Yogurt Benefits Bone Mineralization in Ovariectomized Rats with Concomitant Modulation of the Gut Microbiome.

SCOPE: Evidence supports that gut-modulating foods potentially can suppress bone loss in postmenopausal women. This study aims to investigate the effect of milk calcium-enriched milk, yogurt, and yogurt-inulin combination on the gut-bone association. METHODS AND RESULTS: A 6-week intervention study is conducted in ovariectomized rats. Four pastes containing milk calcium-fortified milk (M-Ca), milk calcium-fortified yogurt (Y-Ca), inulin-fortified Y-Ca (Y-I-Ca), or an isoconcentration of calcium carbonate (Ca-N), and a calcium-deficient paste are provided. M-Ca does not influence bone mineral density and content (BMD and BMC), femur mechanical strength, or femoral microstructure compared to Ca-N, but Y-Ca increases spine BMD. The serum metabolome reveals that Y-Ca modulated glycine-related pathways with reduced glycine, serine, and threonine. No additive effects of yogurt and inulin are found on bone parameters. Correlation analysis shows that increased lactobacilli and reduced Clostridiaceae members in Y-Ca is associated with an increased spine BMD. Increases in Bifidobacterium pseudolongum, Turicibacter, Blautia, and Allobaculum and gut short-chain fatty acids in Y-I-Ca are not reflected in bone parameters. CONCLUSION: Yogurt as calcium vehicle contributes to increased spine BMD concomitant with changes in the gut microbiome and glycine-related pathways, while adding inulin to yogurt does not affect bone mineralization in ovariectomized rats.

Effects of Calcium Source, Inulin, and Lactose on Gut-Bone Associations in an Ovarierectomized Rat Model.

SCOPE: Osteoporosis poses a health challenge especially for postmenopausal women. This study aims to explore nutritional strategies to counteract bone demineralization in ovarierectomized (OVX) rats. METHODS AND RESULTS: OVX rats (n = 49) are fed with one of six different diets, where two different calcium sources (dairy calcium or calcium carbonate) are provided alone or in combination with either inulin (5%) or lactose (0.5%). In addition, a calcium-deficient diet is included. Calcium supplementation increases intestinal concentrations of short-chain fatty acids (SCFAs) and the abundance of fecal Acinetobacter and Propionibacterium. Accompanied with these effects, rats fed with calcium-fortified diets have higher bone mineral density, bone mineral content and femur mechanical strength, lower serum levels of bone markers, and lower expression of calcium absorption-related genes (transient receptor potential vanilloid type 6 (TRPV6), calcium-binding protein (CaBP) compared with control. Inulin supplementation results in a markedly increased production of intestinal SCFAs, a decreased intestinal pH, an increased abundance of Allobaculum and Bifidobacterium, and an increased expression of Trpv6. Inulin and lactose show beneficial effects on spine bone. CONCLUSION: Calcium modulates gut microbiome composition and function. A pronounced effect of inulin on metabolic activity in the gastrointestinal tract is evident, and lactose supplementation decreases jejunal pH that might be associated with slightly enhanced bone mineralization.

Dual nuclear magnetic resonance for probing intrinsic bone structure and a potential gut-bone axis in ovariectomized rats.

Currently, the existence of a gut-bone axis receives massive attention, and while sound premises and indirect proofs exist for the gut-bone axis concept, few studies have provided actual data linking the gut and bone physically. This study aimed to exploit the versatile nature of nuclear magnetic resonance (NMR) to link NMR relaxometry data on bone mineralization with NMR spectroscopic profiling of gut metabolites. For this purpose, sample material was obtained from a 6-week intervention study with ovariectomized (OVX) rats (n = 49) fed with seven different diets varying in calcium content (0.2-6.0 mg/kg) and prebiotic fiber content (0-5.0% w/w). This design ensured a span in (i) calcium available for bone mineralization and (ii) metabolic activity in the gut. After termination of the intervention, longitudinal (T1 ), transverse (T2 ) relaxation, and mechanical bone strength were measured on the excised femur bones. A PLS model with high predictability (Q2 = 0.86, R2 = 0.997) was demonstrated between T2 decay curves and femur mechanical strength. Correlations were established between bone T2 populations and gut short-chain fatty acids. In conclusion, the present dual NMR approach showed strong correlation between T2 relaxation and mechanical strength of the bone, and when metabolic activity in the gut was modulated by inulin, the potential existence of a gut-bone axis was demonstrated.

Metabolic Effects of Bovine Milk Oligosaccharides on Selected Commensals of the Infant Microbiome-Commensalism and Postbiotic Effects.

Oligosaccharides from human or bovine milk selectively stimulate growth or metabolism of bacteria associated with the lower gastrointestinal tract of infants. Results from complex infant-type co-cultures point toward a possible synergistic effect of combining bovine milk oligosaccharides (BMO) and lactose (LAC) on enhancing the metabolism of Bifidobacterium longum subsp. longum and inhibition of Clostridium perfringens. We examine the interaction between B. longum subsp. longum and the commensal Parabacteroides distasonis, by culturing them in mono- and co-culture with different carbohydrates available. To understand the interaction between BMO and lactose on B. longum subsp. longum and test the potential postbiotic effect on C. perfringens growth and/or metabolic activity, we inoculated C. perfringens into fresh media and compared the metabolic changes to C. perfringens in cell-free supernatant from B. longum subsp. longum fermented media. In co-culture, B. longum subsp. longum benefits from P. distasonis (commensalism), especially in a lactose-rich environment. Furthermore, B. longum subsp. longum fermentation of BMO + LAC impaired C. perfringens' ability to utilize BMO as a carbon source (potential postbiotic effect).

Lactose and Bovine Milk Oligosaccharides Synergistically Stimulate B. longum subsp. longum Growth in a Simplified Model of the Infant Gut Microbiome.

Increasing awareness of the importance of a healthy Bifidobacterium-rich microbiome has led to a need for more knowledge on how different prebiotic carbohydrates specifically impact the infant microbiome, especially as a community instead of single bacterial targets. In this study, we combined proton nuclear magnetic resonance (1H NMR) metabolomics and molecular biology methods for quantification of bacteria to compare the prebiotic effect of bovine milk oligosaccharides (BMO) and synthetic galacto oligosaccharides (GOS) using mono- and cocultures of eight major bacteria related to a healthy infant microbiome. The results revealed that BMO treatments supported growth of Bifidobacterium longum subsp. longum and Parabacteroides distasonis, while at the same time growth of Clostridium perfringens and Escherichia coli was inhibited. In addition, there was a synergistic effect of combining lactose and BMO in regards to reducing C. perfringens, maintaining stable numbers of P. distasonis and simultaneously increasing numbers of the beneficial B. longum subsp. longum. These results indicate that the oligosaccharide composition plays a vital role in shaping the developing microbiota.

Chemical and proteolysis-derived changes during long-term storage of lactose-hydrolyzed ultrahigh-temperature (UHT) milk.

Proteolytic activity in milk may release bitter-tasting peptides and generate free amino terminals that react with carbohydrates, which initiate Maillard reaction. Ultrahigh temperature (UHT) heat treatment inactivates the majority of proteolytic enzymes in milk. In lactose-hydrolyzed milk a ß-galactosidase preparation is applied to the milk after heat treatment, which has proteolytic side activities that may induce quality deterioration of long-term-stored milk. In the present study proteolysis, glycation, and volatile compound formation were investigated in conventional (100% lactose), filtered (60% lactose), and lactose-hydrolyzed (<1% lactose) UHT milk using reverse phase high-pressure liquid chromatography-mass spectrometry, proton nuclear magnetic resonance, and gas chromatography-mass spectrometry. Proteolysis was observed in all milk types. However, the degree of proteolysis was significantly higher in the lactose-hydrolyzed milk compared to the conventional and filtered milk. The proteins most prone to proteolysis were ß-CN and αs1-CN, which were clearly hydrolyzed after approximately 90 days of storage in the lactose-hydrolyzed milk.

Lactose-hydrolyzed milk is more prone to chemical changes during storage than conventional ultra-high-temperature (UHT) milk.

The enzymatic hydrolysis of lactose to glucose and galactose gives rise to reactions that change the chemistry and quality of ambient-stored lactose-hydrolyzed ultra-high-temperature (UHT) milk. The aim of the present study was to investigate and compare chemical changes in lactose-hydrolyzed and conventional UHT milk during a 9 month ambient storage period. Several complementary analyses of volatiles, free amino acids, acetate, furosine, and level of free amino terminals were concluded. The analyses revealed an increased level of free amino acids and an increased formation rate of specific compounds such as furosine and 2-methylbutanal in lactose-hydrolyzed UHT milk compared to conventional UHT milk during storage. These observations indicate more favorable conditions for Maillard and subsequent reactions in lactose-hydrolyzed milk compared to conventional UHT milk stored at ambient temperature. Furthermore, it is postulated that proteolytic activity from the lactase-enzyme preparation may be responsible for the observed higher levels of free amino acids in lactose-hydrolyzed UHT milk.

Water distribution and mobility in meat during the conversion of muscle to meat and ageing and the impacts on fresh meat quality attributes--a review.

This paper reviews current knowledge on the distribution and mobility of water in muscle (myowater) ante- and post mortem and factors affecting these in relation to fresh meat quality parameters; water-holding capacity (WHC), tenderness and juiciness. NMR transverse relaxometry (T(2)) using bench-top Low-Field Nuclear Magnetic Resonance (LF-NMR) has characterised myowater distribution and mobility as well as structural features in meat which directly affect WHC. The current literature demonstrates that WHC is correlated to the water located outside the myofibrillar network (extra-myofibrillar). This review identifies the critical stages which affect the translocation of water into the extra-myofibrillar space and thus the potential for decreased WHC during proteolysis (the conversion of muscle to meat). This review discusses how the intrinsic properties of the water held within the meat could contribute to juiciness and tenderness. Tenderness has been shown to correlate to T(2), however breed and species differences made it difficult to draw firm conclusions. Further understanding of the inherent water properties of fresh meat and the factors affecting water distribution and mobility using NMR technologies will increase the understanding of WHC and tenderisation of fresh meat.

The serum metabolite response to diet intervention with probiotic acidified milk in irritable bowel syndrome patients is indistinguishable from that of non-probiotic acidified milk by 1H NMR-based metabonomic analysis.

The effects of a probiotic acidified milk product on the blood serum metabolite profile of patients suffering from Irritable Bowel Syndrome (IBS) compared to a non-probiotic acidified milk product was investigated using (1)H NMR metabonomics. For eight weeks, IBS patients consumed 0.4 L per day of a probiotic fermented milk product or non-probiotic acidified milk. Both diets resulted in elevated levels of blood serum L-lactate and 3-hydroxybutyrate. Our results showed identical effects of acidified milk consumption independent of probiotic addition. A similar result was previously obtained in a questionnaire-based evaluation of symptom relief. A specific probiotic effect is thus absent both in the patient subjective symptom evaluations and at the blood serum metabolite level. However, there was no correspondence between symptom relief and metabolite response on the patient level.

Water distribution and microstructure in enhanced pork.

Water characteristics and meat microstructure of NaHCO3-enhanced pork were compared with NaCl- and Na4O7P2-enhanced pork using low-field proton NMR relaxometry, advanced microscopy techniques, and traditional meat quality measurements. Porcine samples were enhanced at 4 degrees C for 48 h with sodium salts individually and in the following combinations: (i) 5% NaCl, (ii) 5% Na4O7P2, (iii) 3% NaHCO3, (iv) 5% NaCl and 5% Na4O7P2, (v) 5% NaCl and 3% NaHCO3, (vi) 5% Na4O7P2 and 3% NaHCO3, and (vii) 5% NaCl, 5% Na4O7P2, and 3% NaHCO3. Independently of the marinade used, the water-binding capacity was improved, cooking loss was reduced, and the yield was enhanced compared with nonmarinated pork samples. This was also reflected in the water mobility within the samples measured by proton NMR relaxometry. Visualization of samples by confocal laser scanning microscopy (CLSM) revealed salt-dependent microstructural changes in the green pork samples treated with NaHCO3, giving rise to nearly complete disintegration of overall structures. High-resolution visualization by atomic force microscopy (AFM) further suggested that a higher cooking loss in sodium chloride-enhanced samples could be ascribed to less solubilization and higher heat-induced protein denaturation compared with phosphate- and bicarbonate-enhanced samples.

The significance of diet, slaughter weight and aging time on pork colour and colour stability.

The objective of the present study was to investigate the effect of a diet with a low content of digestible starch, slaughter weight and subsequent aging time on meat colour and colour stability. Pork colour was determined as the extent of blooming of M. longissimus thoracis (LT) and M. semimembranosus (SM) after 1, 2, 4, 8 and 15 days postmortem and as colour stability during a subsequent storage period in air for 6 days. Compared to the control diet, the experimental diet resulted in a significantly lower postmortem muscle temperature (1°C; p<0.0001). Moreover, high slaughter weight (110kg) resulted in a higher postmortem temperature in LT (p<0.001) compared to low weight (85kg). Independent of feeding strategy and slaughter weight, the extent of blooming decreased during the first 2-4 days of aging in LT, however, the effect was more pronounced in meat from experimentally fed pigs and pigs with high slaughter weight. This effect was not seen in SM, where a gradual increase in blooming took place throughout the aging period. The colour stability was found to be superior in aged pork from experimentally fed pigs. The discoloration rate was faster in SM compared to LT. In conclusion, the present study shows that the diet composition can be used as a tool to control meat colour and colour stability in pork.

Monitoring of warmed-over flavour in pork using the electronic nose - correlation to sensory attributes and secondary lipid oxidation products.

Sensory analysis of meatballs was carried out to monitor the warmed-over flavour (WOF) development in cooked, cold-stored (at 4°C for 0, 2 and 4days) and reheated meatballs derived from M. longissimus dorsi (LD) and M. semimembranosus (SM) of pigs fed a standard diet supplemented with either 3% of rapeseed oil or 3% of palm oil. This was performed in combination with measurement of volatile compounds using a solid-state-based gas sensor array system (electronic nose) and gas chromatography/mass spectrometry together with measurement of thiobarbitoric acid reactive substances (TBARS). Subsequently, to elucidate the relations and predictability between the obtained data, the gas sensor responses were correlated with chemical (volatile and non-volatile secondary lipid oxidation products) and sensory data (flavour and odour attributes), using partial least squares regression modelling (PLSR). The TBARS, hexanal, pentanal, pentanol and nonanal all correlated to the sensory attributes associated to WOF formation. Moreover, the responses from eight of the MOS (metal oxide semiconductor) sensors within the electronic nose proved to be significantly related to WOF characteristics detected by both sensory and chemical analysis, while six of the MOSFET (metal oxide semiconductor field effect transistor) sensors were related to freshly cooked meat attributes determined by sensory analysis. The obtained results show the potential of the present gas sensor technology to monitor WOF formation in pork.

Nitrosylmyoglobin as antioxidant--kinetics and proposed mechanism for reduction of hydroperoxides.

Nitrosylmyoglobin (MbFe(II)NO), which is believed to have a protective role during ischemia and reperfusion injury, was oxidized by tert-butyl hydroperoxide (t-BuOOH), and by hydrogen peroxide (H(2)O(2)) to the nitrite anion and metmyoglobin (MbFe(III)). Further characterization of the reaction of MbFe(II)NO with excess of t-BuOOH was investigated with respect to reaction stoichiometry, temperature and pH dependence. It was found that the reaction between MbFe(II)NO with excess of t-BuOOH followed a simple stoichiometry and had moderate pH and temperature dependence with the activation parameters DeltaH(double dagger) = 57.4 +/- 1.4 kJ mol(- 1) and DeltaS(double dagger) = - 112.0 +/- 5.1 J mol(- 1) K(- 1), which is consistent with an associative reaction mechanism. Moreover, t-BuOOH-induced oxidation of MbFe(II)NO did not result in any detectable formation of the hypervalent myoglobin (Mb) species, i.e. perferrylmyoglobin, (( radical)MbFe(IV) = O) or ferrylmyoglobin (MbFe(IV) = O), and hereby differed from H(2)O(2)-induced oxidation of MbFe(II)NO, which results in the formation of MbFe(IV) = O. Based on the obtained results and on published data, different mechanisms for the reaction of the MbFe(II)NO with t-BuOOH and H(2)O(2) are proposed.

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.

Post-mortem activity of the glycogen debranching enzyme and change in the glycogen pools in porcine M. longissimus dorsi from carriers and non-carriers of the RN(-) gene.

Glycogen debranching enzyme (GDE) is together with glycogen phosphorylase responsible for the degradation of glycogen. The present study compares the post-mortem activity of GDE and breakdown of the glycogen pools in M. longissimus dorsi of RN(-) carrier pigs and in wild type animals. The activity of GDE (n=14) and pH (n=20) was measured 0.5, 3, 5, 24 and 48h post-mortem. The change in pro-glycogen and in macro-glycogen content (n=20) was followed until 216h post-mortem and the transcription level of GDE, glycogenin and glycogen synthase m-RNA (n=19) were measured 0.5h post-mortem. Both the activity of GDE and the transcription level of GDE were found to be similar in RN(-) carriers and wild type animals shortly after slaughter. However, the activity declined faster in wild type animals compared with RN(-) carriers with increasing time post-mortem. The contents of both pro-glycogen and macro-glycogen were higher in RN(-) carriers compared with wild type animals, and further, the proportion of macro-glycogen was higher in RN(-) carriers compared with wild type animals. During the post-mortem period, only degradation of pro-glycogen was observed in both genotypes. The decrease in pH was faster and the ultimate pH lower in RN(-) carriers than in wild type animals. It was suggested that the higher GDE activity in the late phase of the post-mortem period in muscles from RN(-) carriers renders the extended pH decrease in these muscles.

Development in myofibrillar water distribution of two pork qualities during 10-month freezer storage.

The effects of fresh meat quality (PSE versus DFD), freezing temperature (-20°C versus -80C°) and duration of freezer storage on changes in water mobility and distribution were followed at intervals of 1-2 months during 10-month freezer storage of pork using low-field NMR T(2) relaxometry. Fresh meat quality was found to have a strong significant effect (P<0.0001) on the amount of loosely bound water (relaxation time >100ms) also after freezing, which was reflected in a significantly lower cooking yield in PSE meat compared with DFD meat (P<0.0001). While no significant changes in the cooking yield were observed with increasing length of freezer storage, NMR T(2) relaxation measurements revealed a significant increase in the amount of loosely bound water in PSE meat with increasing length of freezer storage. This finding indicates that NMR T(2) relaxation measurements are quite sensitive to freezing-induced changes in the meat structure, causing a shift in the distribution of water and possibly capable of detecting these before they are reflected in a reduced cooking yield. In addition, an interaction between fresh meat quality and effect of length of freezer storage on the amount of very mobile water easily lost as drip was observed, implying that PSE meat is more susceptible to freezer storage-induced deteriorative changes in the meat structure, causing a shift in the distribution of water, than DFD meat.

Influence of aging and salting on protein secondary structures and water distribution in uncooked and cooked pork. A combined FT-IR microspectroscopy and 1H NMR relaxometry study.

Fourier transform infrared (FT-IR) microspectroscopy and low-field (LF) proton NMR transverse relaxation measurements were used to study the changes in protein secondary structure and water distribution as a consequence of aging (1 day and 14 days) followed by salting (3%, 6%, and 9% NaCl) and cooking (65 degrees C). An enhanced water uptake and increased proton NMR relaxation times after salting were observed in aged meat (14 days) compared with nonaged meat (1 day). FT-IR bands revealed that salting induced an increase in native beta-sheet structure while aging triggered an increase in native alpha-helical structure before cooking, which could explain the effects of aging and salting on water distribution and water uptake. Moreover, the decrease in T2 relaxation times and loss of water upon cooking were attributed to an increase in aggregated beta-sheet structures and a simultaneous decrease in native protein structures. Finally, aging increased the cooking loss and subsequently decreased the final yield, which corresponded to a further decrease in T2 relaxation times in aged meat upon cooking. However, salting weakened the effect of aging on the final yield, which is consistent with the increased T2 relaxation times upon salting for aged meat after cooking and the weaker effect of aging on protein secondary structural changes for samples treated with high salt concentration. The present study reveals that changes in water distribution during aging, salting, and cooking are not only due to the accepted causal connection, i.e., proteolytic degradation of myofibrillar structures, change in electrostatic repulsion, and dissolution and denaturation of proteins, but also dynamic changes in specific protein secondary structures.

Development of inosine monophosphate and its degradation products during aging of pork of different qualities in relation to basic taste and retronasal flavor perception of the meat.

Inosine monophosphate (IMP) and its degradation products, ribose and hypoxanthine, are all considered to be important constituents in meat flavor formation and development. The present study explored the fate of IMP during the aging of two qualities of pork (pH >5.7 and 5.5 < pH < 5.6) and the potential relationship between IMP, hypoxanthine, and sensory attributes of pork registered both as retronasal and basic taste responses in whole meat, meat juice, and the remaining meat residue. During aging the concentration of IMP decreased with a simultaneous increase in the concentrations of inosine, hypoxanthine, and ribose. The rates at which IMP was degraded to inosine and inosine to hypoxanthine during aging were found to be in agreement with the known rate constants of the dephosphorylation of IMP and the hydrolysis of inosine, respectively. Moreover, high-pH pork resulted in a significantly higher concentration of hypoxanthine throughout storage compared with low-pH pork due to an initially higher concentration of IMP in high-pH meat. The sensory analysis showed increasing intensity in bitterness and saltiness of pork as a function of aging, with the intensity being most pronounced in the meat juice. The increasing bitterness of the pork as a function of aging coincided with the higher content of hypoxanthine in these samples, thereby suggesting that degradation of IMP to hypoxanthine might influence pork flavor. In contrast, IMP was associated with nonaged meat and the sensory attributes meaty and brothy.

NMR-based metabonomic studies reveal changes in the biochemical profile of plasma and urine from pigs fed high-fibre rye bread.

This study presents an NMR-based metabonomic approach to elucidate the overall endogenous biochemical effects of a wholegrain diet. Two diets with similar levels of dietary fibre and macronutrients, but with contrasting levels of wholegrain ingredients, were prepared from wholegrain rye (wholegrain diet (WGD)) and non-wholegrain wheat (non-wholegrain diet (NWD)) and fed to four pigs in a crossover design. Plasma samples were collected after 7 d on each diet, and 1H NMR spectra were acquired on these. Partial least squares regression discriminant analysis (PLS-DA) on spectra obtained for plasma samples revealed that the spectral region at 3.25 parts per million dominates the differentiation between the two diets, as the WGD is associated with higher spectral intensity in this region. Spiking experiments and LC-MS analyses of the plasma verified that this spectral difference could be ascribed to a significantly higher content of betaine in WGD plasma samples compared with NWD samples. In an identical study with the same diets, urine samples were collected, and 1H NMR spectra were acquired on these. PLS-DA on spectra obtained for urine samples revealed changes in the intensities of spectral regions, which could be ascribed to differences in the content of betaine and creatine/creatinine between the two diets, and LC-MS analyses verified a significantly lower content of creatinine in WGD urine samples compared with NWD urine samples. In conclusion, using an explorative approach, the present studies disclosed biochemical effects of a wholegrain diet on plasma betaine content and excretion of betaine and creatinine.

Heat-induced changes in myofibrillar protein structures and myowater of two pork qualities. A combined FT-IR spectroscopy and low-field NMR relaxometry study.

Low-field NMR T(2) and Fourier transform infrared (FT-IR) measurements were performed on meat samples of two qualities (normal and high ultimate pH) during cooking from 28 degrees C to 81 degrees C. Pronounced changes in both T(2) relaxation data and FT-IR spectroscopic data were observed during cooking, revealing severe changes in the water properties and structural organization of proteins. The FT-IR data revealed major changes in bands in the amide I region (1700-1600 cm(-)(1)), and a tentative assignment of these is discussed. Distributed NMR T(2) relaxation data and FT-IR spectra were compared by partial least-squares regression. This revealed a correlation between the FT-IR peaks reflecting beta-sheet and alpha-helix structures and the NMR relaxation populations reflecting hydration water (T(2B) approximately 0-10 ms), myofibrillar water (T(21) approximately 35-50 ms), and also expelled "bulk" water (T(2) relaxation times >1000 ms). Accordingly, the present study demonstrates that definite structural changes in proteins during cooking of meat are associated with simultaneous alterations in the chemical-physical properties of the water within the meat.