Showing papers in "Journal of Food Science in 1967"

The Synergistic Taste Effect of Monosodium Glutamate and Disodium 5′-Inosinate

Abstract: SUMMARY— The synergistic phenomenon between the taste of monosodium glutamate (MSG) and disodium 5′-inosinate (IMP) [7.5 H2O] was studied and the relationship expressed as a mathematical model. The phenomenon could be measured quantitatively by fitting the proposed model to the results of the experiment. The concentration of MSG equivalent to the taste intensity of that given by the mixture of MSG and the ribonucleotide is represented by the following equation: y = u +γuv where y is the equivalent taste intensity of the mixture in terms of g/dl of MSG, u is equal to g/dl of MSG in the given mixture, v is equal to g/dl of sodium 5′-inosinate in the given mixture, and γ is a constant. The γ value for IMP was calculated from extensive sensory testing as 1.218 × 108.

The Reaction of Myosin with Malonaldehyde

Abstract: SUMMARY— The protein malonaldehyde reaction was studied as a potential mechanism of protein denaturation in muscle, especially during frozen storage. Myosin, a structural protein of muscle, was reacted at pH 6.8 and ionic strength 0.5 with malonaldehyde, an oxidation product of polyunsaturated fatty acids. The rate of reaction with the s-amino groups of myosin was greater at -20° than at 0° and was almost as great as that at +20°. The same relationship was observed when the decreasing malonaldehyde concentration was measured in the protein-malonaldehyde reaction mixture. Amino acid analyses before and after reaction at 100° for 60 set showed that malonaldehyde reacted preferentially with histidine, arginine, tyrosine, and methionine. In frozen solution, malonaldehyde reacted with lysine, tyrosine, methionine, and arginine in decreasing order of intensity, but it did not react with histidine. The increased rate of reaction in the frozen system is explained as a concentration effect and as a catalytic effect involving the ice structure.

Growth Inhibition of a Pseudomonas by Carbon Dioxide

Abstract: SUMMARY— Growth rate studies were conducted with Pseudomonas aeruginosa to measure the inhibitory effect of CO2 when such variables as temperature, O2, tension, pH, and ionic strength of the glucose-salts medium were controlled. Depletion of O2 did not limit growth until more than 75% (v/v) of the air was replaced with nitrogen. Generation time increased with ionic strength of the medium. The influence of pH in the range of 6.0 to 7.4 on the growth rate was negligible. When these variables were controlled, a linear relationship between generation time and CO2 composition of the gas phase was observed. At 70% CO2 (v/v), the generation time was nearly doubled. Thus, CO2 inhibits the metabolism of the organism, and this inhibition is due to gaseous CO2 in the air only when other environmental factors are controlled.

Factors Affecting Collagen Solubility in Bovine Muscles

Abstract: SUMMARY— Solubility of intramuscular collagen was studied as affected by chronological maturity in 15 bovine longissimus dorsi and 15 semimembranosus muscles and as affected by post-mortem contraction state in the semitendinosus of 7 animals. Collagen solubility decreased significantly with each advancing maturity group in both longissimus dorsi and semimembranosus muscles. Collagen solubility was also higher (P < 0.05) in the longissimus dorsi than in the semimembranosus, except in the E maturity group. It was also related to panel tenderness in both muscles (r = 0.77 and 0.81 (P < 0.01) for longissimus dorsi and semimembranosus muscles, respectively. However, within-maturity group correlations of solubility of collagen and tenderness were low and nonsignificent. Collagen content did not differ significantly in longissimus dorsi muscles of animals of A, B, and E maturity groups; however, the semimembranosus had more collagen (P 0.05) to panel tenderness in either muscle (r =−0.42 and −0.48 for longissimus dorsi and semimembranosus, respectively). Neither collagen solubility nor collagen content was significantly affected by post-mortem contraction state. Furthermore, collagen solubility did not increase significantly with post-mortem aging up to ten days.

Total Pigments and Myoglobin Concentration In Four Bovine Muscles

Abstract: SUMMARY —This research was to determine whether quantitative differences in total pigment and myoglobin concentration could be detected, chemically, in muscles which differed in visual color. For this purpose, a portion of the longissimus dorsi, psoas major, biceps femoris, and semitendinosus muscles was removed at specific locations, from choice-grade steer carcasses, for use as experimental material. Each muscle was subjected to total pigment, myoglobin, fat, and moisture analysis. Hemoglobin content was determined by the difference between total pigment and myoglobin concentrations, Correction of total pigment and myoglobin concentration for fat and/or moisture was used to determine its influence upon the variation in the quantity of muscle pigmentation. Precise results were obtained with the total pigment and myoglobin procedures. Total pigment concentration was greatest in the biceps femoris and least in the semitendinosus. Little difference was obtained between the longissimus dorsi and psoas major. Myoglobin concentration, in decreasing order of magnitude, for the muscles studied was biceps femoris, longissimus dorsi, psoas major, and semitendinosus. The difference between myoglobin and total pigment concentration in the psoas major muscle was a result of hemoglobin constituting a greater portion of the total pigmentation. Results also indicated that hemoglobin contributed more to total pigment concentration and probably to muscle color than previously reported. The significance of the results obtained was not altered by correcting the data for fat and/or moisture.

Formation of Myofibrillar Fragments and Reversible Contraction of Sarcomeres in Chicken Pectoral Muscle

Abstract: SUMMARY— As morphological changes occurred in the pectoral muscles of chicken carcasses during 48 hr storage at 5°C, two notable phenomena were observed: (1) fragmentation of myofibrils and (2) reversible or irreversible contraction of sarcomeres. When blendorized, myofibrils tend to break into small fragments composed of 1-4 sarcomeres with time post-mortem. It was also found that besides an irreversible post-mortem contraction of sarcomeres generally accepted, a reversible contraction can take place under particular conditions.

Studies on the Nutritional Value of Tempeh

Abstract: SUMMARY— Protein, fat, ash, fiber content, amino acid composition, and fatty acid composition including free fatty acids and some B vitamins (thiamine, riboflavin, vitamin B6, nicotinic acid, and pantothenic acid) of tempeh and unfermented soybeans were compared. The following observations, which are significant for evaluation of the nutritional value of tempeh, were made: 1) There were no large differences in protein and ash content between tempeh and unfermented soybeans. 2) Fiber was slightly increased during fermentation. 3) The fat content of tempeh was slightly lower than that of soybeans, but the acid value was noticeably higher. 4) Free amino acids were increased during fermentation. The amount of different free amino acids in the palatable tempeh was from 1 to 8.5 times as much as that of unfermented soybeans. 5) Riboflavin, vitamin B6, nicotinic acid, and pantothenic acid were increased during fermentation, although thiamine was little altered.

Effect of the Drying Method on the Water Sorption of Dehydrated Apple and Potato

Abstract: SUMMARY —The method of drying apple and potato affects primarily the rate of sorption of water of the dehydrated product, and to a lesser degree the equilibrium isotherms. The freeze-dried products adsorbed more water vapor than the puff-dried and air-dried materials. The apparent diffusivity of water vapor was considerably higher in the freeze-dried samples than in the air-dried materials. In puff-dried samples, the diffusivity had an intermediate value. The diffusivity in freeze-dried apple and potato decreased at higher relative humidities, and the effect was opposite in air-dried samples.

Antimicrobial Action of Citrus Oils

Abstract: inhibitory effect of essential oils of orange and lemon oil and the antibiotics tylosin and nisin was tested on bacteria and fungi in nutrient media. Though the degree of inhibition varied with the culture, orange oil was a more effective antimicrobial agent than lemon oil. All other conditions being identical, 2,000 ppm of orange oil had an effect similar to 10 ppm of tylosin, on all the gram-positive cultures tried, including the spores of Bacillus mbtilis. Moreover, orange oil was the only additive that showed inhibition of growth of the gram-negative cultures, excepting Serratia nzarcescens. Yeasts, in general, were more sensitive than bacteria to orange oil, the effective dose being 500 ppm, at a cell concentration of 1 million/ml. This was a definite advantage over the antibiotics, which had no action on fungi. Though not so sensitive as the yeasts, the molds were also suppressed by orange oil at 2,000 ppm. The possibility of using orange oil as a preservative in foods is indicated.

Multiple Forms of Phenoloxidase

Abstract: SUMMARY— The phenoloxidase system in the tissues of mushrooms, potatoes, and apples was investigated using a polyacrylamide electrophoretic technique. The enzyme system was shown to exhibit the phenomenon of multiple forms. The multiple form pattern obtained was highly characteristic for each individual species and variety studied, and substrate specificity was evident. The mushroom phenoloxidase system (Agaricus campestris) was shown to consist of at least nine distinct dl-dopa-reactive multiple forms, and at least three forms reacting with I-tyrosine. Potatoes (var. Rural Russet) showed at least 11 bands of dl-dopa activity, while apples (var. Golden Delicious) had at least three multiple forms of dl-dopa activity. By introducing the “multiphase” gel electrophoretic technique a better resolution of the multiple forms was obtained. A group of closely related dl-dopa multiple forms in mushrooms had the unique ability to withstand the temperature of 70°C for one hour. Sulfite, ethylenediamine-tetraacetic acid (EDTA) and other treatments affected the multiple forms differently. Each multiple form behaved as an individual entity upon repeated elutions and electrophoreses.

Electron Microscopy of a Meat Emulsion

Abstract: SUMMARY— Techniques are described for the electron microscopic evaluation of a meat emulsion. Fat globules as small as 0.1 μ in diameter were observed to have distinct protein membranes. The continuous phase of the emulsion was fibrous, but homogeneous. After thermal processing the globule membranes were highly disrupted and the protein of the continuous phase was coagulated into dense, irregular zones.

Molecular Properties of Post‐Mortem Muscle. 4. Effect of Temperature on Adenosine Triphosphate Degradation, Isometric Tension Parameters, and Shear Resistance of Bovine Muscle

Abstract: SUMMARY– Investigations were conducted on the effect of three storage temperatures, 2°, 16°, and 37°, on the changes and relationships of certain chemical and physical properties of post-mortem bovine semitendinosus and psoas muscle. Post-mortem muscle shortening was measured with the isometer. Isometric tension development was maximal at 2°, minimal at 16°, and at 37° tension was approximately one-half that developed at 2°. The large tension development at 2° very likely originates from the same events as those in “cold shortening.” Differences in isometric tension parameters were noted between muscles in that psoas muscle developed tension and lost the ability to maintain tension more quickly than did the semitendinosus. Loss of ability to maintain tension was observed only at 2°, and this could correspond to a “resolution” of rigor mortis. Adenosine triphosphate (ATP) degradation was measured by two methods, ammonia production and bioluminescent enzymic method; the bioluminescent method proved to be the more satisfactory. A common relationship was observed between pH and ATP for both muscles and the three temperatures studied. No direct relationship was found between ATP degradation and shear resistance with the possible exception of muscle stored at 37°. Isometric tension parameters and shear resistance were related somewhat at 2° in semitendinosus muscle, but no relationship existed at 16° and 37°. Although considerable tension developed in psoas and semitendinosus muscle at 37°, shear resistance values decreased continuously, indicating that factors other than shortening are more important at high temperature and that these factors are temperature-dependent. The role of ATP degradation in tension development was difficult to interpret, since at 2°, only a small change occurred in ATP level during large tension development, and the level of ATP at 2° did not differ from ATP level in muscle stored at 16° which developed little tension. Differences in post-mortem muscle shortening at 2 and 37 are discussed.

Identification of 2‐Pentyl Furan in Fats and Oils and Its Relationship to the Reversion Flavor of Soybean Oil

Abstract: SUMMARY— 2-Pentyl furan is identified as a component of the volatile decomposition products of slightly autoxidized soybean and cottonseed oils and those of thermal oxidation of corn oil and hydrogenated cottonseed oil. The flavor threshold of this compound in oil at room temperature is 1 ppm. At concentrations of 1-10 ppm, it imparts to the oil a characteristic beany odor and flavor reminiscent of those of a reverted soybean oil. Expert organoleptic panels consistently identified a deodorized cottonseed oil containing 5 ppm of 2.pentyl furan as a reverted soybean oil. It is proposed that this compound is formed by autoxidation of linoleic acid.

Volatiles Retention During the Drying of Aqueous Carbohydrate Solutions

Abstract: SUMMARY —A study has been made of volatiles retention during the drying of aqueous solutions, by putting droplets, fixed on a wire, in an air current. The droplets were of an aqueous solution of malto-dextrin, to which small amounts of acetone had been added. Radioactive labeling permitted quick and accurate measurements of the acetone concentration in a drying droplet. During drying, a film forms on the surface of the droplet. The higher the initial carbohydrate concentration, the quicker the film forms. This film is permeable to water, but impermeable to acetone and to other volatile compounds, such as benzene, ethanol, and ethyl acetate. No satisfactory explanation for the retention can be given. In any case, adsorption is not involved.

The Sterols of Seafood

Abstract: SUMMARY The sterol composition of several varieties of seafood was assayed by gas-liquid chromatography. Cholesterol is the major sterol (over 90%) in haddock, pollock, salmon, shrimp, and lobster. The predominant sterols in oyster are cholesterol (41%) and 24.methylenecholesterol (26%), and in crab the major sterols are cholesterol (57%) and brassicasterol (37%). Scallop and clam contain a large number of sterols, the predominant one being cholesterol (26 and 37%, respectively). The sterols other than cholesterol give different chromogens in the calorimetric analysis for sterols, which may account in part for the variability in the “cholesterol” values found in the literature.

Apple Anthocyanins: Identification of Cyanidin‐7‐Arabinoside

Abstract: SUMMARY— The anthocyanin pigments of Red Delicious apples were isolated and identified from their chromatographic, spectral and chemical properties. The maior pigment was cyanidin-3-galactoside. The minor pigments were cyanidin-3-arabinoside and cyanidin-7-arabinoside. Cyanidin-7-arabino-side was isolated from a natural source for the first time. Three pigments were isolated from 74 varieties of apples, two from six varieties and only one from two varieties.

Free and Esterified Cholesterol Content of Animal Muscles and Meat Products

Abstract: SUMMARY —A method was perfected for the precise, accurate measurement of total and free cholesterol in lipid extracts of raw beef and pork muscle and meat products. The average total cholesterol content of beef and pork muscles was estimated to be 58 and 65 mg % (mg per 100 g), respectively. Both beef and pork muscles had an average cholesterol ester concentration of about 6% of the total cholesterol. Regression equations indicated that the total cholesterol content of muscle increased very slightly as the percent lipid value rose. Extramuscular adipose fat from beef and pork carcassess had total cholesterol values between about 43 and 68 mg %. Total cholesterol was estimated for some meat products. During the broiling of ground chuck samples, up to 15% of the total cholesterol in raw meat was lost in the cook drip.

A Probable Flavoring Principle in Vegetable‐Protein Hydrolysates

Abstract: SUMMARY— The characteristic seasoning flavor of hydrolyzed vegetable proteins has previously been attributed to α-ketobutyric acid formed from threonine under the conditions of acid-hydrolysis. However, pure α-ketobutyric acid is virtually odorless and tasteless, and it develops the characteristic flavor only upon ageing. The true flavoring principle is probably α-hydroxy-β-methyl-Δ.α,β-γ-hexenolactone, which is formed from the acid by dimerization, lactonization, and decarboxylation. This conversion occurs spontaneously, but is greatly accelerated under acidic conditions.

Effect of Additives and Refrigeration on Reducing Activity, Metmyoglobin and Malonaldehyde Of Raw Ground Beef

Abstract: SUMMARY— The effect of chlortetracycline (CTC), oxytetracycline (OTC), papain, and refrigerator storage temperatures on metmyoglobin (MetMb) reducing activity (MRA) and oxygen utilizing capacity of ground raw beef was investigated. CTC did not affect either MRA or oxygen utilization. OTC showed variable effects on MRA but did not affect oxygen utilization. Papain increased MRA over that of controls, and papain treated samples maintained higher MRA longer than controls. Reduction of MetMb took place in the refrigerator at both 0° and 9°C; the rate of MetMb reduction decreased with decreasing temperature. Significant positive correlations were found between MetMb and malonaldehyde in stored refrigerated meats. MRA and MetMb were negatively correlated.

Deformation Testing of Foods.

Abstract: SUMMARY— A technique is described for using certain of the special characteristics of a universal testing machine which permits small distances to be measured with precision. A number of foods were compressed to a standard force, and the deformations of the foods were then measured off the strip chart recorder which is an integral part of the machine. The high degree of precision is obtained by driving the chart at a speed which is an exact multiple of the speed of the compressing plate. Differences between the deformation characteristics of different foods are shown. The advantage of using a standard size and shape of test piece is discussed. A method is shown for overcoming the effect of small imperfections in shape of standard pieces. It is also shown that a small deforming force will usually give a better resolution between similar samples than does a large deforming force.

Apple Polyphenol Oxidase Activity in Relation to Various Phenolic Compounds

Abstract: SUMMARY— The role of various polyphenolic compounds in oxidations catalyzed by apple polyphenol oxidase (PPO) was investigated. Quercetin, quercitrin, rutin, cyanidin chloride, phloroglucinol, and resorcinol were neither substrates nor inhibitors of apple PPO. Phloroglucinol and resorcinol increased the rate of PPO catalyzed oxidation of chlorogenic acid. Esculetin and dihydroquercetin were found to be substrates of PPO. No synergistic effect was detected in the browning rates of an esculetinchlorogenic acid mixture or a dihydroquercetin-chlorogenic acid mixture. Ferulic acid, fisetin, and p-coumaric acid were generally non-competitive inhibitors, although ferulic acid inhibited competitively in one test. It was hypothesized that the conjugated system in flavones prevents these compounds from being apple PPO substrates.

An Objective Evaluation of Changes in Firmness of Ripening Bananas Using a Sonic Technique

Abstract: SUMMARY— Firmness in fruits is sometimes evaluated as being the force necessary to attain a given deformation within the product. Since modulus of elasticity is defined as the ratio of stress to strain, it should measure resistance to force and, hence, the firmness of a material. Using a sonic technique, the resonant frequencies of cylindrical specimens of flesh from Valery bananas were measured and Young's modulus of elasticity was calculated. Softening of the banana during ripening was associated with a decrease in Young's modulus of elasticity from 272 × 105 dynes/cm2 at ripeness corresponding to a light green peel color to 85 × 105 dynes/cm2 at the yellow stage. Modulus of elasticity was significantly and directly correlated with starch content, but inversely correlated with luminous reflectance and the logarithm of percent reducing sugars.

Molecular Properties of Post-Mortem Muscle.

Abstract: SUMMARY— Post-mortem changes in nucleoside triphosphatase activity of bovine myosin B have been studied by using several different modifiers with either 5 mM ATP or 5 mM ITP as substrate at ionic strengths (r/2) of 0.09, 0.19, or 0.52. Enzymic activity was determined by measuring the release of inorganic phosphate. There was very little difference in enzymic activity between myosin B isolated from prerigor, rigor (24 hr post-mortem) or post-rigor (312 hr post-mortem) muscle stored at either 2° or 16°C except that the specific activity of myosin B prepared from muscle stored for 12–24, hr post-mortem was higher than activity of myosin B prepared immediately after death. This increase cannot be explained in terms of rigor shortening, but suggests that a change in myosin conformation or in the nature of the actin-myosin interaction occurs in post-mortem muscle. If an actin-myosin interaction occurs during rigor mortis and if this association remains unchanged during extraction of myosin B, then the very low Mg++-modified myosin B enzymic activities obtained at Γ/2 = 0.19 and 0.52 indicate that this interaction is not irreversible. Extraction in the absence of ATP produced a myosin B whose ATPase activity was markedly inhibited by trace amounts of Mg++. This may be due to the absence of a-actinin in these myosin B preparations. No consistent differences in activation energies were found either at Γ/2 = 0.19 or 0.52 among the NTPase reactions of myosin B samples prepared from muscle after various times of post-mortem storage.

Studies on Salting and Drying Fish. I. Equilibrium Considerations in Salting

Abstract: SUMMARY— The following variables were determined at equilibrium between fish muscle and brine, all as functions of the salt concentration in the brine: salt concentration in the muscle, based on the volume of the muscle; salt concentration in the tissue water of the muscle; distribution coefficient of salt between muscle volume and brine; distribution coefficient of salt between muscle tissue water and brine. Secondary variables which further described the salting equilibria were also found as functions of salt concentration in the brine as follows, all based on unit weight of non-salt solids in the salted muscle: weight of salt (S/NSS), weight of water (W/NSS), and volume (V/NSS). The salt concentration based on the muscle volume was found to increase continually with increasing brine concentration, as did the salt concentration in the tissue water and the salt content expressed as S/NSS. The distribution coefficient based on the muscle volume and the water and volume contents (W/NSS) and (V/NSS) were found to increase at first, pass through a maximum, and then decrease, all with increasing brine concentration. Within the limits of experimental error, the salt concentration in the tissue water was found to equal the salt concentration in the brine, so that the distribution coefficient calculated on this basis was always equal to unity and was independent of the salt concentration in the brine. The volume per unit weight of non-salt solids (V/NSS) was found to be a direct linear function of the water content per weight of non-salt solids (W/NSS) at all temperatures studied. Little difference was found between the equilibrium salting variables when salting was carried out at 5 and at 25°C; on the other hand, possibly due to “cooking” or heat denaturation of the muscle with consequent loss of water at that temperature, all variables were considerably lower when salting was carried out at 37°C. The “mean molar activity coefficient” of sodium chloride in fish muscle was determined as a function of salt concentration in the muscle. It was found to be always greater, and to vary more sharply with salt concentration, than the corresponding activity coefficient of salt in aqueous solution.

Problems in Measuring Leucoanthocyanin Content of Pears

Abstract: SUMMARY— Four solvents, 95% ethanol, methanol, and both ethanolic and aqueous acetone, were used to extract leucoanthocyanin from Bartlett pears. Ethanol extracted approximately one-fourth, methanol one-third, and acetone somewhat less than two-thirds, based on the amount in the corresponding slurry. Conversion of leucoanthocyanin to anthocyanidin was influenced by the dispersing medium, the normality of the butanol in which the conversion was effected, and the source of the leucoanthocyanin (pear mart, slurry, or synthetic leucocyanidin). When ethanolic acetone was the dispersing medium, yields of anthocyanidin were greatest. Developer acidified to a normality of 0.025 compared to 0.6 reduced phlobaphene formation and gave higher yields of anthocyanidin except in the case of pear mart previously extracted with 70% ethanol and then dispersed in acetone. When conversion was effected at a normality of 0.025, yield of anthocyanidin from the mart of pear in acetone was somewhat less than half that obtained when ethanol was the dispersing' medium, that from the slurry was 25% greater, and the yield from synthetic leucocyanidin was almost twice as great.

Pectic Enzymes and Development of the Pear (Pyrus communis)

Abstract: SUMMARY— Changes in firmness, protein, pectinesterase (PE) and polygalacturonase (PG) were followed during enlargement, maturation, and abnormal ripening of the Bartlett pear (Pyrus communis) on the tree. Although the PE activity per pear increased during maturation, with a good correlation with total weight (r= 0.93 and 0.87 for 1962 and 1963), the amount of activity per gram fresh weight and per milligram protein decreased. There was a high correlation between PE activity and protein (r= 0.84 and 0.91 for 1962 and 1963). The specific activity of the enzyme decreased during maturation. As the fruit matured and ripened on the tree, the percent recovery of PE decreased. The use of polyvinylpyrrolidone in the extraction procedure to adsorb the phenolic compounds counteracted this trend. It was concluded that the small changes in PE activity could not account for the changes in esterification of pectin observed by other investigators. Variable results were obtained with the PG assays. Weak PG activity was observed in the immature fruit in 1962 and 1963. No activity was observed in 1966, even in the presence of polyvinylpyrrolidone.

Estimation of inosinic acid in chicken muscle and its formation and degradation during post-mortem aging.

Abstract: SUMMARY— A routine method for the extraction, chromatographic separation and ultraviolet spectrophotometric assay of ribonucleotides and their derivatives in chicken muscle was developed to study changes in ribonucleotide content of chicken muscle from the moment of death until tenderness changes are essentially complete. In this method, the mean error of duplicate analyses was ±2%, and recoveries were within ±6% of amounts added. Results indicated that the formation of inosinic acid occurred as a result of breakdown of adenosine triphosphate during the period of time between slaughter and onset of rigor-mortis. During prolonged aging (over 24 hr) or aging in slush ice (compared to aging in drained crushed ice), the Inosinic acid content of muscle decreased. Inosinic acid content of breast muscle was higher than leg muscle and increased in both muscles with the age of the birds.

Effect of Temperature on the Time Course of Rigor Mortis in Ox Muscle

Abstract: SUMMARY— Changes in length and ‘extension’ during the onset of rigor mortis in cyclically loaded strips of ox sternomandibularis muscle were found to be markedly different at 1 °C from those at temperatures over the range 537°C. The delay phase of rigor mortis was longer with lower temperature within the range 1.537°C, but was shorter with lower temperature within the range 1.15°C. The onset phase was longer with lower temperature within the range 5–37°, but was shorter at 1° than at 5°C. The change in extension was completed sooner at l° than at 5° or 15°C. At 37°C, by the time the change in extension was complete, acid-labile phosphorus had fallen to a low level, and the ultimate pH was closely approached or reached; but at 1°C, an appreciable amount of acid-labile phosphorus still remained, and the pH was considerably above the ultimate value. The shortening at 1 °C was compared to thaw contracture.

The Histology of Pre-Rigor and Post-Rigor Ox Muscle Before and After Cooking and Its Relation to Tenderness

Abstract: SUMMARY—Pre-rigor and post-rigor semitendinosus muscle was examined under the light microscope and in the electron microscope before and after cooking. During cooking, pre-rigor samples were unrestrained or restrained on stainless-steel frames at normal length and at 130% normal length. Samples which passed at 0°C into rigor unrestrained, or while restrained to the same degrees of stretch as above, were cooked post-rigor without mechanical restraint after various periods of storage. The treatments produced differences in tenderness of the muscle pieces which were related to differences seen in the ultrastructure in the micrographs. It was concluded that, provided the effects of gross connective tissue are small, tenderness in beef muscle is produced by disruption of the actin filaments and by a breaking down of the linkages between the actin and myosin filaments in the sarcomeres.

Experimental food poisoning with heat-susceptible Clostridium perfringens type A.

Abstract: SUMMARY—Clostridium perfringens type A, S-79 behaves like a gas-gangrene producing strain in its production of heat-susceptible spores both in broth and in the intestinal tract of man. However, vegetative cells ingested by human volunteers produce the food-poisoning syndrome characterized by abdominal pain and diarrhea.