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Vacuum-induced Bubble Formation in Liquid-tempered Chocolate (2005)

Haedelt, Josefin ; Pyle, D. Leo ; Beckett, Steve T. ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

Journal of food science 70 (2005), S. 0

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ISSN: 1750-3841

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology

Notes: : Bubble inclusion is one of the fastest growing operations practiced in the food industry. A variety of aerated foods is currently available in supermarkets, and newer products are emerging all the time. This paper aims to combine knowledge on chocolate aeration with studies performed on bubble formation and dispersion characteristics. More specifically, we have investigated bubble formation induced by applying vacuum. Experimental methods to determine gas hold-up (volume fraction of air), bubble section distributions along specific planes, and chocolate rheological properties are presented. This study concludes that decreasing pressures elevate gas hold-up values due to an increase in the number of bubble nuclei being formed and release of a greater volume of dissolved gases. Furthermore, bubbles are observed to be larger at lower pressures for a set amount of gas because the internal pressure needs to be in equilibrium with the surrounding pressures. Temperature-induced changes to the properties of the chocolate have less of an effect on bubble formation. On the other hand, when different fats and emulsifiers are added to a standard chocolate recipe, milk fat was found to increase, significantly, the gas hold-up values and the mean bubble-section diameters. It is hypothesized that this behavior is related to the way milk fats, which contain different fatty acids to cocoa butter, crystallize and influence the setting properties of the final product. It is highlighted that apparent viscosity values at low shear rate, as well as setting behavior, play an important role in terms of bubble formation and entrainment.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-2621.2005.tb07090.x

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Reverse micellar mass-transfer processes: Spray column extraction of lysozyme (1996)

Lye, Gary J. ; Asenjo, Juan A. ; Pyle, D. Leo

Hoboken, NJ : Wiley-Blackwell

AIChE Journal 42 (1996), S. 713-726

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ISSN: 0001-1541

Keywords: Chemistry ; Chemical Engineering

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology

Notes: Protein partitioning kinetics was measured for the semibatch extraction of lysozyme in a laboratory-scale, liquid-liquid spray column. The organic, isooctane phase contained reverse micelles formed from the anionic surfactant, sodium di-2-ethylhexyl sulfosuccinate. For the extraction of protein from aqueous to reverse micellar phases, experiments were performed over a range of dispersed-phase flow rates for cases of the organic- or aqueous-phase dispersion. The influence of aqueous-phase pH and ionic strength, which influence electrostatic interactions between protein and reverse micelles, was also investigated. Results were interpreted in terms of a two-film model of mass transfer. The nature of the dispersed pahse could significantly influence the partitioning kinetics, while study of the droplet hydrodynamics suggested that stagnant drops were formed regardless of which phase was dispersed. Literature correlations for describing the droplet-formation process and droplet hydrodynamics predicted measured values satisfactorily. Attempts wer also made to predict overall mass-transfer coefficients based on existing correlations describing mass transfer during droplet formation, free rise (or fall), and coalescene. Predicted values of KL were 2-10 times greater than measured values, probably because of large concentrations of surfactant used to formulate the reverse micelle phases. This approach did, however, provide detailed information on the quantity of protein transferred during the successive processes of droplet formation, free rise (or fall) and coalescence.

Additional Material: 7 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/aic.690420312

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Protein extraction by reverse micelles: Studies on the recovery of horseradish peroxidase (1994)

Regalado, Carlos ; Asenjo, Juan A. ; Pyle, D. Leo

New York, NY [u.a.] : Wiley-Blackwell

Biotechnology and Bioengineering 44 (1994), S. 674-681

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ISSN: 0006-3592

Keywords: reverse micelles ; extraction ; horseradish peroxidase purification ; AOT ; Chemistry ; Biochemistry and Biotechnology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology

Notes: Phase transfer studies were carried out on the solubilization of horseradish peroxidase (HRP) (E.C. 1.11.1.7) in reverse micelles formed in isooctane using the anionic surfactant, aerosol OT, at concentrations between 50 and 110mM. The selectivity of this methodology was tested, because the HRP used comprised a mixture of seven different isoenzymes with a wide range of isoelectric points. Forward and backward transfers were carried out in wellstirred vessels until equilibrium was reached. Significant protein partitioning could only be obtained by using NaCl to adjust ionic strength in pH range between 1.5 and 3.5, with a maximum at pH 3. The back transfer process was best at pH 8 with 80mM phosphate buffer and 1 M KCI. A loss of 1% to 3% of the surfactant through precipitation at the interface at pH〈4 was observed, which may be due to instability in this pH region, because, even without protein, a similar precipitate was noticed. Protein partitioning was approximately constant when the ionic strength was increased up to 1 MNaCl at pH 3, but protein recovery in back transfer decreased accordingly. Hydrophobic interactions together with association between the protein and surfactant might be responsible for that behavior. Protein partitioning remained the same when the surfactant concentration was decreased to 50 mM, at the expense of higher variability. HPLC chromatograms showed no apparent damage to the protein after reverse micellar extraction. Protein partitioning is best when the temperature is kept at 25×C. The amount of protein and specific activity recovered strongly depends on the phase ratio used during forward transfer. Overall activity recovery varied from 87% to 136% when the phase ratio was increased from 1:1 to 30:1 in forward transfer. This behavior may be due to a change in the ratio of the three isoenzymes recovered after the backward transfer process, with the most active one being increasingly enriched at higher phase ratios. © 1994 John Wiley & Sons, Inc.

Additional Material: 7 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/bit.260440603

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