PRODUCTION AND BINDING OF MALONALDEHYDE DURING STORAGE OF COOKED PORK

Cooked pork samples were stored at 3°C and analyzed for malonaldehyde (MA). MA increased to a maximum and remained there, typical behavior for a food but contrasting with pure lipid oxidation in which MA increases and then decreases as volatile MA is lost. The failure to lose MA in food products may be attributed to MA binding. Water extracts of cooked pork samples (representing approximately l /3 of the total MA) were fractionated on G-10 Sephadex and analyzed for MA. With increasing storage time, a definite change in elution pattern from free MA to bound MA took place; the binding was not to protein or amino acids.     

ANTIOXIDATIVE AND ANTIMICROBIAL PROPERTIES OF LACTOFERRIN IN HOT-BONED GROUND PORK DURING STORAGE

The effect of lactoferrin concentration on the antioxidative and antimicrobial activities of hot‐boned (4–5 h after death) ground pork during storage at 4C for 9 days was examined. The total iron content increased with the addition of lactoferrin. Meat samples with added lactoferrin (40 or 80 mg/kg) had lower thiobarbituric acid reactive substances (TBARS) than controls at 3, 6 and 9 days; however, the differences in TBARS between the 40‐ and 80‐mg lactoferrin/kg treatments were not significant. With the addition of lactoferrin (40 or 80 mg/kg), ground pork had lower (P < 0.05) total plate counts than controls at 3, 6 and 9 days of storage. However, the differences in total plate counts between the 40‐ and 80‐mg lactoferrin/kg treatments were only significant (P < 0.05) at days 3 and 6. The addition of lactoferrin (80 mg/kg) decreased lactic acid bacterial counts at days 0, 3 and 9. The pH values of hot‐boned ground pork were unaffected by the addition of lactoferrin, but slightly increased with storage time.     

EFFECTS OF NITRITE AND SULFANILAMIDE ON THE 2-THIOBARBITURIC ACID (TBA) VALUES IN AQUEOUS MODEL AND CURED MEAT SYSTEMS

The absorbance of the 2-thiobarbituric acid-malonaldehyde (TBA-MA) complex at 532 nm for aqueous model systems and cured meats were measured. Addition of sulfanilamide played a beneficial role in evaluating the oxidative state of cured meats, prepared with the addition of ≧ 100 ppm NaNO₂, in that it prevented the underestimation of the TBA values. However, in the absence of nitrite, sulfanilamide may interact with malonaldehyde to produce a 1-amino-3-iminopropene derivative. Fluorescence spectroscopic studies showed an excitation maximum at 395 nm and an emission maximum at 460 nm for the adduct of malonaldehyde and sulfanilamide. Therefore, the TBA test for the evaluation of the oxidative state of cured meats may only be used when the content of nitrite in the cure or final product is known.     

EFFECT OF HIDE COLLAGEN ON THE AMINO ACID COMPOSITION OF BEEF PATTIES AND PORK SAUSAGE

Comminuted wet collagen from cattle hide was used to replace lean meat in a ground beef patty formulation at the 0,10 or 20% level and at the same level in a pork sausage formulation. The products were analyzed for amino acid composition by High Performance Liquid Chromatography. The products with collagen at all replacement levels showed a slight decrease in the essential amino acids but still retained approximately 75 to 85% of the total essential amino acids. Therefore, it was concluded that collagen from cattle hide may be used to replace a portion of the lean meat or fat meat in ground beef patties or pork sausage up to a 20% level while still providing much of the required dietary nutrition.     

OPTIMUM CONDITIONS FOR DETERMINING WATER HOLDING CAPACITY OF BEEF BY THE PRESS METHOD

Water holding capacity (WHC) of ground beef was measured by the press method. Three levels of applied force, test duration, sample mass, and salt concentration were investigated. Three types of deformations – plastic, elastic and permanent were used to explain the effects of applied force on WHC. Viscoelastic properties explained the effects of test duration. In general, WHC decreased with additional applied force and test duration, and increased with a larger sample size and salt concentration. Recommended test conditions are: 1 g sample size, 20 kN force for 2 min at a salt concentration of 0, 1 or 2%.     

A NEW METHOD FOR DETERMINING THE APPARENT THERMAL DIFFUSIVITY OF THERMALLY CONDUCTIVE FOOD

Two empirical parameters, j and f, have been used to determine the thermal diffusivity values of food by several researchers. Since there are considerable variations in j values, a new procedure was developed for the experimental determination of thermal diffusivity of foods without using this parametric value. A sample was filled into a cylindrical cell whose diameter and length were approximately 10 and 130 mm, respectively. The temperatures of the sample were monitored at the mid-point of the central axis and on the inside surface of the cell. These temperatures were used to estimate thermal diffusivity values together with an analytical formula for heat conduction in an infinite cylinder. The method was utilized to determine the thermal diffusivity, Biot number, and surface heat conductance values of water, 60% sucrose solution, glycerine, cherry tomato pulp, and apple pulp. There was close agreement between thermal diffusivity values determined experimentally and such values available in published literature. Mathematical procedures are presented for estimating errors in the thermophysical property values determined experimentally, where there are errors in locating temperature sensors in a sample, errors in the shape of the diffusivity cell, and errors in the temperature sensing device.     

ACCEPTABILITY OF VARIOUS GROUND BEEF AND PORK PRODUCTS EXTENDED WITH MECHANICALLY SEPARATED BEEF

Six blends of ground beef and six blends of ground pork containing 0, 15, 30, 45, 60 or 75% mechanically separated beef (MSB) were prepared. Also five batches of fermented sausage and spiced luncheon loaf containing 0, 5, 10, 15 and 20% MSB were formulated. Level of MSB was not related to juiciness rating or mealiness scores of cooked beef/MSB or pork/MSB patties. The level of MSB significantly affected overall eating satisfaction ratings for each blend of MSB patties. MSB at levels of 15% or more had a negative effect on flavor acceptability of cooked ground beef or pork. Fermented sausage products could be extended with only 5% MSB without creating defects in visual appearance or sensory properties. However, the inclusion of 20% MSB yielded a spiced luncheon loaf which was higher in eating quality than an all-beef control. The beef/MSB patties, fermented sausage, and spiced luncheon loaves containing 15% MSB were acceptable for visual appearance. Based on this study, MSB produced from a press type machine, can be blended up to 15% with ground beef, ground pork and sausage products without significantly decreasing raw appearance, sensory properties or storage life. Since MSB is a red meat product available at a similar low cost as textured vegetable protein, the red meat industry would benefit from expanded use of this high protein extender.     

A METHOD FOR DETERMINING THE CONVECTIVE HEAT TRANSFER COEFFICIENT DURING IMMERSION FRYING

The convective heat transfer coefficient is a useful parameter in characterizing heat flow across a fluid/solid interface when the fluid flow field is complex and solution of the coupled transport equations impractical. While convective heat transfer coefficient values for many unit operations have been tabulated, the boiling phase of immersion frying has not been quantified. The objective of this study was to develop a laboratory method for the measurement of the convective heat transfer coefficient during immersion frying. The method that was developed was applied to the immersion frying of potato cylinders at an oil temperature of 180C. The convective heat transfer coefficient was initially 300 W/m²K, it increased sharply to 1100 W/m²K, and gradually decreased to 300 W/m²K over the duration of the process. Use of this new method will allow the study of the effects of oil temperature, oil quality, product shape/size, and product quality on heat transfer coefficients.