PHYSICOCHEMICAL PROPERTIES AND FUNCTION OF PLANT POLYPHENOL OXIDASE: A REVIEW1

Polyphenol oxidase (PPO)‐catalyzed browning reactions are of significant importance in the fruit and vegetable industry. These reactions proceeding in many foods of plant origin cause deterioration and loss of food quality. A better knowledge of the factors that influence the action of PPO is imperative in order to control and manipulate its detrimental activity in plant products. This paper presents an overview of the current understanding of the reaction properties, biochemical characteristics and potential physiological roles of PPO in plants. Reaction properties will include general PPO reactions, specificities and molecular mechanisms of these reactions, and methods available to assess PPO activity. Physicochemical properties will evaluate substrate specificity, environmental influences such as pH and temperature, multiplicity, latency, and activators and inhibitors of PPO. The discussion will conclude with potential physiological roles of PPO in plants.     

Heating Characteristics of Homogeneous Milk-Based Formulas in Cans Processed in an Agitating Retort

Milk-based formulas with proximate analyses similar to infant formulas were heated to determine influence of headspace, reel speed, solids content, and consistency on F_o. Concentrations with 12.5, 25, and 30% solids were heated in three can sizes. Increasing Steritort rpm from 3.4 to 10.9 for 307 × 710 cans (12.5% solids) had greatest effect; the F_o increased from 9.8 to 12.3. The same increase in rpm for a continuous retort would reduce F_o from 9.8 to 2.0 because of reduced processing time. Solids content and consistency influenced heating, but variations in consistency of a given concentration had no measurable effect on F_o. Headspace influenced heating for each concentration, but was not as critical as for more viscous products.     

USE OF A MODIFIED UREA GEL ISOELECTRIC FOCUSING METHOD FOR SPECIES IDENTIFICATION OF RAW OR BOILED WHITE,PINK, AND ROCK SHRIMP1

Isoelectric focusing (IEF) polyacrylamide gel containing an 80% pH 4–6.5 and 20% pH 3–10 ampholyte mixture greatly improved protein banding pattern for species identification of water extracts of raw pink, white and rock shrimp compared with the system using only the pH 3–10 range ampholyte. Identification of a specific species in mixture samples was achieved by the detection of water-extractable shrimp specific protein bands present in the gel. Sodium dodecyl sulfate (SDS) was a better protein extractant than water for cooked shrimp. Both water and SDS extracts of cooked shrimp showed specific protein banding patterns and improved resolution for species identification.     

CONVERSION OF EXOGENOUS CYTOKININS TO BIOLOGICALLY ACTIVE COMPOUNDS IN TOMATO TISSUE. EVIDENCE FOR AN ENZYME MEDIATED REACTION1

High performance liquid chromatography was used to follow the conversion of isopentenyladenine (i⁶ Ade) in tomato pericarp cubes. Exogenously supplied i⁶ Ade introduced by vacuum infiltration into tomato cubes (Lycopersicon esculentum, Mill “Rutgers”) declined 60%, when the cubes were incubated 2 h. The rate of i⁶ Ade disappearance declined as the fruit ripened from mature green to a ripe fruit. Adenosine infiltrated with i⁶ Ade did not alter the rate of i⁶ Ade disappearance. However, adenine at the same concentration as adenosine inhibited (80%) the rate of i⁶ Ade disappearance. Dinitrophenol (DNP) infiltrated 1 h prior to i⁶ Ade infiltration inhibited completely the rate of i⁶ Ade disappearance. However, DNP infiltrated simultaneously with i⁶ Ade caused only partial inhibition (60%) of i⁶ Ade disappearance. Inhibition by DNP could be overcome by increasing the concentration of i⁶ Ade in the infiltrating medium. Tissue culture bioassay showed that i⁶ Ade was converted to a biologically active form with greater activity than i⁶ Ade.     

DEVELOPMENT OF THE PERCEPTION OF FORM.

4 SCHEMES REPRESENTING THE FLOW OF INFORMATION FROM STIMULUS THROUGH SENSORY AND PERCEPTUAL SYSTEMS TO RESPONSE ARE PROPOSED IN THE CONTEXT OF AN EVALUATION OF THE PERCEPTUAL POTENTIALITIES AND ABILITIES OF THE NEWBORN HUMAN BEING. THE EVIDENCE SUGGESTS THAT THE NEWBORN IS PROVIDED AT LEAST SOME SENSORY CAPACITIES WITH WHICH TO SYNTHESIZE A PERCEPTUAL WORLD. SUGGESTIONS ARE OFFERED TO FACILITATE THE STUDY OF THE NEWBORN'S ABILITY TO PERCEIVE FORM. (2 P. REF.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)