Showing papers in "Journal of Food Science in 1968"

Quantitative Methods for Anthocyanins.

Abstract: SUMMARY –A qualitative technique for the determination of the individual flavonol pigments of cranberries was developed, based on cellulose thin-layer chromatography. The method was such that it was suitable for quantitative use by removing the pigment spots and measurement of the selected pigments by spectrophotometry. A quantitative technique for total flavonols, expressed as quercetin, based on spectrophotometry at 374 nm was developed. Total flavonols and total anthocyanins can be determined on the same extract.

Texture Profile of Ripening Pears

Abstract: SUMMARY— Pears of the Ovid variety were harvested at the normal stage of maturity, and ripened in a 70°F storage room. Samples of the fruit were taken out at regular intervals for texture measurements which consisted of the Magness-Taylor pressure test and a modified General Foods Texture Profile. The adhesiveness of the pears was zero. The viscosity of the whole fruit could not be measured. All other parameters of the G. F. Texture Profile (hardness, cohesiveness, elasticity, brittleness, chewiness, and gumminess) decreased during ripening at approximately the same rate as the pressure test. It is suggested that this characteristic of ripening pears is responsible for the success of a simple single measurement (the puncture test) for measuring the complex phenomenon that is called “textural quality” of pears.

Direct Spectrophotometric Determination of Fat and Moisture in Meat Products

Abstract: SUMMARY— The near-infrared spectral absorption properties of P-mm-thick samples of meat emulsions were measured by direct spectrophotometric techniques. The resulting spectra are interpreted in terms of absorptions from O-H and C-H stretching vibrations combined with scatter losses. Optical-density differences are correlated with fat and moisture contents. The difference in optical density between 1.80 and 1.725 p gave a high correlation with moisture content and the difference between 1.725 and 1.65 P gave a high correlation with fat content. Direct spectrophotometric analysis predicted fat content within a standard error of ± 2.1% and moisture content within ± 1.4%. The possibilities of this technique are explored and the problems to be solved in developing a rapid, accurate method are discussed

Olfactory Threshold, in Relation to Age, Sex or Smoking

Abstract: SUMMARY— The individual olfactory thresholds of 97 persons toward 18 odorants were analyzed statistically. There is a significant logarithmic deterioration with age, the average loss of sensitivity being 50% in 22 years. Any influence of sex or smoking is negligible.

Studies in Meat Tenderness.

Abstract: SUMMARY— The tenderness of lamb loin is affected greatly by the time-temperature pattern imposed on the dressed carcazs during the onset of rigor mortis. Very significant toughness develops in the longissimus dorsi muscles of carcasses exposed to low temperatures within about 16 hr of slaughter. This “processing toughness” is shown to be unrelated to the lack of aging. It appears to be due to muscle fiber shortening, earlier demonstrated to be responsible for massive toughening in excised muscles. Both cold shortening and thaw shortening are capable of toughness production, the latter type becoming prominent when meat, previously frozen before rigor completion, is cooked without a preliminary thawing.

Chemical deterioration of frozen bovine muscle at -4°C.

Abstract: SUMMARY— During an 8-week storage period of bovine muscle at −4°C, the total extractable protein content dropped from 91 to 51%. This decline, accompanied by a decrease in water-binding capacity of muscle, was primarily caused by the insolubilization of both sarcoplasmic proteins and actomyosin. The increase in the free fatty acid content from about 1.6 to 9.1% over the 8-week period may be attributed to phospholipid hydrolysis. The TBA number rose progressively throughout the entire storage period while the peroxide value increased to a maximum in 2 weeks of storage and then decreased to a constant value of 7.

Thermal Degradation of Black Raspberry Anthocyanin Pigments in Model Systems

Abstract: SUMMARY— The thermal degradation of anthocyanin pigments of black raspberries as influenced by pH, oxygen, sugars and their degradation products were studied. The degradation of the major anthocyanin component (cyanidin-3-digluco-side), the total isolated pigments and the pigment in the natural berry juice was retarded as the pH decreased. Under the same conditions, cyanidin was much more unstable than any of the anthocyanin containing systems. In all cases studied, replacement of the oxygen atmosphere with nitrogen enhanced pigment stability. The rate constants for the thermal degradation of cyanidin-3-diglucoside at various pH levels under oxygen and nitrogen were determined. The sugars studied accelerated pigment destruction to the same extent. Sugar degradation products were more effective than sugars in accelerating anthocyanin breakdown.

Low Temperature Growth of Salmonella

Abstract: SUMMARY—Salmonellae, normally grown at 3.5–37°C, can grow at much lower temperatures. Experimentally, minimum growth temperatbres were obtained when salmonellae were grown on the surface of agar in a temperature-gradient incubator over a temperature range of 1.1 to 12.3°C. These minimum temperatures, as determined by visible growth for 7 serotypes, ranged from 5.5 to 6.8°C. The pattern of survival or growth of S. derby, S. heidelberg, and S. typhimurium was followed by inoculating the organisms into tubes of broth and incubating the tubes in a polythermostat over a temperature range of 1.1 to 12.3°C. Minimum growth temperature obtained for S. heidelberg after 19 days' incubation was 5.3°C. The minimum growth temperature for the same length of time for S. typhimurium and S. derby were 6.2 and 6.9°C respectively. The results indicate a growth temperature shift during extended incubation of Salmonella at low temperatures. This phenomenon and the low temperature. growth capability of Salmonella could be significant in foods stored for long periods of time at temperatures above 5°C.

Cellulase Activity during the Maturation and Ripening of Tomato Fruit

Abstract: SUMMARY An enzyme that attacks carboxymethyl cellulose may be extracted efficiently from tomato fruit by salt solutions. From a high initial value in small green fruit, activity fell gradually during fruit swelling. With incipient ripeness, the activity increased again and continued to rise to the full red condition. The green areas of “blotchy” ripened fruit showed 40% less activity than the adjacent red tissue. Fruit of tomato species in the sub-genus Eriopersicon contained considerably more activity than examples from the sub-genus Eulycopersicon. Firmness measurements on fruit from both sub-genera were not significantly correlated with the cellulase activities, and from this and other evidence it is concluded that is is not a major factor controlling the softening of at fruit, at least during the ripening period.

Photoxidation of Cholesterol in Spray‐dried Egg Yolk Upon Irradiation

Abstract: SUMMARY Photoxidation products of cholesterol in spray-dried yolk exposed to nonionizing radiation were examined by thin-layer chromatography (TLC), gas-liquid chromatography (GLC) and infrared spectroscopy Irradiation of yolk solids by radiant energy from either a 40-watt fluorescent lamp (about 280 hr) or summer sunlight (5 hr) brought about the formation of at least 5 photoxidation derivatives of cholesterol as demonstrated by TLC and GLC The major oxidation products were identified as 7-ketocholesterol, 7α and 7β-hydroxycholesterols, cholesterol-5β,6β-oxide and cholestane-3β,5α,6β-triol Neither fresh yolk or unirradiated spray-dried yolk (held at 25°C for 1 year) contained significant amounts of typical autoxidation products of cholesterol

Composition of Bovine Muscle Lipids at Various Carcass Locations

Abstract: SUMMARY— Bovine intramuscular lipids extracted from the semitendinosus, triceps brachii and longissimus dorsi muscles were fractionated into phospholipids and neutral fats by silicic acid column chromatography. In spite of the wide range in total fat content at each location, phospholipids were present in all three muscles at a level of approximately 500 mg per 100 g of muscle tissue. This result, coupled with the lower total fat content of the semitendinosus as compared to the other two muscles, indicated a significantly higher percentage of phospholipid material in the total fat from the semitendinosus as compared to the triceps brachii or longissimus dorsi. The fatty acids were identified in both lipid fractions using retention time data obtained on both a polar and a non-polar column. The identity of the unsaturated fatty acids was confirmed when their peaks did not appear on the chromatographs obtained from brominated samples. There was significantly more C14:0 in the longissimus dorsi neutral fat fractions than in the semitendinosus neutral fat fractions. In the phospholipids, there was significantly more C16:0 and significantly less C18:0 in the longissimus dorsi as compared to either the semitendinosus or triceps brachii. Although the two lipid fractions of the longissimus dorsi contained slightly higher percentages of total saturated fatty acids than the corresponding fractions in the other two muscles, the effects were not significant.

Glycolytic Intermediates and Co‐Factors in “Fast‐” and “Slow‐Glycolyzing” Muscles of the Pig

Abstract: SUMMARY— The Longissimus dorsi muscles from Chester White, Hampshire and Poland China animals were used to establish certain differences in metabolic intermediate patterns between muscles with “fast” and “slow” rates of post-mortem glycolysis. Metabolic intermediate patterns were consistent with the concept that phosphorylase is the primary control site of postmortem glycolysis. Adenine nucleotide levels appeared to be the primary regulatory factors for phosphorylase. The phosphofructokinase and pyruvate kinase enzymes were also involved in post-mortem glycolytic control. Levels of high-energy intermediates (adenosine triphosphate, phosphocreatine and pyridine nucleotides) were much higher in the “O” hr samples of “slow-glycolyzing” muscles than in similar samples from muscles having “fast” rates of post-mortem glycolysis. No significant differences in levels of lactate or glucose were observed among these three groups in blood samples taken either at or 24 hr prior to the time of exsanguination.

Stepwise Discriminant Analysis of Gas Chromatographic Data as an Aid in Classifying the Flavor Quality of Foods

Abstract: SUMMARY— Stepwise discriminant analysis for classifying food samples (known independently to differ in flavor) is illustrated by computer analysis of gas chromatograms from roasted coffee and potato chips. Four lots of coffee prepared so as to differ in flavor were scored organoleptically, steam distilled, and the distillate examined gas chromatographically. By calculating all possible ratios among peak heights and subjecting these ratios to discriminant analysis, the coffee could be classified into the four flavor categories from the gas chromatographic data. The discriminant analysis procedure was set to select the ratio most critical in differentiating among the chromatograms, then move on to the next most efficient ratio until the samples were classified. The same thing was done for potato chips except headspace volatiles were used for the gas chromatographic analysis. Not only does the procedure described enable flavor to be correlated with gas chromatographic data, but the efficiency values for each ratio are useful. A compound devoid of flavor can conceivably be highly correlated with flavor; however, there is a good chance that a compound highly correlated with flavor is a flavor substance itself.

Limonin Monolactone, the Nonbitter Precursor Responsible for Delayed Bitterness in Certain Citrus Juices

Abstract: SUMMARY– Tissues of early-season navel oranges and grapefruit were found by paper electrophoretic procedures to contain a nonbitter precursor of limonin, but no significant amounts of limonin. Limonin is the intensely bitter triterpenoid dilactone responsible for the bitterness which develops in certain navel orange juices on standing. The nonbitter precursor was identified as limonin monolactone by comparison with the authentic compound prepared by partial hydrolysis of limonin and by acid-catalyzed conversion into limonin. Limonin monolactone is stable in the tissues of the intact fruit (which are not bitter) because it is apparently not in direct contact with the acidic juice. It is slowly converted into limonin (and the juice becomes bitter) when the fruit tissues come in contact with the juice, after the juice is expressed from the fruit. Limonin monolactone was not detected in late-season navel oranges or grapefruit. This agrees with the fact that juice made from these fruits does not contain limonin. Work is in progress to determine whether the naturally occurring limonin monolactone is the A-ring monolactone, the D-ring monolactone, or a mixture of the two.

The Formation of Carbonyl Compounds in Cucumbers

Abstract: SUMMARY The carbonyl contents of benzene extracts of aqueous cucumber homogenates were estimated spectrophotometrically as the 2, 4-dinitrophenylhydrazones. A large increase in the formation of carbonyl compounds occurred when cucumbers were blended with water in the presence of oxygen. This formation of carbonyl compounds was prevented by three methods: blending the cucumbers at pH 1.0; blending in an oxygen-free atmosphere; and heating whole cucumbers to an internal temperature of 77°C before blending. Chromatographic assays indicated that negligible amounts of the 2-enals, 2, 6-nonadienal, 2-nonenal, and P-hexenal are present in intact cucumbers; but a rapid synthesis of this class of carbonyl compounds occurred when fresh cucumbers were blended in the presence of oxygen. The most significant increase occurred in the formation of 2, 6-nonadienal, the aldehyde largely responsible for the flavor of fresh cucumbers. There were indications that ethanal and propanal were present in appreciable levels in intact cucumbers. These observations suggest that the characteristic flavor components of fresh cucumbers are generated enzymatically as a consequence of cutting or mechanically rupturing the fruit.

Free Amino Acids in Ham Muscle During Successive Aging Periods and Their Relation to Flavor

Abstract: SUMMARY— The free amino acids and total ninhydrin positive material (NPM) in a 1% picric acid extract from dry-cured hams were measured after six different periods of aging. Correlation coefficients were calculated between amino acid values and taste panel scores. Significant (P < .051 increases were observed for NPM, serine, glutamic acid, threonine, leucine and isoleucine (not separated), valine, phenylalanine, proline, tyrosine, alanine, glycine and histidine during successive aging periods. Correlation coefficients between NPM and the organoleptic measurements of aged flavor, acidity, elasticity, crumbliness and softness were all highly significant. It k postulated that the increase in free amino acids can be attributed to action of the naturally occurring cathepsins. The free amino acids and their changes in concentration in relationship to flavor are discussed.

Rate of Deterioration of Freeze‐Dried Salmon as a Function of Relative Humidity

Abstract: SUMMARY— The rates of several deteriorative reactions, including lipid oxidation, astacene pigment loss, carbon dioxide production, and production of non-enzymatic browning pigments, were studied in freeze-dried salmon at 37°C and at several relative humidities. Results previously obtained in cellulosic model systems containing methyl linoleate were confirmed by data on oxygen absorption as a function of moisture content. Both the rate of the initial peroxide mono-molecular decomposition and the peroxide value decreased as the water content was increased. Astacene pigment loss was reduced significantly by the higher moisture contents; non-enzymatic browning was increased. The significance of the reactivity of water at low moisture contents was demonstrated by its effect on the various reactions.

Organoleptic Identification of Roasted Beef, Veal, Lamb and Pork as Affected by Fat

Abstract: SUMMARY— A taste panel was used to study the identification of roasted beef, pork, lamb and veal by flavor alone and the effect of fat on identification. Only about one-third of the panel could identify correctly all four meats by memory of the flavors. There was an increase in the total number of correct identifications made by comparison of the unknown roasted meat samples with known standards but this was not significantly greater than the total correct responses by memory of the flavor alone. Beef and lamb, but not pork and veal, were identified significantly less often when lean ground roasts were tested than when normal ground roasts (containing fat) were used. Texture, color, mouth feel, and other factors may be important in the identification of meat. Beef, lamb and pork fat, as well as these fats after extraction with chloroform: methanol, were added to lean veal prior to roasting. Addition of beef fat did not increase recognition of veal as beef. Pork fat contained a factor increasing identification of veal as pork, but this factor was water-soluble and could be removed. Lamb fat contained a component, or a fat-soluble component, that significantly increased the identification of veal as lamb.

Formation of Nitric Oxide Myoglobin: Mechanisms of the Reaction with Various Reductants

Abstract: SUMMARY– The concentration, temperature and pH dependences of the formation of nitric oxide myoglobin (NOMb) from metmyoglobin nitrite (MetMb·NO2) were determined for nitrite and the reductants, ascorbic acid, cysteine, hydro-quinone, nicotinamide adenine dinucleotide (NADH) and glyceraldehyde. The reaction for all reductants except glyceraldehyde involves the production of a nitroso-reductant intermediate which breaks down to release nitric oxide. The latter forms a nitric oxide metheme complex (Fe+++) which is then reduced to the ferrous state (Fe++). With cysteine and NADH there is a second pathway which probably involves the direct reduction of MetMb NO2. Ascorbate and hydro-quinone form nitroso intermediates that are stabilized in alkali. The effects of oxygen, ethylenediaminetetraacetic acid and cytochrome c on the reaction were determined. Oxygen slows or inhibits the reaction, while the latter two have no effect on the reaction as studied.

Determination of Flavor Threshold Levels and Sub‐Threshold, Additive, and Concentration Effects

Abstract: SUMMARY— The flavor threshold concentrations were determined for 23 compounds composing an artificial peach beverage base. The threshold levels ranged from 52 ppm to 0.4 ppb. The threshold values were used in sub-threshold, additive sub-threshold, and concentration trials. Sub-threshold and additive sub-threshold effects resulted from only a few of the flavor combinations tried. Change in concentration of one compound in a mixture of six compounds was not readily detectable organoleptically. The difference in concentration could be detected gas chromatographically, but only if the mixtures were extracted with pentane and concentrated. By dividing the respective threshold values into the amount of each compound present in the beverage, a factor was calculated, called the “unit flavor base,” which indicated the relative importance of each compound as a flavor substance in the peach beverage. By dividing the gas chromatographic peak heights by the respective threshold values, gas chromatographic response was weighted for flavor importance. When the unit flavor base and weighted gas chromatographic response were converted into logarithms, the relation between the values was nearly linear. The correlation coefficient was 0.8691 (significant @ 0.01).

A Quantitative and Morphological Study of Bovine Longissimus Fat Cells

Abstract: SUMMARY— A quantitative and morphological study was made of bovine fat cells from three marbling groups of longissimus muscle. Tracings on acetate paper were made of the visual marbling depots and the area measured at three positions with an ocular grid for both size and distribution of fat cells. Comparisons were also made of subcutaneous, intermuscular and intramuscular fat cell size. Intrafiber lipid accumulation was observed and the average number of red fibers per bundle determined. These results indicate that traceable intramuscular fat is not a good measure of total intramuscular fat. There did not appear to be a consistent medial, central and lateral marbling pattern among the three marbling groups; however, significant differences were apparent within groups. Fat cell size increased with increases in cell mass, marbling and total chemical fat of the muscle. Fat cells accumulated and grew in close proximity to portions of the circulatory system. Lipid deposits adjacent to the muscle contained larger fat cells than was evident in the extrafascicular spaces within the muscle. Intrafiber lipid was readily apparent in approximately 35% of the muscle fibers and probably represented either mitochondria or triglyceride. The interrelationship of subjective marbling scores, chemically determined fat, fat cell size, fat cell distribution and intrafiber lipid characteristics are complex and require complete investigation before the association of muscle fat and meat quality can be resolved.

Substrates and Intermediates in the Enzymatic Reduction of Metmyoglobin in Ground Beef

Abstract: SUMMARY– Various substrates were tested for their ability to increase the reduction of metmyoglobin by donating electrons to NAD. Intermediates of the glycolytic pathway which proved to be effective were glyceraldehyde-3-phosphate and fructose-1, 6-diphosphate. Other substrates, oxidized by NAD-linked dehydrogenases known to be present in meat are a-glycerophosphate, malate and glutamate. These also increased metmyoglobin reduction when added to meat. The pathway of electron transport from NADH to metmyoglobin is believed to be mainly by way of DT diaphorase (menadione reductase) and quinones, since dicumarol, a specific inhibitor of this enzyme, partially blocked the reaction in meat. Higher levels of quinones did not accelerate the reaction.

Dielectric Properties of Commercial Cooking Oils

Abstract: SUMMARY— The finished drying of potato chips represents the first large-scale use of microwaves in the food industry on a continuous basis. Hence it was deemed desirable to study the dielectric properties of various types of commercial cooking oils. The dielectric constant (ɛ), and loss tangent (tans) of 11 commercial fats and oils have been determined at three different temperatures and at three different frequencies in the microwave range. The differences in dielectric properties among these fats and oils appear to be attributable to the phase (solid vs. liquid) of the material and generally correspond to the degree of unsaturation as evidenced by iodine values. The differences in loss factors among these fats and oils at any given temperature and frequency (within the range at which the measurements were made) are too small to be of any practical importance in selecting any one of them for use in heating processes using microwaves or in choosing an optimal frequency (300, 1000 or 3000 megahertz, MHz). Data for one of the oils (number 9) were obtained over a wider range of frequencies and indicate that the loss factor peak(s) is/are found in the frequency range of 100 to 1000 MHz. Furthermore, from the data obtained for the other oils, it should be safe to assume that this oil is representative of dielectric properties of the entire group. The dielectric properties of bacon fat rendered by microwaves are almost identical to those of bacon fat rendered by conventional means.

Studies in Meat Tenderness.

Abstract: SUMMARY— Changes during aging in the extractability of the myofibrillar proteins of meat from beef and rabbit carcasses have been examined, using a buffer which dissociates the actomyosin complex of the muscle cell. Approximately 52% of the myofibrillar proteins of unaged meat is extracted in 40 min at 2°C whereas from aged meat as much as 78% is extracted. The rate and extent of these changes are determined largely by the ultimate pH value of the meat. Similar increases in protein extraction, displaying the same pH dependence, occur during the aging of well-washed myofibrillar preparations. The increase in the percentage of myofibrillar protein extracted during aging results from either a progressive weakening of the fibrous protein linkages with the insoluble stroma of the meat cell, or from a disintegration of the insoluble stroma itself.

Action of Microorganisms on the Peroxides and Carbonyls of Rancid Fat

Abstract: SUMMARY— The effects of 26 species of bacteria, molds, and yeasts on the hydroperoxides and monocarbonyls in rancid fat have been determined. All of the cultures were capable of decomposing the hydroperoxides. The activity of microorganisms on the monocarbonyl content of the rancid fat was quite varied and could be divided into: 1) microorganisms which produced large increases in at least two monocarbonyl classes; 2) microorganisms which removed 2,4-dienals; 3) microorganisms which removed 2,4-dienals and 2-enals, and 4) microorganisms which caused decreases in at least two classes of monocarbonyb (without destroying completely any class). Two microorganisms produced methyl ketones, a monocarbonyl class which does not appear in rancid lard. There appeared to be a relationship between the ability to decompose peroxides strongly and the ability to produce a great increase in the monocarbonyl content. There apparently is no relationship between the ability to decompose peroxides and lipolytic activity. The possible importance of microorganisms in controlling hydroperoxides and monocarbonyls in fats is discussed.

Photomicrographic Studies of Dynamic Changes in Muscle Fiber Fragments. 1. Effect of Various Heat Treatments on Length, Width and Birefringence

Abstract: SUMMARY– Photomicrographs were made of muscle fiber fragments as the stage of the microscope was heated from room temperature to 80°C, or as fibers were held at 37, 45, 53, 61, 69, or 77°C on the heated stage for an hour. The possible relationship of changes in width, length and in birefringence brought about by heating to loss of moisture, water-holding properties, loss of acidic groups, and changes in tenderness are discussed. Changes in width appeared to be related to changes in water-holding capacity. Changes in length and loss of birefringence were related to loss of acidic groups, to coagulation of proteins, to volume change in cooked meat, and to changes in tenderness.

Volatile Compounds from‐ Heated Glucose

Abstract: SUMMARY— Volatiles from anhydrous glucose heated in air at 25OT for 30 min were collected in a trap maintained at the temperature of solid carbon dioxide. A concentrated ether extract of the distillate was shown by gas chromatography to contain at least 100 compounds. Among those identified and heretofore unreported from heated glucose were the gamma lactone of 4-hydroxy-2-pentenoic acid, l-(2′-furyl)-propane-1,2-dione (acetylfuroyl), 3-methylcyclopentane-1,2-dione, phenol and methylfuroic acid.

Carbonyls in Oxidizing Fat. 11. The Effect of the Pro‐oxidant Activity of Sodium Chloride on Pork Tissue

Abstract: SUMMARY -Oxidation of freezer-stored, sodium chloridecured pork was characterized by a rapid rate and moderately high monocarbonyl/peroxide ratios. Increase in the concentration of NaCl accelerated autoxidation, but did not affect hydroperoxide decomposition to monocarbonyl compounds. High proportions of lean increased autoxidation and the monocarbonyl-peroxide ratios. Sodium nitrite (0.03%) catalyzed autoxidation by reaction with the meat pigment in an apparently independent effect to that exerted by NaCl. Composition of the free monocarbonyl compounds indicated linoleate specificity in peroxide decomposition, although hematin catalysis is nonspecific in its attack on unsaturated fatty acids. Possible direct effects of NaCl did not appear to involve a reactive chloride ion.