- Description: The possibility of using milk permeate (MP) to lower the protein level of skim milk powder (SMP) in producing powders of 34% and lower protein is explored. Skim milk suspensions with various levels of MP were prepared by mixing SMP and MP powder (MPP) at the ratios of 1: 0, 7: 3, 3: 7, and 0: 1: from 34 to 5.3% protein. The suspensions were dried in a spray dryer with inlet and outlet temperatures of 180 and 80 degrees C, respectively. Increasing permeate concentration in the mixture showed a greater tendency to stickiness manifested by lowered the cyclone recovery of the powder as more powder stuck on the wall of the dryer. Increasing permeate concentration in the resultant powder did not significantly affect the bulk density but led to a reduction in the particle size and also made the powder slight green and yellowish in color. It also found to lower the glass transition temperature (T-g) of the skim milk powder (SMP) and induce crystallization of lactose at lower water activity (a(w) >= 0.328 for SMP: MPP of 3: 7 and 0: 1 compared to a(w) >= 0.0.432 for SMP: MPP of 1: 0 and 3: 7). Addition of MP in SMP lowered the Tg values of the resulting powders. The permeate fraction in spray-dried SMP/MPP mixtures found to lower the critical aw and moisture content, suggesting the SMP mixed with MPP is more likely to become sticky than SMP alone (at 34% protein) when stored at a similar water activity and moisture content.
In situ characterization of stickiness of sugar-rich foods using a linear actuator driven stickiness testing device
- Authors: Adhikari, Benu , Howes, Tony , Bhandari, Bhesh , Truong, V.
- Date: 2003
- Type: Text , Journal article
- Relation: Journal of Food Engineering Vol. 58, no. 1 (2003), p. 11-22
- Full Text: false
- Reviewed:
- Description: A stickiness testing device based on the probe tack test has been designed and tested. It was used to perform in situ characterization of drying hemispherical drops with an initial radius 3.5 mm. Tests were carried out in two drying temperatures, 63 and 95 degreesC. Moisture and temperature histories of the drying drops of fructose, honey, sucrose, maltodextrin and sucrose-maltodextrin mixtures were determined. The rates of moisture evaporation of the fructose solution was the fastest while those of the maltodextrin solution was the lowest. A profile reversal was observed when the temperature profiles of these materials were compared. Different modes of failure were observed during the stickiness tests. Pure fructose and honey solutions remained completely sticky and failed cohesively until the end of drying. Pure sucrose solution remained sticky and failed cohesively until complete crystallization occurred. The surface of the maltodextrin drops formed a skin shortly after the start of drying. It exhibited adhesive failure and reached a state of non-adhesion. Addition of maltodextrin significantly altered the stickiness of sucrose solution. (C) 2002 Elsevier Science Ltd. All rights reserved.
The effect of food-grade low-molecular-weight surfactants and sodium caseinate on spray drying of sugar-rich foods
- Authors: Jayasundera, Mithila , Adhikari, Benu , Adhikari, Raju , Aldred, Peter
- Date: 2010
- Type: Text , Journal article
- Relation: Food Biophysics Vol. 5, no. 2 (2010), p. 128-137
- Full Text: false
- Description: The effect of low-molecular-weight surfactants (LMS) and sodium caseinate (NaCas) on spray drying of sugar-rich foods has been studied. Sucrose and NaCas were selected as a model sugar-rich food and protein, respectively. Sodium stearoyl lactylate (SSL) and Polysorbate 80 (Tween 80) were chosen as model ionic and nonionic LMS. Sucrose-NaCas solutions with the solids ratio of 99.5:0.5 in the absence and presence (0.01% and 0.05%) of SSL and Tween 80 were prepared. The feed solutions had 25% solid concentration in all cases. The dynamic surface tension (DST) values of the solutions were measured for 100 s and the solutions were subsequently spray dried at inlet and outlet temperatures of 165 and 65 °C, respectively. The glass-rubber temperature (Tg-r), the surface elemental composition and amorphous-crystalline nature of the powders were also determined. At these concentrations and experimental time frame, it was found that the proteins preferentially migrated to the air-water interface reasonably swiftly. The addition of LMS resulted in partial or complete displacement of the proteins from the air-water interface. For spray-drying trials with the yield of 82.0%, it was found that 52.0% of the powder particle surface was covered with proteins. The powder recovery was greatly reduced by the LMS concentration and type. At 0.05% on dry solid basis, in the case of nonionic surfactant (Tween 80), the displacement of protein from the surface was such that no powder was recovered. The ionic surfactant (SSL) displaced 2.0% and 29.3% proteins from the droplet surface at concentrations of 0.01% and 0.05%, respectively, resulting in 75.5 ± 1.8% and 30.1 ± 1.4% powder yield. The Tg-r results revealed that the amount of protein required for successful spray drying of the sucrose-protein solution depends on the amount of proteins present in the droplet surface but not in the bulk. X-ray diffraction and scanning electron microscopy results confirmed that the powders of both sucrose-NaCas and sucrose-NaCas with 0.01% SSL were mostly amorphous, while those with sucrose-NaCas-Tween 80 (0.01%) and sucrose-NaCas-SSL (0.05%) were crystalline. © 2010 Springer Science+Business Media, LLC.
The effect of addition of flaxseed gum on the emulsion properties of soybean protein isolate (SPI)
- Authors: Wang, Yong , Li, Dong , Wang, Li Ming , Adhikari, Benu
- Date: 2011
- Type: Text , Journal article
- Relation: Journal of Food Engineering Vol. 104, no. 1 (2011), p. 56-62
- Full Text: false
- Reviewed:
- Description: The effect of addition of flaxseed gum on the emulsion properties of soybean protein isolate (SPI) were investigated in this study. Flaxseed gum with 0.05-0.5% (w/v) concentration was used together with 1% (w/v) SPI to emulsify 10% (v/v) soybean oil. The emulsion was analyzed for emulsion activity (turbidity), stability, particle size, surface charge, and rheological properties. The turbidity and absolute zeta-potential values decreased initially by the addition of flaxseed gum and subsequently increased with further increase in the gum concentration to reach their peak around 0.35% (w/v) gum. The particle size of the emulsion decreased and reached a minimum value at 0.1% (w/v) gum concentration. Any increase in gum concentration beyond this value resulted into increase in the particle size. This study would help to widen the application of SPI and flaxseed gum mixture, and also contribute to the understanding of protein-gum interaction in emulsion. © 2010 Elsevier Ltd. All rights reserved.
The effect of low molecular weight surfactants and proteins on surface stickiness of sucrose during powder formation through spray drying
- Authors: Adhikari, Benu , Howes, Tony , Wood, B. J. , Bhandari, Bhesh
- Date: 2009
- Type: Text , Journal article
- Relation: Journal of Food Engineering Vol. 94, no. 2 (2009), p. 135 -143
- Full Text:
- Reviewed:
- Description: The effect of competitive surface migration of proteins and low molecular weight surfactants (LMS) on the powder recovery in spray drying of highly sticky sugar-rich food has been studied. Sucrose was chosen as a model sugar-rich food because it cannot be easily converted into a pure amorphous powder through spray drying. Sodium caseinate (Na-C) and hydrolyzed whey protein isolate (WPI) were used as model proteins. Polysorbate 80 (Tween-80) and sodium dodecyl sulfate (Na-DS) were used as model non-ionic and ionic LMS. A sucrose solution was spray dried without any additives to establish a base case. Following this, spray drying trials of sucrose-protein solutions were conducted. The sucrose: protein ratio was maintained at 99.5:0.5 and 99.0:1.0. Finally, 0.05% of Tween-80 and Na-DS, on a nominal feed basis, were individually added to the solutions and spray dried. The solid concentration of all of the feed solutions was set at 25% and the inlet and outlet temperatures were maintained at 170 °C and 70 °C, respectively. Powder recovery was determined using a standard procedure and taken as an indicator of the surface stickiness. Coverage of the particle surface by the proteins was determined through elemental surface analysis and a nitrogen balance. It was found that in the absence of LMS, the proteins covered up to 55% of the particle surface and increased the powder recovery to between 84% and 85%. Formation of a glassy protein-rich film acts to reduce the surface stickiness of sucrose droplets. However, when LMS was added to the sucrose-protein solutions, the recovery dropped to zero in the case of Tween-80. In the case of Na-DS the recoveries ranged to 39% and 68%. At these recoveries 83% and 59% of the protein, respectively, was displaced from the surface. This drastic effect of surfactant types on the powder recovery is explained using the Orogenic Displacement model. © 2009 Elsevier Ltd. All rights reserved.
Preparation of gelatin microparticles using water-in-water (w/w) emulsification technique
- Authors: Kong, Yin. Q. , Li, Dong , Wang, Li. J. , Adhikari, Benu
- Date: 2010
- Type: Text , Journal article
- Relation: Journal of Food Engineering Vol. 103, no. 1 (2010), p. 9-13
- Full Text: false
- Reviewed:
- Description: Gelatin microparticles were prepared using water-in-water (w/w) emulsification technique, in which aqueous solutions of gelatin and polypropylene glycol (PEG) were employed as dispersed phase and continuous phase, respectively. The effect of gelatin and PEG concentrations on the size of gelatin microparticles were evaluated. The size of the gelatin microparticles decreased with the increase in PEG concentration and increased with the increase in gelatin concentration. The gelatin microparticles obtained through this process were nearly perfect spheres with smooth surface. The gelatin microparticles, both un-crosslinked and crosslinked, were found to be fully amorphous in nature. The un-crosslinked gelatin microparticles were found to swell instantaneously (within 10 s) whereas the crosslinked ones were quite resistant to water uptake. © 2010 Elsevier Ltd. All rights reserved.
Surface modification of spray dried food and emulsion powders with surface-active proteins : A review
- Authors: Jayasundera, Mithila , Adhikari, Benu , Aldred, Peter , Ghandi, Amir
- Date: 2009
- Type: Text , Journal article
- Relation: Journal of Food Engineering Vol. 93, no. 3 (2009), p. 266-277
- Full Text:
- Reviewed:
- Description: Spray drying is a well-established and widely used method for transforming a wide range of liquid food products into powder form. Stickiness is the limitation in spray drying of different sugar and acid-rich food products. To minimize this problem process and material science based approaches are in place. However, these remedies have their own drawbacks. Surface modification of droplets/particles is a novel way to minimize stickiness. It is timely that the research efforts on surface modification of droplets/particles be reviewed. Therefore, this review highlights the recent research dealing with surface modification of emulsions and spray dried powders. The theoretical foundation, mechanisms and methods used to achieve surface modification of food and emulsion powders are highlighted. © 2009 Elsevier Ltd. All rights reserved.
Effect of temperature and plasticizer molecular size on moisture diffusion of plasticized-starch biopolymer
- Authors: Chaudhary, Deeptangshu , Adhikari, Benu
- Date: 2010
- Type: Text , Journal article
- Relation: Starch Vol. 62, no. 7 (2010), p. 364-372
- Full Text: false
- Reviewed:
- Description: Using starch pellets as precursor for traditional edible food packaging for making thermoformed products is an excellent idea. We report here the complex water migration behaviour of starch pellets as influenced by plasticizer type and concentration at various temperatures. The evidence for synergistic interaction between plasticizers and water within starch is shown by the reduced effective moisture diffusivities and moisture migration fluxes at different overall plasticizer concentrations. In addition, the effective moisture diffusivities showed stronger dependence on moisture concentration and the plasticizer molecular weight even though the moisture flux was comparable. The drying process was characterized by two effective diffusion coefficients (D 1, D2) and interestingly, the coefficients were an order of significance apart. Peleg model was investigated for predicting the drying behaviour and it is shown that the Peleg constants k1 and k 2 increase with temperature. k2, a material structure parameter, showed variation by addition of plasticizers, indicating that plasticizers were able to modify fundamental structure; and xylitol showed greater average k2 values than glycerol. Further, k1, a moisture diffusivity parameter, was affected by temperature and Arrhenius relationship was used for activation energy values for k1 of plasticized starch. It is shown that compared to starch and water, presence of plasticizer had many order of significance higher k1 and confirm the hypothesis that plasticizers can 'lock' in water within the new structure. Xylitol showed better stability in controlling moisture diffusivities and migration fluxes as compared to glycerol. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA.
- Description: 2003008252
Effect of metal chlorides on the sintering and densification of hydroxyapatite adsorbent
- Authors: Nzihou, A. , Adhikari, Benu , Pfeffer, R.
- Date: 2005
- Type: Text , Journal article
- Relation: Industrial & Engineering Chemistry Research Vol. 44, no. 6 (2005), p. 1787-1794
- Full Text: false
- Reviewed:
- Description: This work is part of a series of studies dealing with the evaluation of the effects of major elements of solid waste, especially metallic oxides, nitrates, sulfates, and chlorides, on the sintering and the densification of calcium hydroxyapatite (Ca-HAP) adsorbent. The effects of chloride salts of potassium (KCl) and zinc (ZnCl2) on sintering and densification of Ca-HAP were studied using surface area reduction and shrinkage measurements. The addition of KCl (2% w/w) activated the sintering process by bringing a swift reduction in surface area and lowering the densification temperature. However, a low final densification was achieved. Increasing the amount of this additive to 10% w/w further lowered the final densification and lowered the densification temperature of hydroxyapatite by 150 oC. On the other hand, the addition of 2 wt % of ZnCl2 deactivated the sintering process by slowing down the densification process and raising the densification temperature. However, the reduction of surface area was comparable to that of Ca-HAP. The densification rate contained two or more rate maxima indicating the additives (salts) bring multiple speeds in the densification process.
- Description: 2003007545
Understanding polymeric amylose retrogradation in presence of additives
- Authors: Chaudhary, Deeptangshu , Adhikari, Benu
- Date: 2009
- Type: Text , Journal article
- Relation: Journal of Applied Polymer Science Vol. 115, no. 5 (2009), p. 2703 - 2709
- Full Text: false
- Reviewed:
- Description: Polymeric aging in starch is an important equilibrating process leading to long-chain amylose recrystallization and anisotropic properties of material made from starch. Investigations into a number of plasticizers and hydrocolloids showed that their water retention/binding capability influence the starch polymer’s crystallinity. Addition of up to 8 wt % glycerol and 3 wt % xylitol acted as an antiplasticizer and apparently increased the total crystalline phase, which reduced the degree of elongation of amylose matrix by 15%. Maltodextrin and xanthan gum also reduced matrix elongation capability but X-ray diffraction (XRD) analysis showed samples with varying crystallinity, and the extent of crystallinity did not correlate with respective tensile properties. Additives such as maltodextrin, with similar molecular structure as amylose, were ineffective in increasing degree of elongation even at 15 wt % addition rate, because of formation of pockets of crystalline region, as observed by XRD analysis. Both xylitol and xanthan gum samples showed similar tensile strength and elongation properties, but the water retention capability of xylitol-filled starch samples was about 27% lower than xanthan gum samples, at their respective higher concentrations. A dynamic structural unit is proposed to satisfy the isotropic increase in tensile strength and degree of elongation in oriented starch matrix. VVC 2009Wiley Periodicals, Inc. J Appl Polym Sci 000: 000–000, 2009
Sticky and collapse temperature : Measurements, data and predictions
- Authors: Adhikari, Benu , Bhandari, Bhesh
- Date: 2009
- Type: Text , Book chapter
- Relation: Food properties handbook Chapter 11 p. 347-380
- Full Text: false
- Description: 2003007516
Characterization of the surface stickiness of fructose-maltodextrin solutions during drying
- Authors: Adhikari, Benu , Howes, Tony , Bhandari, Bhesh , Truong, V.
- Date: 2003
- Type: Text , Journal article
- Relation: Drying Technology Vol. 21, no. 1 (2003), p. 17-34
- Full Text: false
- Reviewed:
- Description: A probe tack test has been used for the in situ characterization of the surface stickiness of hemispherical drops with an initial radius of 3.5 mm while drying. Surface stickiness of drops of fructose and maltodextrin solutions dried at 63degreesC and 95degreesC was determined. The effect of addition of maltodextrin on fructose solution-was studied with fructose/maltodextrin solid mass ratios of 4: 1, 1: 1, and 1:4. Pure fructose solutions remained completely sticky and failed cohesively even when their moisture approached zero. Shortly after the start of drying, the surface of the maltodextrin drops formed a skin, which rapidly grew in thickness. Subsequently the drop surface became completely nonsticky probably due to transformation of outer layers into a glassy material. Addition of malto,dextrin significantly altered the surface stickiness of drops of fructose solutions, demonstrating its use as an effective drying aid.
Effect of plasticizers on the moisture migration behavior of low-amylose starch films during drying
- Authors: Adhikari, Benu , Chaudhary, Deeptangshu , Clerfeuille, E
- Date: 2010
- Type: Text , Journal article
- Relation: Drying Technology Vol. 28, no. 4 (2010), p. 468-480
- Full Text: false
- Reviewed:
- Description: We report the synergistic and competitive interactions between multiple plasticizers in plasticized low-amylose starch that result in either enhanced or reduced water migration fluxes and effective moisture diffusivities. The starch was plasticized using glycerol and xylitol either individually or in 1:1 combination. The water migration fluxes and moisture diffusivities were higher in xylitol plasticized films compared to the glycerol plasticized ones. For low plasticizer concentrations, the presence of both the plasticizers competitively reduced the effective moisture diffusivities and moisture migration fluxes due to antiplasticization. However, at higher plasticizer contents (at and above 15wt%), the presence of multiple plasticizers enhanced the moisture migration fluxes and effective moisture diffusivities due to synergistic plasticization. The moisture migration fluxes and effective moisture diffusivities exhibited both moisture and plasticizer concentration dependence and the former was found to be stronger than the latter. These findings can be used for designing and controlling the vapor barrier properties of starch-based bioplastics during drying and formulation phase.
- Description: 2003008138
A composite reaction engineering approach to drying of aqueous droplets containing sucrose, maltodextrin (DE6) and their mixtures
- Authors: Patel, Kamlesh , Chen, Xiao Dong , Lin, Sean , Adhikari, Benu
- Date: 2009
- Type: Text , Journal article
- Relation: AIChE Journal Vol. 55, no. 1 (2009), p. 217-231
- Full Text: false
- Description: Recently, several studies have been published on the spray drying of sucrose and other low-molecular-weight sugars which are typically sticky materials. Sticky materials can not be processed under normal drying conditions and may require addition of high-molecular-weight carbohydrates such as maltodextrin. Predicting appropriate drying conditions are however difficult due to the unavailability of drying kinetics. In this article, we have formulated the drying kinetics model using the reaction engineering approach (REA) for the drying of aqueous sucrose and aqueous maltodextrin (DE6) droplets. The relative activation energy was empirically obtained based on experimental measurements. To model the drying of droplets containing both solutes (sucrose and maltodextrin), a new "composite" REA has been established and presented here for the first time. Results demonstrated that the composite REA forms a reliable framework to model the drying of aqueous solutions of pure carbohydrates and their mixtures. © 2008 American Institute of Chemical Engineers.
Glass transition behavior of spray dried orange juice powder measured by differential scanning calorimetry (DSC) and thermal mechanical compression test (TMCT)
- Authors: Shrestha, A. , Ua-Arak, T. , Adhikari, Benu , Howes, Tony , Bhandari, Bhesh
- Date: 2007
- Type: Text , Journal article
- Relation: International Journal of Food Properties Vol. 10, no. 3 (2007), p. 661-673
- Full Text: false
- Description: Spray drying behavior of orange juice concentrate with various levels of maltodextrin (DE 6) was studied. Five combinations of orange juice concentrate and maltodextrin (25:75, 30:70, 35:65, 40:60, and 50:50) were spray dried at 160 and 65 degrees C inlet and outlet temperatures, respectively. The product recovered with 50% maltodextrin concentration was sticky and only 20% powder was recovered. The recovery of orange juice powder increased as the amount of maltodextrin in powders increased. The particle size and bulk density remained almost the same in all except in 50% maltodextrin powder which was slightly larger and more dense. The moisture content of spray dried powders was high and desiccated before measuring glass transition temperature. The anhydrous spray dried powders showed increased T-g values with increasing maltodextrin concentration, from 66 degrees C in 50% maltodextrin to 97 degrees C in 75% maltodextrin containing powders. The glass rubber transition ( Tg-r) values of all the products measured using novel Thermal Mechanical Compression Test (TMCT) were higher than T-g values measured by DSC; the difference in values increased with increase in maltodextrin concentration.
The impact of various drying kinetics models on the prediction of sample temperature-time and moisture content-time profiles during moisture removal from stratum corneum
- Authors: Kar, S. , Chen, Xiao Dong , Adhikari, Benu , Lin, S. X. Q.
- Date: 2009
- Type: Text , Journal article
- Relation: Chemical Engineering Research and Design Vol. 87, no. 5 (2009), p. 739-755
- Full Text:
- Reviewed:
- Description: An attempt has been made here to model the moisture transport kinetics across porcine stratum corneum. Samples of porcine skin were dissected in the form of 'thin layers' (i.e. stratum corneum) of dimensions of 11.3 × 11.3 mm (70-200 μm thick). These layers were dried in a laboratory convection air dryer at 37 °C (normal human body temperature). The changes in weights of the samples were noted. The weight loss data was then converted in terms of moisture content (dry basis) and were monitored over time. Thereafter they were fitted against an empirical equation notably the Page model (Model 1) and the solution generated by the Fickian diffusion equation (Model 2). The current paper demonstrates the effectiveness of these two models in prediction of the sample temperature during drying. Furthermore, it also demonstrates the variation in spatial distribution of moisture content within the skin sample when moisture content and temperature dependency are introduced in the diffusivity. Such findings are important especially when developing skin multi-compartment physiologically based pharmacokinetic (PBPK) models to assess transdermal permeation of various hydrophilic penetrants. © 2008 The Institution of Chemical Engineers.
- Description: 2003006794
Thin-layer isothermal drying of fructose, maltodextrin, and their mixture solutions
- Authors: Adhikari, Benu , Howes, Tony , Shrestha, A. , Tsai, W. , Bhandari, Bhesh
- Date: 2006
- Type: Text , Journal article
- Relation: Drying Technology Vol. 24, no. 11 (2006), p. 1415-1424
- Full Text: false
- Reviewed:
- Description: Solutions of fructose, maltodextrin (DE 5), and their mixtures at the ratios of 20:80, 40:60, 50:50, 60:40, and 80:20 were gelled with 1% agar-agar and dried under convective-conductive drying conditions. The thin slabs were maintained at isothermal drying condition of 30 and 50 degrees C. Yamamoto's simplified method based on regular regime approach was used to calculate the (effective) moisture diffusivity. Both the drying rates and the moisture diffusivity exhibited strong concentration dependence. The concentration dependence was stronger in the case of fructose and fructose rich solutions. Both the moisture diffusivity and drying rates of the mixture solutions were enhanced due to plasticization of fructose on maltodextrin, which is explained through free volume theory.
Sticky behavior of whey protein isolate and lactose droplets during convective drying
- Authors: Adhikari, Benu , Howes, Tony , Shrestha, A. , Bhandari, Bhesh
- Date: 2006
- Type: Conference paper
- Relation: Paper presented at 2006 AIChE Spring National Meeting - 5th World Congress on Particle Technology, Orlando, Florida :
- Full Text: false
- Description: Stickiness of whey protein isolate (WPI) and spray dried lactose droplets was studied at two air temperatures (65±0.5°C, 80±0.5°C), 0.75 m/s air velocity and 2-2.5% relative humidity using an in situ stickiness testing device. A stainless steel probe with 50 mm/min contact/withdrawal speed was used. The moisture and temperature histories were measured through parallel experiments. In each case, the surface of the lactose droplet remained sticky and failed cohesively until the surface was completely surrounded with crystals. The crystal layer remained fragile, fractured upon the probe contact and a thin layer of solution came out to the probe surface even after the moisture (u, dry basis) was lower than 0.2. WPI droplets formed thin and smooth skin immediately after coming in contact with hot air. The tensile strength of this skin increased rapidly and peaked (u = 2.14 at 45°C and u = 1. 47 at 65.7°C) fairly early during drying process. WPI droplet surface became completely non-sticky soon after attaining the peak tensile strength (u =1.32 at 53.4 °C and u= 1.05 at 68.8°C), mainly due to transformation of the outer layer of the skin into glassy material. The skin forming and surface active nature of WPI was exploited to minimize the stickiness of honey during spray drying. Replacement of 5% (w/w) maltodextrin with WPI raised the powder recovery of honey solids from 28% to 80%. Stickiness of the WPI on glass, Teflon and polyurethane surfaces was studied by replacing the contact surface of the probe with these materials. It was found that the stickiness of glass surface was the highest at test temperatures. Teflon surface offered the lowest stickiness at the test temperatures making it suitable materials to minimize solution/particle stickiness through coating.