摘要:

ABSTRACTData are presented supporting a new model of spore populations during isothermal and dynamic lethal heat treatments. the model incorporates activation, injury, and preliminary inactivation of less‐resistant fractions as well as the usual predominant inactivation. Rate constants of those transformations were determined experimentally forBacillus subtilisstrain A and were found to vary with temperature according to Arrhenius equations. Model generated and experimental isothermal survivor curves compared well. Comparison of model and experimental survivor curves for this species in a time‐varying temperature regime showed the model to be a potentially good predictor of survivors during dynamic lethanl heat treatment. the new model could be particularly important in simulating sterilization and pasteurization processes, especially short duration UHT treatments, and microbiological validation of arbitrary, dynamic thermal proces

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1992.tb00140.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTTemperature and heat distribution studies were carried out in a single basket horizontal water cascading retort at two temperatures and two air over‐pressure levels under fully loaded operating conditions. Various heat transfer parameters (heating and cooling rate indices, fhand fc), lag factors (jchand jcc) and process lethality (Fo) were used as indicators of the retort performance. Time‐temperature data gathered from 24 LexanTMtransducers were used for calculation of the heating and cooling rate indices as well as lethality. There were significant variations in the temperature distribution and heat transfer parameters at the different tray levels; however, these variations did not contribute to large variations in the accumulated overall process lethal

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1992.tb00141.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTThe effect of reel speed, can size, and percent air during steam and steam/air processing in a Steritort on the heating rate of tomato concentrate (an induced convection‐heating product) was investigated. A Taylor expansion equation, relating Ball process times with the above three variables, considering first order, second order, and interaction effects, was presented. A correlation equation for the Nusselt number as a function of the Reynolds and Prandtl numbers, the can length over the diameter ratio, and the steam content was also presented. Percent reduction in process lethality increased with increasing can size and air content, and decreasing reel speed and target lethality. Increase in percent air in the steam/air mixture could be compensated by an increase of the rotational spee

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1992.tb00142.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTThe stress‐volume characteristics of crushed grape cultivars: Baco Noir, Cabernet Sauvignon, Catawba, Cayuga White, Chardonnay, Concord, Delaware, Melody, Niagara, Johannisberg Riesling, and Seyval Blanc, with and without paper and rice hulls press aids were studied in an expression cell and an Instron Universal Testing Machine. the slopes of ln stress vs volume in compression were significantly (P<0.001) dependent on the grape cultivar. Addition of 1–3% press aid by weight decreased the magnitudes of slopes by about 11% with Seyval Blanc to about 51% with Catawba; i. e., the ease with which pressing could be performed increased with the addition of press aid. With Cabernet Sauvignon grapes, addition of press aid 0.5, 1.0, and 2.0% resulted in increase in slopes ranging between 14.7 and 24.9%. the slopes of the ln stress‐ln time during the relaxation portion of the experiment were also significantly dependent (P<0.001) on the grape cultivar; the magnitudes of the slopes increased with the addition of 1–3% paper press aid. the juice yields were affected significantly (P<0.001) by the addition of paper press aid, with maximum yields being obtained when 1–2% (w/w) paper press aid was added. As expected, juice yields (w/w%) were significantly dependent (P<0.001) on grape

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1992.tb00143.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY