Differential Scanning Calorimetry of Beef Muscle: Influence of Postmortem Conditioning

Differential scanning calorimetry (DSC) was used to follow the changes in the endothermic transitions of beef muscle during conditioning. Sternomandibularis muscle held at 5°C from 2–8 days postmortem resulted in a significant (P < 0.05) drop in the total heat of transition (ΔH) from 3.8 to 3.0 J/g. The myosin transition decreased from 57.8° to 55.2°C while the actin transition increased from 81.8° to 83.2°C (P < 0.05). Storage time and temperature were varied to generate a response surface of thermal data for psoas major and semimembraneosus muscle. The decrease in °H of psoas major was optimal between 10° and 13°C. Total ΔH of semimembraneosus (3.9 J/g) was significantly greater (P < 0.05) than that of psoas major (3.4 J/g).     

Differential Scanning Calorimetry of Beef/Kappa-Carrageenan Mixtures

The thermal properties of kappa-carrageenan (KC) and/or beef under various ionic conditions were evaluated using Differential Scanning Calorimetry (DSC). The single endotherm observed for 2% aqueous KC (Tmax at 53°C) shifted to 54–59°C with addition of 1–3% NaCl and 0.35% sodium tripolyphosphate. Three endotherms were observed for post-rigor bovine semimembranosus meat (Tmax at 57, 66 and 80°C). Addition of salt/phosphate to beef had greater effects on Tmax than did 2% KC. On rescanning following 24 hr refrigerated storage, beef samples showed no thermal response, while KC treatments and beef/KC mixtures showed single endotherms at 53–63 and 69–76°C, respectively, indicating a wide shift in melting temperature of KC both in the presence of meat and at higher ionic strength.     

Differential Scanning Calorimetry of Fish Muscle: The Effect of Processing and Species Variation

Differential Scanning Calorimetry (DSC) has been used to study the thermal properties of fish muscle proteins and to measure the extent of their denaturation under various processing conditions. Fish myosin was susceptible to denaturation by frozen storage and dehydration. Denaturation of certain fish proteins was partially reversible. Although fish myosin was very unstable, its thermal stability was found to increase in species adapted, to higher environmental temperatures.     

Comparison of Sarcomere Length to Other Predictors of Beef Tenderness

SUMMARY– Sarcomere length in the longissimus dorsi muscles of 20 bovine animals was compared to other variables in predicting tenderness (Allo-Kramer shear) in two muscle positions (medial and lateral) and at four cooking temperatures (60, 64, 68 and 72°C). The medial muscle position was less tender, had shorter sarcomeres and had higher correlations between sarcomere length and tenderness than the lateral muscle position. In neither position did sarcomere length account for tenderness variation that was unaccounted for by combinations of other commonly-used carcass variables indicating that a single measure of sarcomere length at a given position is of little value in predicting tenderness if certain carcass parameters are known.
Comparison of sarcomere length with resistance to shear across the cross section of 5 additional longissimus dorsi muscles showed that very small differences in contraction state were associated with marked differences in tenderness in restricted muscle areas. The study emphasizes the importance of post-rigor contracture to tenderness but indicates that several estimates are necessary to characterize a single muscle.     

Differential Scanning Calorimetry of Rice Starches

DSC thermograms from 5–135°C of eight rice starches, pretreated with sodium dodecyl benzenesulfonate (DoBS) to remove milled rice proteins, gave gelatinization endotherms with characteristic temperature ranges. Good positive correlations were found between gelatinization temperatures measured by DSC and photometry, and between gelatinization enthalpies and gelatinization temperatures. The enthalpy of the amylose-lipid endotherm at 90–97°C was less for two DoBS-prepared rice starches than for the same pronase-treated starches. The endotherm was absent in waxy starch, and its enthalpy followed the level of lipids extracted by cold water-saturated butanol (WSB). It was concluded that DoBS treatment removed and replaced some of the starch lipid. Although this DoBS did not form a complex with amylose that was observable by DSC, the adsorbed DoBS was extracted by hot WSB.     

Differential Scanning Calorimetry of Mung Bean Starch

Mung bean starch-water mixtures at water content between 13.6% and 90.2% (volume fraction of water V₁ 0.20 and 0.94) were studied by differential scanning calorimetry (DSC) and subjected to microscopic examinations afterwards. Only a monophasic endotherm appeared for water contents above 67% while for water contents between 67% and 37.3% a biphasic endotherm was found by DSC. No endothermic transition was observed for water levels below 37.3%. The melting temperature of the most perfect crystallites was correlated to the volumetric fraction of water, thus, enthalpy, entropy and extrapolated melting temperature of the transition were calculated.     

Determination of Amylose by Differential Scanning Calorimetry

A differential scanning calorimetry (DSC) method for the determination of amylose as its amylose-L-α-lysophosphatidylcholine (LPC) complex is described. Potato amylose/amylopectin mixtures covering the range of 0–95% amylose were heated in the presence of LPC, cooled and then reheated to follow melting of the amylose-LPC complexes formed during the cooling phase. A linear relationship (r = 0.98) was obtained between the amylose content of the mixtures and the enthalpies of the amylose-lipid complexes. This linear calibration was used to predict the amylose content of various native starches, rice flours, wheat flour, durum wheat semolina, and lyophilized raw potato on the basis of the melting enthalpy of their amylose-LPC complexes. Except for the potato samples, amylose contents determined by the DSC method were in good agreement with those obtained from a colorimetric assay.     

Amylose Chain Association Based On Differential Scanning Calorimetry

Amylose and lipid depleted starches from amylomaize, pea, maize, wheat, potato, and waxy maize were heated from 20°C to 180°C, cooled to 4°C, and then reheated to 180°C in a differential scanning calorimeter (DSC) in excess water. Cooling curves of the amylose and starch melts showed exothermic transitions (< 70°C) attributed to the mechanism of amylose chain association. Amylose/amylopectin mixtures covering the range 0–95% amylose were similarly heated and cooled. The association of linear amylose chains was restricted by amylopectin.     

Measurement of Food Thermal Conductivity Using Differential Scanning Calorimetry

To measure thermal conductivity of foods, an attachment to a differential scanning calorimeter was constructed. A needle probe with a 40 gauge type-T thermocouple was used to measure the temperature of a cylindrical food sample. The DSC heating pan temperature was maintained at 40°C, and then raised to 50°C. The average thermal conductivities of rutabagas, radish, parsnip, turnip, potato, green apple, and carrot were 0.447, 0.499, 0.392, 0.480, 0.552, 0.405, and 0.564 W/m°C, respectively, for a temperature range between 40–50°C. The DSC method was reliable, precise, and a relatively rapid technique for determining thermal conductivity of foods.     

Differentiation of Honey from Melipona Species Using Differential Scanning Calorimetry

Differential scanning calorimetry (DSC) was used to study the thermal behavior of Colombian honeys produced by the honey-bee Apis mellifera and by three species of stingless bees: Melipona fuscipes, Melipona favosa favosa, and Melipona compressipes. The honey samples were collected every 2 months over the course of year (August 2014 to August 2015). Up to four thermal transitions (trs₁–trs_4a, trs_4b) were found in the honey samples: M. fuscipes (trs₁–trs_4a), M. favosa (trs₁–trs_4a, trs_4b), M. compressipes (trs₁, trs₃, trs_4a), and A. mellifera (trs₁, trs₃, trs_4a). Statistical analyses showed significant differences in enthalpies of each transition between species; therefore, DSC analysis can be used as a finger-print to differentiate the honeys of species.     

Differential Scanning Calorimetry. Study of Amylose and Its Derivatives

Glass transition (T_g) and melting (T_m) temperatures of aliphatic and aromatic esters of amylose have been measured. As the chain length of pendent group is increased both T_g and T_m get decreased. An average value of T_g/T_m≃0.8 obtained for these esters, showed that they are moderately less flexible unsymmetrical polymers. Heat of fusion (ΔH_f) for the esters has been calculated. In the case of aliphatic esters, it has been found that as the chain length of pendent group is increased, the heat of fusion is decreased.     

Differential Scanning Calorimetry Study of the Wheat Grain Cooking Process

Gelatinization of wheat grain endosperm during cooking was studied under simulated cooking conditions using differential scanning calorimetry (DSC). A DSC thermogram of the wheat grain section heated in excess water shows biphasic transition characterized by peak temperatures of 64.5°C and 86°C. Similar shape and temperatures are indicated on the thermogram of isolated wheat starch heated in limited water conditions (48.8% w.b.). During the cooking process, exposure of wheat grain endosperm to heat without adequate moisture causes alteration of the starch structure, which in turn, causes a broadening of the gelatinization temperature range and shifting of endothermal transition toward higher temperatures.     

Screening Potato Starch for Novel Properties Using Differential Scanning Calorimetry

Thermal and other physicochemical properties of starch from 42 potato genotypes were studied to find those with unique properties for food use, and to analyze relationships between thermal and other physicochemical properties. Onset and peak transition temperatures and gelatinization enthalpy intercorrelated. Transition temperatures intercorrelated with pasting temperature using a Brabender Visco-amylograph. Gelatinization entbalpy correlated with Brabender pasting temperature and peak paste viscosity, and onset temperature correlated with phosphorus content. Genotype E55–3.5 with highest onset and peak transition temperatures also had highest phosphorus and peak Brabender viscosity. DSC might be useful for rapidly screening samples of <1g starch for such. Potato starch DSC characteristics did not correlate with amylose, intrinsic viscosity, or water-binding. For 10 genotypes from successive years, correlations were observed for pasting temperature (r = 0.83), phosphorus content (r = 0.80), and stability ratio (r = 0.66). Direct comparison between samples from consecutive years showed good reproducibility for amylose, but not for phosphorus or pasting.     

Studies of Thermal Denaturation of Oat Globulin by Differential Scanning Calorimetry

Thermal denaturation of oat globulin was studied by differential scanning calorimetry (DSC). Prior heat treatments at 100°C and 110°C resulted in a progressive decrease in enthalpy (ΔH) indicating partial denaturation. Marked increase in denaturation temperature (T_d) and onset temperature (T_m) and decrease in width at half peak height (ΔT_1/2) suggest that the preheated protein assumed a more compact conformation or associated to a complex structure with higher thermal stability and cooperativity. The heated globulin was segregated into soluble and insoluble fractions containing native and denatured protein respectively. The denaturation kinetics of oat globulin was studied and results show a reaction order of 2.5 and an activation energy of 505 KJ/mol. Heat treatments caused a pronounced increase in activation energy and pre-exponential factor.     

用差示扫描量热法测定调温针织物的热性能

介绍了差示扫描量热法（DSC）的原理、用途及用法,测定了罗纹空气层织物的相变温度和相变焓,得到了其DSC曲线图。结果表明该织物具有良好的温度调节功能。     

Study of Thermal Properties of Oat Globulin by Differential Scanning Calorimetry

The thermal behavior of oat globulin was studied by differential scanning calorimetry (DSC). The effects of pH, salts, and of various structure perturbants upon thermal characteristics were determined. Raising or lowering pH from near neutrality reduced denaturation temperature. (T_d), enthalpy (ΔH) and cooperativity indicated by increase in width at half height (ΔT_1/2). The effect of salts on thermal stability was related to their position in the lyotrophic series and suggests involvement of hydrophobic interaction in the thermal stability of oat globulin. Increasing concentrations of urea progressively lowered T_d and ΔH and increased ΔT_1/2; sodium dodecyl sulfate (SDS) lowered ΔH without affecting T_d; ethylene glycol (EC) lowered T_d without changing ΔH. Dithiothreitol did not affect DSC characteristics suggesting that disulfide bonds do not contribute to the thermal response of oat globulin.     

Differential Scanning Calorimetry Properties and Paper-Strength Improvement of Cationic Wheat Starch

Cationic derivatives of normal corn and wheat starch were produced and investigated. Differential scanning calorimetry showed that substitution lowered the starch gelatinization temperature, the gelatinization endotherm, and the temperature of amylose-lipid V-complex dissociation. Substitution lowered the starch-iodine color and inhibited precipitation of the amylose-alcohol complex by standard fractionation techniques. Cationic derivatives of normal corn and wheat starch gave similar improvements in dry strength of paper when added at the wet-end.     

Retrogradation of Rice Starches Studied by Differential Scanning Calorimetry and Influence of Sugars, NaCl and Lipids

In waxy and nonwaxy rice starch gels the retrogradation process was a function of time. The enthalpy for rice starch gel with high amylose content was higher than those for low amylose content or for waxy starch samples. In all rice starch gels, samples stored under 25°C had lower enthalpy and higher endothermic onset temperature. In presence of sucrose, extent of retrogradation increased, while in presence of NaCl, it decreased. Effects of maltose, glucose and lipids were dependent on rice starch gel and storage temperature.     

A Comparison of Isometric Tension and Differential Scanning Calorimetry Measurements on Meat

The isometric tension developed in strips of stretched and cold-shortened muscle samples while heated up to 85°C showed six transitions. Preheating at 50°C or 60°C eliminated most transitions in samples from very young animals except for those near 80°C. Differential scanning calorimetry results obtained for samples from young and old animals were similar, but the peak assigned to connective tissue changed from 61°C to 65°C with age. The age effect indicated some of these differences were due to collagenous connective tissue. The transitions near 80°C were effectively eliminated by a pressure treatment known to denature actin—an indication that actin might still be structurally viable at temperatures under or close to 80°C.