摘要:

SUMMARYChanges were determined in total and water‐soluble calcium and magnesium content and in the pectic substances of Bartlett pears during maturation and storage. The data indicate a change in metabolic processes when the fruit is removed from the tree. In maturing fruit, about 48% of calcium and 65% of magnesium are present in soluble form. Both cations generally decreased during maturation. The Mg/Ca ratio varied with growing conditions and may be related to soil composition. The data indicate that mare, total pectin, water‐soluble pectin, total calcium, and total magnesium arc correlated with firmness. The relationship of soluble calcium and magnesium to firmness is radically different in detached fruit from that in fruit on the tree. Analyses of data indicate that the “bound” calcium and magnesium are present in concentrations far greater than the total available carboxyl groups of pectin, and that protopecin content is not related to calcium‐ or magnesium‐bound pectinic acid chains. In detaching ripening fruit, when a general breakdown begins there is a good correlation of all data wi

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1962.tb00135.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

SUMMARYShear‐force values were markedly and significantly higher at meat temperatures of 80°C (well‐done) than at 61 °C (rare) in longissimus dorsi (LD) steaks, but only slightly higher in biceps femoris (BF) steaks from 180 animals. Neither muscle showed significant differences between shear‐force values at 80 and 100°C. The two muscles had similar shear‐force values at 61 °C, although the connective tissue scored much tougher in BF than in LD steaks. Correlations were low between shear‐force values and panel scores for tenderness of connective tissue. The highest coefficients between shear‐force values and panel scores were in LD cooked to 80 and 100°C—for softness to. tooth pressure, ease of fragmentation, and adhesion. These indicate that low scores (tough meat) were associated with high shear‐force values. Correlations for all possible combinations of shear‐force values for the two muscles and the three conditions of cooking were made. Within LD all coefficients were significant and high, which indicated that ranking of the animals for shear‐force value was similar at all temperatures within this muscle. Within BF the only high coefficient was for 80 vs. 100°C. Those involving the two muscles together were not high and not always significant. Thus, shear‐force values of one muscle would not be satisfactory for indicating the tenderness of another muscle in the same carcass. Variation was found among the various core positions within a steak.Extensibility of muscle fibers was greater at 100 than at 61 °C. This was significant in LD but frequently not significant among the lots in BF. Extensibility was rather closely related to shear‐force values at both temperatures in LD, but only at 100°C in BF. Availability of muscle fibers long enough for these determinations (5 mm) varied widely in BF. This availability in the BF steaks cooked to 100°C appeared to be

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1962.tb00136.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

SUMMARYReticulataxanthin and tangeraxanthin were obtained from tangerine peel; both occurred in the diol fraction on countercurrent distribution, and on chromatography were found on the column above zeaxanthin as violet‐red and violet bands, respectively. Both contained a carbonyl group as a part of the conjugated‐double‐bond system. Reticulataxanthin was shown to be different from capsanthin, hydroxycanthaxanthin, and citraurin. Both of these carbonyl earotenoids apparently contained fewer than 40 carbon atoms, perhaps 34

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1962.tb00137.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

SUMMARYEarlier work has shown that when the concentration of tissue salts in liquid solution in frozen cod is increased by freezing at a certain rate, the rate of denaturation of the proteins of the flesh is enhanced during subsequent cold storage. The present work is concerned with conditions under which the proportion of ice and concentration of tissue salts decreases, and with the subsequent behavior of the muscle in cold storage.Cod were frozen before the onset of rigor mortis, vacuum‐dried at –29°, embedded in paraffin and histologically sectioned. The ice crystals showed up as holes. Measurements of the areas of muscle and ice in photographic enlargements of the sections showed that the pre‐rigòr frozen fish formed relatively less ice than post‐rigor frozen fish under the same conditions. It was further shown that the pre‐rigor fish then underwent less denaturation after cold storage than did the controls.Storage time/denaturation curves at narrowly‐spaced temperatures near the melting point showed that the rate of denaturation did not continue to increase as the melting point was approached. Above a certain temperature the rate began to decrease, and this again appeared to be due to the decrease in the proportion of ice, increase in free water, and consequent dilution of tissue salts.The effect of decreasing the amount of ice in the tissue by the use of glycerol, and of the abolition of ice altogether by ultra‐rapid freezin

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1962.tb00138.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

SUMMARYIn the flesh of certain species of fish, autolytic hydrolysis of some lipids may he totally inhibited. Examples are the hydrolysis of triglycerides in herring and of phospholipids in dogfish. In other cases an initially slow rate of hydrolysis of phospholipids may be followed by a faster rate. Such initial partial inhibition is exhibited, for example, in cod flesh maintained at 0°C. This initial “lag” may be abolished by freezing at either a very fast or a very slow rate, followed by thawing, but not by freezing at an intermediate rate. No comparable lag has been observed in fish maintained in the frozen state at any temperature, regardless of freezing rate. In unfrozen cod, or in cod maintained at −7°C and below, a terminal inhibition to the “rapid” phase becomes evident at about 75% hydrolysis of the total phospholipids, and this is followed by extremely slow further breakdown. At −2.5 to −4.7°, however, the “rapid” phase appears to proceed to completion. Hydrolysis of phospholipids is promoted by the frozen state in two ways: a) abolition of any initial lag, b) increase of reaction rate. The reaction rate passes through a maximum at about −4°C and even at −

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1962.tb00139.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

SUMMARYAn apparatus was developed to study the extensibility and elasticity characteristics of muscle fibers before and during the onset of rigor mortis. A variable load (weight) was applied to a muscle specimen held in a chamber under controlled conditions maintained by a thermostatically regulated cartridge heater, cooling coil, and gas inlet. A solenoid cell, energized by a cyclic timer, was used to release and apply the load in a direction longitudinal to the vertically mounted specimen. A lever attached to the specimen‐loading, system transmitted the extensibility and elasticity of the specimen to the armature of a differential transformer. The output voltage, from the secondary transformer winding was directly proportional to displacement of the armature. This AC output signal was rectified and transferred to a DC recording microammeter. The time course of rigor mortis was not influenced by loading and unloading interval or size of muscle strip, and was found to be temperature‐dependent, being prolonged as temperature was decreased. The white fibers of the semitendinosus muscle were found to have a considerably longer delay phase than the red fibers. The relations between the time course of rigor mortis and the ultimate properties of the muscle were discus

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1962.tb00140.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

SUMMARYDiethylaminoethyl‐cellulose (DEAE) was used in an ion‐exchange chromatographic fractionation of commercially prepared horse‐radish peroxidase. One major fraction was separated from other minor fractions and used for heat inactivation and reactivation work. Heat inactivation was carried out at 250–300° F, with most of the inactivation work at 280° F. Peroxidase activity was assayed in measuring the rate of utilization of hydrogen peroxide in the formation of tetraguaiacol from guaiacol. The concentration of tetraguaiacol was measured with a recording spectrophotometer. The ionic strength of the buffer solution in which the peroxidase was heated had an effect on its inactivation. Within limits, the higher the ionic strength the greater the heat inactivation of the enzyme. Activity was maximum at pH 7. Purified peroxidase heated 30 set at 280° F and stored 24 hr at 72° F, with the heat treatment and storage time repeated three times, decreased in activity as a first‐order reaction. The storage temperature of heat‐inactivated peroxidase affected the rate and degree

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1962.tb00141.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

SUMMARYColor changes in disrupted tissue of red beets were studied under various conditions with a Hunter color and color‐difference meter. Results showed that both autoxidation and enzyme‐catalyzed oxidation of brown‐pigment precursors were responsible for the darkening of beet tissue. Histochemical studies on the localization of phenolase in red, beets showed that the vascular tissue was the major site of enzyme activity. Apparently, the cell walls contained a small amount of phenolase. High phenolase activity was observed in both a beet extract and washed pulp of beets. Data are presented on the optimum pH and substrate specificity of beet phenolase. A solution containing 2% sodium carbonate and 5% sodium chloride was found to be a good solvent for extraction of the phenolase from washed beet pulp. At least four phenolic compounds were separated by paper chromatog

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1962.tb00142.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

SUMMARYNineteen free amino acids were identified and quantified in the dialyzable fraction from fermented bread doughs ready for baking. Amino acids account for the majority of the dialyzable nonvolatile amino compounds in this fraction. Nine of the amino acids found in bread doughs were also identified in a preferment brew. peptides did not appear in the dialyzable extracts, and are assumed to be absent, or present in very low concentrations, in the doughs. Most of the amino nitrogen of fermented doughs remains in the nondialyzable fraction. The amino acid fraction, soluble‐protein fraction, and volatile nitrogen compounds, measured as ammonia, make minor contributions to the total amino content of bread dough

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1962.tb00143.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

SUMMARYThe kinetics of thermal inactivation of peroxidase were found to he first‐order for the range of temperatures 85–100°C. The experimental activation energy was 25.1 kilocalories per mole; free energy change, 27.0–27.5 kilocalories per mole; and entropy change, a negative 7.39–7.89 calories per mole degree. This indicated that the transfer of energy was extremely slow or the activated molecule was actually more rigid than the native molecule, the latter being more likely than the former. No regeneration occurred when peroxidase had been completely inactivated.Regeneration was found to involve a lag period of approximately 20 hr, a rapid rate period of l‐2 days, a point of maximum regeneration at 2–10 days, and finally a decrease in activity after inactivation.The thermal destruction time (z value) of 49.8°F indicated that in high‐temperature short‐time processes the criterion for sufficiency might necessarily be based on the time required to inactivate peroxidase rather than on the time required to ster

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1962.tb00144.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY