Abstract:Raffinose is a major impurity in sugar production from sugar beets. It exists to the extent of 0.3 to 1.2% of the sugar present in the beet (McGinnis, 1971). Previous research (Smythe, 1967b Mantovani and Fagioli, 1964;Binder and Murphy, 1982;Vaccari et al., 1986) has shown that raffinose has a strong effect on both the habit and the growth rate of sucrose crystals grown in its presence. Powers (1960). Hungerford and Nees (l934), Smythe ( 1967a), and Vaccari et al.(1 986) among others have shown that raffinos… Show more
“…Because of its chemical structure and orientation, raffinose was not only adsorbed onto the surface, it was physically incorporated into the sucrose crystal. The accompanying galactose created a steric hindrance, which stopped further growth on that face of the sucrose crystal (Liang et al. , 1989).…”
Whey protein films plasticised with sucrose have excellent oxygen barrier properties and high gloss that are reduced with time as sucrose crystallises. Whey protein isolate (WPI) films plasticised with sucrose were stored in 53% relative humidity for up to 60 days. The oxygen permeability, tensile properties and gloss of the films were measured periodically following ASTM (American Society for Testing Materials) methodology. Changes in properties were compared with changes in WPI films plasticised with glycerol (no crystallisation) or plasticised with sucrose (crystallisation) plus a crystallisation inhibitor. The two inhibitors studied were lactose and raffinose. Crystallisation in WPI/sucrose films decreased tensile strength and elongation at break. However, the inhibitors hindered sucrose crystallisation, and the desired film properties were maintained for a longer period of time. Raffinose was the more effective inhibitor, maintaining the film flexibility and barrier properties for over 28 days and maintaining gloss at almost 90% of the initial value for 60 days of storage.
“…Because of its chemical structure and orientation, raffinose was not only adsorbed onto the surface, it was physically incorporated into the sucrose crystal. The accompanying galactose created a steric hindrance, which stopped further growth on that face of the sucrose crystal (Liang et al. , 1989).…”
Whey protein films plasticised with sucrose have excellent oxygen barrier properties and high gloss that are reduced with time as sucrose crystallises. Whey protein isolate (WPI) films plasticised with sucrose were stored in 53% relative humidity for up to 60 days. The oxygen permeability, tensile properties and gloss of the films were measured periodically following ASTM (American Society for Testing Materials) methodology. Changes in properties were compared with changes in WPI films plasticised with glycerol (no crystallisation) or plasticised with sucrose (crystallisation) plus a crystallisation inhibitor. The two inhibitors studied were lactose and raffinose. Crystallisation in WPI/sucrose films decreased tensile strength and elongation at break. However, the inhibitors hindered sucrose crystallisation, and the desired film properties were maintained for a longer period of time. Raffinose was the more effective inhibitor, maintaining the film flexibility and barrier properties for over 28 days and maintaining gloss at almost 90% of the initial value for 60 days of storage.
“…This value is typical for the crystallization of simple sugars. Previous research on crystal growth of sucrose for example, gives an activation energy of crystal growth as 28.9 to 33.1 kJ/mol for growth from pure solutions, and 45.6 to 57.7 kJ/mol for growth from solutions having raffinose as an impurity. 9 Mean size crystal growth rates for α-glucose monohydrate as a function of relative supersaturation at 10 (·), 25 (▪), and 40 °C (◆). 10 An Arrhenius plot of the growth rate constant for determination of the activation energy of crystal growth.…”
Section: Resultsmentioning
confidence: 99%
“…This value is typical for the crystallization of simple sugars. Previous research on crystal growth of sucrose 22 for example, gives an activation energy of crystal growth as 28.9 to 33.1 kJ/mol for growth from pure solutions, and 45.6 to 57.7 kJ/mol for growth from solutions having raffinose as an impurity.…”
Section: Effect Of Observation Time and Temperature On Sntmentioning
Investigation of the secondary nucleation threshold (SNT) of R-glucose monohydrate was conducted in aqueous solutions in agitated batch systems for the temperature range 10 to 40 °C. The width of the SNT decreased as the induction time increased and was found to be temperature independent when supersaturation was based on the absolute concentration driving force. Nonnucleating seeded batch bulk crystallizations of this sugar were performed isothermally in the same temperature range as the SNT experiments, and within the SNT region to avoid nucleation. The growth kinetics were found to be linearly dependent on the supersaturation of total glucose in the system when the mutarotation reaction is not rate limiting. The growth rate constant increases with increasing temperature and follows an Arrhenius relationship with an activation energy of 50 ( 2 kJ/mol. R-Glucose monohydrate shows significant crystal growth rate dispersion (GRD). For the seeds used, the 95% range of growth rates was within a factor of 6 for seeds with a narrow particle size distribution, and 8 for seeds with a wider distribution that was used at 25 °C. The results will be used to model the significance of the mutarotation reaction on the overall crystallization rate of D-glucose in industrial crystallization.
“…A large number of experiments, including early work in growth cells by the group of Berglund, − have shown that individual crystals within a population grow at a constant rate over time if the solution conditions remain constant; these results preclude the mechanism of size-dependent growth since the size of the crystals does change significantly over the time of the experiment, whereas the growth rate is constant. However, the individuals within the population (under the same conditions) do not all grow at the same rate; there is a distribution of growth rates within the population.…”
Crystal growth rate dispersion (GRD) and size-dependent crystal growth (SDG) models are models to extend McCabe's ΔL Law to more accurately account for variation in the crystal growth rates within a population of crystals. GRD is a phenomenon where the crystal growth rate either fluctuates randomly over time or varies over a population of crystals. SDG is where the growth rate of a crystal depends on its size, typically with growth rates assumed to increase monotonically with crystal size. Although it has been recognized for more than 30 years that, except for extremely small crystals, SDG is an artifact of GRD, it is still common in the literature for GRD in experimental results to be modeled using SDG models. This discussion will present some background and new experiments on the mechanism and extent of GRD to demonstrate that GRD is a real phenomenon, whereas SDG is largely an artifact, and some modeling work to demonstrate that SDG models cannot successfully replicate crystal size distribution data that originate due to GRD. More work needs to be done in accurate population balance modeling for processes where GRD is significant rather than assuming that SDG models are adequate.
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