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.
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.
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
Glass transition behaviour of fructose
- Authors: Truong, V. , Bhandari, Bhesh , Howes, Tony , Adhikari, Benu
- Date: 2004
- Type: Text , Journal article
- Relation: International Journal of Food Science and Technology Vol. 39, no. 5 (2004), p. 569-578
- Full Text: false
- Reviewed:
- Description: The glass transition temperature and the second transition (the endothermic change between the glass transition and melting temperatures) of fructose were studied. The thermal history strongly affected both transitions of fructose. Storage for 10 days at 22degreesC increased the dynamic glass transition temperature from 16 to 25degreesC and decreased the second transition of fructose from 110 to 98degreesC in the first differential scanning calorimetric (DSC) scan. The amplitude of the second transition increased slightly with storage time and reached 260% of the first transition for vacuum oven dried samples. The effect of thermal history on the glass transition temperature of fructose can be removed by scanning the sample in a DSC to 130degreesC. The effects of water content, glucose and sucrose on the two transitions were also investigated.
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.
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.
Surface stickiness of drops of carbohydrate and organic acid solutions during convective drying : Experiments and modeling
- Authors: Adhikari, Benu , Howes, Tony , Bhandari, Bhesh , Troung, V.
- Date: 2003
- Type: Text , Journal article
- Relation: Drying Technology Vol. 21, no. 5 (2003), p. 839-873
- Full Text: false
- Reviewed:
- Description: Drying kinetics of low molecular weight sugars such as fructose, glucose, sucrose and organic acid such as citric acid and high molecular weight carbohydrate such as maltodextrin (DE 6) were determined experimentally using single drop drying experiments as well as predicted numerically by solving the mass and heat transfer equations. The predicted moisture and temperature histories agreed with the experimental ones within 6% average relative (absolute) error and average difference of +/- 1degreesC, respectively. The stickiness histories of these drops were determined experimentally and predicted numerically based on the glass transition temperature (T-g) of surface layer. The model predicted the experimental observations with good accuracy. A nonsticky regime for these materials during spray drying is proposed by simulating a drop, initially 120 mum in diameter, in a spray drying environment.