摘要:

Heat conduction during cooking of foodstuffs with heterogeneous thermal properties was simulated, mainly for irregularly shaped geometries. A code employing boundary‐fitted grids was implemented in a numerically conservative form (control volume formulation). This technique consists of finding a numerical coordinate transformation which fits a regular grid to the domain of integration. With the grid as data, coefficients for a transformed differential equation are then obtained.The proposed model was experimentally verified on irregularly shaped pieces of beef containing a nonuniform distribution of fat. Relative errors between predicted and measured temperatures were less than 2%.The effects of heat transfer coefficient and temperature of the cooking medium on the temperature distribution during the process were analyzed. the influence of different fat patterns was also considere

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1993.tb00314.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Differences in cooling rate of Cheddar cheese from pressing (35C) to aging temperature (3.5–12C) has been reported to be responsible for flavor variation within a production lot. During aging, starter and nonstarter bacteria contribute extensively to flavor quality. Temperature effects on these bacteria were quantified using cheese from a local processor. At day 1, starter counts were 8 × 107cfu/g but as aging continued, starter counts decreased and non‐starters became dominant. At 35C, starter counts reached 3 × 106cfu/g by day 3 and were below 106cfu/g by day 5. At 25, 20, 15 and 12C, starter bacteria were below 106cfu/g by day 10, 20, 24 and 40, respectively. Nonstarter counts, initially at 104cfu/g, reached = 108cfu/g at increasingly shorter times with higher temperatures. Kinetic analysis of growth in cheese and in a liquid medium suggested the possibility of diffusion growth limitations in cheese. Computer simulations for the growth of nonstarters suggests the individual cooling of small blocks (18 kg) would reduce the contribution of nonstarter counts to Cheddar cheese

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1993.tb00315.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The technical feasibility of separating cholesterol from butteroil by contacting it with aqueous solutions of Quillaja saponaria saponins followed by separation of the cholesterol‐saponin complex was studied. Alternative processes and controls compared were (1) Water Control (W): butteroil was contacted with pure water; (2) Reaction (R): butteroil was contacted with aqueous solution of saponins; (3) Adsorption Control (A): butteroil was contacted with water, diatomaceous earth was then added; (4) Reaction + Adsorption (R+A): diatomaceous earth was added to the Reaction medium (from 2); (5) Reaction + Washing (R+W): the aqueous phase resulting from Reaction (2) was discarded and pure water contacted with the fat. the last step in all the above processes and controls was the separation of the fat phase where cholesterol was determined. Statistical analysis indicated that the Adsorption Control did not yield any significant cholesterol reduction over the Water Control, while all other processes gave significant reduction. the order of cholesterol separation observed was R+A>R+W>R. the levels of cholesterol reduction were significantly affected by pH of quillaja solution and amount of adsorbent used; the time of contact with quillaja solution had no significant effect over the range investigated. These results indicate the technical feasibility of reducing the cholesterol levels of butteroil using food grade quillaja saponin

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1993.tb00316.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The separation of cholesterol from butteroil was achieved by various processes based on contacting it with aqueous solutions of Quillaja saponaria saponins followed by separation of the cholesterol‐saponin complex. Alternative processes and controls studied were (1) Water Control (W): butteroil was contacted with pure water; (2) Reaction (R): butteroil was contacted with aqueous solution of saponins; (3) Adsorption Control (A): butteroil was contacted with water, diatomaceous earth was then added; (4) Reaction + Adsorption (R+A): diatomaceous earth was added to the Reaction medium (from 2); (5) Reaction + Washing (R+W): the aqueous phase resulting from Reaction (2) was discarded and pure water contacted with the fat. the last step in all the above processes and controls was the separation of the fat phase, after which analyses were made. ANOVA indicated that the Adsorption Control process did not yield any significant cholesterol reduction over the Water Control; all other processes resulted in significant cholesterol separation in the order R+A>R+W>R. the levels of cholesterol reduction achieved by the R, R+W, and R+A processes were significantly affected by the concentration of quillaja solution and temperature; the level of agitation had no significant effect over the range investigated. Quillaja powder residue was present in the fat phase after Reaction (2) but both adsorption and washing procedures significantly reduced i

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1993.tb00317.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

A steady state technique was used to measure thermal conductivity of whole wheat dough (rolled chapati) and baked chapati (round disc prepared mostly from whole wheat flour dough) at various stages of cooking. Based on the experimental data of chapati at various stages of cooking, a linear equation K = ‐0.5677 + 0.01396 M + 0.005131 T is proposed for conductivity of wheat flour dough and baked chapati at moisture levels (M): 35

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1993.tb00318.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Bulk density, true density, angle of repose, coefficient of friction on metal surfaces, specific heat, thermal diffusivity and conductivity of gorgon nut were determined using standard techniques for different sizes of nuts at moisture contents and temperatures ranging from 15 to 60% (dry basis) and 25 to 55C, respectively. the physical properties varied quadratically with moisture content. Specific heat increased with moisture and temperature but decreased with the size of the nut; whereas, the thermal diffusivity showed a reverse trend. Thermal conductivity increased with moisture content but did not follow any trend with temperature within the range of the study. the physical and thermal properties data at various moisture contents and temperatures were used to develop equations for different sizes of gorgon nuts.

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1993.tb00319.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY