Short Thermal Treatment Effect on Carp Myofibril and Sarcoplasmic Reticulum: Possible Mechanisms in Rigor Mortis Acceleration by "Arai" Treatment

Inorganic γ-phosphate liberation from adenosine 5′-triphosphate (ATP) by carp myofibrillar ATPase was measured at 0-60°C to elucidate mechanisms in rigor mortis acceleration of sliced carp muscle during washing at a moderately high temperature. ATP splitting within 20 sec in the presence of 5 mM MgCl₂ plus 0.25 mM CaCl₂ was maximal at 45°C, which agreed well with the commercially adopted condition for preparing carp “arai” muscle. In addition, the maximum Ca²⁺ uptake by sarcoplasmic reticulum was observed at 30°C and decreased at higher temperatures. The acceleration of carp muscle rigor mortis at around 45°C was suggested to be partly due to enhancement of myofibrillar Mg²⁺-ATPase activity by increase of intracellular Ca²⁺ concentration.     

Effect of heat shock on thermal tolerance and susceptibility of Listeria monocytogenes to other environmental stresses

In the present study, Listeria monocytogenes Scott A, V7 and CCRC 14930 were first subjected to heat shock at 45°C for 1 h or at 48°C for 10 min. Thermal tolerance at 55°C and survival of the heat shocked as well as non-heat shocked cells of L. monocytogenes in the presence of 25% NaCl, 0.01% crystal violet, 0.1% H₂O₂, and 18% ethanol were examined.It was found that heat shock response of L. monocytogenes varied with strains, the condition of heat shock treatment and type of subsequent stress. Compared with the non-heat shocked cells, the 45°C-1 h heat shocked cells of strains Scott A and V7 showed an increased survival after exposure to 55°C for 60 min. Meanwhile, survival of the 48°C-10 min heat shocked L. monocytogenes cells, regardless of strain, exhibited no significant difference (p>0.05) with their respective control cells. Generally, heat shocking at 45°C for 1 h increased the tolerance of L. monocytogenes to NaCl, ethanol and crystal violet. On the other hand, heat shocking at 48°C for 10 min although increased the resistance of L. monocytogenes to NaCl reduced its resistance to H₂O₂ and crystal violet.     

Inactivation of Escherichia coli in a Tropical Fruit Smoothie by a Combination of Heat and Pulsed Electric Fields

ABSTRACT: Moderate heat in combination with pulsed electric fields (PEF) was investigated as a potential alternative to thermal pasteurization of a tropical fruit smoothie based on pineapple, banana, and coconut milk, inoculated with Escherichia coli K12. The smoothie was heated from 25 °C to either 45 or 55 °C over 60 s and subsequently cooled to 10 °C. PEF was applied at electric field strengths of 24 and 34 kV/cm with specific energy inputs of 350, 500, and 650 kJ/L. Both processing technologies were combined using heat (45 or 55 °C) and the most effective set of PEF conditions. Bacterial inactivation was estimated on standard and NaCl‐supplemented tryptone soy agar (TSA) to enumerate sublethally injured cells. By increasing the temperature from 45 to 55 °C, a higher reduction in E. coli numbers (1 compared with 1.7 log₁₀ colony forming units {CFU} per milliliter, P < 0.05) was achieved. Similarly, as the field strength was increased during stand‐alone PEF treatment from 24 to 34 kV/cm, a greater number of E. coli cells were inactivated (2.8 compared with 4.2 log₁₀ CFU/mL, P < 0.05). An increase in heating temperature from 45 to 55 °C during a combined heat/PEF hurdle approach induced a higher inactivation (5.1 compared with 6.9 log₁₀ CFU/mL, respectively {P < 0.05}) with the latter value comparable to the bacterial reduction of 6.3 log₁₀ CFU/mL (P≥ 0.05) achieved by thermal pasteurization (72 °C, 15 s). A reversed hurdle processing sequence did not affect bacterial inactivation (P≥ 0.05). No differences were observed (P≥ 0.05) between the bacterial counts estimated on nonselective and selective TSA, suggesting that sublethal cell injury did not occur during single PEF treatments or combined heat/PEF treatments.     

Thermal Inactivation of Clostridium perfringens After Growth at Several Constant and Linearly Rising Temperatures

Inactivation kinetics of Clostridium perfringens strains NCTC 8238 and NCTC 8798 vegetative cells were evaluated in autoclaved ground beef after growth at constant (37, 41, 45, or 49°C) or linearly rising temperatures (4.0, 6.0, or 7.5 C°/hr) representative of long-time, low-temperature (LTLT) cooking. Inactivation temperatures of 55, 57, 59, 60, and 61°C were used. D values and z values were determined. For strain NCTC 8798 cells grown at 45°C, the average D₅₉°C was 7.2 min and the z_D was 3.8 C°. Both strains exhibited greater heat resistance after growth at higher constant temperatures. Also, NCTC 8798 was more heat resistant than NCTC 8238. With linearly rising temperature, terminal growth temperatures appeared dominant in resistance to inactivation. These data will permit predictions of growth and survival of C. perfringens during LTLT cooking of beef roasts.     

Movement of Cryptolestes ferrugineus out of wheat kernels and their mortalities under elevated temperatures

The rusty grain beetle, Cryptolestes ferrugineus (Coleoptera: Laemophloeidae), is a common pest in stored grain. The present study examined the time taken for larvae of C. ferrugineus to exit wheat kernels at 40–55 °C, stage-specific mortality at 40–60 °C, and whether a combination of heat and shaking could be used to control this pest. The average time larvae took to leave wheat kernels ranged from 130 min at 40 °C to 6 min at 55 °C. At 55 °C and 6 min exposure, 81 ± 2% of larvae exited the kernels, 10 ± 1% of larvae were alive inside kernels and 9 ± 2% were dead inside kernels. Under constant temperature of 55 °C, less than 5% of the larvae escaped in 2 min, but under the rising temperature of 40, 45, 50 and then to 55 °C, over 50% of the larvae escaped in 2 min at 55 °C. The time taken to reach 50 and 95% mortality was similar for all stages. Higher temperatures resulted in higher mortality in a shorter exposure time. The longest LT₉₅ for pupae was 6480, 293, 50 and 3.7 min at 45, 50, 55 and 60 °C, respectively. At 55 °C for 88 min, combined with shaking gave 88% control in a 100-g wheat bulk. Time needed to kill eggs and pupae were much longer than the time needed to force larvae out of kernels. Therefore, the combination of heat and shaking would only provide partial disinfestation of C. ferrugineus.     

Influence of hot‐air treatment,superatmospheric O2 and elevated CO2 on bioactive compounds and storage properties of fresh‐cut pomegranate arils

The impact of heat treatment using hot air (HT 45 °C and 55 °C for 1 h) and two active modified atmosphere packaging (MAP) conditions of high oxygen atmosphere (HOA: 80 kPa O₂, 20 kPa N₂) and high CO₂ atmosphere (HCA: 20 kPa CO₂, 80 kPa N₂), individually or combined, on the antioxidant capacity, polyphenols, vitamin C content, total anthocyanins, polyphenoloxydase (PPO) activity and shelf life of fresh‐cut (FC) pomegranate arils stored for 14 days at 4 °C was studied. The results indicate that HT 45 °C along with HOA inhibited PPO activity and prevented loss of antioxidant capacity, vitamin C and phenolic compounds in arils, in comparison with control and HT 55 °C. All treatments reduced the accumulation of anthocyanins, but HCA‐treated arils lost more anthocyanins besides having worse a* colour parameter values. No significant differences in titrable acidity (TA) and total soluble solids (TSS) were observed between treatments. The combination of HOA and HT 45 °C enhanced the benefits of applying each treatment separately and could be useful to improve and extend postharvest life of pomegranate FC arils.     

Enzymatic Production of Ribonucleotides from Autolysates of Kluyveromyces marxianus Grown on Whey

After 20h fermentation of medium containing 5% (w/v) dehydrated whey, at 30°C, pH 4.5, yeast cells were harvested, diluted in 0.1M KH₂PO₄, and autolyzed at different pHs (6.5–7.5) and temperatures (45–55°C). Phosphodiesterase (0.2–1.0% w/v, 65°C, pH 6.5, 6h) and adenyl deaminase (0.5-1.0% w/v, 60°C, pH 5.5, 4h) were added to the autolysates. After heat treatment (100°C, 15 min), samples were analyzed by RP-HPLC and LC/MS. Production of 5′-ribonucleotides was maximized at 50°C, pH 6.5. Yields of 5′-AMP (800 μg/g of biomass) and 5′-GMP (2000 μg/g) increased considerably after addition of 1.0% phosphodiesterase. 5′-IMP increased only after addition of 1.0% adenyl deaminase.     

Rheological and Morphological Comparison of Thermal and Hydrostatic Pressure-Induced Filamentous Myosin Gels

The structure and rheological properties of heat‐ and pressure‐induced myosin filament gels were investigated. The apparent elasticity of heat‐induced gel peaked at 55 °C (4.35 ± 0.57 kPa), whereas that of pressure‐induced gel increased with elevating pressure, and the gel formed at 500 MPa had a value of 4.79 ± 0.25 kPa. All pressure‐ and heat‐induced gels showed similar internal structure, namely, the gels were composed of a fine‐strand network. The detailed structures of the strands induced by pressure‐ and heat‐treatment of myosin filaments were observed using an atomic force microscope. The structural differences among the strands were not observed, whereas the elasticity of the strands measured by atomic force microscope revealed differences among the strands formed with varying heating temperature and pressure. The elasticities of the heat‐induced strands were 1.19 ± 0.09 MPa, 10.24 ± 1.16 MPa, and 3.09 ± 0.25 MPa at 40 °C, 55 °C, and 70 °C, respectively. On the other hand, the elasticity of the pressure‐induced strand increased with elevating pressure. The elasticity values were 1.24 ± 0.09 MPa, 2.32 ± 0.17 MPa, and 9.80 ± 0.84 MPa at pressures of 150, 300, and 500 MPa, respectively. Because the changes in the elasticity of the whole gel corresponded to those of the strand, it is concluded that the rheological properties of the constituting strands determine that of myosin filamentous gel.     

Thermal inactivation ofClostridium perfringensvegetative cells in ground beef and turkey as affected by sodium pyrophosphate

The heat resistance (55–65°C) ofClostridium perfringensvegetative cells in ground beef and turkey that included 0, 0.15 or 0.3% (w/w) sodium pyrophosphate (SPP) was assessed in bags heated using a water bath. The surviving cell population was assayed on tryptose–sulfite– cycloserine agar. The decimal reduction (D)-values in beef that included no SPP were 21.6, 10.2, 5.3, and 1.6min at 55, 57.5, 60, 62.5°C, respectively; the values in turkey ranged from 17.5min at 55°C to 1.3min at 62.5°C. Addition of 0.15% SPP resulted in concomitant decrease in heat resistance as evidenced by reduced bacterialD-values. TheD-values in beef that included 0.15% SPP were 17.9, 9.4, 3.5, and 1.2min at 55, 57.5, 60, and 62.5°C, respectively; the values in turkey ranged from 16.2min at 55°C to 1.1min at 62.5°C. The heat resistance was further decreased when the SPP level in beef and turkey was increased to 0.3%. Heating such products to an internal temperature of 65°C for 1min killed >8log₁₀cfug^-1. The z-values in beef and turkey for all treatments were similar, ranging from 6.22 to 6.77°C. Thermal death time values from this study should assist institutional food service settings in the design of thermal processes that ensure safety againstC. perfringensin cooked beef and turkey.     

Therapeutic profile of a latent heat eyelid warming device with temperature setting variation

PurposeTo compare the effects on ocular temperature and tear film parameters following a single application of a latent heat eyelid warming device at a range of temperature settings.MethodsFifteen subjects were enrolled in a prospective, investigator-masked, randomised, cross-over trial. On separate days, participants were randomised to 10-minute application of a research latent heat device (Laboratoires Théa) at device temperature settings of 45 °C, 50 °C and 55 °C. Outer eyelid and corneal temperatures, tear film lipid layer grade, and non-invasive tear film breakup time (NIBUT) were measured at baseline and immediately after 10 min of device application.ResultsBaseline measurements did not differ between treatment groups (all p > 0.05). Ocular temperatures, lipid layer grade and non-invasive tear film stability rose significantly following device application in all treatment groups (all p < 0.05). The 55 °C setting effected a mean ocular surface temperature rise in the order of +4 °C from baseline, which was 1.46 and 1.26 times greater than at the 45 °C and 50 °C temperature settings, respectively (all p < 0.05). Similarly, improvements in mean non-invasive tear film stability from baseline in the order of +7 s were observed, which were 2.43 and 1.66 times greater than those at the lower temperature settings of 45 °C and 50 °C, respectively (all p < 0.05).ConclusionsAt all temperature settings, the latent heat device resulted in clinically and statistically significant increases in ocular temperature, lipid layer grade, and non-invasive tear film stability. However, the 55 °C setting proved to be most effective at raising ocular temperature (in the order of +4 °C from baseline) and improving tear film stability.     

Dynamic rheological behaviour and biochemical properties of rabbit skeletal actomyosin during storage at 0° C

The relationship between the dynamic rheological properties of heat induced gels of actomyosin (natural actomyosin) and the denaturation of actin in actomyosin during storage without ATP at pH 6.0 and 0°C was investigated using biochemical and dynamic rheological measurements. The complex modulus of gels after heating actomyosin containing 0.5 or 1.5 M KCl (pH 6.0) at 80°C increased with increasing storage time. The dynamic rheological behaviour during heat gelation of actomyosin in 1.5 M KCl indicated that the first rheological transition peak in the 50–53°C range induced by the presence of F-actin gradually disappeared with increasing storage time. However, in 0.5 M KCl, this transition peak clearly remained even after 15 days. The time course of denaturation of actin in actomyosin treated with 1.5 M KCl at pH 6.0 showed an increase in the percent denaturation after the storage was started, and about 100% of the actin became denatured after 21 days. In the case of 0.5 M KCl, unlike 1.5 M, the denaturation of actin occurred quickly within the first 5 days and then did not proceed. A sigmoidal relationship was found between the percent denaturation of actin and the KCl concentration added, the greatest change occurring at KCl concentrations between 0.5 and 1.0 M. The data indicated that the change in the property of actin in actomyosin during storage at low temperature exerts a great influence on the viscoelasticity of heat-induced gels of actomyosin.     

Changes in Physicochemical Properties of Bighead Carp (Aristichthys mobilis) Actomyosin by Thermal Treatment

Physicochemical properties of actomyosin from bighead carp during heat-treatment were investigated. Turbidity, solubility, and surface hydrophobicity showed significant changes from 40–55°C (P < 0.05). Heat-treatment before 45°C could make actomyosin unfold, and the disulfide bonds were formed at temperatures above 45°C. Three enthalpy transitions at 41.2, 61.7, and 63.4°C were found in differential scanning calorimetry thermogram of bighead carp actomyosin. Storage modulus (G′) increased gradually and reached the first peak at 36.5°C and the second peak at 50°C. Myosin suffered conformation changes and lead to aggregation during the heating period.     

Canning Quality Evaluation of Pinto and Navy Beans

Thermal processing of pinto and navy beans at 121.1°C for 16 or 14 min in a still retort gave similar sterilization value (F_o= 10) as the processing at 115.6°C for 45 min. The 121.1°C/16 or 14 min process produced beans with greater firmness than the 115.6°C/45 min process. The addition of CaCl₂ and EDTA improved firmness and color of canned beans. Calcium chloride also reduced clumping and splitting of the canned beans. Sensory evaluation showed that the acceptability of canned beans was reduced when CaCl₂ was increased up to 10 mM. High correlation between firmness and soluble pectin in various bean cultivars implied that soluble pectin content could be used as a parameter for screening bean cultivars with desirable firmness.     

Differences in properties of myofibrillar proteins from bovine semitendinosus muscle after hydrostatic pressure or heat treatment

Hydrostatic pressure (HP) and heat treatments of myofibrillar proteins have both been shown to induce protein denaturation, but different gel formation properties result from these treatments. To characterise differences in the properties of proteins resulting from HP or heat treatment, Ca‐ and Mg‐ATPase activities (ATP, adenosine triphosphate) and protein solubility in 0.1 and 0.6 mol L^?1 KCl buffers (pH 7) were evaluated in this study. The inactivation rate of Ca‐ATPase of myofibrillar proteins (Mf) induced by HP was slower than that of Mg‐ATPase at each of the tested pressures. However, the inactivation rate of Ca‐ATPase induced by heating was faster than that of Mg‐ATPase at each of the tested temperatures. The level of soluble proteins in Mf suspension induced by HP in 0.1 mol L^?1 KCl buffer increased with increasing pressure up to 400 MPa and then decreased slightly at 500 MPa. However, the level of soluble proteins in Mf suspension induced by heat treatment in 0.1 mol L^?1 KCl buffer increased with increasing temperature up to 55°C. According to the results of sodium dodecyl sulfate polyacrylamide gel electrophoresis, the levels of soluble myosin heavy chain and actin in Mf suspension induced by HP in 0.6 mol L^?1 KCl buffer decreased simultaneously at pressures higher than 300 MPa. The level of soluble MHC in 0.6 mol L^?1 KCl buffer decreased gradually with increasing temperature, but there were no changes in the level of soluble actin in 0.6 mol L^?1 KCl buffer with increasing temperature up to 50°C. These results showed that the mechanism of HP‐induced protein denaturation was different from the mechanism underlying heat‐induced protein denaturation. Copyright © 2006 Society of Chemical Industry     

Development of Muscle Thermal Rigorometer and Characterization of Heat-induced Muscle Shortening of Tilapia

A muscle thermal rigorometer was constructed, allowing muscle shortenings induced by dynamic heating or isothermal aging to be monitored. Operating isothermally like a traditional rigorometer at 10 °C, postmortem dorsal muscle shortening (S_10°C) developing from 0% to 10% of its initial length in corresponding to RI_fiber along fiber‐direction developing from 0% to 100% within 16 h was monitored for freshwater tilapia. Monitoring meat cooking in the dynamic heating mode, heat‐induced shortenings could be observed for all muscle samples possessing different degrees of rigor induced by 10°C aging. The heat‐induced shortening (S_dynamic) plus its 10°C aging shortening (S_10°C) for each sample was the same, S_overall= S_10°C+ S_dynamic= 10%. Their heat‐induced shortening peak temperatures (Ts) from 30°C to 48°C were inversely correlated with the sample RI_fiber from 0% to near 100%. These findings together with an additional calcium/adenosine triphosphate (ATP) model studies showed that the ATPase related myofibrillar contractile system was responsible for these low‐temperature cooking shortenings, which along with Ts values could thus be adopted as new rigor indices.     

Effect of Hydrothermal Treatment on Formation and Structural Characteristics of Slowly Digestible Non‐pasted Granular Sweet Potato Starch

The formation and structural characteristics of slowly digestible non‐pasted granular starch in sweet potato starch were investigated under various hydrothermal treatment conditions. The moisture content of the sweet potato starch was adjusted to 20, 50 or 90%, and the starch was heated at 40, 55 or 100°C for 12 h in a dry oven. The relative crystallinity of the hydrothermally treated samples was decreased with increasing temperature, and the X‐ray diffraction patterns of the samples were altered from C_b‐type to A‐type. Microscopic observations did not reveal any changes in the starch granules of any samples except those with moisture contents of 50 and 90% that were heated at 100°C. When gelatinization parameters were examined, samples with moisture contents of 50 and 90% that were heated at 55°C and samples of all moisture contents that were heated at 100°C had peak temperatures higher than that of raw starch but gelatinization enthalpies lower than that of raw starch. The swelling factor of the samples heated at 40°C did not change significantly, whereas that of samples heated at 55 and 100°C was decreased at increased moisture levels. The sweet potato starch with 50% moisture content that was heated at 55°C had the highest content of granular slowly digestible starch, about 200% that of raw starch, although our study did not involve further hydrothermal treatment conditions. Further study is required to complete a process for more efficient production of heat stable and slowly digestible starch.     

Thermal Aggregation of Myosin Subfragments from Cod and Herring

Turbidity of fish myosin subfragment solutions increased with temperature, except cod heavy meromyosin turbidity leveled above 45°C. Extent of aggregation and number of cross-linking sites for cod heavy and light meromyosins were significantly higher than for herring (p<0.05), but only at temperatures above 35°C and 45°C, respectively. Thermal aggregation ability increased linearly with increased surface hydrophobicity (S_o) for the myosin subfragments, except cod heavy meromyosin where the increase in S_o between 45–55°C did not correspond to an increase in cross-linking ability. The lessened aggregation ability of herring myosins may be due to the low cross-linking of the HMM (S-2) region.     

Extraction of Cholesterol and Other Lipids from Dried Egg Yolk Using Supercritical Carbon Dioxide

Supercritical carbon dioxide extraction was investigated for removal of cholesterol and lipid components from dried egg yolk. Four different combinations of pressure and temperature were used including 163 atm/40°C, 238 atm/45°C, 306 atm/45°C and 374 atm/55°C. As temperature and pressure were increased, more lipids and cholesterol were removed. Extraction at 306 atm/45°C or 374 atm/55°C removed approximately two-thirds of the cholesterol. Phospholipids and protein were concentrated under the supercritical extraction conditions used. Sponge cake volume was significantly (P < 0.05) improved at extraction conditions of 163 atm/40°C, 238 atm/45°C and 306 atm/45°C, which may have been due to higher phospholipid and protein concentrations. Only extraction at 374 atm/55°C significantly (P < 0.05) impaired emulsion stability of egg yolk.     

On the Acid Resistance of Starch Granules

When potato starch was hydrolyzed to form Nägeli amylodextrin by 16% sulfuric acid at 30°C, only the amorphous portion of the starch granules was deteriorated. The crystallinity of Nägeli amylodextrin showing the hydrolysis ratio of 0.22 was 1.28 times as large as that of original starch. The hydrolysis process at above 45°C was given by two exponential equations. The value of acid resistance portion (C_o) at 30 and 38°C was 100%, while the values at 45, 50 and 55°C were 67, 38 and 18%, respectively. The high value of C_o generally showed the high acid resistance in the various starches. Sweet potato and waxy rice starches were more easily hydrolyzed than other starches, although they gave the relatively high value of C_o. Thus, it was slightly more difficult for low acid resistance portion of potato starch to be hydrolyzed than for that of other starches. Moreover, that of waxy rice was easily hydrolyzed.     

Effect of preheating temperature on the microstructure of walleye pollack surimi gels under the inhibition of the polymerisation and degradation of myosin heavy chain

BACKGROUND: The physical attribute of heat‐induced gel texture is highly dependent on the microstructure of the gel. In this study the microstructures of walleye pollack surimi gels preheated at various temperatures with and without inhibitors (ethylenediamine‐N,N,N′,N′‐tetraacetic acid, iodoacetamide and leupeptin) were observed with a natural scanning electron microscope. RESULTS: Without inhibitors, gels preheated at 30 °C showed a fine and uniform network structure together with the highest polymerisation of myosin heavy chain (MHC) and the highest gel strength. At 60 °C, gels exhibited a broken, disrupted and loose cluster‐like structure together with the highest degradation of MHC and the lowest gel strength. Under the inhibition of polymerisation and degradation of MHC a fine network was observed up to 40 °C during preheating. However, after a second step of heating at 80 °C the microstructures were disrupted and resembled each other regardless of the preheating temperature. CONCLUSION: Heat‐induced gel formation is related to the polymerisation and degradation of MHC and the microstructure of the gel during preheating. Gelation occurred during setting even under the inhibitory condition, and the formation of covalent bonding by transglutaminase is not essential to the formation of a three‐dimensional network during setting but is essential to the gel strength enhancement effect of setting by subsequent heating at 80 °C. Copyright © 2010 Society of Chemical Industry