Volume Relaxation Far from Equilibrium

Narayanaswamy's model of structural relaxation is applied to the data of Hara and Suetoshi on volume relaxation in plate glass. Both the Adam-Gibbs and Arrhenius equations are used to represent the relaxation time. Equally good fits are obtained with both equations, but only the Adam-Gibbs model gives Physically meaningful fitting parameters. The exponent b describing the shape of the relaxation time spectrum decreases at small values of reduced time, as it does for stress relaxation Discrepancies between calculated and measured densities at 350°C are not resolved by allowing for a nonlinear driving force or thermorheological complexity.     

Shiraz berry size in relation to seed number and implications for juice and wine composition

This study was conducted over three seasons on irrigated Shiraz grapevines growing in a warm climate. We addressed the question of whether differences in berry size (within a population of berries from minimally pruned, own‐rooted or Ramsey‐grafted vines), would lead to differences in juice composition, wine composition or wine sensory score. Predictably, berry mass was found to increase with seed number, but berries in the smallest mass categories (0.3–0.7 g) still had similar juice soluble solids and pH; and similar concentrations of K+, tartaric acid and malic acid, compared with larger berries (1.4–2.0 g). Only for the very smallest mass category (0.3–0.55 g) was there any indication of better colour density (both for own‐rooted and Ramsey‐grafted vines) or higher anthocyanin concentration (for own‐rooted vines) compared with larger berries (1.4–2.0 g). Concentrations of tartaric acid and K+ in berry skins were highest in the smallest berry mass categories (0.3–0.7 g) and decreased with increasing berry mass (up to 1.4–2.0 g). A strong correlation (R²= 0.85) between skin tartaric acid and K+ concentrations was observed across that range. Small‐scale wine lots based on small berries (0.8–0.9 g) versus large berries (1.2–1.3 g) showed no differences in measures such as soluble solids, total acids or pH of juice; nor any differences in pH, total acids, K+, tartrate, malate, spectral characteristics or sensory score of corresponding wines. Moreover, small berries had a similar skin to fruit ratio, and a similar juice yield, compared to large berries. However, when measured post‐fermentation, the ratio of seed weight to skin weight was higher for small berries. The mass range of berries used here for small‐scale winemaking (i.e. from 0.8–0.9 g up to 1.2–1.3 g), covered the range of Shiraz berry mass typically found in irrigated vineyards (from 0.8 to 1.5 g), and thus confirms the relevance of present outcomes to practical winemaking. Finally, our data for variation in juice and wine composition as a function of berry size, showed consistent trends for all seasons, and thus implies that reported instances of improved wine quality from small berries (often associated with certain pruning treatments or deficit irrigation strategies), are more likely due to treatment effects that lead to small fruit, rather than to intrinsic developmental differences between large and small berries.     

Denaturation of Lactate Dehydrogenase During Spray-Drying of Bovine Plasma

Denaturation kinetics of lactate dehydrogenase (LDH) during spray-drying and heating of bovine plasma showed the free energy of denaturation was constant about 100 kJ/mol. Protein denaturation was investigated by polyacrylamide gel electrophoresis and solubility. At low outlet drying temperatures LDH denaturation was low and powders were completely soluble. At high outlet temperatures LDH denaturation was high and associated with powder insolubility. Electrophoretic patterns of dried samples showed differences from raw plasma at high outlet temperatures, perhaps due to production of soluble aggregates. However, LDH was not a general index of heat denaturation in spray-drying.     

FATTY ACID COMPOSITION OF LIPIDS FROM BROILERS FED SATURATED AND UNSATURATED FATS

SUMMARY— The effect of feeding saturated fat (tallow) and unsaturated fat (safflower oil) to broilers on the change in fatty acid composition of lipids deposited in broiler tissues at 4, 6, 8, and 10 wk of age was determined. Fatty acids from raw and cooked skin, excluding that on the neck and third wing joint, breast meat, thigh meat, and abdominal fat were identified by using gas liquid chromatography. Fatty acids from water in which carcasses were cooked were also identified. The degree of unsaturation of fatty acids in these tissues wars influenced by the degree of unsaturated fatty acids in the diet and tended to assume the fatty acid composition of the diet. In some cases, however, the higher levels of certain fatty acids in depot fat was not present in broilers fed the higher levels in the diet. Fatty acids in the larger amounts in all broiler tissues were palmitic, stearic, ofeic, and linoleic but varied in amount among the different age broilers fed the same ration as well as different rations. In most cases there tended to be an inverse relationship between oleic and linoleic acids in the tissues. Lipids from cooked tissues contained a larger amount of 18-carbon unsaturated fatty acids than the other fatty acids combined. Fatty acids collected from cooking water were similar to those in cooked tissues. The presence of 13- and 25-carbon chain fatty acids noted in tissues of 4 wk-old broilers suggests a difference in the metabolism of fat in different age birds. Futher research is needed to substantiate this finding.     

CHARACTERISTICS OF TYROSINE PHENOL-LYASE FROM AEROMONAS PHENOLOGENES ATCC 29063

Tyrosine phenol-lyase catalyzes the conversion of L-tyrosine to phenol, pyruvate, and ammonia. The activation energy for the reaction was calculated to be 13,000 calories per mole. The heavy metal Cu⁺⁺ was found to result in a mixed type of inhibition (Ki 0.20 mM). The addition of mercaptoethanol was found to reverse the inhibition by Cu⁺⁺. Competitive inhibition was found with the amino acids L-alanine (Ki18 mM) and L-phenylalanine (Ki 4.4 mM). Phenol, an end product of the tyrosine phenol-lyase reaction, was also found to inhibit enzyme activity (Ki 50 mM). Tyrosine phenol lyase catalyzed the formation of pyruvate from L-tyrosine methyl ester, S-methyl-L-cysteine, and L-serine but at rates lower than with L-tyrosine. Km values for L-tyrosine methyl ester, S-methyl-L-cysteine, and L-serine were found to be 0.37 mM, 0.40 mM, and 1.2 mM, respectively. The reverse reaction by which L-tyrosine is produced from phenol, pyruvate, and ammonia was demonstrated. The pH optimum for the reverse reaction was found to be 9.0 and the Km for phenol 5.0 mM.     

Limonoids and Flavonoids in Juices of Oroblanco and Melogold Grapefruit Hybrids

Oroblanco and Melogold are hybrids obtained from pummelo and grapefruit. Limonoids and flavonoids in both juices were analyzed. Oroblanco and Melogold juices contained low concentrations of limonoid glucosides, an average of 99 and 59 ppm, respectively. However, they contained relatively high concentrations of bitter limonoid aglycones, limonin and nomilin, at levels above the limonin bitterness threshold. For comparison, limonoid glucosides in juices of grapefruit, another pummelo hybrid, were also analyzed. Limonin glucoside was the major limonoid glucoside in all juices analyzed. Nomilin glucoside and nomilinic acid glucosides were also present. Oroblanco and Melogold juices contained bitter flavonoids normally found in grapefruit and pummelo including naringin, neohesperidin and poncerin in total amount of 440 ppm in Oroblanco juice and 495 ppm in Melogold juice. They also contained several other nonbitter flavonoids found in grapefruit.     

BONE PARTICLE CONTENT OF SOME MINCED FISH MUSCLE PRODUCTS

Minced fish muscle recovered by flesh separators may vary in bone particle content depending on the type of machine and the size of the openings that the fish are passed through to screen out the skin and bones. Orderly marketing of these materials will require some measure of control of the bone particle content. The method presented here for quantifying the bone particle content of minced flesh by gravity-flotation involves (1) shredding the flesh with a low-speed stirring device and (2) gravity separation of the bone, cartilage and other high-density components from the lower-density floatable muscle fibers. Experimental samples obtained by passing various fish materials through flesh separators and then through 1- and 2-mm flesh strainers were analyzed for their bone particle content by the proposed method. The bone particle content of flesh containing 25 to more than 100 particles per pound could be reduced by 70–100% by passage through strainers. Imported commercial samples displayed bone particle contents of 4 to over 400 per pound. Sensory panels could not detect more than 10% of the particles found by objective analysis. The gravity-flotation method may serve as a useful quality control tool.