Viscous Food Products Research Articles

Intensification of thermal and rheological processes in a scraped-surface apparatus

The operation parameters of a special heat exchange scraped-surface apparatus ware studied and mathematically described in the article. The feature of the apparatus was the use of perforated cleaning devices in order to increase the turbulence of a product. The developed device can be used in the dairy, meat, and fat and oil industry to cool cream, animal fats, margarine emulsions, cooking fats, and other viscous food products. The increase in the productivity of the apparatus was achieved as a result of the more intensive mixing of the cleaned wall layers with the bulk of the cooled product due to the presence of cylindrical holes in the slats with a diameter of at least 
 0.05–0.1 of the diameter of the working cylinder. As a result of processing experimental data on heat exchange taking into account energy dissipation, a calculated criterial heat exchange equation for the nonisothermal motion of products and their different flows – laminar and transient – was obtained explicitly. In addition, the article considers the effect of starting modes on the operation of apparatus with mixing devices. These data can make it possible to take into account the possible deviations of parameters caused by nonsteady operating modes. On the basis of the data obtained, we have proposed assumptions about the degree of impact of viscosity and inertia in the considered range of parameters on a starting mode. The results of the study are relevant since they allow us to intensify the thermal processes in this type of common apparatus by 10–12%.

Thermal mixing via acoustic vibration during continuous flow cooling of viscous food products

During conventional continuous flow cooling of viscous foods, laminar flow and low thermal conductivity lead to a wide temperature distribution within the product, resulting in non-uniformity, slow cooling processes and degradation of final food quality. It was hypothesized that continuous flow cooling would be enhanced by equalizing the temperature profile (thermal mixing) during cooling. In this study, a computer-controlled frequency, audio transducer amplifier was used to impose transversal vibration motion on a 180° bend pipe and generate thermal mixing of viscous foods, such as sweet potato puree, banana puree, apple sauce and cheese sauce, at the temperature range of 110–60°C. Applying vibration at the maximum amplifier volume and 20Hz, the resonance frequency of the unit, the initial radial temperature distribution of 3–20°C was reduced to a temperature difference of 0–4°C, for all the food products. Although parameters such as the magnitude of the initial temperature difference and the gel formation at the pipe wall, which occurs during the cooling of these kinds of food materials, need to be controlled better for future applications of this method.

PENGARUH METODE FERMENTASI SUBSTRAT PADAT DAN SUBSTRAT TERENDAM PADA BIJI SORGUM TERHADAP KUALITAS TEPUNG

The utilization of sorghum as food products is restricted by its lack of digestibility and the presence of anti-nutrients factors. Fermentation process has been recommended to improve cereal-based flour quality. This study was aimed to evaluate the effect of two fermentation methods namely solid state (a method adopting tempeh processing procedure with fermentation course of 60 and 72 h) and submerged fermentation (similar to ampok processing procedure with fermentation course of 72 and 84 h). The fermented-sorghum grains were then dried, and milled to produce sorghum flour. Analyses of proximate, physical poperties (particle size index/PSI, Water Absorption Index/WAI, swelling power) and amylograph profiles were carried out to obtain the flour characteristics. The results showed that both fermentation methods significantly influenced the proximate, physical and amilograph properties of the sorghum flour. Solid state fermentation of sorghum grains decreased the starch content, reduced its lightness, swelling power and viscosity, while increased the PSI and WAI. However, the solid state fermentation did not significantly change the protein, fat, ash and moisture content of the sorghum flour. Submerged fermentation of sorghum grain decreased the starch and protein content, increased the lightness, swelling power and viscosity, while did not significantly modify fat, ash and moisture content of the flour. Based on the characteristics obtained, it is suggested that sorghum flour made from solid state fermented-sorghum grain may be applicable for making–not viscous-food products, such as porridge. On the other side, the sorghum flour made from submerged-fermented-sorghum grain may be used as thickening agent, binder or for making highly viscous food products.

Design Aspect of Scraper Blade Assembly for Enhancing Film Heat Transfer Coefficient of Scraped Surface Heat Exchanger

AbstractScraped surface heat exchangers (SSHEs) are known for thermal processing of viscous food products. Heat transfer coefficient is one of the main parameter which influences the performance of processing liquid products in SSHE. The present study was undertaken to determine the film heat transfer coefficient for different blade assembly configurations. Milk was concentrated from 15 to 26% total solids using SSHE. Effect of number of blades (2, 4, 6), weight of blades (1.6, 1.75, 2.0 kg) and rotor speed (150, 175, 200 rpm) was investigated on scraped film heat transfer coefficient (hs) using Response Surface Methodology. The results showed that hs increased linearly with increase in number of blades as well as rotor speed and that it was inversely related to blade weight. The hs varied from 695.3 to 1,415.4 W/m2K. The study was helpful in determining the design factors affecting film heat transfer coefficient of SSHE.Practical ApplicationsIn many of the earlier studies on SSHE, effect of scraper speed, flow rate or the number of blades has been individually studied. Therefore, effort was made to study the combined effect of these parameters. This article gives important insights on the design aspect of rotor blade assembly for thin film SSHE.

Applicability of the Foodtexture Puff Device for Rheological Characterization of Viscous Food Products

AbstractThe Foodtexture Puff Device (FPD) is a noncontact rheological measurement device, which applies an air pulse on the sample and measures the subsequent deformation of the sample surface with a laser distance sensor. The deformation behavior is considered as a measure for the rheological properties of the sample. The applicability of this device was studied for use on viscous food products with a broad range of rheological characteristics. In this study, sugar and fat‐based systems with a viscosity range of respectively 0.001–6.1 Pa.s and 0.01–5.9 Pa.s were tested. Comparison of the FPD with classical rheological analyses showed that the maximum deformation created by the FPD is strongly correlated to the viscosity. Hence, the FPD is well suited for measurements on sugar‐based and fat‐based systems. It is capable of providing accurate, noncontact, fast, easy and nondestructive rheological measurements on food products.Practical ApplicationsThe FPD is a new, noncontact rheological measurement device that can be used for a wide range of food products, including sugar solutions, fruit purees and concentrates, oils and fats, molten chocolate, batter, soft pastry, among others. Furthermore, more solid food products like dough can be measured accurately. The device outputs a displacement signal over time from which information can be extracted. For simple behaviors, this can be performed based on one or a few characteristic values derived from the signal. For more complex foodstuff, the signal as a whole can be used, and techniques such as partial least squares can be used to create a calibration curve that translates the full displacement signal over time into the desired rheological values. Seen the fact that measurement time is short, the FPD is suitable for in‐line as well as for R&D applications and can replace classical devices that are often time consuming and require sample preparation.

Mixing and heat transfer of highly viscous food products with a continuous chaotic duct flow

We discuss the Rotated Arc Mixer (RAM) for continuous mixing and heat exchange of highly viscous foods. Principal advantages of the RAM are the simplicity of construction/disassembly and the attendant large energy savings due to the absence of internal elements. The absence of internal obstructions benefits the performance of the RAM in several ways. The geometry is amenable to in-depth analysis and is easier to scale up and optimize for specific applications. The absence of internals also has the benefit of making the RAM less susceptible to clogging and fouling, which can reduce downtime and maintenance cost. The RAM exploits chaotic advection to mix and transport heat in viscously dominated (low Reynolds number) flows. Among other things the RAM can effect good in-line mixing of viscous materials with a pressure drop that is the same as that of an open pipe; moreover, the RAM has several control parameters to tune the chaotic advection, making it flexible for applications. Examples are presented from confectionary and diary processing.

ACCELERATED COOLING OF HOT PACK VISCOUS PRODUCTS BY INTERNAL BOILING

ABSTRACTA method is suggested for accelerated cooling of hot‐pack viscous food products, with the effect based on removal of noncondensable gases from the can. This removal of the noncondensable gases promotes rapid condensation of vapor in the headspace, creates a pressure drop which, above a certain level, in turn induces boiling of the content, and the resulting agitation and mixing together with the condensation make for substantial improvement in heat transfer. For example, with this method only 15 min were needed to cool a #10 can of comminuted orange from 90 down to 45°C (mass average temperature), as compared to 100 min required in the commercial process.