Isothermal gelation behavior of myofibrillar proteins from white and red chicken meat at different temperatures.

This paper provides insights in the isothermal gelation behavior of white and red chicken myofibrillar proteins (CMP) at different temperatures (20 to 80°C) and the underlying aggregation mechanism, allowing understanding of structure formation in poultry products during thermal processing. At low temperatures (20 to 60°C), an increase in aromatic surface hydrophobicity (SoANS) was found, suggesting potential formation of hydrophobic interactions between CMP. At higher temperatures (60 to 80°C), high SoANS and a significant decrease in total sulfhydryl amount (SH-amount) strongly indicate the presence of hydrophobic interactions and disulfide bonding, resulting in aggregation, as suggested by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The elastic modulus G' after 60 min isothermal heating (G'60min) significantly increased at 70 or 80°C, depending on the type of CMP. Differences in G'60min between white and red CMP were rather small at low temperatures (20 to 60°C). However, at 70°C, white CMP reached higher G'60min compared to red CMP, while the opposite was observed at 80°C. Overall, for every temperature studied, SoANS and SH-amount of red CMP were higher compared to white CMP. The differences in G'60min, SoANS, and SH-amount between white and red CMP were probably due to different isoforms. The results may help to steer quality characteristics of poultry products through intelligent choice of processing conditions.

Influence of putrescine, cadaverine, spermidine or spermine on the formation of N-nitrosamine in heated cured pork meat.

The influence of biogenic amines (i.e. putrescine, cadaverine, spermidine and spermine) on the N-nitrosamine formation in heated cured lean meat was studied in the presence or absence of sodium nitrite and at different meat processing temperatures. Experimental evidence was produced using gas chromatography with thermal energy analysis detection (GC-TEA). Concentration of N-nitrosamines was modelled as a function of the temperature and the nitrite concentration for two situations, i.e. presence or absence of added biogenic amines to the meat. The significance of the influence of the changing parameters was evaluated by ANOVA (Analysis of Variance). It was found that higher processing temperatures and higher added amounts of sodium nitrite increase the yields of N-nitrosodimethylamine (NDMA) and N-nitrosopiperidine (NPIP). Spermidine and putrescine amplify the formation of NDMA, but spermine and cadeverine do not influence the formation of this N-nitrosamine. Spermidine and cadeverine cause a significant increase of NPIP. Beside N-nitrosopyrrolidine (NPYR) in some rare cases, no other volatile N-nitrosamines are detected.

Influence of NaCl reduction and replacement on the growth of Lactobacillus sakei in broth, cooked ham and white sauce.

The growth inhibiting effects of NaCl and selected simple salt replacers (CaCl(2), MgCl(2), KCl and MgSO(4)) on the growth of Lactobacillus sakei were studied in de Man Rogosa Sharpe broth at 7 degrees C over a water phase concentration of 0 to 6.4%. The divalent chloride salts (CaCl(2) in particular) generally had the largest antimicrobial activities at equivalent water phase concentrations, molalities or water activity (a(w)) values. MgSO(4) had not only the least antimicrobial activity but also the smallest a(w) depressing capacity. The results also showed that the antimicrobial effects of CaCl(2) were not fully accounted for by its a(w) depressing effects. Challenge tests performed on cooked ham and white sauce showed that reduction of NaCl levels by 28 and 33%, respectively, had no influence on the microbial stability of these products to L. sakei. Ultimately the study concluded that the microbiological consequences of the full or partial replacement of NaCl on the growth of L. sakei largely depend on the initial level of NaCl, the level of replacement and the nature of the salt replacer used. Altered stability to L. sakei is most likely given a high initial NaCl level, combined with a large level of partial replacement with either CaCl(2) (increased stability) or MgSO(4) (reduced stability) as the replacer.

Evaluation of the influence of proline, hydroxyproline or pyrrolidine in the presence of sodium nitrite on N-nitrosamine formation when heating cured meat.

N-nitrosamines are meant to be probable or possible carcinogenic components, possibly formed out of a reaction between nitrite and N-containing substances such as amino acids and secondary amines. Nitrite is often used for processing meat products because of its colouring and antimicrobial properties. During this experimental setup, the influence of proline, hydroxyproline or pyrrolidine on N-nitrosamine formation in meat samples was evaluated. The N-nitrosamines concentrations were measured with gas chromatography-thermal energy analyzer. Only the concentrations of N-nitrosodimethylamine and N-nitrosopyrrolidine were found above the limit of detection in a number of tested experimental conditions. The concentration of these two N-nitrosamines was modelled as a function of temperature and nitrite concentration for different situations (presence or absence of added natural N-containing meat components). It could be concluded that proline and pyrrolidine promoted the formation of N-nitrosopyrrolidine. It could also be confirmed that the higher the temperature of the meat processing procedure and the higher the sodium nitrite amounts added, the higher were the yields of the respective N-nitrosamines.

Role of proline and hydroxyproline in N-nitrosamine formation during heating in cured meat.

N-Nitrosamines are formed in a multi-step reaction of nitrite with free amino acids and amines in the meat products. The aim of this study was to determine the role of proline and hydroxyproline in N-nitrosamines formation during heating of cured meat. A lean meat model was used with different nitrite concentrations (0, 120, and 480mg/kg), and addition of proline and hydroxyproline (1000mg/kg), followed by heating at different temperatures. Volatile nitrosamines were analyzed with GC-TEA. The nitrosamine content never exceeded 10µg/kg and stayed 120°C.

Evaluation of the spoilage lactic acid bacteria in modified-atmosphere-packaged artisan-type cooked ham using culture-dependent and culture-independent approaches.

AIMS: To investigate microbial diversity and population dynamics of spoilage-sensitive modified-atmosphere-packaged (MAP) artisan-type cooked ham in relation to storage temperature. METHODS AND RESULTS: Modified-atmosphere-packaged cooked ham samples were stored at different temperatures (4, 7, 12 and 26 degrees C). Traditional methods were combined with polymerase chain reaction (PCR)-based techniques, i.e. a culture-dependent, repetitive DNA sequence-based method (rep-PCR) and a culture-independent approach (PCR-denaturing gradient gel electrophoresis of 16S rRNA gene fragments; PCR-DGGE). rep-PCR on DNA extracted from MRS isolates indicated that Leuconostoc carnosum and Enterococcus faecalis prevailed at all temperatures, with the latter becoming more important above 7 degrees C. PCR-DGGE indicated the additional presence of Carnobacterium divergens and Brochothrix thermosphacta at all temperatures. Discriminant analysis related variation within the Leuc. carnosum cluster to the storage temperature. High performance liquid chromatography revealed that lactic acid was the main metabolite because of glucose consumption. CONCLUSIONS: Leuconostoc carnosum, C. divergens, E. faecalis and Br. thermosphacta are the main spoilage bacteria of artisan-type MAP cooked ham. Their population dynamics are affected by storage temperature. SIGNIFICANCE AND IMPACT OF THE STUDY: Temperature can condition the development of spoilage in artisan-type MAP cooked ham, acting at both species and biotype level.

A survey of pork quality in relation to pre-slaughter conditions, slaughterhouse facilities, and quality assurance.

A survey at five pigs' slaughterhouses was performed to investigate the effect of a quality assurance system, pre-slaughter conditions and slaughterhouse facilities on pork quality. Totally, 2246 pigs were included over four transports per slaughterhouse, i.e. two transports were produced according to a quality assurance system and the other two were conventional pigs. Meat quality was measured on 446 pigs. The pH in the longissimus dorsi muscle and the electrical conductivity in the semimembranosus muscle were measured 30min post-mortem. Twenty-four hours later pH and electrical conductivity in both the longissimus dorsi and the semimembranosus muscle were measured. Pigs managed according to a chain quality protocol showed an overall higher potential for improved meat quality. Differences in meat quality between the different slaughterhouses were also found, however they were dependent on muscle type and time of measuring. Influencing factors on pork quality seemed to be stocking density during transport, the handling during offloading the pigs from the truck, stocking density, and air temperature during lairage.

Effect of dietary antioxidant and fatty acid supply on the oxidative stability of fresh and cooked pork.

The effect of dietary oil (linseed or soybean oil) and antioxidant treatment (α-tocopheryl acetate (AT; 40ppm) versus a cocktail (AOC; 200ppm): α-tocopheryl acetate+rosemary+citric acid+gallic acid) on colour, lipid and protein oxidation of fresh and processed pork was investigated. No effect of oil source on different parameters of oxidation was seen. No effect of antioxidant treatment on colour stability of fresh longissimus thoracis (LT) or cooked cured ham (CCH) was observed. For both antioxidant treatments, lipid oxidation in fresh LT and CCH was well controlled during display. However, lipid oxidation increased significantly in pre-frozen uncured cooked meat under aerobic conditions. No unambiguous effect of antioxidant treatment on protein oxidation was observed. There seemed to be no clear link between colour, protein and lipid oxidation. At the dose used in this study, no additional or synergistic effects of the extra components of the AOC on the different oxidation parameters was found.

A combination of buprenorphine and naloxone compared with buprenorphine administered intramuscularly in postoperative patients.

Sixty patients suffering from moderate to severe pain following either orthopaedic or gynaecological surgery were treated with intramuscular buprenorphine (0.3 mg) or an intramuscular combination of buprenorphine (0.3 mg)/naloxone (0.2 mg) and the analgesic efficacy and safety of the two treatments was compared. The evaluation of efficacy showed that both treatments provided good analgesia which was apparent at the first assessment time (10 minutes) and continued for approximately 10 hours. Only seven patients suffered from unwanted side-effects with only drowsiness/sleepiness and nausea being reported by more than one patient. Over-all analysis of the results showed that there were no significant differences between the two treatments with regard to efficacy and safety.