Lipid oxidation in minced beef meat with added Krebs cycle substrates to stabilise colour.

Krebs cycle substrates (KCS) can stabilise the colour of packaged meat by oxygen reduction. This study tested whether this reduction releases reactive oxygen species that may lead to lipid oxidation in minced meat under two different storage conditions. KCS combinations of succinate and glutamate increased peroxide forming potential (PFP, 1.18-1.32 mmol peroxides/kg mince) and thiobarbituric acid reactive substances (TBARS, 0.30-0.38 mg malondialdehyde (MDA) equivalents/kg mince) under low oxygen storage conditions. Both succinate and glutamate were metabolised. Moreover, under high oxygen (75%) storage conditions, KCS combinations of glutamate, citrate and malate increased PFP (from 1.22 to 1.29 mmol peroxides/kg) and TBARS (from 0.37 to 0.40 mg MDA equivalents/kg mince). Only glutamate was metabolised. The KCS combinations that were added to stabilise colour were metabolised during storage, and acted as pro-oxidants that promoted lipid oxidation in both high and low oxygen conditions.

Protein expression and oxygen consumption rate of early postmortem mitochondria relate to meat tenderness.

Oxygen consumption rate (OCR) of muscle fibers from bovine semimembranosus muscle of 41 animals was investigated 3 to 4 h and 3 wk postmortem. Significant relations (P < 0.05) were found between OCR measurements and Warner-Bratzler shear force measurement. Muscles with high mitochondrial OCR after 3 to 4 h and low nonmitochondrial oxygen consumption gave more tender meat. Tender (22.92 ± 2.2 N/cm2) and tough (72.98 ± 7.2 N/cm2) meat samples (4 samples each), separated based on their OCR measurements, were selected for proteomic studies using mitochondria isolated approximately 2.5 h postmortem. Twenty-six differently expressed proteins (P < 0.05) were identified in tender meat and 19 in tough meat. In tender meat, the more prevalent antioxidant and chaperon enzymes may reduce reactive oxygen species and prolong oxygen removal by the electron transport system (ETS). Glycolytic, Krebs cycle, and ETS enzymes were also more abundant in tender meat

Mitochondrial oxygen consumption in permeabilized fibers and its link to colour changes in bovine M. semimembranosus muscle.

Animal and muscle characteristics were recorded for 41 cattle. The oxygen consumption rate (OCR) of M. semimembranosus was measured between 3.0-6.4h post mortem (PM3-6) and after 3 weeks in a vacuum pack at 4°C. Colour change measurements were performed following the 3 weeks using reflectance spectra (400-1,100 nm) and the colour coordinates L, a and b, with the samples being packaged in oxygen permeable film and stored at 4°C for 167 h. Significant individual animal differences in OCR at PM3-6 were found for mitochondrial complexes I and II. OCR of complex I declined with increased temperature and time PM, while residual oxygen-consuming side-reactions (ROX) did not. OCR of stored muscles was dominated by complex II respiration. A three-way regression between samples, colour variables collected upon air exposure and OCR of 3 weeks old fibres revealed a positive relationship between OCR and complex II activity and also between OCR and OCR(ROX). The presence of complex I and ß-oxidation activities increased metmyoglobin formation.

Live chilling of Atlantic salmon: physiological response to handling and temperature decrease on welfare.

Investigation of the physiological effects of live chilling in Atlantic salmon, Salmo salar, has been performed in two experiments. In the first, fish (mean weight 840 g) acclimatized to either 16, 8, or 4°C were directly transferred horizontally or vertically (9 combinations) to water temperatures of 16, 8, 4, or 0°C using a dip net. Blood samples were collected at 1 and 6 h (h) post-transfer. In the second experiment, fish (mean weight 916 g) acclimatized to 16°C were exposed to four temperature-drop regimes (no physical handling): 16-4°C (over 5 h), 16-4°C (over 1 h), 16-0°C (over 5 h), and 16-0°C (over 1 h). Blood samples were collected 1 h post-temperature drop. Physical transfers in the first trial, i.e., temperature drops, resulted in immediate (1 h) increases in blood lactate concentrations at all three temperatures, but levels were significantly reduced and close to pre-transfer levels after 6 h. Horizontal transfers, i.e., 16-16°C, 8-8°C, and 4-4°C, resulted in similar increases and were not significantly different from the groups exposed to temperature drops. The most severe vertical transfer (16-0) resulted in a swift loss of equilibrium and eventually death. In experiment 2, temperature drops from 16 to 4°C and from 16 to 0°C over a period of one or 5 h, without physically handling the fish, resulted in no significant increases in any of the measured parameters 1 h post-transfer, except in the 16-0 (1 h) group. The latter experienced a significant increase in blood sodium, glucose, lactate, and cortisol levels compared to all other groups. The results suggest that salmon are capable of tolerating relatively steep temperature drops without any significant negative effects on blood stress parameters and that physical stress from handling overrides the effect of thermal insults.

Characterization of volatile compounds in a fermented and dried fish product during cold storage.

The northern European production technique for dry-cured meat sausages was used to produce a sliceable, fermented, and dried fish product rich in omega-3 polyunsaturated fatty acids (PUFA). The fatty fish Atlantic salmon (Salmo salar), the lean fish saithe (Pollachius virens) (1:1, w/w), Lactobacillus sakei, and 4 different milk protein-based ingredients were used in the recipes. The changes in the volatile compounds during cold storage (+4 degrees C) of vacuum-packed dried sausages were studied by dynamic headspace gas chromatography-mass spectrometer (GC-MS). Of the 117 volatile compounds identified, alcohols, alkanes, esters, aldehydes, ketones, and compounds derived from amino acids were the most prevalent groups of volatiles. Thirty volatiles decreased and 17 increased significantly (P < 0.1) during storage for 15 wk. Despite the high content of PUFA, amino acid catabolism and ester synthesis led to larger changes in the composition of volatiles in the fish product than did lipid oxidation reactions. The milk-protein-based powders that were used to physically stabilize the fish oil did not affect the lipid oxidation compounds.

Production of salami from beef, horse, mutton, Blesbok (Damaliscus dorcas phillipsi) and Springbok (Antidorcas marsupialis) with bacteriocinogenic strains of Lactobacillus plantarum and Lactobacillus curvatus.

Lactobacillus plantarum 423, producer of bacteriocin 423, Lactobacillus curvatus DF38, producer of curvacin DF38, and a bacteriocin-negative mutant of L. plantarum 423 (423m) were evaluated as starter cultures in the production of salami from beef, horse, mutton, Blesbok (Damaliscus dorcas phillipsi) and Springbok (Antidorcas marsupialis). Growth of L. plantarum 423 and L. curvatus DF38 was best supported in Blesbok salami, as revealed by the highest growth rate during sweating, cold smoking and maturation, and final cell numbers after 70 days (1×10(8) and 5×10(7)cfu/g, respectively). Growth of Listeria innocua was the best suppressed in Blesbok salami fermented with L. plantarum 423 and L. curvatus DF38. Growth of L. innocua in horse salami was best suppressed when fermented with L. curvatus DF38. The final pH of salami fermented with L. plantarum 423 and L. plantarum 423m was slightly lower (4.4) compared to the pH of salami produced with L. curvatus DF38 (pH 4.7). No significant differences (P>0.05) were recorded by a trained sensory taste panel amongst the three starter cultures regarding colour and venison like aroma. Horse, Blesbok and Springbok salami were rated significantly higher (P⩽0.05) in salami flavour than mutton salami, which was rated the lowest for this attribute. Blesbok salami was rated the highest for sour meat aroma, while beef salami was rated the lowest. Springbok salami was rated the highest in terms of oily mouth feel. Beef salami had the most compact structure and horse salami the softest structure of all meat types fermented. In general, salami produced with L. plantarum 423 yielded the best sour meat aroma, colour, texture, venison like flavour, sour meat flavour and oily mouthfeel and is considered superior to the L. plantarum mutant (strain 423m) and L. curvatus DF38.

Fatty acid alpha-oxidation of tetradecylthioacetic acid and tetradecylthiopropionic acid in cucumber (Cucumis sativus).

Fatty acid alpha-oxidation in cucumber (Cucumis sativus) involves enzymatic conversion of long-chain Cn-fatty acids to the C(n-1)-aldehyde and CO2. However, the mechanism of this process is not well understood. In this study, the alpha-oxidation of the fatty acid analogues tetradecylthioacetic acid (TTA) and tetradecylthiopropionic acid (TTP) with a sulphur atom substituting the methylene group in positions 3 and 4, respectively, was investigated and compared to palmitic acid. Both [1-14C]TTA and [1-14C]TTP could be alpha-oxidised in the cucumber subcellular 150000xgmax fraction. [1-14C]TTP was an even better substrate compared to the natural palmitic acid, while [1-14C]TTA was alpha-oxidised to a lower extent. [2-14C]TTA revealed no 14CO2, indicating that only one cycle of alpha-oxidation occurred. TTA was an inhibitor of the palmitic acid alpha-oxidation, and the inhibitory effects were examined.

Long-chain saturated fatty acids can be alpha-oxidised by a purified enzyme (M(r) 240,000) in cucumber (Cucumis sativus).

An enzyme (M(r) 240,000) with high fatty acid alpha-oxidation activity has been purified from the fruit of cucumber (Cucumis sativus). The specific alpha-oxidation activity in the purified fraction was 370 nmol/min per mg protein determined as liberation of 14CO2 from [1-14C]palmitic acid. alpha-Oxidation activity was observed both in the 12,000 x g pellet and 150,000 x g pellet by differential fractionation of cucumber homogenate. The enzyme was purified about 220-fold to near homogeneity from a 12,000 x g fraction by solubilisation with Triton X-100R, ammonium sulphate precipitation, hydrophobic interaction and anion-exchange chromatographies and Superose 12 gel filtration. The molecular mass of the native enzyme was 240,000, and the major subunit molecular mass of 40,000 indicated an oligomeric structure.

Composition of muscle fibre types and connective tissue in bovine M. semitendinosus and its relation to tenderness.

The distribution of muscle fibre types and connective tissue in bovine M. semitendinosus is described. A parallel increase in the volume fraction of type I muscle fibres (from 10% to 30%) and a decrease in the IIB volume fraction (from 58% to 34%) was recorded from superficial to deep layers. A positive correlation was observed between the frequency and the cross-sectional area of both type I and IIB fibres. The elastic fibres formed irregularly shaped bundles that made up about 50% of the volume of the perimysium. Thin elastic fibres extended into the endomysium. The relative proportion of elastic fibres in the perimysial connective tissue increased towards the deeper layers of the muscle. A taste panel evaluation of the sensory properties was performed and the data were correlated to the histological observations. A gradual decrease in scores of four tenderness-related traits was recorded from the superficial to the deep layer of the muscle. The superficial layer was rated as most tender, whereas the consecutive layers were rated less tender. The possible relationship between the composition of muscle and the meat quality is discussed.

Z-disc digestion of isolated bovine myofibrils by an endogenous calcium activated neutral proteinase.

Calcium activated neutral proteinase (CANP) activity has been purified from bovine M. semimembranosus. The effect of the enzyme on purified fractions of beef myofibrils is described. The Z-discs were the main target of the enzyme; small holes developed and the Z-discs were fragmented into smaller units of equal size. The Z-discs fragments were also split transversely, leaving half to each of the neighbouring sarcomeres. Prolonged digestion removed the entire Z-discs and its set of thin myofilaments. The functional importance of the proteinase in meat tenderization is discussed.

Variations in the activity of microsomal palmitoyl-CoA hydrolase in mixed micelle solutions of palmitoyl-CoA and non-ionic detergents of the triton X series.

The kinetics of palmitoyl-CoA hydrolase were influenced by both the availability of the substrate and formation of micelles. At palmitoyl-CoA concentrations below the critical micelle concentration, addition of non-ionic detergent increased the activity until the critical micelle concentration of the mixed micelles was reached. At palmitoyl-CoA concentrations above the critical micelle concentration, inhibitor of the activity was observed, but addition of detergents of the Triton X series reversed the inhibition. Maximum palmitoyl-CoA hydrolase activity was found when the ratios (w/v) of palmitoyl-CoA: Triton X-100 and palmitoyl-CoA: Triton X-405 were approximately 0.35 and 0.05, respectively. At these above the mixed critical micelle concentration. The results indicate that monomer palmitoyl-CoA is the substrate and that monomer forms of the non-ionic detergents of the Triton X series activate the enzyme. Isolated microsomal lipids activated the microsomal palmitoyl-CoA hydrolase, suggesting that a hydrophobic environment is advantageous for interaction between enzyme and substrate in vivo. The maximum activity in the presence of mixed micelles is discussed in relation to a model where mixed micelles are regarded as artificial membranes to which the enzyme may adhere in an equilibrium with the monomer substrate and detergent in the monomer form. It is suggested that intracellular membranes may resemble mixed micelles in equilibrium with detergent-active substrates such as palmitoyl-CoA.

Characteristics of some lactic Acid bacteria used as starter cultures in dry sausage production.

The fermentation characteristics of two commercial (Duploferment 66 and Saga II) and five Norwegian lactic acid bacteria used in dry sausage production were compared with those of Lactobacillus plantarum ATCC 8014. The Norwegian strains lacked the ability to ferment mannitol, sorbitol, lactose, and d-(+)-raffinose and grew at 8 but not at 42 degrees C, in contrast to the ATCC culture and the two commercial strains. The lactate dehydrogenase activity of the Norwegian strains was not stimulated by pyruvate. All strains were capable of peroxide destruction when grown in the presence of myoglobin.

Intracellular localization of long-chain acyl-coenzyme A hydrolase and acyl-L-carnitine hydrolase in brown adipose tissue from guinea pigs.

The activities of long-chain acyl-CoA hydrolase (palmitoyl-CoA hydrolase, EC 3.1.2.2) and long-chain acyl-L-carnitine hydrolase, EC 3.1.1.28) in brown adipose tissue from cold-exposed and control guinea pigs were studied. Mitochondria from cold-exposed animals hydrolysed 21 nmol of palmitoyl-CoA/min per mg of protein and 1.3 nmol of palmitoyl-L-carnitine/min per mg of protein, and the specific activities were respectively 2 and 5 times as high in cold-exposed as in control animals. The subcellular-localization studies showed that both the long-chain acyl-CoA hydrolase and long-chain acyl-L-carnitine hydrolase were localized in the mitochondria. A location also in the soluble fraction cannot be excluded. The long-chain acyl-CoA hydrolase activity was doubled when the mitochondria were disrupted; this indicates that the enzyme is localized in the matrix compartment.

Effect of the hydrophile-lipophile balance of non-ionic detergents (Triton X-series) on the solubilization of biological membranes and their integral b-type cytochromes.

The solubilization of four integral membrane proteins (i.e. cytochrome b-561 of the chromaffin granule membrane, cytochrome b5 of the endoplasmic reticulum and the mitochondrial b-type cytochrome(s) as well as cytochrome c oxidase) has been studied at 0 degrees C using the non-ionic detergents of the Triton X-series having the common hydrophobic 4(1,1,3,3-tetramethylbutyl)phenoxy (t-octyl-phenoxy) group and a variable average number (n) of polar ethylene oxide units added. Following a pre-extraction of peripheral membrane and matrix proteins with low and high salt concentration and a weak non-ionic detergent (Tween 20, average hydrophile-lipophile balance (HLB) = 16.7), the amount of heme proteins solubilized by subsequent Triton X-solutions was measured. With the detergents tested the degree of solubilization decreased in the sequence cytochrome b-561 greater than cytochrome b5 greater than mitochondrial cytochrome(s) b and parallelled the effect of the detergents on light scattering and the phospholipid to protein ratio of the three membranes. For all the b-cytochromes, the solubilizing power of the detergent increased with decreasing average length of the polar ethylene oxide chain and the hydrophile-lipophile balance as long as clouding did not occur (e.g. Triton X-114,n = 7.5 and HLB = 12.4). Thus, the greatest difference in the degree os solubilization of the three cytochromes was observed with Triton X-405 (n = 40 and HLB = 17.9). All the cytochromes were most efficiently solubilized (i.e. approx. 90%) by Triton X-100 (n = 9.5 and HLB = 13.5).