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Hold Time (hold + time)
Selected AbstractsInfluence of Cooking Rate, Endpoint Temperature, Post-cook Hold Time, and Myoglobin Redox State on Internal Color Development of Cooked Ground Beef PattiesJOURNAL OF FOOD SCIENCE, Issue 3 2006Suzanne M. Ryan ABSTRACT: Three experiments investigated cooking rate, endpoint temperature, post-cook holding time, and raw myoglobin redox-state effects on ground beef internal cooked color. In Experiment 1, patties were cooked to endpoint temperatures of 65.6°C, 71.1°C, 76.7°C, 82.2°C, or 87.8°C rapidly (1°C/s), slowly (0.2°C/s), or rapidly with 6-min post-cook holding time at 104°C. Patties cooked slowly to less than 76.7°C were more well done (P < 0.05) in appearance than those cooked rapidly. Rapidly-cooked patties cooked to less than 82.2°C and held for 6 min after cooking had less pinkness, more myoglobin denaturation, and a more well-done appearance than did rapidly cooked patties with no holding time (P < 0.05). In Experiment 2, increasing post-cook holding time (1, 3, 6, or 12 min) after rapid cooking to 71.1°C, 76.7°C, or 82.2°C decreased pinkness and increased myoglobin denaturation (P < 0.05), with no benefit beyond 6 min (P > 0.05). In Experiment 3, patties cooked rapidly to 71.1°C, 76.7°C, or 82.2°C from a predominantly raw oxymyoglobin state were less pink and had more denatured myoglobin than did those cooked from a predominantly deoxymyoglobin state (P < 0.05). Prediction equations determined that 80% of myoglobin must be denatured to create a well-done appearance. Using a slow cooking rate, post-cook holding time, or cooking from a highly oxygenated state will increase myoglobin denaturation and foster a well-done appearance. [source] EFFECT OF HIGH-PRESSURE TREATMENT OF MILK ON LIPASE AND ,-GLUTAMYL TRANSFERASE ACTIVITYJOURNAL OF FOOD BIOCHEMISTRY, Issue 6 2004P. K. PANDEY ABSTRACT High-pressure (HP) treatment (0,180 min at 300,400 MPa) was applied to milk to evaluate the pressure effects on the activities of lipoprotein lipase and ,-glutamyl transferase. Short time pressure exposure resulted in some enhancement in the activity of both enzymes, and for lipase, there was no inactivation during the entire pressure hold time (up to 100 min). With ,-glutamyl transferase, the extent of enhancement in activity was pressure level dependent, with lower pressure resulting in a greater enhancement. Furthermore, longer pressure treatment times resulted in inactivation of ,-glutamyl transferase, following a first order kinetic model. The pressure sensitivity of the inactivation parameters (k and D -values) for ,-glutamyl transferase was adequately described by the pressure death time and Arrhenius models with a zpof 543 MPa and an associated volume of activation, ,V,, of ,3.28 × 10,8 m3/mole. [source] VALIDATION OF PATHOGEN DESTRUCTION DURING MANUFACTURE OF A MEAT-BASED POTATO SNACK (CHIPAROO)JOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 6 2003S. J. KIERAS ABSTRACT A Chiparoo is a comminuted rabbit and sweet potato dehydrated snack chip manufactured using a process suitable for underdeveloped regions of the world. The purpose of this study was to evaluate the ability of the Chiparoo manufacturing process to adequately deliver 5 log reductions in Listeria monocytogenes, Escherichia coli O157:H7, Salmonella typhimurium, and Staphylococcus aureus per gram of food product. These four pathogens were inoculated into regular (pH , 6.0) and lime juice added (pH , 5.0) formulations of rabbit and sweet potato Chiparoos. They were inoculated as a cocktail of four microorganisms at concentrations of approximately 106/g of each pathogen. Individual inoculations of each pathogen at the same concentration (106/g) were also prepared. After inoculation, the product was held for 5 h at 37C, to simulate the maximum hold time in a sub-Saharan Africa manufacturing facility, then dehydrated at 55C (+/- 5C) for 9 h. Samples of the product were taken during the hold and dehydration steps, decimally diluted and plated on the appropriate enumeration medium. The regular formulation (pH , 6.0) did not achieve the required 5 log reduction of each of the four pathogens, while the lime juice added formulation (pH , 5.0) achieved the desired minimum 5 log reduction for each of the four foodborne pathogens tested. [source] Crack Growth in Soda,Lime,Silicate Glass near the Static Fatigue LimitJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2002Sheldon M. Wiederhorn The atomic force microscope (AFM) was used to explore the nature of features formed on the surfaces of cracks in soda,lime,silicate glass that were held at stress intensity factors below the crack growth threshold. All studies were conducted in water. Cracks were first propagated at a stress intensity factor above the crack growth threshold and then arrested for 16 h at a stress intensity factor below the threshold. The stress intensity factor was then raised to reinitiate crack growth. The cycle was repeated multiple times, varying the hold stress intensity factor, the hold time, and the propagation stress intensity factor. Examination of the fracture surface by optical microscopy showed surface features that marked the points of crack arrest during the hold time. These features were identical to those reported earlier by Michalske in a similar study of crack arrest. A study with the AFM showed these features to be a consequence of a bifurcation of the crack surface. During the hold period, waviness developed along the crack front so that parts of the front propagated out of the original fracture plane, while other parts propagated into the plane. Crack growth changed from the original flat plane to a bifurcated surface with directions of as much as 3° to 5° to the original plane. This modification of crack growth behavior cannot be explained by a variation in the far-field stresses applied to the crack. Nor can the crack growth features be explained by chemical fluctuations within the glass. We speculate that changes in crack growth direction are a consequence of an enhancement in the corrosion rate on the flank of the crack at stresses below the apparent crack growth threshold in a manner described recently by Chuang and Fuller. [source] | ||||||||||