摘要:

ABSTRACTThe coagulation of renneted skim milks was monitored by dynamic measurement of elastic shear modulus (G) based on low amplitude oscillation. Four alternative time‐dependency models were fitted to the measurements and compared with respect to their ability to describe the development of curd firmness and their usefulness in deriving parameters of practical interest in cheesemaking.All models described the development of G over the course of the experimental time‐scale (≈ 60 min), with the Scott‐Blair and Carlson models following the experimental course of G more accurately than the other models. The fit of the Douillard model was consistent with a systematic error in the region of onset of gelation, owing to its nonsigmoidal nature. The fit of the linearized Scott Blair model was poor at the upper end of the experimental range of G.Apart from gel time as defined by G = 0.2 Pa, there was no significant difference between the Carlson and Scott Blair models in simulating most coagulation parameters, including set‐to‐cut time, firmness at 2.4 ks, rate of curd firming and time of maximum curd firming rate.Where significant differences occurred between the Carlson and Scott Blair models, on one hand, and either the Douillard or linearized Scott Blair model on the other, as for set‐to‐cut time, the mean deviations from experimental data were smaller when using th

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1996.tb00986.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTThe main effects and interactions of mixtures of sodium caseinate, k‐ or t‐ carrageenan, sodium chloride, calcium chloride and hydrogen ions on the rheological properties in aqueous systems cooled to 5 C were quantified. Response surface methodology was used to display the results for five different response variables: gelation temperature, consistency index (k*), dynamic power law factor (n*), critical strain (γc), and syneresis. The gelation profiles observed for both k‐ and t‐carrageenan systems demonstrated that the sol‐gel transition in sodium caseinate‐carrageenan mixtures was due to electrostatic interactions of free carrageenan loops or tails with the intervention of cations. Caseinate molecules did not play a major role in this process. The electrostatic nature of the interactions was further demonstrated by the significant influence of salts and pH on the consistency and brittleness of the gels (represented by k*and γc, respectively). Consistency and brittleness were inversely related as well as consistency and syneresis. Syneresis was negligible in t‐carrageenan gels and was reduced by sodium caseinate and sodium chloride in the k‐ca

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1996.tb00987.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTThe water sorption isotherm at 25C and glass transition temperature were determined in a typical Spanish confectionery product (Xixona turrón), as well as in the fat‐free product. The samples were equilibrated at water activity levels from 0.113 to 0.755. The GAB and BET models were fitted to sorption data and the monolayer moisture contents were 2.8 and 6.0 (g of water/100 g of dried sample) for turrón and fat‐free turrón, respectively. The sorption data indicate a lipid interaction with hydrophilic constituents. The analysis of the glass transition temperature (Tg) of the product as a function of its moisture content is used to determine the critical water content (CWC) at which the product becomes rubbery, at a determined temperature. From sorption isotherm at the same temperature (25C) we can also determine the critical water activity (CWA). The plasticizing effect of water in Xixona turrón can be modeled by the Gordon and Taylor equation. The fat also has a plasticizing effect, which is more obvious at low water content. A Texture Profile Analysis (TPA) was performed on samples with different moisture contents. Only samples with a moisture content lower than CWC showed fracturability, due to its glassy state. In the rubbery state hardness, gumminess and chewiness decrease when water content increases. Elasticity and cohesiveness increase in line with water content, more strongly for those moisture levels which are higher than BET monolaye

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1996.tb00988.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTUsually, uniaxial compression of food materials is performed at constant speed, which causes an increase of the true strain rate during experiments. By using a method described previously (Jaros and Rohm 1994) highly elastic biopolymer gels were compressed at standard conditions and with decreasing crosshead speed in order to maintain constant strain rate conditions during test. In the case of gels showing failure at a Hencky deformation of>0.5‐0.6, significantly lower values for apparent fracture strain were found in constant strain rate compression. Differences in stress at apparent fracture showed good agreement with respect to this critical value. Implications and consequences on interrelation between sensory and instrumental measurements as well as on relationships between rheological and fracture properties are discusse

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1996.tb00989.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTThe mechanical properties of hydrocolloid gels with high gum concentrations (agar 1–5%, gellan 1–3% and K‐carrageenan 0.5–3.0%), were measured under uniaxial tension. A simple power law model was used to describe the stress‐strain curves which tended to be concave upward. The overall stiffness and the extent to which the stress‐strain curve deviated from a straight line were estimated by the calculated constants of this model, using linear regression of the model's logarithmi

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1996.tb00990.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTThe jaggedness of the filtered and compressed acoustic signatures of cheese balls and croutons at various levels of water activity was determined in terms of an apparent fractal (Kolmogorov) dimension. The plot of the mean dimension vs water activity had a characteristic sigmoid shape that could be adequately described by a modified version of the Fermi equation. Regression analysis yielded that the apparent fractal dimension, DfK, of the cheese balls and croutons when dry was around 1.45 and 1.38, respectively. The inflection point, awc, that is, the water activity level where half the drop in DfKoccurred, was awc= 0.50 and awc= 0.55, respectively. The steepness of the jaggedness versus water activity relationship in terms of the awrange where about 90% of the drop of jaggedness occurred was 0.27 in the cheese balls and about 0.29 in the croutons.

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1996.tb00991.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTWe adapted the squeezing flow technique to make compression and relaxation tests on Mozzarella cheese at temperatures ranging from 30 to 60C during one month of refrigerated storage. The deformability modulus of the cheese decreased with aging and temperature but increased with deformation rate. The average decrease in the deformability modulus was 0.4 kPa/day and 0.5 kPa/C. Relaxation data also indicated a continuous increase in viscous character of Mozzarella with aging and temperature. Apparent relaxation time was less than 10 s. Relaxation parameters showed a strong temperature dependency in the range of 10‐60C. Lubricated squeezing flow data showed that the resistance of Mozzarella to flow decreased with aging and temperature indicating an increased meltabilit

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1996.tb00992.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The Science of Cookie and Cracker Production. Edited by Hamed Faridi, Chapman and Hall, New York. 516 pp. 1994. $99.95.

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1996.tb00993.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

General Principles:Kinetic Energy Correction Factor of a Herschel‐Bulkley Fluid. J.L. Briggs and J.F. SteffeGeneral Principles:The Role of Pulp Interparticle Interaction in Determining Tomato Juice Viscosity. Viscosity. N. Beresovsky, I.J. Kopelman and S. MizrahiGeneral Principles:Rheological Properties of Dextran Related to Food Applications. R.D. McCurdy, H.D. Goff, D.W. Stanley and A.P. StoneGeneral Principles:Texture of the Flesh of Common Whelk (Buccinum undutum L.): 1. Effect of Thermal Treatment on Some Physico‐Chemical Characteristics (in French). L.T. AdambounouGeneral Principles:Pseudoplasticity and Thixotropy of Different Types of Starch Hydrogels Prepared with Microcrystalline Cellulose‐Sodium Carboxymethyl Cellulose. J. Delegido, M. Dolz, M.J. Hernandez and J. PellicerGeneral Principles:Kinetics and Thermal Behaviour of the Structure Formation Process in HMPlSucrose Gelation. J.A. Lopes da SilvaGeneral Principles:Viscoelastic Properties of Raisins. V. T. Karathanos, A.E. Kostaropoulos and G.D. SaravacosGeneral Principles:Fracture Stress of Frozen Food Analyzed by a Two‐Component Model Consisting of Pure Water Ice and Concentrated Amorphous Solution. H. Watanabe, C.Q. Tang and T. MihoriGeneral Principles:The Starch Gelatinization in Potatoes during Cooking in Relation to the Modelling of Texture Kinetics. B.E. Verlinden, B.M. Nicolai and J. De Baer

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1996.tb00994.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY