S. Barbut

Progress in reducing the pale, soft and exudative (PSE) problem in pork and poultry meat.

Research in the area of the pale, soft and exudative (PSE) pork and poultry meat is reviewed in this article with an emphasis on genetic, biochemical and metabolic factors contributing to the problem. Over the past five decades, there has been much more work in the pork meat area where a few genetic markers have been identified, and are currently used to remove susceptible animals from the herd. Some of the markers are linked to aberrant calcium regulation in the early postmortem muscle. The poultry industry is still not at the point of using genetic marker(s); however, some recent work has revealed several potential markers. The review also discusses environmental factors such as antemortem stress and early postmortem processing practices (e.g. chilling rate) that can influence the development and severity of the PSE phenomenon. Some of these factors are known to cause protein denaturation at the early stage of postmortem and directly contribute to poor water-holding capacity and inferior texture in fresh meat and later in processed products. A newer hypothesis suggesting that variation in protein oxidation, in response to antemortem stress and early postmortem tissue environment, can contribute to development of PSE pork is also discussed. Finally, a few recommendations for future work are proposed.

Problem of pale soft exudative meat in broiler chickens

1. The occurrence of the pale, soft exudative (PSE) problem in broiler breast meat was monitored in 700 birds (random samples from 7 flocks). A rapid method of colour measurement was used in the plant to assess the colour of skinless pectoralis muscles at 24 h post mortem. In addition, 10 selected samples from each flock were further evaluated for pH, water holding, cook loss, and texture. 2. The average L* value (lightness) was 47.1 with a variance of 5.38, skewness 0.33 and kurtosis 0.66. Minimum and maximum L* values recorded during the study were 35.3 and 55.5 respectively. 3. Correlations between colour and most of the physical measurements were observed, suggesting that a rapid colour measurement method could be used to recognise PSE meat or identify flocks with a high incidence of PSE. 4. Breast muscle samples with L* > 49 showed poor water holding capacity, which indicated that these samples would be classified as PSE meat. Using this criterion it was shown that the occurrence of PSE ranged from 0% to 28%. However, the precise cut off point for PSE muscle should be determined by each processor depending on final product requirements.

Colour measurements for evaluating the pale soft exudative (PSE) occurrence in turkey meat

Abstract The CIELAB colour measuring system was used to measure the colour of turkey breast muscle from young toms, ranging from very light to very dark in colour. Lighter exhibited lower pH, lower gel strength, and higher cooking loss compared to darker samples. The ‘L’ value (lightness) was significantly correlated with pH of the intact (r = −0·71, p ⩽ 0·01) and chopped muscle (r = −0·66), cooked gel strength (r = −0·84) and cooking loss (r = 0·87). The results indicate that a type of pale soft and exudative (PSE) condition may exist in turkey breast meat from young toms and that such meat can be identified by a fast and non-destructive colour evaluation

Mechanical properties of ethylcellulose oleogels and their potential for saturated fat reduction in frankfurters.

Ethylcellulose has been recently shown to be an excellent organogelator for vegetable oils. The resulting gels maintain the fatty acid profile of the vegetable oil used, but posses a solid-like structure that can be useful for the replacement of saturated fats in food products. Texture profile analysis and the back extrusion technique were used to assess the mechanical properties of canola, soybean, and flaxseed oil oleogels consisting of 10% ethylcellulose and 90% vegetable oil. Oils with a higher degree of unsaturation were shown to produce harder gels. Oleogels containing ethylcellulose of three molecular weights and reduced polymer concentrations from 4-10% ethylcellulose were also tested using the back extrusion technique, resulting in an increase in gel strength as polymer concentration and molecular weight increased. Therefore, oleogel strength was shown to be dependant on polymer molecular weight, concentration, and the fatty acid composition of the vegetable oil. Scanning electron microscopy was also used to provide a greater understanding of the gels microstructure. In addition, frankfurters were made using canola oil oleogels to assess the possibility for replacement of the more highly saturated animal fat in such a product. Cooked frankfurters made with oleogels showed no significant differences in chewiness or hardness compared to the control products made with beef fat. These results provide the first in-depth characterization of ethylcellulose oleogels, and could potentially aid in the design/manufacture of ethylcellulose oleogels with specific textural properties to replace saturated fat in a variety of food products.

Seasonal effect on pale soft exudative (PSE) occurrence in young turkey breast meat

Colour distribution of turkey breast meat was evaluated in different flocks during the year to assess the frequency of the pale soft exudative (PSE) problem. The pH, water-holding capacity, cooking loss, and texture of selected samples were also evaluated. Significant correlations (P ≤ 0.05) were found between ‘L’ value and the other parameters, indicating that a colour measurement could be used, on a commercial scale, to assess PSE conditions in turkey breast meat. Overall, mean L value was the highest during the summer (P ≤ 0.05), lowest during the winter, and intermediate during the spring and autumn. Colour measuring time (3 vs 24 h) post mortem had an effect on the measured L value, especially at the low range (L value < 45). The approach for selecting an appropriate cut-off L value, for industrial purposes, by targeting a certain water-holding capacity level is also discussed.

Fat reduction in comminuted meat products-effects of beef fat, regular and pre-emulsified canola oil

The effects of fat reduction (25.0%, 17.5%, and 10.0%) and substituting beef fat with canola oil or pre-emulsified canola oil (using soy protein isolate, sodium caseinate or whey protein isolate) on cooking loss, texture and color of comminuted meat products were investigated. Reducing fat from 25 to 10% increased cooking loss and decreased hardness. Canola oil or pre-emulsified treatments showed a positive effect on improving yield and restoring textural parameters. Using sodium caseinate to pre-emulsify the oil resulted in the highest hardness value. Cohesiveness was affected by fat type and level. The color of reduced fat meat batters was darker for all, except the beef fat treatments. Using canola oil or pre-emulsified oil resulted in a significant reduction in redness. The results show that pre-emulsification can offset some of the changes in reduced fat meat products when more water is used to substitute for the fat and that pre-emulsification can also help to produce a more stable meat matrix.

Rheological characteristics of fresh and frozen PSE, normal and DFD chicken breast meat

1. Textural and rheological differences among broiler breast meat ranging from pale, soft and exudative (PSE) to dark, firm and dry (DFD) in their fresh and frozen (and thawed) forms were investigated. 2. The PSE meat showed significantly higher lightness values and lower pH and water holding capacity values than normal and DFD meats; DFD meat was also significantly different from normal meat. 3. During cooking, PSE meat lost significantly more liquid and produced a softer gel than normal or DFD meats; texture profile analysis parameters were lower for the PSE meat. 4. The storage modulus values (G′, rigidity of elastic response of the gelling material) showed that DFD meat produced a more rigid gel during cooking (especially above 54°C) and later during cooling (back to 30°C) compared with the PSE meat. 5. Freezing resulted in a trend of lower G′ values before, during and after cooking. The results indicated that meat proteins were damaged during freezing and PSE meat was more severely affected, or that more protein denaturation occurred in the PSE meat.

Molecular interactions of polymer oleogelation

We have successfully gelled ethyl cellulose (EC) in different vegetable oils. This work investigated the molecular interactions responsible for such gelation process. Rheological measurements show that flaxseed oil gels need a larger yield force than soybean and canola analogues. We have used both Raman and IR spectroscopy to elucidate which functional groups are involved in the gelation process. We have found that the glycerol group of the triglycerides behaves in the same way in the free oil as in the gel. This is an indication that the specificity seen by using different oils is not due to electrostatic interactions involving this functional group. Our results show that the conformation of the lipid chains is mainly responsible for solvent–solvent interaction. However, the difference seen in the rheological properties is explained in terms of polymer–solvent interactions. These are influenced by the molar volume of the solvent, which is dependent on the amount of unsaturations, such that the larger volume leads to an increased separation of the polymer strands and a decrease in the number of tie points in the polymer network.

Effects of fat reduction on frankfurters' physical and sensory characteristics

Abstract The composition of commercial Canadian frankfurters and the composition, texture, viscoelastic, hydration, colour, and sensory attributes of experimental reduced fat pork/beef frankfurters were investigated. In the commercial products, the fat content varied from 21 to 26%. Frankfurters were prepared with fat varying from 23 to 10% by replacing the fat with water. Lower values of water holding capacity were observed in the high fat products which were related to a lower initial moisture content. The expressed free water depended on the fat and moisture contents of the product. Medium fat products were harder than the low and high fat products. The viscoelastic properties (relaxation time, elastic moduli) were not significantly affected by the changes in fat level. Sensory analysis results indicated that the low fat products were more tender and less juicy. The overall acceptability results indicated high preference for the low fat products.

Physicochemical effects of the lipid phase and protein level on meat emulsion stability, texture, and microstructure.

The effects of beef fat (25%) substitution with rendered beef fat, canola oil, palm oil, or hydrogenated palm oil at varying meat protein levels (8%, 11%, and 14%) were studied in emulsified beef meat batters. There was no significant difference in fat loss among meat batters made with beef fat, rendered beef fat, or palm oil. Hydrogenated palm oil provided the most stable batters at all protein levels. Increasing meat protein to 14% resulted in high fat loss in batters prepared with canola oil, which did not occur in the other formulations. This indicates that the physicochemical characteristics of fat/oil affect emulsion stability. Cooked batter hardness was higher (P < 0.05) when protein level was raised; highest in hydrogenated palm oil batters when compared at similar protein levels. As protein level was raised springiness values were increased in all the meat treatments. Springiness was higher in the canola oil treatments. Light microscopy revealed fat globule coalescence in canola oil meat batters prepared with 14% protein, as well as the development of fat channels and more protein aggregation; both seem to result in lower emulsion stability. Hydrogenated palm oil batters showed fat particles with sharp edges as opposed to the round ones seen in all other treatments.