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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of texture studies 30 (1999), S. 0 
    ISSN: 1745-4603
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Rheological properties of three commercial samples of the typical Argentine sweet spread “Dulce de Leche” (common, low calorie and confectionery types) were measured by transient tests (constant shear rate time dependency) using rotational viscometry and dynamic measurements with oscillatory rheometry. All the samples showed a strong time dependency but no recovery of the structure was detected in a 24-h period. A prominent overshoot was evidenced in all transient assays; at long times, the Leider-Bird model converges to the power law equation. The linear-viscoelastic range for the confectionery “Dulce de Leche” determined by the dynamic test ranged up to a limit deformation of 9% whereas the other two types had a range up to 3.5%. The behavior of the three types of “Dulce de Leche” was intermediate between a concentrated solution and a gel but the confectionery type was closer to a gel-like behavior than the other two. Differences found in the rheological behavior of the three “Dulce de Leche” types were related to their different compositions and the presence or absence of thickening agents.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    International journal of food science & technology 39 (2004), S. 0 
    ISSN: 1365-2621
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Red delicious apple cubes were packed in fresh orange juice containing chemical preservatives (citric and ascorbic acid, potassium sorbate) and covered with plastic films of different gas permeabilities (polyethylene and EVA-SARAN-EVA) before storage at 4, 10 and 20 °C. The concentration of potassium sorbate in the product was optimized with respect to colour and microbial growth. Yeast and mould growth was modelled by Gompertz and linear equations to derive parameters such as lag phase, maximum microbial population and specific microbial growth or rates of decline. Activation energies for the specific growth rates were estimated from Arrhenius-type equations and the time required to reach microbial counts of 106±0.2 CFU g−1 was determined in all cases. At 4 °C, these values were longer than 25 days in all systems tested. The use of a low gas permeability film and an adequate potassium sorbate concentration extended storage life at higher temperatures.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    International journal of food science & technology 28 (1993), S. 0 
    ISSN: 1365-2621
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effects of freezing rate on exudate production, rheological behaviour, ice crystal size, and starch retrogradation of corn starch and wheat flour pastes (10% w/w) with and without xanthan gum (0.3% w/w) were studied by means of capillary suction, rotational viscometry, indirect microscopy, and differential scanning calorimetry (DSC).Higher freezing rates preserved textural characteristics and produced less exudate. In corn starch pastes, rates 〈1 mm h-1 caused a marked spongy structure, undesirable for a sauce-like product, but only a slightly spongy structure in wheat flour pastes. Xanthan gum addition maintained the smoothness characteristic of the unfrozen pastes, avoiding amylose retrogradation. However, effects on ice crystal formation and amylopectin retrogradation were not observed. Although high freezing rates are mostly recommended, low levels of xanthan gum maintained quality characteristics even at low freezing rates, decreasing equipment cost.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food process engineering 6 (1982), S. 0 
    ISSN: 1745-4530
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: During the various stages of marketing, frozen food products are frequently subjected to changes in temperature which affect their quality.In the present work, a mathematical model is developed to analyze the thermal behaviour of frozen meat subjected, under different insulation conditions, to thermal step functions and periodic fluctuations in temperature varying in amplitude and frequency.The heat transfer equation has been numerically solved, since it is a system with physical properties that vary with the temperature, and fluctuating boundary conditions.At the same time, laboratory experiments were performed to verify that the mathematical model is applicable to one-dimensional and three-dimensional heat transfer problems.The obtained results were compared with analytical solutions for the heat transfer equation, with constant coefficients, determining the temperature range for which it is possible to use average values in the physical properties.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    International journal of food science & technology 35 (2000), S. 0 
    ISSN: 1365-2621
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The effects of ripening temperature, type of packaging film and storage period before packaging were related to the degree of proteolysis and the texture of Gouda cheese, so as to determine the optimum ripening conditions. Gouda cheeses from a local plant were subjected to different ripening conditions. A factorial design of 23× 5 was used, where the three factors selected in two levels were: (1) time of storage before packaging, 4 and 10 days, (2) ripening temperature, 10 and 20 °C and (3) plastic film, BK1 and BK5 (Grace, Quilmes, Argentina). Ripening time was a fourth factor analyzed; sampling times were 15, 25, 35, 49 and 70 days after production. Cheeses traditionally ripened (without packaging) were also analyzed. Water content and pH were determined. Nonprotein nitrogen (soluble in 12% trichloracetic acid (TCA)) was quantified by the Kjeldhal method. Cheese texture was analyzed by compression and relaxation tests which were done by using an Instron Universal Testing Machine (Instron Corp., Canton, MA, USA). The pH and water content of cheeses which ripened at 20 °C were lower than the corresponding ones ripened at 10 °C. Only ripening time and temperature had a significant effect on water content, nonprotein nitrogen concentration and rheological parameters. Results show that texture properties of Gouda cheese ripened in plastic films with low gaseous permeability are similar to those of traditionally ripened Gouda. Texture development was accelerated by increasing the storage temperature.
    Type of Medium: Electronic Resource
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