Crystallization kinetics of emulsified triglycerides

Özilgen, Sibel; Catherine, Simoneau; German, J. Bruce; McCarthy, Michael J.; Reid, David

doi:10.1002/jsfa.2740610116

Cited by 25 publications

(11 citation statements)

References 9 publications

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“…Firstly, the lower viscosity of 0.2 % SFW/1 % PA emulsion could affect the particle properties of polymorphism and polydispersion. Some authors showed that the esters of some alcohols with an odd number of carbon atoms presented different morphologies depending on the cooling conditions, the wax concentration in the oil [24][25][26][27] droplet size, and the nature of the emulsifier [28][29][30]. It is often assumed that an emulsified fat crystallizes via a homogeneous mechanism, but in fact homogeneous nucleation will only dominate if the particle size is reduced, so there is much less than one nucleus per droplet and hence the dominant mechanism may depend on the composition and purity of the fat as well as the structure of the emulsion.…”

Section: Stabilitymentioning

confidence: 99%

Physical Properties of Aqueous Solutions of Pectin Containing Sunflower Wax

Baümler

Carelli

Martini

2013

J Americ Oil Chem Soc

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The aim of this study is to investigate the physical properties of aqueous solutions of pectin (PA) containing sunflower wax (SFW), which are used as a basis for producing edible films. The stability and the rheological and microstructural characteristics of SFW/PA mixtures were evaluated. SFW/PA mixtures formed oil-in-water emulsions that were milky and opaque in appearance and were stable towards phase separation. Polarized micrographs revealed the presence of wax crystals, whose size decreased as pectin concentration increased. The rheological behavior of the aqueous solutions of pectin containing different amounts of SFW were best described by the generalized power law model of Herschel- Bulkley (H-B), which gave the best fit in all the range of shear rate values. Apparent viscosities and yield stress were determined using this model, and both properties increased with increasing pectin content. The apparent viscosity values were between 0.0095 and 0.1031 Pa s. SFW addition resulted in a small decrease in viscosity for emulsions formulated with 1 and 2 % PA, but the opposite effect was observed for emulsions formulated with 3 % PA. In addition, shear stress values were higher for emulsions with higher PA content, but were not affected by SFW addition.

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Section: Stabilitymentioning

confidence: 99%

Physical Properties of Aqueous Solutions of Pectin Containing Sunflower Wax

Baümler

Carelli

Martini

2013

J Americ Oil Chem Soc

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“…Owing to its experimental simplicity and its potential to follow the process in situ, this NMR technique seems to be superior to the previous radiolabeling method. NMR spectroscopy (typically 1 H) is frequently used for the determination of total solids content in oil mixtures (5)(6)(7)(8), and 1 H NMR imaging has been applied to visualize crystallization in lipid dispersion (9)(10)(11). Deuterium ( 2 H) NMR also has been applied to characterize the molecular mobility in and the transitions between the αand β-crystalline states of PPP (12).…”

mentioning

confidence: 99%

Molecular exchange in thermal equilibrium between dissolved and crystalline tripalmitin by NMR

Löfborg¹,

Smith²,

Furó

et al. 2003

J Americ Oil Chem Soc

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An NMR technique to measure exchange kinetics at thermal equilibrium in dispersions of moderately soluble crystalline material is presented. By monitoring the exchange of molecules between pools in solid and dissolved form, one can characterize the surface specific exchange rate. Illustrative experiments were performed in a model system with β-type crystals of tripalmitin as the solid phase and tripalmitin, a fraction of it deuterated, dissolved in a medium-chain TG oil as the liquid phase. The concentration of deuterated tripalmitin in the solvent was followed by 2 H NMR after the crystals, which initially lack deuterated tripalmitin, were immersed in the liquid. The variation of the 2 H concentration in the solvent provided the surface specific exchange rate. No systematic errors, due to the slight difference in properties of the deuterated tripalmitin compared to hydrogenated tripalmitin, were observed. The methodology worked well between crystal concentrations of 2 and 4 wt%. Molecular or atomic crystallization or dissolution rates are relatively easy to measure in systems that are out of thermal equilibrium, e.g., by exhibiting a concentration or a chemical potential gradient. In contrast, exchange between different phases of the same molecular species under conditions of thermal equilibrium has drawn significantly less attention. This type of exchange can be imagined as molecular diffusion in and out over a phase boundary between two phases in equilibrium. In a suspension, this exchange is most pronounced at the outermost atomic/molecular layers of the solid particles involved, although there also may be an exchange between the inner and outer molecular layers. Hence, diffusion in and out of the solid phase predominantly represents solidification and dissolution of molecules on/from the solid-liquid interface, respectively.The exchange between solution and solid phase determines the rate of destabilization in systems with metastable compound solid phases. One example of such an exchange is TAG (fat) systems where several metastable and stable structures may exist, as exemplified by the cacao butter model recently reviewed by Sato et al.(1). Those authors identified several compound structures whose changing composition allows the formation of more stable forms. Hence, molecular exchange can strongly influence the kinetics of cacao butter and, in general, fat recrystallization.In general, exchange experiments performed at thermal equilibrium require marking the molecules by particular isotopes of the constituting atoms. Thereafter, the marked molecules or atoms can be followed by isotope-selective techniques such as radiochemical methods or NMR spectroscopy. If, as usual, one can assume that the marker isotope does not significantly alter the intermolecular interactions, such experiments can yield the exchange rates at thermal equilibrium. One methodologically related example (but not so concerning the nature of the exchange process) is NMR studies of hydrogen exchange rates in proteins (2): These provide vi...

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“…pNMR is a standard method for the measurement of solid fat content 63 and whilst water reduces accuracy methods have been developed for the measurement of solid fat content in food emulsions [64][65][66] . In comparison, ultrasound is more sensitive and accurate at low solid contents, however it becomes increasingly inaccurate at later stages in crystal growth where crystal networks are developing.…”

Section: A Brief Comparison Between Ultrasound Dsc Infra Red and Nmrmentioning

confidence: 99%

Nucleation in food colloids

Povey

2016

The Journal of Chemical Physics

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Nucleation in food colloids has been studied in detail using Ultrasound Spectroscopy. Our data shows that classical nucleation theory (CNT) remains a sound basis from which to understand nucleation in food colloids and analogous model systems using n-alkanes. Various interpretations and modifications of CNT are discussed with regard to their relevance to food colloids. Much of the evidence presented is based on ultrasound velocity spectrometry measurements which has many advantages for the study of nucleating systems compared to light scattering and NMR due to its sensitivity at low solid contents and its ability to measure true solid contents in the nucleation and early crystal growth stages. Ultrasound attenuation spectroscopy also responds to critical fluctuations in the induction region. We show however, that a periodic pressure fluctuation such as a quasi-continuous (as opposed to a pulse comprising only a few pressure cycles) ultrasound field can alter the nucleation process, even at very low acoustic intensity. Thus care must be taken when using ultrasound techniques that the measurements do not alter the studied processes. Quasi-continuous ultrasound fields may enhance or suppress nucleation and the criteria to determine such effects are derived. The conclusions of this paper are relevant to colloidal systems in foods, pharmaceuticals, agro-chemicals, cosmetics and personal products.

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Crystallization kinetics of emulsified triglycerides

Cited by 25 publications

References 9 publications

Physical Properties of Aqueous Solutions of Pectin Containing Sunflower Wax

Physical Properties of Aqueous Solutions of Pectin Containing Sunflower Wax

Molecular exchange in thermal equilibrium between dissolved and crystalline tripalmitin by NMR

Nucleation in food colloids

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