Total Process Lethality as Related to Residual Catalase Activity in Cooked Chicken Breast

We investigated the effects of total process lethality on the decomposition of hydrogen peroxide, presumably due to catalase activity. Ground chicken breast meat was heated to various end-point temperatures (EPTs) in 10 heating treatments varying heating time and rate. Within each treatment, residual catalase activity was affected by the product EPT. However, samples heated to the same EPT under different treatments retained less enzymatic activity as heating time increased. Total process lethality was calculated to assess the severity of heating at each EPT under each heating condition. Residual enzymatic activity was directly related to the total lethality.     

A Factorial Approach to Modeling aw of a Multicomponent Food in the High Moisture Range (aw 0.90–1.00)

Water activity (a_w) depression in a multicomponent food such as fish sausage was investigated using a 4x3x3 factorial design on combinations of NaCl, nonfat dry milk (NFDM) and lard added to a fixed amount of minced fish. The effects of NaCl, NFDM, lard and the interaction NaCl x NFDM, were significant. The responses across levels of the above factors were linear. From the magnitude of effect of each factor, two extended models for predicting a_w were derived in terms of molal salt concentration and two empirical parameters called water activity depressing capacity, d_i, and water binding capacity, WBC, respectively. Both were demonstrated to predict accurately a_w of newly formulated fish sausage.     

Influence of Sugars on Heat Inactivation, Injury and Repair of Saccharomyces cerevisiae

The type of sugar in the heating and recovery media affected the rate of inactivation and repair capability of a Chablis strain of Saccharomyces cerevisiae. The rate of heat inactivation decreased with decreasing a_w in glucose and fructose but not in sucrose solutions. At any a_w the order of susceptibility to inactivation of yeast cells was consistently: fructose, glucose, and sucrose. In fructose, a major proportion of the survivors exhibited sublethal injury. When suspended in solutions containing the various sugars after heating and incubated for up to 18 hr prior to plating, the type of sugar in the solution influenced the ability of cells to repair injury.     

EFFECT OF PHOSPHATE AND PECTIN ON QUALITY AND SHELF-LIFE OF MARINATED CHICKEN BREAST

Fresh split chicken breasts were injected with 5% sodium acid pyrophosphate (SAPP), 5% sodium tripolyphosphate (STPP), 2.5% Genu pectin (GENU), or the combination of 5% SAPP with 2.5% GENU and 5% STPP with 2.5% GENU. Calcium lactate (0.1 M) solution was sprayed on the surface of chicken marinated in pectin. Marinated samples were stored at 4C for 7 days to evaluate changes in the psychrotrophic bacterial count and quality. STPP injected chicken breast had highest (α=0.05) marinade pickup, net weight increase, cook yield and moisture content. SAPP injected chicken had intermediate marinade pickup, but lowest retention in the muscle among all treatments. Marinades with pectin or pectin combined with phosphate had lower pickup but higher marinade retention compared with SAPP injected breasts. The water holding capacity (WHC) of STPP and GENU injected cooked chicken breast was higher than SAPP injected samples or control. All marinated chicken breasts had significantly lower shear force than noninjected control. Neither phosphate nor pectin had a significant influence on microbial activity of marinated chicken.     

Thermal Destruction of Immunoglobulin A, Lactoferrin, Thiamin and Folic Acid in Human Milk

Kinetic parameters for thermal destruction of immunoglobulin A (IgA), lactoferrin, thiamin and folic acid in human milk were determined. Degradation proceeded following first order reaction kinetics. The times for 90% degradation (D value) at 60°C were, in seconds, 4.9 × 10⁴ (68°C C 78°C) for IgA; 2.4 × 10³ (58°C 70°C) for lactoferrin; 7.7 × 10⁵ (95°C C 110°C) for thiamin and 1.9 × 10⁴ (62°C C 78°C) for folic acid based on inactivation data at four constant temperatures between the range indicated. Z values (temperature change to alter degradation rate by a factor of 10) were 5.5°C, 4.7°C, 28.4°C, and 6.4°C for IgA, lactoferrin, thiamin and folic acid, respectively.     

Heat Transfer and Simulated Sterilization of Particulate Solids in a Continuously Flowing System

The heat transfer coefficients (h) between a cube and water were 239 and 303 W/m²K at 0 and 0.86 cm/s relative velocity. In 35% sucrose and 0 cm/sec, h was 146 W/m²K. A model for heat lethality in cubes during continuous sterilization which used finite difference equations for heat conduction and above values of h, revealed that hold times for 6D inactivation of PA 3679 (F₀= 7.2 min) in an isothermal fluid at 132.2°C were 1.78 and 5.2 min for 1 and 2 cm cubes when h was 303 W/m²K and 1.23 and 4.13 min when h was 2500 or higher. When h was 239 W/m²K, hold times were 2.36 and 6.02 min for 1 and 2 cm cubes. When fluid entered the hold tube at 132.2°C and particle to fluid ratio was 0.56, fluid-particle heat exchange increased hold time to 12.2 and 119 min for 1 and 2 cm cubes.     

Fat and Water Composition Affects Residual Catalatic Activity in Chicken Breast Heated to Specific End-point Temperatures

Fat and water contents of meat tissues strongly influence their thermo-physical properties. Seven groups of ground chicken breast meat containing varying amounts of fat and water were prepared for this investigation. Each group was heated to end-point temperatures (EPTs) of 69.0 to 71.0°C at 0.5°C intervals. Severity of heat treatments was evaluated by the total process lethality calculated using the General Method. The fat and water contents affected the heating time to reach specific EPTs and the residual catalatic activity at EPTs of 69.0, 69.5 and 70.0°C, but did not affect total process lethality. The variation of the catalase method for determining EPT was related to the sample composition.     

Vacuum Infusion of Citrus Pectinmethylesterase and Calcium Effects on Firmness of Peaches

Vacuum infiltration of Majestic peaches (Prunus persica) for 1 hr with a solution of Marsh grapefruit pectinmethylesterase (PME) containing 100 mg/L CaCl₂ significantly increased firmness of canned peaches. Mean firmness of peaches infused 2 hr and thermally processed was 13.9 J/Kg as compared to 3.2 J/kg for noninfused, processed controls. The calcium content increased from 278 to 432 mg/kg during 2 hr infusion of blanched peaches. Specific activity of PME in peach halves increased more than 20 fold after infusion.