Polyphenol Oxidase System in Red Delicious Apples

The polyphenol oxidase system (E.C. 1.14.18.1) in‘Red Delicious’apples (Malus domestica) was investigated. Polyacrylamide gel electrophoresis (PAGE) revealed two active isoenzymes as detected with pyrocatechol substrate. The crude enzyme extract (acetone powder) was found to have one optimum pH of 6.2 and one optimum temperature for the browning reaction of 30°C with the experimental conditions described. The Michaelis constant (Km) as an average of the two active enzyme forms was 2.2 × 10^?lM pyrocatechol and the average maximum velocity (Vmax) was 4.8 × 10^?l AA390 per minute.     

Establishing Thermal Processes for Products with Straight-Line Heating Curves from Data Taken at Other Retort and Initial Temperatures

Heat penetration data were obtained at high and low retort temperatures (RTs) and at high and low product initial temperatures in two can sizes for food products displaying straight-line heating curves in an agitating retort. The extrapolation of data to other RTs was found to be a safe practice for products heating with conduction or significant induced convection. Extrapolating to lower RTs for intermediate viscosity products slightly underpredicted required processing times. The effect of initial temperature was consistent with that found in a previous study for broken-heating products in a still retort, in that heat penetration tests conducted at different initial temperatures can have a significant influence on process establishment, depending on the product.     

Physicochemical Properties of Ovalbumin and Lysozyme Treated with Oleic Acid

Results from polyacrylamide gel electrophoresis confirmed that proteins were more negatively charged in the presence of oleic acid. The electrophoretic mobility of unmodified and modified lysozyme was of opposite but similar magnitude. Critical micelle concentration (50.0 μ M) of oleic acid suggested that association between the fatty acid and proteins was mostly hydrophobic. Muramidase activity of modified lysozyme and difference spectra of modified ovalbumin suggested that oleic acid was partially or totally surrounding the proteins. Improved freeze-thaw characteristics of treated egg white were attributed to greater negative charge and instability of proteins produced by oleic acid.     

Impediments to the enforcement of youth access laws

OBJECTIVE: To recognise obstacles to the implementation of the effective enforcement of tobacco sales laws and to identify measures that could be taken to overcome these obstacles. DESIGN: Interviews were conducted with health department officials in Massachusetts communities to determine why their efforts to prevent illegal sales of tobacco to minors had been only partially successful. SETTING: Urban, suburban, and rural communities in Massachusetts, USA. RESULTS: Organisational problems, court challenges to citations, budgetary threats, and political pressure all combined to reduce the frequency of enforcement inspections to half the intended rate. Political pressure resulted in the exclusion of older youths from compliance tests, further undermining enforcement efficacy. CONCLUSIONS: Suggestions for addressing the problems include obtaining support from the community, keeping elected and court officials informed about plans for merchant education and law enforcement, using efficient enforcement protocols, setting merchant compliance goals, and advising the public and government officials about progress towards those goals, using older youths to make purchase attempts, and testing all merchants frequently.     

KINETIC ANALYLSIS OF THE FORMATION OF NITROSYLMYOGLOBIN

The formation of nitric oxide myoglobin (nitrosylmyoglobin) was followed in buffered solutions in which the concentrations of ascorbate, nitrite, chloride, myoglobin and hydrogen ion were varied systematically to determine their effect on the rate constants. The rate of formation of nitrosylmyoglobin was zero order with respect to the pigment. The orders for the other reactants were determined by plotting the zero order rate constants as functions of varying orders of each reagent to determine which order gave a linear plot. The results were used to develop a mechanism and a mathematical expression for the reaction. Two reaction sequences involving different nitrosating species were involved; 1, direct action of nitrous acid and 2, the formation of nitrosyl chloride. Both species then nitrosated ascorbate and ascorbic acid, by different mechanisms. The nitric oxide for nitrosylmyoglobin formation came from the nitrosated ascorbate.     

Carrot Dehydration—Optimization Process Studies on the Explosion-Puffing Process

A carrot dehydration process that includes the unique continuous explosion-puffing system (CEPS) is described. A drying study included moisture distribution throughout a two-stage pilot scale dryer as well as bed temperature during first stage drying. Shrinkage losses of carrots by two dehydration methods were investigated, and volume differences were obtained. Measurements of dried carrot properties such as bulk density, color, nonenzymatic browning, rehydration, and disintegration were used to determine optimum operating pressure, temperature, and feed moisture for CEPS. Response surfaces developed from these properties were used simultaneously to establish a constrained optimum.     

MULTI-RESIDUE DETERMINATION AND CONFIRMATION OF TEN HETEROCYCLIC AMINES IN COOKED MEATS

Heterocyclic aromatic amines (HAAs) have been identified in various cooked meat products. HAAs are formed from pyrolysis of proteins and amino acids and are of interest because many of these primary arylamines are mutagens and rodent carcinogens. We developed a screening method for ten HAAs using liquid-liquid extraction, reverse-phase HPLC separation, and tandem electrochemical (ECD) and fluorescence (FLU) detectors. This detection system exhibited greater sensitivity (50-100 fold) for HAAs than the HPLC-UV methods. HPLC-FLU has detection limits of 100 pg to 1 ng for six HAAs, and HPLC-ECD detection limits of four HAAs were 250 pg to 1 ng. We also developed a confirmatory procedure for ten HAAs using HPLC coupled to positive ion APCI-MS. This technique has subnanogram detection limits. These methods were used to quantify HAAs in meat products at levels formed by typical Western cooking methods.     

APPLICATION OF ATTRITION-MILLED SOY FLOUR IN A BEVERAGE APPLICATION

A soy beverage mix was created using thermally treated, attrition-milled soy powder, anticaking agent (1.0, 1.5 and 2.0%) and adjunct ingredients (salt, sugar, carrageenan, calcium phosphate) commonly found in a soy beverage. Thermal processing of defatted soy flake at specific moisture levels (30, 35 and 40%) from two different sources was evaluated for effective denaturation of the soy trypsin inhibitor complexes. Identification of an optimal thermal treatment was then used to produce a soy flake milled in a cyclone-assisted attrition mill. Soy beverage mixes were homogenized with a handheld blender at solution temperatures of 4, 30, and 70C. Separation rates were highest at all treatment levels consisting of the 70C solution temperature (1.67 mL/min) and were lowest for all treatment levels at 4C (0.55 mL/min). Thermal treatment of defatted soy flake resulted in solutions with lower viscosities (87.32 and 151.90 cP for Archer Daniels Midland Co. and L-Star, respectively).

PRACTICAL APPLICATIONS

This article establishes the milling conditions to create an instant soy beverage system. The soy drink mix can be easily used by consumers to make soy beverage or soymilk and is stable for up to 10 min.     

Biological role of alcohol dehydrogenase in the tolerance of Drosophila melanogaster to aliphatic alochols: utilization of an ADH-null mutant

The toxicity of the first eight primary alcohols and of four secondary alcohols was compared in a wild-type strain (having active ADH) and an ADH-negative mutant. Differences between LC50 measured in the two strains allowed an evaluation of the biological activity of the enzyme. In vitro, ADH is mainly active on secondary alcohols, while in vivo its main role is the detoxification and metabolism of ethanol. These observations suggest that originally ADH was involved in unknown metabolic pathways and that its utilization in ethanol metabolism could be a recent event.     

Effects of exogenous hormones and glucose on plasma levels and hepatic metabolism of amino acids in the fetus and in the newborn rat

The present study examines the role of insulin, glucagon and cortisol in the regulation of gluconeogenesis from lactate and amino acids in fetal and newborn rats. Injection of glucagon in the full-term fetal rat caused a rise in glucose (and insulin) and a fall in blood levels of most individual amino acids, stimulated hepatic accumulation of 14C-amino isobutyric acid and 14C-cycloleucine and increased the conversion of 14C lactate, alanine and serine to glucose in vivo and in vitro (liver slices). Such changes were equivalent to the changes seen in 4 h old newborn rats. When glucagon was administered at birth, little difference was observed between control and treated animals in plasma amino acids and a smaller increment in conversion of 14C substrate to glucose occurred. By contrast, insulin injection at birth caused hypoglycemia, suppression of levels of certain amino acids and inhibition of conversion of 14C substrates into glucose. Glucose injection at birth caused elevated glycemia and plasma insulin and suppression of most amino acid levels and of conversion of 14C substrate into glucose. Cortisol injection at birth caused a marked, generalized by hyperaminoacidemia, a stimulation of glucagon secretion and of conversion of 14C substrates into glucose. These observations support the thesis that glucagon plays a major role in the induction of hepatic gluconeogenesis and that insulin acts as an antagonist hormone.