A. M. Booren

Nitrite stabilization of lipids in cured pork

Peroxidation studies indicated that phospholipids, microsomes and mitochondria from cured pork samples are less susceptible to metmyoglobin/hydrogen peroxide-catalyzed peroxidation than their counterparts from nitrite-free pork samples. The reaction of phospholipids and polyunsaturated fatty acid ethyl esters with dinitrogen trioxide increased their stability to peroxidative changes. Phospholipids from cured pork and those lipids reacted with dinitrogen trioxide were capable of nitrosating a secondary amine. These data, together with infrared analyses, indicate that nitrite or dinitrogen trioxide reacts with unsaturated lipids to form nitro-nitroso derivatives, thus stabilizing the lipids toward peroxidation changes. This mechanism can, in part, explain the antioxidant role of nitrite in cured meats.

Effect of sodium chloride concentration on pH, water-holding capacity and extractable protein of prerigor and postrigor ground beef☆

Fifteen beef cattle of similar age and management history were randomly allotted by slaughter days into three groups. Paired sternomandibularis were removed immediately following bleeding and trimmed of visible fat and connective tissue. They were randomly labelled as prerigor and postrigor and assigned to a 0, 0·5, 1·0, 2·0 or 4·0% NcCl treatment. Water-holding capacity (WHC), pH, the ratio of absorbance at 250 nm over the absorbance at 260 nm (R-values), and 1·0m NaCl extractable protein (EP) were monitored over treatment times. The 0 h samples were defined as when the NaCl was incorporated with the muscle. R-values verified that 0 h samples were in the prerigor or postrigor state. Ultimate pH remained higher (P < 0·05) in prerigor homogenates with increasing NaCl concentration. EP and WHC were higher (P < 0·05) in prerigor than in postrigor homogenates with 2 and 4% NaCl at all time periods. Prerigor homogenates containing 0·5 and 1·0% NaCl had higher (P < 0·05) WHC at 12, 24, 24, 48 and 96h than similarly treated postrigor homogenates and as high or higher WHC than any postrigor treatment. Results of this study indicate an advantage to using low NaCl concentrations in prerigor salted beef.

The effect of heat stress on thyroid hormone response and meat quality in turkeys of two genetic lines

The current study evaluated the effect of heat stress on thyroid hormone (T(3) and T(4)) response and meat quality traits in two turkey lines: a growth-selected commercial line and a genetically unimproved control line. Birds were subjected to heat stress for different durations before harvest. Commercial line had higher pH(15min), and lightness values, but lower cook loss and marinade uptake than control line during the heat stress. There was no difference in drip loss between the two lines. The T(3) concentration was positively correlated with cook loss and was negatively correlated with marinade uptake. The thyroid hormone response during heat stress was less stable in the commercial line than in the control line and the unstable thyroid hormone response in commercial turkeys caused by heat exposure might influence the consistency of meat quality. Results of this study may provide an application in selecting turkeys which yield consistent meat quality.

Effect of reduced sodium chloride concentration and tetrasodium pyrophosphate on pH, water-holding capacity and extractable protein of prerigor and postrigor ground beef

The effect of tetrasodium pyrophosphate (TSPP) (0, 0·25, 0·5% w/w) alone or in combination with salt (NaCl) (0, 0·5, 1·0% w/w) on water-holding capacity (WHC), pH, the ratio of absorbance at 250 nm over the absorbance at 260 nm (R-values) and 150m CaCl extractable protein (EP) was studied in prerigor and postrigor sternomandibularis homogenates over time. The 0 h samples were defined as when the NaCl was incorporated with the muscle. R-values verified that 0 h samples were in a prerigor or postrigor state. In prerigor homogenates, increasing phosphate concentration increased the time required to reach ultimate pH. Ultimate pH values of prerigor homogenates containing phosphate were lower (P < 0·05) than homogenates without phosphate and similarly treated postrigor homogenates. After six hours, no differences (P > 0·10) were noted in EP or WHC at different phosphate concentrations when averaged over NaCl concentrations in prerigor homogenates. With increasing phosphate concentration of postrigor homogenates, there was an increase (P < 0·05) in pH and EP at the initial sampling time. However, 0 and 0·25% phosphate WHC values could not be differentiated (P > 0·10). Results of this study indicate no advantages, after six hours post mortem, to using TSPP alone or in combination with NaCl in prerigor meat homogenates at concentrations added in this study.

Moisture content, processing yield, and surface color of broiler carcasses chilled by water, air, or evaporative air

This study was conducted to investigate the effects of water chilling (WC), air chilling (AC), and evaporative air chilling (EAC) on the moisture content, processing yield, surface color, and visual appearance of broiler carcasses. For the WC treatment, 1 group of birds was hard scalded and submersed into ice slush, whereas for AC, 1 group of birds was soft scalded and exposed to blowing air (1.0 m/s at 0°C) and for EAC, or 1 group of birds was soft scalded and exposed to blowing air and a cold water spray (every 5 min). During chilling, carcass temperature was reduced most effectively by WC (55 min), followed by EAC (120 min) and AC (155 min). After chilling, both WC and EAC carcasses picked up moisture at 4.6 and 1.0% of their weights, respectively, whereas AC carcasses lost 1.5% of their weight. On cutting at 5 h postmortem, WC carcasses showed the highest (2.5%), EAC showed the second highest (0.4%), and AC showed the least (0.3%) moisture loss. After 24 h of storage, almost 83% of the absorbed water in the WC carcass parts was released as purge, whereas EAC and AC carcasses maintained weights close to the prechilled weights. In an instrumental color evaluation and a visual evaluation by panelists, AC carcasses showed a darker appearance, a more yellow color, and more surface discoloration compared with WC or EAC carcasses.

Differential expression of calcium-regulating genes in heat-stressed turkey breast muscle is associated with meat quality

Aberrant postmortem Ca(2+)-regulation in the early postmortem period is associated with the occurrence of inferior meat quality in turkeys, described as pale, soft, and exudative (PSE). The objective of the current study was to quantify expression of 4 candidate genes responsible for maintaining Ca(2+) homeostasis in turkey skeletal muscle as a function of heat stress: α and β ryanodine receptors (RYR; Ca(2+)-release channels), the sarco/endoplasmic reticulum Ca(2+)-ATPase 1 (SERCA1), and the sarcoplasmic reticulum, Ca(2+)-storage protein calsequestrin (CASQ1). Two genetic lines of turkeys were used: a growth-selected commercial line and a randombred control line. Market-age birds were subjected to one of 5 heat stress treatments: no heat, 1 d, 3 d, 5 d, or 7 d of heat followed by 7 d of ambient temperature. Breast muscle samples were harvested and classified as normal or PSE using the meat quality parameters percentage of marinade uptake and percentage of cook loss. These parameters differed significantly by line, heat stress treatment, and meat quality status. Expression of candidate genes was measured using TaqMan quantitative PCR. Heat treatment was associated with significantly enhanced expression of αRYR, βRYR, and CASQ1 in normal muscle from both lines. Conversely, mRNA abundance of these genes was reduced in PSE muscle from both lines and recovered or increased by 7 d + 7 d of rest. Genetic line differences were observed at several time points. Expression of SERCA1 in both normal and PSE samples from both lines was unchanged or trended downward with heat stress. Taken together, genetic line and heat-stress treatment affected the expression of important Ca(2+)-regulating genes in association with meat quality status. The data suggest that birds whose meat leads to PSE may fail to respond to heat stress appropriately due to a delay in the upregulation of the important calcium-regulating genes: αRYR, βRYR, and CASQ1.

A research note on radio frequency transponder effects on bloom of beef muscle

This study was designed to determine if radio frequency transponders affect the bloom of tray-packed beef muscle. A radio frequency identification (RFID) passive transponder was applied to the overwrap film of beef strip loin steaks. Overwrapped tray packs were vacuum packaged and stored for two days at 4 °C. Samples were removed from the vacuum package and CIE L(*), a(*), and b(*) values were measured through the overwrap until CIE a(*) values stabilized (40 min). Overwrap was removed and CIE L(*), a(*), and b(*) values were measured directly below the RFID and an adjacent control area for 40 min. All CIE L(*), a(*), and b(*) values were statistically different (P<0.05) directly below the RFID when compared to the adjacent control area. The greatest differences were observed in the initial values and may be of consumer concern. After achieving full bloom (40 min post-overwrap removal), the difference between these areas were negligible.