Gunilla Lindahl

Contribution of pigment content, myoglobin forms and internal reflectance to the colour of pork loin and ham from pure breed pigs

The colour of loin, M. longissimus dorsi (LD), and ham, M. biceps femoris (BF), from pure breed Hampshire, Swedish Landrace and Swedish Yorkshire pigs was studied. The contribution of the pigment content, the myoglobin forms deoxymyoglobin (Mb), oxymyoglobin (MbO) and metmyoglobin (MetMb) and the internal reflectance to the colour of pork of normal meat quality was evaluated using partial least squares regression (PLS). The colour of LD and BF from the Hampshire breed was more red and yellow and more saturated than the colour of the same muscles from the Swedish Landrace and the Swedish Yorkshire breeds. Furthermore, BF from Hampshire was darker than BF from the other two breeds. These differences in colour were related to the lower pH in Hampshire, resulting in more blooming and in higher internal reflectance, and to the higher pigment content. The colour of BF was darker and more red than the colour of LD within each breed. No colour difference was found between gilts and castrates within each breed. Most of the variation (86-90%) in lightness (L* value), redness (a* value) and yellowness (b* value), chroma (saturation) and hue angle of pork of normal meat quality was explained by the pigment content, myoglobin forms and internal reflectance. The L* value, a* value, chroma and hue angle were influenced by both the pigment content and by the myoglobin forms to almost the same extent, while the internal reflectance was of no significance to these colour parameters. The b* value was influenced most by the myoglobin forms, less by the internal reflectance and almost not at all by the pigment content.

Influence of vacuum or high-oxygen modified atmosphere packaging on quality of beef M. longissimus dorsi steaks after different ageing times

The objective of the study was to determine if beef quality parameters differ between steaks in modified atmosphere packaging (MAP; 80% O₂and 20% CO₂) and in vacuum packaging. Both M. longissimus dorsi (LD) from ten young bulls were cut in steaks day 3 postmortem and frozen either directly or after storage for 5 or 15 days in MAP and/or vacuum. The parameters studied were Warner Bratzler shear force, colour stability, α-tocopherol content, protein oxidation, water holding capacity and sensory attributes. Steaks stored in MAP had higher shear force than steaks stored in only vacuum at all ageing times. Tenderness and juiciness were negatively affected by storage in MAP. Ageing in MAP induced higher levels of metmyoglobin compared with vacuum ageing. In conclusion, high-oxygen MAP negatively influenced shear force, thawing loss, α-tocopherol content and colour stability, as well as the sensory attributes tenderness, juiciness and to some extent meat flavour.

Significance of early postmortem temperature and pH decline on colour characteristics of pork loin from different crossbreeds

The significance of early postmortem (pm) temperature and pH decline and the level of the muscle metabolites creatine phosphate (CP) and adenosine triphosphate (ATP) on the colour of porcine M. longissimus dorsi was studied in a factorially designed experiment. Two stress levels peri mortem (minimal stress vs treadmill exercise and electrical stunning of the pigs) and four genotypes (Duroc boars crossed with Landrace-Yorkshire sows vs. Hampshire-Duroc boars crossed with Landrace-Yorkshire sows, including carriers and non-carriers of the halothane and RN(-) genes, respectively) were included. Early pm muscle temperature and the accompanying pH decline had a significant influence on the pork colour independent of genotype. The combination of high temperature and low pH early pm increased lightness and yellowness, which is ascribed to inactivation of oxygen-consuming enzymes and protein denaturation. The effect of early pm temperature and pH on pork redness was more complex. It appears to be closely related to the extent of heat generation, CP and ATP levels and pH immediately pm in the muscle, which influence the activity of oxygen-consuming enzymes.

Influence of vacuum skin packaging on color stability of beef longissimus lumborum compared with vacuum and high-oxygen modified atmosphere packaging

The objective of this study was to investigate how color stability of beef is affected by vacuum skin packaging (VSP) compared with vacuum packaging (VP) and high-oxygen modified atmosphere packaging (MAP; 80% O₂ and 20% CO₂). Longissimus lumborum muscles were aged in vacuum for 7 days and then cut into 2-cm-thick slices and repacked using VSP, VP and MAP for another 7 days. Color stability was measured during the next 5 days in air and samples for α-tocopherol and NADH analyses were obtained at the beginning and end of aerobic storage. Color stability, α-tocopherol and NADH of steaks were affected by packaging methods and storage time in air (P<0.05). Higher a* value was obtained in VSP on day 5 compared with VP. Steaks packed in VSP had better color stability than in VP and their color was similar to MAP at the end (day 5) of storage.

Ageing of large cuts of beef loin in vacuum or high oxygen modified atmosphere--effect on shear force, calpain activity, desmin degradation and protein oxidation.

The aim was to investigate the effect of ageing large beef cuts directly in high oxygen modified atmosphere (MA) and how ageing time in vacuum influence meat quality when followed by retail packaging in high oxygen MA. Large cuts (10 cm long) of beef loin (LD) were aged for up to 25 days postmortem in different ageing systems at 4 degrees C. Ageing solely in high oxygen modified atmosphere (MA, 80% O(2)+20% CO(2)) for 5 or 10 days and ageing in vacuum for 5 or 15 days followed by high oxygen MA for 5 or 10 days were compared with ageing in vacuum for 5, 15 and 25 days. Warner-Bratzler shear force, purge and cooking losses, calpain activity and desmin and carbonyl contents were measured. Shear force decreased to the same level when ageing this large beef cut solely in high oxygen MA for 5 or 10 days as when ageing in vacuum. The activity of mu-calpain disappeared, the activity of m-calpain decreased and purge loss increased between 5 and 10 days, but cooking loss and the contents of desmin and carbonyls were unaffected. The ageing time in vacuum before packaging of this large beef cut in high oxygen MA did not affect the ultimate shear force. The m-calpain activity decreased and the content of carbonyls increased compared with solely in vacuum after 15 days of total ageing, but there was no difference in the content of desmin or cooking loss between these ageing systems at the same ageing time.

Significance of storage time on degree of blooming and colour stability of pork loin from different crossbreeds

The objective was to investigate the effect of ageing time (1 day vs. 8 days postmortem) and sire breed used in the crossbreed (Duroc sired vs. Landrace sired pigs) on blooming ability and colour stability of pork M. longissimus dorsi (LD). The colour was measured during blooming (0, 10, 30, 60, 90min and 24h after cutting) and during subsequent display (1, 2, 3 and 6 days) at 3°C. The contents of deoxymyoglobin (Mb), oxymyoglobin (MbO(2)) and metmyoglobin (MetMb) were calculated. Ageing improved the blooming of LD from both crossbreeds with increased content of MbO(2) and decreased content of Mb, resulting in increased lightness, redness and yellowness. Ageing had smaller effect on colour stability with slightly lower MetMb in aged meat. Crossbreed affected both blooming and colour stability. LD from Landrace-sired pigs bloomed more than LD from Duroc-sired pigs, but more MetMb was formed during subsequent storage, although at a low level in both crossbreeds. The present data show superior colour characteristics of fresh pork aged for 8 days.

Colour stability of steaks from large beef cuts aged under vacuum or high oxygen modified atmosphere

The aim was to investigate the effects of ageing large beef cuts, 10-cm-long longissimus dorsi (LD) and 4-cm-long semimembranosus (SM), on colour stability during subsequent storage of steaks in air for 5 days. Ageing solely in high oxygen modified atmosphere (MA, 80% O₂ + 20% CO₂) for 5 or 10 days or ageing in vacuum for 5 or 15 days followed by high oxygen MA for 5 or 10 days were compared with ageing in vacuum for 5, 15 and 25 days at 4 °C. Ageing system and ageing time influenced colour stability. For short ageing times, 5 to 10 days, large beef cuts could be aged in high oxygen MA without negative effect on colour stability compared with vacuum ageing. Longer ageing times, 15 to 25 days, decreased colour stability. Then vacuum ageing was preferable to ageing in vacuum for 5 or 15 days followed by high oxygen MA.

Perceptual masking of boar taint in Swedish fermented sausages.

Surgical castration of male piglets has traditionally been practiced to avoid development of boar taint in pork meat which can occur if entire male pigs are raised. Boar taint is commonly characterised as exhibiting the odour and flavour of urine and manure. This study involves sensory characterisation of the possibilities to mask boar taint in meat from entire male pigs by fermentation and smoking to maintain high sensory quality in meat products if castration is prohibited. Model and commercial type Swedish fermented sausage products based on low or high levels of boar tainted fat, three different starter cultures and two different levels of smoking were studied. In the model sausages, liquid smoke masked the perception of boar taint. In contrast, the smoking procedure of the commercial sausages was insufficient to totally mask the perception of boar taint. In both the model and commercial sausages, the aroma development from the starter cultures lowered the perception of boar taint but was insufficient for total perceptual masking. Due to the total masking effect of smoking in the model sausages, it was clear that smoke may present a potential solution to remove the perception of boar taint in fermented sausages if the smoking procedure is optimised.

Significance of fat supplemented diets on pork quality - : Connections between specific fatty acids and sensory attributes of pork

The influence of two diets with different fatty acid compositions has been studied with regard to overall pork quality and significance of specific fatty acids on sensory attributes in fried chops and oven roasts. Twenty castrates and 20 females were in a balanced experimental set-up fed with a standard diet supplemented with α-tocopherol (200mg/kg feed) where the fat source was either 3% of palm oil or 3% rapeseed oil. After slaughter, despite differences in lipid composition and sensory attributes, no significant difference in overall meat quality parameters and flavour precursors was found. Comparison of the two diets showed that supplementation with rapeseed oil resulted in a significantly higher content of C18:3n-3 (polar lipid (PL), neutral lipid (NL)), C18:2n-6c (NL) and C20:2 (NL) in LD and C18:1n-9c, C18:2n-6c, C18:3n-3, C20:3n-3, C22:5n-3 in backfat, while supplementation with palm oil resulted in a higher content of C16:0 (NL), C16:1 (PL), C18:1n-9t (NL) in LD and C16:0, C17:0, C18:0, C16:1, C20:4n-6 in backfat. A positive and significant correlation between the contents of C18:2n-6c, C20:3n-6 in the PL fraction and the sensory attributes fried meat odour and sweet odour were found in fried pork chops from female pigs. Likewise, positive correlations were seen between the content of C18:1n-9c in the PL fraction and sensory attributes such as sourish odour, piggy odour and piggy flavour in whole oven roasts. These data substantiate the view that specific fatty acids in the PL fraction influences flavour attributes in pork.

Effect of high pressure, temperature, and storage on the color of porcine longissimus dorsi

The color of pork longissimus dorsi high pressure (HP) treated at 200 to 800 MPa at 5 and 20 °C for 10 min was determined to a high degree by pressure level and to a lesser degree by temperature. Severe color changes appeared up to a threshold pressure at 400 MPa. HP treatment at 20 °C compared to 5 °C resulted in meat, which was less red and slightly lighter. Storage at 2 °C for 6 days had no effect on lightness due to no further protein denaturation, but meat HP treated above 300 MPa became significantly less red and more yellow within the first day of storage. Reflectance spectra showed that a short-lived ferrohemochrome myoglobin species was formed during HP treatment at 300 to 800, but transformed into a brown, ferric form of the pigment within the first day of storage. This explains the observed changes in the redness and yellowness after one day of storage.