Characterization of ice recrystallization in ice cream during storage using the focused beam reflectance measurement

3rd IIR International Conference on Sustainability and the Cold Chain, ICCC 2014, London, , 23-/06/2014 - 25/06/2014International audienceIce recrystallization was investigated in two commercial and differently stabilized ice creams using an original and real time particles counting and sizing method: the focused beam reflectance measurement (FBRM). Ice cream A (with locust bean gum - LBG - as primary stabilizer) and ice cream B (with carrageenan as primary stabilizer) were stored for 154 days at four different temperatures (-5, -8, -12 and -18 °C) and three amplitudes of temperature fluctuations (±0.1°C, ±0.75°C, ±2.5°C). Crystal's size distributions were assessed at various time and recrystallization kinetic data were derived by fitting the experimental results to the asymptotic Ostwald ripening model. As expected, recrystallization rates increase with mean storage temperature and amplitude of temperatures fluctuations. Carrageenan seems to be more effective than LBG in slowing down ice crystal growth during storage. Mean ice crystal size increased as a function of time1/3 for both ice creams. The temperature dependence of recrystallization rate fitted Arrhenius well, with activation energies fairly similar for ice creams A and B

Caractérisation de la recristallisation de cristaux de glace dans la crème glacée stockée par la méthode de mesure focalisée de la réflectance d'un faisceau laser

International audienceIce recrystallization was investigated in two commercial and differently stabilized ice creams using an original and real time particles counting and sizing method: the focused beam reflectance measurement (FBRM). Ice cream A (with locust bean gum - LBG - as primary stabilizer) and ice cream B (with carrageenan as primary stabilizer) were stored for 154 days at four different temperatures (-5, -8, -12 and -18°C) and three amplitudes of temperature fluctuations (±0.1°C, ±0.75°C, ±2.5°C). Crystal's size distributions were assessed at various time and recrystallization kinetic data were derived by fitting the experimental results to the asymptotic Ostwald ripening model. As expected, recrystallization rates increase with mean storage temperature and amplitude of temperatures fluctuations. Carrageenan seems to be more effective than LBG in slowing down ice crystal growth during storage. Mean ice crystal size increased as a function of time1/3 for both ice creams. The temperature dependence of recrystallization rate fitted Arrhenius well, with activation energies fairly similar for ice creams A and B

Characterization of ice recrystallization in ice cream during storage using the focused beam reflectance measurement

International audienc

Couplage entre les modèles de bilan de population et de transfert de chaleur pour la description de la recristallisation des cristaux de glace au sein de la crème glacée entreposée à long terme

International audienceA coupled population and energy balance model describing separately growth and dissolution of the ice crystals was developed to simulate recrystallization by Ostwald ripening during long-term storage of ice cream. The model reproduced accurately (R2 > 0.90) measurements of the ice crystal average diameter for two ice creams (ICA and ICB) stored at temperatures between −5 and −18 °C for 104 days. Simulations indicated that ice crystal dissolution controls recrystallization during the early stages of storage, after which both growth and dissolution occur at decreasing rates. Carrageenan, ICB primary stabilizer, seemed to better preserve small ice crystals than locust bean gum, ICA primary stabilizer, by reducing ice crystal growth and dissolution rates. A sensitivity analysis indicated that the activation energy for ice crystal dissolution is the most significant model parameter and that the impact of heat transfer parameters is negligible because of the rapid change of the ice cream temperature

Numerical study of energy performance of nanofluids for refrigeration systems

3rd IIR International Conference on Sustainability and the Cold Chain, ICCC 2014, London, , 23-/06/2014 - 25/06/2014International audienceA mathematical model was developed to predict the energy performances of refrigerating systems using nanofluids for application in refrigeration plants of cold chain. The model was based on a combination of the Effectiveness-Number of Transfer Units method and classical heat transfer and fluid hydrodynamic correlations. Simulations were done for a tubular heat exchanger in laminar and turbulent regimes, for various types of NPs and a wide range of volume fraction. It was shown that heat transfer coefficients significantly increased with the increase of NPs concentration whatever the flow regime, but the pressure drop also increased. Calculation of a Performance Evaluation Criterion has shown that the energy performance is strongly dependent on the type of NPs, their volume fraction and the flow regime. These criterion data also showed the existence of optimum parameters for which the use of nanofluids is energetically interesting. The model was validated using published data

Influence of whey protein aggregation on the residence time distribution in a helically holding tube during heat treatment process

International audienceThe residence time distribution (RTD) of a flowing whey protein (WP) suspension through a helically tubular system was studied. The experimental system is the helical holding section of a thermal process pilot. RTD was measured in isothermal conditions at 60°C, a temperature involving any WP aggregation, and at 87°C, temperature at which WP aggregates. Two flow rates (20 L/h and 49 L/h) were tested with two different lengths of holding tube in order to maintain the same order of magnitude of the holding time. Methylene blue was used as tracer and spectrophotometer analysis were performed to determine the outlet concentration. These investigations yielded to great differences between the RTD in aggregation and no aggregation conditions. The minimum residence time is shorter when WP aggregation occurs due to the modification of the velocity field inside the holding tube with the enhancement of the viscosity. The mean residence time remains the same whatever the holding temperature at the low flow rate. However, it is slightly shorter when the flow rate increases probably due to the increasing of secondary flow circulation which narrows the RTD in curved tubes. Fitting the experimental results with the generalized laminar model confirms the shorter minimum residence time when WP aggregate. These results help to understand the WP aggregates size dispersion

Thermal protection of ice cream during storage and transportation

24ième Congrès International du Froid ICR 2015, Yokohama, JPN, 16-/08/2015 - 22/08/2015International audienceIce cream is a very temperature sensitive product and temperature fluctuations during the storage and distribution steps of the food cold chain may result in changes in ice crystal size due to recrystallization phenomenon. An excessive increase of the mean ice crystal size results in a reduction of ice cream quality and a shortening of its shelf life. It is possible to improve the ice cream storage and transportation conditions by using an additional packaging with a low thermal diffusivity. Insulation material is usually chosen to reduce temperature fluctuations, but this paper proposes to evaluate the thermal protection of a phase change material (PCM) packaging and to compare its performance to a polystyrene configuration. The impact on temperature fluctuations and ice crystal size was characterized experimentally for a 5 months storage period and 3 different packaging materials: cartonboard, polystyrene and PCM. Measurements during a temperature abuse for 40 minutes at 20°C were also performed to evaluate the thermal protection provided by the different types of packaging. The results demonstrate that the use of an additional PCM packaging can have a significant impact on the final quality of the product during long term storage or for a product exposed to heat shock

Modélisation de l'agrégation de protéines par bilan de population - Exemple de la béta-lactoglobuline

International audienceAggregation phenomena are important in food products where many interactions between components are possible. These interactions can occur during food processing: heating, pH change, high pressure process, separation process, etc. Desired or not, they must be well understood to have a perfect control of food quality. Indeed, size and structure of the aggregates influence the texture and taste properties. In this study, a modified version of a classical model for colloidal aggregation (Population Balance Model of Smoluchowski) is presented for heat-induced aggregation of whey proteins. Experimental data were obtained on β-lactoglobulin (β-lg) solution (6% + CaCl2) using process simulator (85°C for 60 s) with different shear conditions. In agreement with literature and experimental observations, three stability factors (W) have been introduced in the model, each one related to an interaction involved in β-lg aggregate formation. Characteristics of the suspensions (residual native fraction, aggregate size distribution and viscosity) were used for fitting between experimental and simulated data. By adjusting the stability factors (W) to the composition, we successfully integrated the role of physico-chemical environment variations such as CaCl2 concentration. The role of shear upon aggregate growth is also well predicted by the model. Prediction of aggregate properties in function of thermo-mechanical treatment can help to better design the processes

X-ray micro-tomography to quantify frozen ice cream structure

24ième Congrès International du Froid ICR 2015, Yokohama, JPN, 16-/08/2015 - 22/08/2015International audienceX-ray micro-tomography (X-ray μ CT) provided high resolution 3D images of frozen ice cream samples for use in studying the structure and particle size distribution of air bubbles, fat and ice. Ice cream samples were prepared in a laboratory continuous freezer that allowed a feasibility study of microstructure of frozen samples, which were produced in the continuous freezer then stored in a laboratory freezer at -30°C. X-ray microfocus computed tomography (μ CT) (Skyscan 1172, Bruker microCT, Kontich, BE) with a temperature-controlled cooling stage was applied to stored frozen samples to investigate the 3-D microstructure of ice cream produced in a continuous process conditions. This provided a unique insight of the fat destabilization and structure network obtained after production and storage. Morphological analysis revealed microstructural properties of the ice cream samples. Significant differences between the phases were observed. In addition, the particle size distribution of ice crystals, fat and air bubbles was obtained. Results showed that microstructure analysis is a powerful tool for quantifying frozen ice cream structure in relation to process, storage and formula changes

Evaluation de la qualité et de la sécurité des produits prêt-à consommer à base de porc dans la chaîne du froid.

International audienceIt is of crucial importance for Ready-To-Eat (RTE) foodstuffs producers to guarantee the quality and safety of their products under the cold chain variations related to different time–temperature profiles. Experimental designs were used to investigate and model the effects of temperature on safety and quality attributes of selected RTE meat products. Three types of RTE sliced pork products (cooked ham, cooked paté and smoked ham) were stored at different temperatures (5, 8, 12 and 15 C) up to 6 weeks. Microbiological and physico-chemical attributes were followed. Growth parameters of Listeria monocytogenes were investigated by challenge testing for the three RTE products at the four temperatures. Two lactic acid bacteria (Lactobacillus sakei and Leuconostoc mesenteroïdes) were also investigated by challenge testing but only for cooked ham and cooked paté at 8 C. Changes in quality indicators including colour, texture and water content, water activity and water dripping were evaluated over storage time for the three RTE products. Spoilage experiments were conducted (at 2, 8, 12, 15 C for 48 days) on cooked ham and the production of ethanol, as a representative volatile deriving from bacterial metabolism, was correlated to bacterial outgrowth. Growth parameters of the three strains for the given food were mathematically modelled and validation tests were performed for L. monocytogenes in cooked ham and cooked paté. Physico-chemical attributes were not significantly affected by time–temperature storage. The production of ethanol on spoiled cooked ham was related to growth of lactic acid bacteria, especially Leuconostoc. A threshold value of ethanol concentration was defined in relation with a threshold count numbers of LAB under the conditions studied