Simulation of the Vacuum Infusion Process using Idealized Components: Effects of Pore Size and Suspension Concentration

Vacuum infusion of porous food matrices (i.e., extruded starch crackers) with calorically dense suspensions of food powders in fat was investigated in an ideal system. Experiments involved infusion of model matrices with lipid suspensions consisting of milled, size-characterized sucrose in corn oil. The influences of pore size/particle size ratio and suspension concentration on the penetration of liquid and particles were determined. A mathematical model that allows prediction of future behavior was fitted to the test results. The model indicates that dry-weight particle penetration is strongly correlated with pore size and independent of initial particle concentration. Infusion of liquid plus particles was increased by raising porosity and lowering particle concentration.     

A Quasi-Chemical Kinetics Model for the Growth and Death of Staphylococcus aureus in Intermediate Moisture Bread

ABSTRACT: The "quasi-chemical" kinetics model accounts for all 4 phases of the microbial lifecycle based on a proposed series of chemical rate equations. The model fits continuous growth-death kinetics for Staphylococcus aureus in intermediate moisture bread in various conditions of water activity, pH, and temperature. Growth rates evaluated using the quasi-chemical model are compared with values obtained with the Gompertz model. Kinetics data obtained with the quasi-chemical model are integrated with a probabilistic approach to estimate the boundary between growth and no-growth conditions. Continuous modeling of microbial growth/death kinetics in actual foods advances predictive modeling that conventionally separates growth and death models.     

Effect of Radiation and Conventional Processing on the Thiamin Content of Pork

A study was undertaken to compare the effect of ionizing radiation and thermal processing on the thiamin content of pork. Ground pork was either thermally processed in cans or, after enzyme-inactivation, irradiated in pouches with electrons or gamma rays. Thiamin in treated and untreated samples was measured by the thiochrome method. The results show that thiamin retention in pork decreases as the irradiation dose increases, but that retention increases as the temperature of irradiation decreases. Moreover, irradiation with gamma rays (low dose-rate) leads to lower retention than irradiation with electrons (high dose-rate). Results also show that conventional thermal processing causes loss of thiamin comparable to or greater than irradiation at effective processing conditions for sterilization.     

CELLULARITY, MECHANICAL FAILURE, AND TEXTURAL PERCEPTION OF CORN MEAL EXTRUDATES

Relationships among cellular structure, fracturability, and sensory properties in porous, brittle extrudates were investigated. Corn-based extrudates intentionally processed to exhibit a range of physical structures were characterized in terms of cell size distribution, bulk density, mechanical strength, fracturability, and sensory attributes. These measurements show both mechanical strength, defined by average compressive stress during extended deformation, and fracturability, quantified by fractal and Fourier analyses of stress-strain functions, increasing with either decreasing mean cell size or increasing bulk density. Fracturability parameters or structural characteristics are furthermore correlated with sensory scores for crunchiness, crispness, hardness and perceived density. These results indicate that cellularity strongly influences the pattern of mechanical failure and that failure characteristics, such as fractal dimension or power spectrum of stress-strain functions, are reflective of sensory texture.     

PHYSICAL AND SENSORY PROPERTIES OF MEATSTICK PRODUCTS AS AFFECTED BY FORMULATION AND DRYING: SENSORY-INSTRUMENTAL RELATIONSHIPS

Shelf‐stable meats are of interest to industry and are important in military ration development. Stability is commonly achieved through control of pH and water activity. However, reduction in moisture as a means to lower a_w can significantly affect texture. Other ingredients, such as fat, can also potentially affect texture and possibly mitigate hardening due to lowered moisture. Meatsticks dried to three water activities, 0.88, 0.90, and 0.92, each from batters at three fat levels, 14, 17, and 21%, were produced, yielding products varying in both moisture and fat content. Products were subjected to mechanical and sensory testing and image and color analysis. Meatstick modulus, shear force, L* value, and percent of area of cut surfaces covered by separated fat were correlated with sensory assessments of interior hardness, hardness with skin, color, and visual fat, respectively. These parameters were significantly influenced by composition, particularly fat and protein contents and fat‐protein interaction.     

A Re-Evaluation of the Products of Gamma Irradiation of Beef Ferrimyoglobin

Quantitative analysis of the interactions of ·OH and e_āq? with ferri-myoglobin in neutral aqueous solution provides a basis for evaluating earlier studies of the radiolysis of myoglobin. γ-radiolysis of deaerated solutions in which either ·OH or e_āq? predominates leads to the formation of both deoxymyoglobin and ferrimyoglobin peroxide. Correction for a post-irradiation thermal process allows radiation-induced composition changes to be separately investigated. Depending on the radical system under consideration, a specific steady-state composition is reached at moderate doses that involves the ferri, deoxy, and ferri-peroxide forms of the myoglobin. Aeration of irradiated solutions quantitatively converts the deoxymyoglobin to oxymyoglobin. Radiolysis of oxygenated solutions containing N₂O generates only ferrimyoglobin peroxide. Earlier studies on the radiolysis of ferrimyoglobin have been reevaluated in light of novel features that have emerged in this investigation.     

Myosin Cross-Linking in Freeze-Dried Meat

Myosin cross-linking in freeze-dried meat has been investigated. Extraction of proteins and electrophoretic separation of the extracted proteins were used to monitor the cross-linking in freeze-dried meat. The extractability of proteins decreases upon heating and the loss of solubility of myosin is evident. Treating the freeze- dried meat with N-α-acetyl-L-lysine or L-lysine·HCl prevents this loss. The decrease in extractability of myosin is accompanied by the development of brown color. The cross-linking is attributed to a Maillard-type reaction and is suggested to be responsible for textural changes in freeze-dried meat. Treating the meat with hydrolyzed vegetable protein is proposed as a practical method of preventing such cross-linking in freeze-dried meat.     

EFFECTS OF SIGNAL AND STIMULUS RATES ON VIGILANCE PERFORMANCE.

INVESTIGATED THE RELATIVE EFFECTS OF CRITICAL SIGNAL RATE, NORMAL NONCRITICAL SIGNAL RATE, AND CRITICAL SIGNAL PROBABILITY ON DETECTION IN A VISUAL VIGILANCE TASK. 72 COLLEGE SS MONITORED A CLOCK DISPLAY FOR 54 MIN. RESULTS SUGGEST THAT NORMAL SIGNAL RATE MAY BE OF GREATER IMPORTANCE IN A VIGILANCE SITUATION THAN EITHER CRITICAL SIGNAL RATE OR CRITICAL SIGNAL PROBABILITY. IN GENERAL, BOTH PERCENTAGE OF DETECTIONS AND PERCENTAGE OF STIMULI FALSELY RESPONDED TO WERE INVERSELY RELATED TO NORMAL SIGNAL PRESENTATION. (PsycINFO Database Record (c) 2010 APA, all rights reserved)