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.     

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).     

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 of Air-Classified Starch and Protein Fractions from Eight Legume Species

The thermodynamic parameters of eight legume flours were interpreted following differential scanning calorimetry (DSC) of their air-classified starch and protein fractions. Samples of legumes from different sources, and their air-classified fractions, showed consistent peak gelatinization (T_G) and peak denaturation/aggregation temperatures for each legume species. However, enthalpies of gelatinization and denaturation/aggregation were highly variable, were not specific to species, and appeared to be determined primarily by environmental conditions during seed development. The T_G values for the starch fractions were closely correlated to the initial pasting temperatures but the viscosity characteristics of the starch slurries were not associated with DSC parameters or the amylose contents of the starch fractions. The amylograph viscosity curves lacked a distinct pasting peak and showed stable viscosities during the heating cycle.     

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.     

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.     

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.     

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.     

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.     

Effect of Moisture on the Thermal Behavior of Strawberries Studied using Differential Scanning Calorimetry

Differential scanning calorimetry was used to determine the thermal transitions in fresh and freeze-dried strawberries and the moisture dependence of these transitions. The freeze-dried strawberry samples had a glass transition at 30–60°C, and the melting endotherm of the dried products was similar to that for freeze-dried sugars. The glass transition temperature of humidified samples was a linear function of the water activity; it decreased with increasing moisture content. Ice was found to melt at a moisture content of 21.4% or above. The melting of ice in strawberries was similar to that in sugar solutions and fruit juices.     

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.     

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.     

差示扫描量热技术研究甘油二酯的热力学性质

甘油二酯是存在于各种动植物油脂中的天然微量成分,因其具有安全、营养、人体相容性高和加工适应性好等优点而被作为一种多功能添加剂,广泛应用于食品和化妆品等行业中。甘油二酯的热力学性质对其功能性有很大的影响,不同来源的甘油二酯的初始结晶温度、峰值温度和热晗值等热力学性质不同。差示扫描量热技术是甘油二酯热力学性质研究中应用最广泛的热分析技术之一,具有灵敏度高、分辨率高、适用范围广、操作简单、快速和重现性好等优点。主要对差示扫描量热技术的原理和分类进行论述,进一步对该技术在甘油二酯的热力学性质的研究方面进行综述。     

Effect of Chlorine Treatment on Wheat Flour and Starch: Measurement of Thermal Properties by Differential Scanning Calorimetry

Differential scanning calorimetry (DSC) was used to study the effect of chlorine treatment of wheat flour on the heat of gelatinization of the wheat flour and starch. The DSC thermograms were corrected for heat capacity changes and thermal lag. An endothermic transition occurred in both flours and starches at a temperature commonly associated with starch gelatinization. The enthalpy (ΔH) for the starches was concentration dependent. The chlorine treatment did not affect significantly the transition temperatures nor enthalpies of either the flour or the starch isolated from it. Addition of sucrose delayed the onset of gelatinization and increased the ΔH for both treated and untreated wheat flours and starches.     

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.     

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.     

A Kinetic Study of Bread Staling by Differential Scanning Calorimetry. The Effect of Painting Loaves with Ethanol

Differential scanning calorimetry (DSC) has been used to follow changes in the rate of development of an endotherm associated with the starch fraction of bread during ageing, as a result of ethanol treatment. Treatment consisted in painting the surface of loaves with ethanol after they had been baked and allowed to cool. DSC data were fitted to Avrami equations. The rate of development of the “staling endotherm” was lower for bread treated with alcohol than for untreated controls. For comparison, crumb compressibility measurements were made. It could be concluded that painting loaves with ethanol led to a reduction in the rate of increase of crumb modulus with storage time. The site of action of the alcohol remains to be established, although one possibility could be the amylose.     

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。