摘要:

The rate of softening in several canned vegetables during the retort process was studied. The rate of softening is consistent with two simultaneous first order kinetic mechanisms; mechanism 1 acting on substrate “a” and mechanism 2 acting on substrate “b”. The rate constants for mechanism 1 are 20 times or more greater than the rate constantsfor mechanism 2. Approximately 85% to 97% of the firmness of the raw commodity is contributed by substrate “a” and the remaining firmness is contributed by substrate “b”. Mechanism 1 is probably due to pectic changes in the interlamellar layer. The biochemical nature of substrate 2 is a matter of speculation. The apparent Arrhenius activation energies range from 5.1 to 35.0 Kcal/mole. The data indicates that softening kinetics of vegetables is more complex than has been f

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1983.tb00329.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The addition of sodium chloride to milk is traditionally used in some areas to prevent microbial and enzymatic spoilage. The effects of salting on the rheological properties of curd have been studied. An increase of the salt content from 0% to 5% induced a progressive decrease of the pH from 6.65 to 6.40 and of the luminosity from 78.23 to 75.68. Clotting and hardening times increased by up to 300%. When pH was adjusted with sodium hydroxide to 6.50 after adding salt and before adding rennet, times were increased by more than 600%.

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1983.tb00330.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Viscosities of dispersions of raw and various processed rice flours in water were examined with a coaxial cylinder viscometer. The measured viscosity increased with increasing degree of processing and with a reduced level of apparent starch reassociation in the processed rice. Measurement of the apparent viscosity of cold slurries could thus be a simple practical test of processed, including parboiled, rice and of the degree of processing. The system showed time‐dependent thinning and a typical loop in the shear rate‐viscosity curve, showing that it was thixotropic in nature. The viscosities were proportional to the hydration power and slurry‐sedimentation behaviour of the sa

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1983.tb00331.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The Scott Blair cheese torsiometer designed in the late 60's was rendered automatic by combining an angular transducer with the stress measuring system. A linear transducer was used to verify that the device had sinusoidal movement. The absolute error of the improved system was 3 times lower than that of the original.Gelification kinetics were determined with the automated version. We report an example in which experimental points could be fitted to the Scott Blair model as well as to the Douillard equation (the former is biphasic with an inflection point, and the latter describes a simple exponential curve). In both cases, the standard error of estimation was smaller than or equal to the absolute error of the torsiometer.Even the automated version cannot measure the phase difference between stress and strain with the required precision. Thus, neither the viscosity or elasticity modulus can be determined.

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1983.tb00332.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

A modified torsiometer (Gervais and Vermeire 1983) was used to determine the coagulation kinetics of raw milk and of milk heated for 14.7 s at temperatures ranging from 105 to 125°C with a direct U.H.T. unit. Two coagulation kinetics models (Scott‐Blair and Burnett 1963; Douillard 1973) were equally satisfactory. From the strict point of view of mathematical adjustment, the two models can be taken as equivalent. In all cases, the residual standard deviation was equal to experimental error.The Scott‐Blair equation is not suitable since it may give a negative gel time for some heated milks. The authors demonstrate that this is a mathematical artifact, arising from the form of this equation. The Douillard model is best adapted for determining the time at which curd rigidity will reach a given value. The results also show that heating milk modifies its coagulation rate constant, rather than gelling time and maximum rigi

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1983.tb00333.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Cracking in two varieties of potatoes was investigated by compressing whole tubers between flat plates at low compression rates. It was found that resulting crack areas correlated directly with the energy stored at cracking. Of the energy imparted to the tuber, a large proportion is dissipated during compression.Cracking occurs when the stored energy exceeds a critical value, approximately 1.6 J for Sebago and 0.9 J for Pontiac. The extent of cracking is determined by the fracture toughness, calculated to be 1350 Jm−2for Sebago and 1230 Jm−2for Pontiac. The Sebago variety is thus more resistant to cracking than Pontiac. The energy dissipative mechanisms in hysteresis and crack propagation are explained in terms of the structure of potato tis

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1983.tb00334.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Source Book of Food Enzymology.S. Schwimmer. AVI Publishing Co., Inc., Westport, Conn. 967 pp., 1981. U.S. $85.00. Other Countries $93.50.

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1983.tb00335.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY