Normal pH Meat Research Articles

The relationship between pH of pH-model beef and impedance measured using touch-type electrodes.

Meat pH affects its color, texture, and water-holding capacity; however, a method for nondestructively distinguishing high-pH from normal-pH meat is unknown. We investigated the method of preparing an extensive pH-model of beef immersed in different pH buffers and the relationship between pH of the pH-model beef and impedance, measured using touch-type electrodes. The results showed that a model beef of pH 4.91-6.39 could be obtained when a beef steak (pH 5.68) was immersed in a solution of pH 4.0-7.0. In addition, we found a significant negative correlation between immersion pH and drip loss, and between immersion pH and impedance measured at 50 kHz (P < 0.01). These results provide an estimation equation (y = -16.5x + 195.3) that can be used to nondestructively determine the pH (x) of pH-model beef by measuring its impedance (y) using touch-type electrodes at 50 kHz (P < 0.01). Hence, the study shows the possibility of nondestructively estimating the pH of pH model beef by measuring impedance using touch-type electrodes.

Protein Biomarkers of Bovine Defective Meats at a Glance: Gel-Free Hybrid Quadrupole-Orbitrap Analysis for Rapid Screening.

An understanding of biological mechanisms that could be involved in the stress response of animal cattle prior to slaughter is critical to create effective strategies aiming at the production of high-quality meat. The sarcoplasmic proteome of directly extracted samples from normal and high ultimate pH (pHu) meat groups was studied through a straightforward gel-free strategy supported by liquid chromatography hybrid quadrupole-Orbitrap high-resolution mass spectrometry (LC-HRMS) analysis. A stepped proteomic pipeline combining rapid biomarker hunting supported by qualitative protein Mascot scores followed by targeted label-free peptide quantification revealed 26 descriptors that characterized meat groups assayed. The functional study of the proposed biomarkers suggested their relevant role in metabolic, chaperone/stress-related, muscle contractility/fiber organization, and transport activities. The efficiency, flexibility, rapidity, and easiness of the methodology proposed can positively contribute to the creation of innovative proteomic alternatives addressing meat quality assessment.

Effects of Aging, Modified Atmospheric Packaging, and Display Time on Metmyoglobin Reducing Activity and Oxygen Consumption of High-pH Beef

The objective of current research was to determine the effects of extended aging, modified atmospheric packaging (MAP), and display time on metmyoglobin reducing activity (MRA) and oxygen consumption (OC) of high-pH beef using pH sensitive methodology for MRA and OC. Ten normal-pH (mean pH = 5.6) and 10 high-pH loins (mean pH = 6.4) were vacuum packaged on d 3 postmortem and aged for 0, 21, 42, and 62 d at 2°C. Following aging, 2.0-cm-thick steaks were cut from each of the normal- and high-pH loin sections and packaged in either PVC film, high-oxygen (HiOx-MAP), or carbon monoxide modified atmospheric (CO-MAP) packaging. Surface color, OC, and MRA were measured on d 0 and 6 of the respective aging periods. Steaks in HiOx-MAP and CO-MAP had similar (P &gt; 0.05) L* values, which were greater (P &lt; 0.05) than high-pH steaks packaged in PVC film. On 21-d of aging, steaks with at both pHs in CO-MAP and HiOx-MAP had greater (P &lt; 0.05) a* values than steaks packaged in PVC. As aging time increased, MRA decreased (P &lt; 0.05) for steaks with normal- and high-pH when packaged in PVC and HiOx-MAP. Steaks with a high-pH in CO-MAP had greater (P &lt; 0.05) MRA than steaks with a normal-pH in CO-MAP at all aging periods. Steaks with a high-pH had greater (P &lt; 0.05) OC on d 0 and 6 than normal-pH steaks. Steaks with a normal-pH aged for 21 d and packaged in PVC and HiOx-MAP had greater (P &lt; 0.05) lipid oxidation than high-pH steaks aged for 21 d and packaged in PVC and HiOx-MAP. After 62 d of aging and 6 d of display, the greatest color stability chemistry (based on MRA and OC for all package types) were: high-pH meat &gt; normal-pH meat; thus the MRA and OC methodology was useful in relative comparison of packaged meat color stability differences due to pH.

The influence of normal and high ultimate muscle pH on the microbiology and colour stability of previously frozen black wildebeest (Connochaetes gnou) meat

Changes in pH, colour and microbiological counts were investigated in previously frozen Biceps femoris (BF) muscles from black wildebeest. Samples were stored under vacuum at refrigerated conditions (4.2±0.8°C) for 12days. Seven BF muscles had a high pH (DFD) (pH≥6) and five had a normal pH (pH<6). Overtime the pH of DFD did not significantly change whilst that of normal pH meat decreased. Browning under anaerobic storage conditions was seen, more for normal meat than DFD meat. Initial total viable counts, lactic acid bacteria and coliform counts from samples with normal pH, were significantly higher than counts from the DFD samples. However, overtime DFD meat showed a faster increase for all microorganisms tested compared to normal pH meat. Overall, this study revealed that DFD meat can have a shorter shelf-life than normal pH meat stored at 4.2±0.8°C.

Effects of meat pH on growth of 11 species of psychrotolerant clostridia on vacuum packaged beef and blown pack spoilage of the product

The aim of the study was to determine the effects of meat pH on the abilities of 11 psychrotolerant Clostridium spp. to grow on, and to possibly cause blown pack spoilage of vacuum packaged beef. Beef steaks of pH 5.4–5.6, 5.7–5.9 or ≥6.0, i.e. of normal, intermediate or high pH were prepared and vacuum packaged. Groups of 3 steaks of the same pH range were inoculated with log phase cultures of Clostridium algoriphilum, Clostridium algidixylanolyticum, Clostridium bowmanii, Clostridium estertheticum, Clostridium frigoris, Clostridium frigidicarnis, Clostridium gasigenes, Clostridium lacusfryxellense, Clostridium psychrophilum, Clostridium tagluense or Clostridium vincentii. Each pack was resealed immediately after the steak was inoculated, and pack volumes were determined by water displacement, immediately after resealing and at intervals during storage at 2 °C for 56 days. All of the clostridia grew in packs of high pH beef but none caused pack swelling. Packs of intermediate pH beef inoculated with C. estertheticum began to swell after 14 days, with a mean rate of increase of pack volumes of 6.80 ml/day. One pack of intermediate pH beef inoculated with C. frigoris was swollen after 37 days. Packs of normal pH beef that had been inoculated with C. estertheticum began swelling after 14 days with a mean rate of increase of pack volumes of 7.70 ml/day. Packs of normal or intermediate pH beef inoculated with other clostridia did not swell. After storage, the numbers of most Clostridium spp., as determined by real-time PCR were greater on beef of high pH than of lower pH values, but the numbers of C. frigidicarnis and C. lacusfryxellense were highest on intermediate pH meat, the numbers of C. estertheticum were higher on meat of lower than of high pH, and the numbers of C. tagluense were the same on meat of all pH values. With high pH meat, glucose was reduced to very low level in rinse fluids from packs that had been inoculated with any Clostridium sp. With intermediate and normal pH meat, glucose was reduced to very low concentrations in only rinse fluids from beef that had been inoculated with C. estertheticum.

Functional and rheological properties of proteins in frozen turkey breast meat with different ultimate pH

Functional and rheological properties of proteins from frozen turkey breast meat with different ultimate pH at 24 h postmortem (pH24) have been studied. Sixteen breast fillets from Hybrid Tom turkeys were initially selected based on lightness (L*) values for each color group (pale, normal, and dark), with a total of 48 breast fillets. Further selection of 8 breast samples was made within each class of meat according to the pH24. The average L* and pH values of the samples were within the following range: pale (L* >52; pH ≤5.7), normal (46 <L* < 52; 5.9 < pH <6.1), and dark (L* <46; pH ≥6.3), referred to as low, normal, and high pH meat, respectively. Ultimate pH did not cause major changes in the emulsifying and foaming properties of the extracted sarcoplasmic and myofibrillar proteins. An SDS-PAGE profile of proteins from low and normal pH meat was similar, which revealed that the extent of protein denaturation was the same. Low pH meat had the lowest water-holding capacity compared with normal and high pH meat as shown by the increase in cooking loss, which can be explained by factors other than protein denaturation. Gel strength analysis and folding test revealed that gel-forming ability was better for high pH meat compared with low and normal pH meat.Dynamic viscoelastic behavior showed that myosin denaturation temperature was independent of pH24. Normal and high pH meat had similar hardness, springiness, and chewiness values as revealed by texture profile analysis. The results from this study indicate that high pH meat had similar or better functional properties than normal pH meat. Therefore, high pH meat is suitable for further processed products, whereas low pH meat may need additional treatment or ingredient formulations to improve its functionality.

Effect of ultimate pH and freezing on the biochemical properties of proteins in turkey breast meat

Biochemical and functional properties of proteins from turkey breast meat with different ultimate pH at 24h post-mortem (pH24) in fresh and frozen conditions have been studied. Meat with different pH24 was referred to as low, normal and high pH meat. Low and normal pH meat showed similar properties indicating their similarity in the extent of protein denaturation. Total (193mg/g) and sarcoplasmic (99mg/g) protein solubilities were significantly (p<0.0001) higher in high pH meat compared to those of low and normal pH meat, and hence expected to have better functional properties. Freezing caused denaturation and oxidation of proteins as revealed by a significant decrease in Ca2+-ATPase activity (p<0.0001), total protein solubility (p<0.0001), reactive (p<0.05) and total sulphydryl groups (p<0.0001) and an increase in the formation of carbonyl groups (p<0.0001), which may have implications for functionality.

Effects of pH adjustment with phosphates on attributes and functionalities of normal and high pH beef

Longissimus dorsi muscles from six normal- and six high-ultimate pH bulls were selected for fine mincing and subsequent pH adjustment with acid and alkaline pyrophosphate. Four pH treatments were prepared: initially high remains high (mean of pH 6.37), high becomes normal (5.62); initially normal remains normal (5.65), and normal becomes high (6.21). The addition level of phosphate as P 2O 5 was the same in all replicates. Before pH adjustment, colour and water holding capacity (WHC) values were strongly affected by higher (initial) pH in expected ways: darker, lower chroma, higher capacity. After pH adjustment, these values were affected only by the final pH, not the initial pH (the pH history). Total protein solubility was likewise affected by final pH but not initial pH. In contrast, the combination high initial pH-high final pH improved sarcoplasmic protein solubility by 20% over the combination normal initial pH-high final pH. Sarcoplasmic protein solubility is an indicator of strain required to fracture cooked batters made from the minced meats; in the event, the rank order of the four treatments for strain-to-fracture matched that of sarcoplasmic protein solubility. Statistically, sarcoplasmic protein solubility and strain-to-fracture were both affected by initial pH ( P < 0.01) and final pH ( P < 0.001). However, stress required to fracture cooked batters was entirely controlled by initial pH ( P < 0.01). In other words, the stress-to-fracture advantage of initially high pH meat was not matched by upward pH adjustment of initially normal pH meat. Emulsion stability, which is better with higher pH meat, was affected by initial and final pH (both P < 0.01). Cook yield, like WHC of pH-adjusted raw meat, was more due to final pH than initial pH, similarly cooked batter colour, whereas final pH had a significant effect on quality attributes (generally better when higher). An initially high pH history conferred an enduring advantage on three important batter attributes, stress-to-fracture, strain-to-fracture, and emulsion stability. Therefore, prior exposure of beef to normal pH conditions (pH 5.4–5.7) renders it less useful as a manufacturing grade product.

Functional stability of frozen normal and high pH beef

The functional properties of whole, diced or minced high and normal pH beef were determined after 0, 1, 2, 3 and 7 month’s storage. There was no interaction between pH, degree of comminution and storage time for most of the attributes measured. Regardless of storage time or comminution method, high pH meat had significantly ( P < 0.001) higher sarcoplasmic protein solubility, water holding capacity, cooked batter torsion stress and strain, yield and emulsion stability than normal pH meat. Normal pH meat had significantly ( P < 0.01) higher myofibrillar protein solubility and hue angle than high pH meat. Water holding capacity significantly ( P < 0.01) decreased and hue angle increased with the increase in the degree of comminution. Protein solubility in raw meat and the cooked batter stress, strain, yield and emulsion stability of both high and normal pH meat deteriorated with time. However, this deterioration was faster in the normal pH meat compared to high pH meat except for total and myofibrillar protein solubility. Within the parameters of the present study, it is concluded that frozen high pH meat possesses superior functional attributes compared to normal pH meat regardless of the degree of comminution or storage time.

Processing characteristics of beef roasts made from high and normal pH bull inside rounds

The processing characteristics of roasts manufactured from either high or normal pH bull inside rounds ( semimembranosus and adductor muscles), which had been stored chilled or frozen, were investigated. Roasts were injected with a salt/phosphate brine and cooked to an internal temperature of 63 °C in a 70 °C water bath. High-pH meat that had been frozen had less purge than normal pH meat. However, pH did not affect purge from chilled meat. Meat pH and storage conditions did not affect retention of pumped brine. Cook yields were significantly ( P<0.05) higher for roasts made from high pH meat (103.8 vs 98.8%). Raw and cooked meat colour was affected by meat pH but not storage condition. Cooking reduced the effect of pH on meat colour but cooked roasts manufactured from high pH meat were redder than roasts manufactured from normal pH meat.

Liberation of peptides during meat storage and their interaction with proteinase activity

The content of nitrogenous material extracted in perchloric acid from kid longissimus lumborum (LL), semimembranosus (Sm) and triceps brachii (TB) muscles increased 30% during storage for three weeks at 4 °C. The extract of fresh muscle contained a range of molecular sizes up to 13 kDa, the majority less than 4 kDa. The amount of the larger polypeptides (> 4 kDa) extracted from meat decreased to 50% of its initial level in meat stored for five days and to 20% after 25 days. The amount of intermediate sized peptides (1.9 to 4 kDa) remained largely constant throughout storage of meat of normal pH, whilst in meat of high ultimate pH, they showed a transitory increase during the first two weeks storage. Smaller size peptides increased with storage time; increasing more slowly in meat of high ultimate pH. This time-dependent pH effect indicates a sequential autolysis involving neutral followed by acidic proteolytic and peptidic activity. Calpain from beef muscle degraded peptides in the extract and the extract acted as a competitor against a synthetic substrate. This implies that the in-situ autolysis and tenderisation of meat postmortem could be reduced by peptide products.

Effect of Co2 or vacuum packaging on normal and high pH meat shelf‐life

In order to extend meat shelf‐life, normal‐pH and high‐pH beef steaks were packaged under vacuum or in 100% C 0 2 atmosphere. Microbiological, colour (L*, a*, b*)and reflectance (R630‐R580 values) characteristics were measured.After packaging under vacuum, Enterobacteriaceae, Brochothrix thermosphacta and Pseudomonas numbers were 10‐ to 100‐fold greater on high‐pH meat than onnormal‐pH meat.Packaging under C 0 2 improved the shelf‐life of meat, particularly that of high‐pH meat up to 42 days. For both high‐ and normal‐pH meats, the bacterial flora wascomposed only of lactic acid bacteria. Normal‐pH meat in C 0 2 atmosphere and vacuum packaging had a purple colour. After C02‐pack opening the meat colourbecame bright red and R630‐ R580 measurements were high, whereas after opening of vacuum packaging R630‐R580 decreased rapidly with increasing aerobic exposure.High‐pH meat became paler with increasing storage time in C02. Simultaneously R630‐R580 values increased and the pH fell. In addition it lost less exudate andoxidized less in air than the normal‐pH meat under the same conditions.

Volatile compounds associated with microbial growth on normal and high pH beef stored at chill temperatures.

Volatile compounds produced by Pseudomonas fragi and mixed, natural floras on beef of normal pH (5.5-5.8; glucose greater than 1500 micrograms/g) and high pH (6.3-6.8; glucose less than 10 micrograms/g) included a range of alkyl esters and a number of sulphur-containing compounds including dimethylsulphide but not hydrogen sulphide. Production of the last was a property common to the other Gram-negative organisms tested viz. Hafnia alvei, Enterobacter agglomerans, Serratia liquefaciens, Alteromonas putrefaciens and Aeromonas hydrophila, all of which produced similar off-odours and, with the exception of E. agglomerans, 'greening' on high pH meat. Serratia liquefaciens also produced greening of normal pH meat. Acetoin and diacetyl were major end products of Brochothrix thermosphacta but the related 2,3-butanediol was formed only on normal pH meat. The Enterobacteriaceae produced the same compounds but only on normal pH meat and together with Br. thermosphacta were probable sources of these compounds and of the free and esterified branched-chain alcohols detected in the naturally contaminated samples.

The effect of the initial gas volume to meat weight ratio on the storage life of chilled beef packaged under carbon dioxide

Normal pH (5·5–5·7) and high pH (>6·0) beef cuts of 400 g were vacuum packaged in polyvinylidine chloride (PVDC) laminate, in aluminium foil laminate or in foil laminate with a CO 2 scavenger (Ba(OH) 2); or were packaged under CO 2 in foil laminate with CO 2 added at 200, 400, 700, 1000 or 2000 ml per kg of meat. The process used to prepare meat before packaging resulted in an initial flora containing a high fraction of eneterobacteria but with undetectable numbers of lactobacilli. During storage at +1°C, all vacuum packaged meat developed floras containing substantial fractions of enterobacteria. The enterobacteria fractions were larger on high pH than on normal pH meat, and on normal pH meat in PVDC or in foil laminate plus CO 2 scavenger packs than on normal pH meat in foil laminate without the CO 2 scavenger. All vacuum packaged meat was spoiled by putrid flavours, high pH meat at 7 weeks and normal pH meat at 12 weeks. Increasing amounts of added CO 2 progressively retarded the development of putrid spoilage, as growth of the spoilage floras was slowed while the relative numbers of lactobacilli in the floras were enhanced. With the two largest amounts of added CO 2, spoilage was delayed until 15 weeks and 21 weeks for high pH meat and normal pH meat, respectively, and enterobacteria were detected in the spoilage floras only at later sampling times. With lesser amounts of added CO 2, enterobacteria persisted or re-emerged at earlier times, in the floras.

Volatile compounds associated with the spoilage of normal and high pH vacuum‐packed pork

AbstractPork of normal (5.5–5.6) and high (6.3–6.6) pH was stored in vacuum packs at 5°C until spoiled. At spoilage the bacterial flora of the normal pH meat was dominated by lactic acid bacteria, that of the high pH meat by Gram‐negative organisms. Volatile compounds in the packs were analysed by a headspace entrainment technique and gas chromatography‐mass spectrometry. Major differences between the two types of meat were confined mainly to a series of sulphur‐containing compounds which were more numerous, and present in higher concentrations, in the headspaces above high pH meat.

Effect of lactic acid concentration on growth on meat of Gram-negative psychrotrophs from a meatworks.

The inhibitory effect of the lactic acid in meat on gram-negative psychrotrophs appears to be due mainly to the decrease in pH, not to action of the undissociated acid. Species of Pseudomonas were essentially unaffected by the pH of normal meat. Other gram-negative psychrotrophs isolated from a meatworks included a large number of strains which would not grow on meat of normal pH at chill temperatures. Raising either the pH or the incubation temperature allowed many of the pH-sensitive strains to initiate growth. However, the growth rates of pH-insensitive strains were not affected by increasing the pH, and there were no significant differences in the composition of the spoilage floras which developed on chilled meat of normal and high pH.

Growth of bacteria on meat at room temperatures.

The development of spoilage flora and the growth of individual psychrotrophs and pathogens on meat held at 20 or 30°C were studied. Under aerobic conditions psychrotrophic pseudomonads accounted for 60% of the spoilage flora at 20°C, but &lt;20% at 30°C where they were displaced by species of Acinetobacter and Enterobacteriaceae which included both mesophilic and psychrotrophic strains. Mesophiles dominated the anaerobic spoilage flora at 30°C when clostridia were the major species, but at 20° the flora contained mesophiles and psychrotrophs in similar proportions and was dominated by Enterobacteriaceae. These results were largely predictable from the growth rate data for individual organisms.Interactions between species occurred more frequently at 20°C than at 30°C. When pathogenic species were grown at 20 or 30°Cin competition with equal numbers of psychrotrophic spoilage organisms, no interactions were observed. When pathogens were grown in competition with high numbers of psychrotrophs, only Lactobacillus growing anaerobically inhibited Salmonella typhimurium and Escherichia coli, but other pathogens were inhibited to varying degrees depending on the competing species and the incubation conditions. In general, the degree of inhibition was greater at 20 than at 30°C and facultative organisms were more susceptible under anaerobic than aerobic conditions. It appears that the cumulative stresses of low pH, suboptimal temperatures and competition with large numbers of saprophytic organisms can inhibit many of the pathogens likely to be present on meat. The organisms least affected by the conditions on meat surfaces, Salmonella and Esch. coli, are likely to be the main hazards on meat of normal pH held at room temperatures.

Isolation of Yersinia enterocolitica-resembling organisms and Alteromonas putrefaciens from vacuum-packed chilled beef cuts.

Yersinia enterocolitica‐resembling organisms were found at levels of 107/g on a high pH (pH ≧ 6·0) vacuum‐packaged beef striploin held for 6 weeks at 0·2°C, but did not exceed 105/g on normal pH (pH &lt; 6·0) striploins held for 10 weeks. Gram negative bacteria that produced H2S on peptone iron agar were isolated from high pH vacuum packed striploins. These organisms were identified as Alteromonas putrefaciens. They attained levels of about 107/g in 6 weeks at 0–2°C, at which time greening of the fat surface and ‘drip’had occurred. On meat of normal pH, counts of A. putrefaciens were less than 104/g after 6 weeks and no greening was evident.

Hie effect of meat pH and package permeability on putrefaction and greening in vacuum packed beef

SummaryBeef joints at three pH levels were vacuum packed and stored at 1°C in materials with different gas permeabilities. Dark‐cutting, high pH beef (pH 6.2–6.7) developed a green discoloration (greening) in all the packaging materials and had a putrid odour when the packs were opened after 9 weeks. the same type of spoilage occurred at pH 5.9–6.1 in materials of relatively high gas permeability (73 and 92 cm3 O2/m2‐day‐atm. O2 at 90%r.h.). Greening and putrefaction did not occur at pH 5.9‐6.1 in materials of very low gas permeability (25 and 23 cm3 O2/m2‐day‐atm. O2 at 90%r.h.) or in any packs of meat of normal pH (5.4‐5.5).