Jong-Youn Jeong

Effects of thawing temperature on the physicochemical properties of pre-rigor frozen chicken breast and leg muscles

The objective of this study was to evaluate effects of thawing temperature on the biochemical and physicochemical properties of pre-rigor frozen chicken breast and leg muscles. Breast and leg muscles from 24 broiler chickens were excised within 10min postmortem. Pre-rigor muscles were frozen at -20°C and thawed at 0 and 18°C, and pH, R-value, sarcomere length, muscle shortening, thaw and cook loss, shear force and myofibrillar fragmentation index (MFI) compared with those in pre-rigor or 2°C chilled muscles. The ultimate pH of 18°C thawed muscle was lower than that of 0°C thawed and 2°C chilled muscles. As expected, the shortening of sarcomere length and muscle length of thaw rigor muscles were more than those of chilled muscle, but there were no significant differences between chilled muscle and 0°C thawed muscle. Also, there were no significant differences in R-value (Abs 250/Abs 260) and cook loss due to thawing temperature. Samples thawed at 0°C had higher MFI and lower shear value than samples thawed at 18°C. Shear force value and MFI were not significantly different between chilled muscle and 0°C thawed muscle. By thawing at 0°C, thaw shortening was prevented, and tender meat comparable to the chilled meat was obtained.

Effects of pork/beef levels and various casings on quality properties of semi-dried jerky

The aim of this study was to investigate the effects of pork/beef levels and the casings on the quality properties of semi-dried jerky. The pork/beef levels in the four test formulations were as follows: T-1 (pork: beef=100:0), T-2 (95:5), T-3 (90:10), and T-4 (80:20). After tumbling for 30min with curing solution, the cured meats were stuffed into natural sheep casings, collagen casings, or cellulose casings, and then dried. The restructured jerky with cellulose casing had the lowest water content and the highest protein content, with no significant differences between various formulations. There were no significant differences among all formulations with regard to pH and total microbial counts, and jerky with cellulose casing had the lowest value of water activity. The processing yields of jerky made from the T-3 formulation were not significantly different with the various casings. The shear force of jerky with cellulose casing was lower than with other casings, and the metmyoglobin contents were more than 85% in all formulations. With regard to sensory properties, jerky made with the T-3 formulation and cellulose casings rated most favorable in evaluations than other treatments.

Variability in temperature distribution and cooking properties of ground pork patties containing different fat level and with/without salt cooked by microwave energy.

This study was carried out to evaluate the cooking effects of fat level (10% and 20%) with and without NaCl (1.5%) on the microwave cooking pattern and properties of ground pork patties. Each patty was cooked from a thawed state to 76.7°C in a microwave oven with full power (900W). Cooking rate in patties produced without salt was not affected by fat level, but the addition of salt in pork patties decreased cooking rate, regardless of fat levels. The temperatures at the edges of the patties increased faster than those at the center or the mid-way positions. In the patties with NaCl, the temperature of the center position was higher than that of the mid-way position. Patties containing salt within the same fat level had higher moisture content and lower fat content than those without salt, although no significant differences in compositional properties were observed between the center, midway, or edge positions. Total cooking loss, drip loss, and reduction in diameter and thickness were higher in patties with 20% fat compared to those with 10% fat, but the addition of salt resulted in reduction, regardless of fat level. Also, the addition of salt increased the redness and reduced yellowness of the cooked products.