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
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- 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.
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 :
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- 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.
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
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- 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.
Effect of addition of proteins on the production of amorphous sucrose powder through spray drying
- Authors: Adhikari, Benu , Howes, Tony , Bhandari, Bhesh , Langrish, Tim
- Date: 2009
- Type: Text , Journal article
- Relation: Journal of Food Engineering Vol. 94, no. 2 (2009), p. 144 -153
- Full Text:
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- Description: Spray drying trials were carried out to produce amorphous sucrose powder. Firstly, pure sucrose solutions were prepared and spray dried at inlet and outlet temperatures of 160 °C and 70 °C, respectively. No amorphous powder was obtained and only 18% of the feed solids were recovered in a crystalline form, with the remaining solids lost as wall deposits. Secondly, sodium caseinate (Na-C) and hydrolyzed whey protein isolate (WPI) were added in sucrose:protein solid ratios of (99.5:0.5) and (99.0:1.0) and drying trials were conducted maintaining the initial drying conditions. In both these cases, greater than 80% of the feed solids were recovered in an amorphous form. The increase in protein concentration from 0.5% to 1% on dry solid basis did not further improve the recovery. The remarkable increase in recovery from a small addition of protein is attributed to preferential migration of protein molecules to the droplet-air interface, and the subsequent transformation of the thin, protein-rich film into a non-sticky glassy state upon drying. This film overcomes both the particle-to-particle and particle-to-wall stickiness. The measured bulk glass rubber transition temperature (Tg-r) values of the bulk mixtures at various moisture contents were very close to the corresponding mean glass transition temperature (Tg) of the pure sucrose indicating that surface layer Tg rather than the bulk Tg is responsible for this. Electron spectroscopy for chemical analysis (ESCA) studies revealed that the particle surface was covered by 50-58% (by mass) proteins. The calculated glass transition temperature of the surface layer (Tg,surface layer), based on the surface elemental compositions, showed that the Tg,surface layer has increased to the extent that it remained within the safe drying envelope of spray drying. © 2009 Elsevier Ltd. All rights reserved.