DIFFERENTIAL SCANNING CALORIMETRY CAN DETERMINE KINETICS OF THERMAL DENATURATION OF BEEF MUSCLE PROTEINS

Differential scanning calorimetry (DSC) of beef muscle produced three large endotherms occurring at 55–57°C, 65–67°C and 81–83°C. Based on earlier DSC research on isolated proteins (Privalov 1979), the concept of cooperative units participating in thermal transition phenomena was applied to beef muscle endotherms. Analysis of these endotherms by the van't Hoff relationship and Borchardt and Daniels kinetics analysis revealed reaction orders of ca. 0.6 to 2.1, 3.5 to 5.1 and 1.5 to 3.1, respectively, for the three muscle endotherms. The reaction orders for these endotherms were influenced by muscle type, fiber sarcomere length and conditioning. Aging led to an increase in reaction order whereas increased sarcomere length was accompanied by a decrease in reaction order or number of cooperative units. Changes in the number of cooperative units participating in the endotherms is discussed in the context of meat tenderization and conditioning. It appears reaction order analysis of the T₃ transition (81–83°C) may correlate with meat tenderness.     

Kappa-Carrageenan, Sodium Chloride and Temperature Affect Yield and Texture of Structured Beef Rolls

Structured lean beef rolls (4–5% fat), formulated with 33% added water, 1% sodium chloride and 0.35% sodium tripolyphosphate and cooked to 63°, 73° and 83°, had low cook yields and poor texture and bind. Kappa-carrageen an (KC) added at 0.5–1% and NaCl at 2–3% increased cook yield and improved textural properties (bind, force to fracture, hardness). Rolls with 1.0% KC and 3% NaCl had the highest cook yield (154% meat weight basis) and the highest values for force to fracture and hardness. Cook yield decreased and hardness increased with increased cooking temperature. Effects of KC on yield and texture were most pronounced at the lowest NaCl level (1%) and the highest temperature (83°). KC also reduced purge of vacuum-packaged slices during refrigerated storage.     

Heat-induced Gelation of Myofibrillar Proteins and Sausages: Effect of Blood Plasma and Globin

The gelation of meat myofibrils and sausages was monitored during heating with and without added blood globin and plasma by the dynamic rheological method. During heating of beef myofibrils (pH 6.5; prot conc 6.0%) the storage modulus (G') reached a minimum at 47.7°C, decreased on further heating, and increased above 53°C. At higher pH (6.9) the G’value was lower and the magnitude of tanδ increased substantially between 37 and 42°C. Addition of blood globin and plasma changed the thermal gelation of myofibrils. During heating of control and protein-supplemented sausages, we observed two minor peaks in storage modulus in the range 40–55°C and a steep increase at 55–80°C. The storage modulus of low fat sausages, where 25% of meat was replaced by globin or plasma, was greater than that of control sausages.     

Effect of Cooking on the Thermal Conductivity of Whole and Ground Lean Beef

The probe method was used to measure thermal conductivity of beef through a temperature range of 30–120°C. Thermal conductivity of beef increases with temperature up to 70°C followed by a decrease during the denaturation of proteins and subsequent loss of water. The thermal conductivity of beef again increases with temperature after protein denaturation. The thermal conductivity of cooked beef is lower than raw beef up to about 80°C. The rate of increase for cooked meat thermal conductivity is fairly constant with temperature at a given moisture content. Models based on composition and temperature were found to predict the thermal conductivity of meat during cooking at an average standard percent error of 7%.     

Differential Scanning Calorimetry of Beef Muscle: Influence of Sarcomere Length

Contraction state of beef muscle at onset of rigor influences tenderness of cooked meat. Loss in tenderness during cooking has been related, through use of differential scanning calorimetry (DSC), to thermal denaturation of myofibrillar proteins. Contraction of beef sternomandibularis muscle was controlled at sarcomere lengths of 2.4, 2.1, 1.9, 1.7, and 1.4 μm. Samples were scanned from 25- 105°C at 10°C/min; ΔH (change in heat of transition) between 45° and 92°C dropped from ca. 4 J/g muscle at 2.4 μm to ca. 3 J/g at 1.4 μm. This difference (P < 0.05) amounts to less than 1% of the total energy resuired to heat meat from 45° to 92°C. The decrease is attributed to a greater actomyosin contribution to the overall thermal curve resulting from increased overlap of the filaments.     

Heat resistance of Escherichia coli O157:H7 in cook‐in‐bag ground beef as affected by pH and acidulant†

Summary The heat resistance of a four‐strain mixture of Escherichia coli O157:H7 was tested. The temperature range was 55–62.5 °C and the substrate was beef at pH 4.5 or 5.5, adjusted with either acetic or lactic acid. Inoculated meat, packaged in bags, was completely immersed in a circulating water bath and cooked to an internal temperature of 55, 58, 60, or 62.5 °C in 1 h, and then held for pre‐determined lengths of time. The surviving cell population was enumerated by spiral plating meat samples on tryptic soy agar overlaid with Sorbitol MacConkey agar. Regardless of the acidulant used to modify the pH, the D ‐values at all temperatures were significantly lower (P < 0.05) in ground beef at pH 4.5 as compared with the beef at pH 5.5. At the same pH levels, acetic acid rendered E. coli O157:H7 more sensitive to the lethal effect of heat. The analysis of covariance showed evidence of a significant acidulant and pH interaction on the slopes of the survivor curves at 55 °C. Based on the thermal‐death–time values, contaminated ground beef (pH 5.5/lactic acid) should be heated to an internal temperature of 55 °C for at least 116.3 min and beef (pH 4.5/acetic acid) for 64.8 min to achieve a 4‐log reduction of the pathogen. The heating time at 62.5 °C, to achieve the same level of reduction, was 4.4 and 2.6 min, respectively. Thermal‐death–time values from this study will assist the retail food processors in designing acceptance limits on critical control points that ensure safety of beef originally contaminated with E. coli O157:H7.     

Differential Scanning Calorimetric Studies of Meat Protein-Alginate Mixtures

Differential scanning calorimetry thermal curves of beef semimembranosus muscle showed peaks at 58, 67 and 78°C. Addition of algin/calcium binder or 5-10% connective tissue increased magnitude of the 58°C peak. For crude myofibrillar, sarcoplasmic and connective tissue proteins thermal destabilization was lowered by 7.5, 23.6 and 8.6°C, respectively, with addition of algin/calcium binder. Destabilization of tendon by the binder from about 67°C to 58°C was similar in magnitude to the shift of the 67-68 and 58°C thermal transitions reported in semimembranosus and probably indicated collagen destabilization. Thermal destabilization by algin/calcium may indicate change in physical state of proteins which could influence texture of algin/calcium restructured meat products.     

L-Ascorbic Acid and Its 2-Phosphorylated Derivatives in Selected Foods: Vitamin C Fortification and Antioxidant Properties

Two carbonated beverages fortified with 30 mg L-ascorbic acid (AsA) equivalents/250 mL in the form of L-ascorbate 2-monophosphate (AsMP) and stored at 25–35°C retained more vitamin C than those with added AsA or L-ascorbate 2-polyphosphate (AsPP). Breads enriched with ferrous iron and fortified with 560 AsA eq./100g flour in the form of AsPP and AsA retained 40% and 5% vitamin C, respectively, after 6 davs at 25°C. Bran (40%) flakes fortified with 0.19% AsA ea. as AsMP and AsPP gave much improved retention of vitamin C during storage for 7 mo at 25–40°C and 7–11% moisture levels. The sodium salts of AsA, AsMP, and AsPP, when injected into whole eye of round beef at 0.18% AsA eq., inhibited hexanal formation after the meat was roasted and stored for 5 days at 5°C. Those sodium salts did not prevent accumulation of peroxides in peanut paste.     

Assessment of Previous Heat Treatment of Laboratory Heat-Processed Meat and Poultry using a Commercial Enzyme System

The APIZYM enzyme system was assessed with respect to: enzyme activity in aqueous and saline extract filtrates from raw and heat processed (60° and 71.1°C) beef; effect of rate of heating (0.2–0.3°C, 0.4–0.5°C, and 0.9–1.0°C/min) to internal temperatures of 66.7°, 67.8°, 68.9°, 70.0°, and 71.1°C and holding times of 0, 15, 30, 45, and 60 min at these temperatures on residual enzyme activity; reduction of enzyme assay incubation time; and reproducibility of the system. Results showed that slightly higher enzyme activity in heated samples was obtained with 0.9% saline extraction compared to water. Greater enzyme activity was observed in filtrates from pork samples heat-processed at a fast rate than at a slow rate. Enzyme activity could be detected after 2 hr incubation, but 4 hr were needed for the enzymes to react with their respective substrates. The system was found to be reproducibile. The results of this study also indicated the potential of using leucine aminopeptidase as an indicator enzyme for determining the adequacy of heat treatment of meat and poultry products.     

Thermal Destruction of Listeria monocytogenes in a Meat Slurry and in Ground Beef

Thermal destruction of Listeria monocytogenes cells was determined in phosphate buffer, a meat slurry (20% ground beef/80% water) and in ground beef. D-values at 60°C, 65°C and 70°C in phosphate buffer, and in the meat slurry were 0.63, 0.29 and 0.15, and 2.54, 0.75 and 0.23 min, respectively. Heating of ground beef (80% lean) in a 75°C water bath to 50°C, 60°C or 65°C required 6.2, 8.4 and 10.6 min, respectively, and resulted in 0.2-0.9, 1.6-3.4 and 4.4-6.1 log reductions in L. monocytogenes cells, from the initial inoculation level of 8.08 log CFU/g. Viable cells were also detected after cold (21 days) or selective enrichment (24 hr) in eight out of nine samples of ground beef inoculated with 7.84-8.08 log CFU/g and cooked to 70°C.     

Carrageenan Effects on Thermal Stability of Meat Proteins

Meat myofibrillar protein (MP) gels and ground pork were used as model systems for studying thermal transition temperatures. Addition of up 2% of κ, ι, or λ carrageenan (CGN) to MP caused a very slight change in the thermal denaturation of the meat proteins. Three transition temperatures were found in ground pork samples, which were characteristic of myosin (59.4°C), sarcoplasmic proteins (67.8°C), and actin (82.4°C). Mixtures of high ionic strength had lower thermal transition peaks. CGN did not cause major shifts in transition temperatures, suggesting that molecular interactions between CGN and meat proteins did not occur.     

Comparison of Sample Storage Methods for Vitamin B6, Assay in Broiler Meats

Five methods were compared for storage stability of vitamin B₆ in broiler meat samples. Maximum retention of vitamin B₆ was observed in the N₂-packed freeze-dried samples at -34°C (101–103% up to 20 mo). Good retentions occurred in the intact tissues of half birds at -34°C (90% in 16 mo) and in ground meat samples (200g portions) at -34°C (91% up to 12 mo). Significantly lower retentions were found in freeze-dried samples stored at room temperature (85–77% in 1–5 mo, respectively) and for ground meat small portion samples (5g) at -34°C (84–72% in 3–5 mo, respectively).     

Metabolite Profile Differences Among Different Storage Time in Beef Preserved at Low Temperature

Storage temperature influences meat color stability and quality. This study was performed to quality change‐associated metabolites profiles using a nontargeted liquid chromatography‐mass spectrometry (LC‐MS/MS)‐based method. Beef longissimus dorsi samples were purchased immediately after slaughter, and then stored at room temperature, 4 °C and 0 °C. Water holding capacity (WHC), moisture content and pH value of the muscle samples were detected. Muscle samples and quality control samples were then prepared for nontargeted LC‐MS/MS system, followed by identification of distinct metabolites. Pearson correlation coefficients between metabolites and quality indexes were calculated. Storage reduced pH values of beef, and room temperature and 4 °C displayed the lowest pH value. Moisture content and WHC in beef muscles, especially WHC declined obviously during the first 24 hr. The significantly altered metabolites profiles in meat samples at 0, 3.5, and 7 days during 4 °C storage were identified using LC‐MS/MS. Most metabolites showed linear changes during storage (0 to 7 days). Using Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis, we found 1(α)‐naphthol, urocanic acid, tyramine, guanine, histamine, picolinic acid, 4‐hydroxybenzaldehyde, and hypoxanthine were increased, and 2‐(S‐glutathionyl)acetyl glutathione and glutathione were decreased in beef during 4 °C storage. Correlation analysis showed there were significantly correlations between metabolites and meat quality indexes (WHC, moisture content, and pH). In summary, 1(α)‐naphthol, urocanic acid, tyramine, guanine, histamine, picolinic acid, 4‐hydroxybenzaldehyde, and hypoxanthine, proved to be harmful to human body, accumulated gradually, especially after 3.5 days during storage at 4 °C. While the contents of beneficial substances, including 2‐(S‐glutathionyl)acetyl glutathione and glutathione, were decreased, which provided reference for the nutrition guidance of using beef meat.     

Microbiological and Sensory Changes in Minced Beef Treated with Potassium Lactate and Sodium Diacetate during Refrigerated Storage

The effect of potassium lactate and sodium diacetate on the microbiological changes and sensory properties of vacuum-packaged minced beef was investigated. The meat samples both with a preservative (in the amounts 0.65% and 1.3%) and without were stored at temperatures of 0–1°C and 5–6°C. The influence of storage time on changes in total bacteria count (TBC), lactic acid bacteria (LAB), Brochothrix thermosphacta, and the microbes of the Enterobacteriaceae family was investigated, as well as changes in pH and sensory quality. It was found that the addition of the preservative to the minced meat caused a significant extension (p < 0.05) of the lag phase and an inhibition of microbial growth rate, depending on temperature, storage time, and its concentration. The antibacterial effect was significantly higher (p < 0.05) at a temperature of 0–1°C than at 5–6°C and most susceptible to it were the bacteria belonging to the Enterobacteriaceae. The study results showed that the minced beef containing the preservative which had been vacuum stored at 0–1°C, presented a better sensory quality and had a shelf-life of about 6 days longer, in relation to the quality and shelf-life of the control samples. For each of the refrigeration storage temperatures however, there was no statistically significant change (p < 0.05) in the pH for the various storage periods and preservative quantities present.     

Development of twoListeria monocytogenesgrowth models in a meat broth and their application to beef meat

Growth variation ofListeriastrains was taken into account by building two growth models with strains previously characterized, respectively, by their slow (L. monocytogenes CLIP 19532) and fast (L. monocytogenes 14) growth in different conditions of pH, a_wand temperature. Strains of intermediate growth were studied in a meat broth and strains used for the models were grown on the surface of beef meat. Ten growth repetitions at 14°C– a_w0.98–pH 6.2 showed that generation times were similar [ratio value (R=standard deviation/average): 3.2%] but that range of lag times was wide (R=27.4%). In broth, calculated lag and generation times were not significantly different between strains from 30 to 14°C, but variations became larger as temperatures came close to 4°C. Model values corresponded well to experimental generation times and to a lesser extent to lag times. On meat at 4°C and 14°C both strains had experimental lag times three-fold longer than predicted lag times. Experimental generation times were shorter than predicted values at 14°C and longer at 4°C: differences between growth in broth and on meat could be due to the characteristics of the meat, the experimental conditions of growth, the mode of inoculation and the way of adjustment of a_w. Growth variations were found between available predictive models.     

Effect of Gradual Heating and Fat/Oil Type on Fat Stability,Texture, Color,and Microstructure of Meat Batters

The effects of endpoint cooking temperature (40, 50, 60, 70, 80, and 90 °C) on emulsion stability, texture, color, and microstructure of meat batters prepared with different fats/oils were studied. Canola oil treatments showed the highest cooking loss whereas hydrogenated palm oil provided the most stable meat batters. Rendered beef fat was less stable than regular beef fat. Increasing endpoint cooking temperatures resulted in a progressive reduction of water holding capacity in all treatments. As temperature was raised, meat batters showed higher hardness and cohesiveness values, but no appreciable changes in cohesiveness above 60 °C. Canola and hydrogenated palm oil treatments showed the highest hardness and chewiness values. Lightness (L^*) values of all meat batters increased significantly with increasing temperature from 40 to 60 or 70 °C; no major changes observed above 70 °C. Light microscopy revealed no substantial changes in the microstructure of all the stable meat batters cooked to between 50 and 70 °C. Heating to 90 °C changed the microstructure in all meat batters except the hydrogenated palm oil treatments, which still showed nonround fat particles and a less aggregated protein matrix.     

GELATION KINETICS of MEAT EMULSIONS CONTAINING VARIOUS FILLERS DURING COOKING

A cylindrical shaped thermal scanning rigidity monitor (TSRM) was developed to determine shear rigidity modulus of meat batters during cooking. A meat fatprotein ratio of 1.8, moisture content of 62% and 8.6% filler were used. the fillers were buttermilk powder, corn starch, micro-crystalline cellulose, modified corn starch, modified wheat flour, soy-protein concentrate and whey-protein concentrate. Plots of rigidity modulus versus product-temperature showed two major thermal transitions. the first and most important transition (53 to 61°C) was due to myosin gelation. the second transition (64 to 69°C) was ascribed to the collagen softening. the maximum rigidity-temperature slopes of 0.60 to 1.02 kPa/°C occurred after the first transition.     

Effect of heating rate at different moisture contents on starch retrogradation and starch–water interactions during gelatinization

The objective of this research was to investigate the effect of heating rate at different moisture contents on starch retrogradation and gelatinization process. Starch retrogradation was not influenced by either moisture content (water/starch ratio of 0.7 or 2.0) or heating rate (5°C/min, 20°C/min, or 40°C/min). In order to further understand the effects of heating rate on starch–water interactions, starch suspensions at a water/starch ratio ranging from 0.7 to 3.0 were heated at 5, 15, or 25°C/min by using a DSC to different final temperatures and rescanned. The deconvoluted G and M1 endotherms and the corresponding additional unfrozen water (AUW) were determined. The results showed that the G and M1 endotherms merged at higher heating rates and at higher moisture contents as expected. A significant interaction was observed between moisture content and heating rate. The results suggest that the gelatinization process is governed by moisture content at the lower heating rate (5°C/min) and by heating rate at the higher heating rates (15 or 25°C/min). Results from the AUW data suggest that the M1 component of gelatinization dominated at moisture content below water/starch ratio of 1.5 and at 5°C/min heating rate. However, at moisture contents above water/starch ratio 1.0, an interaction was observed between moisture content and heating rate. The data suggest that at higher moisture content (>1.5 water/starch ratio) and at higher heating rate (≥15°C/min), there is still a kinetic limitation to the complete melting of the M1 endotherm.     

Binding of Meat Pieces: Influence of Some Processing Factors on Binding Strength and Cooking Losses

Evacuation of the chamber of the press used to form flaked beef into a restructured meat product (patty) did not affect the binding strength of the cooked patty but under some conditions decreased the cooking loss. In studies using patty mixes containing 0–1.0% added sodium chloride, meat binding strength increased with decrease in the temperature of the mix when formed into patties over the temperature range - 1° to -5°C. The largest effect generally occurred between - 1° and -2°C. However, the effect was only noted in patties that were frozen (-30°C) before being cooked for assessment. With decrease below - 1°C of the temperature of patties when pressed, cooking losses increased for the patties without added salt but decreased for those with added salt (0.5% or 1%). Change in the pressure applied to form the patty (in the range 1.4–13.7 MPa) can affect binding strength.     

Microbiological Method to Identify Irradiated Meat

Beef, chicken, mutton and pork exposed to -γ-radiation doses of 0–5 kGy were inoculated with Aeromonas hydrophila initially, after 7 days and 15 days of storage at 3°C and -11°C. After 18 hr incubation at 30°C TVBN values of nonirradiated samples were found to be 210 mg% and TVA value were 205 while the corresponding irradiated samples showed 30–80 mg% and 40–80. A similar pattern was observed in stored samples. A rapid method was developed by incubating chicken meat at 37°C for 6–7 hr with bacteria followed by estimation of volatile acids (TVA) and bases (TVBN). A 40–50% reduction in TVA and TVBN in irradiated samples was observed suggesting its possible application for detecting irradiated meat samples.