A Comparison of Enzymatic and Lime Treatments for Extraction of Alcohol Soluble Solids from Citrus Peel

Digestion of citrus wastes by pectolytic and cellulolytic enzymes was compared to the currently employed lime method of solubilizing solids from citrus peel. Maximal soluble solids removed from the pressed peel occurred after 6 hr incubation at 45°C with a pectinase concentration of 1.0 PGu/g peel mixture. Decreasing the particle size of the peel caused a 4 - 10% increase in solids removal after enzyme treatment. Addition of cellulase enzyme (20 CEu/g peel mixture) to pectinase enzyme (1.0 PGu/g peel mixture) removed an additional 15% soluble solids from peel. Glucose, fructose, arabinose, and xylose were the major sugars extracted from enzymetreated peel, while sucrose was the major sugar in lime-treated peel samples. Organic acids (citric, malic, and quinic) were present at higher concentrations in lime-treated peel extracts than in enzymetreated peel extracts.     

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.     

Micromechanics of Flaw Growth in Static Fatigue: Influence of Residual Contact Stresses

Residual contact stresses about indentation flaws are demonstrated to have a strong deleterious effect on specimen lifetime in static fatigue. The underlying basis of conventional fatigue analysis is first examined critically and is argued to be deficient in the way the stress intensity factor for the flaws is related to the characteristic parameters of crack geometry and applied loading. In general, it is necessary to incorporate a residual term into the stress intensity formulation. A modified theory of static fatigue is accordingly developed, in which the residual contact stresses play a far from secondary role in the micromechanics of flaw evolution to failure. Strength tests on Vickers-indented soda-lime glass disks in water environment provide clear experimental confirmation of the major theoretical predictions. Implications of the residual stress effect concerning fracture mechanics predictions of lifetimes for "real" ceramic components under service conditions are discussed.     

Strength Degradation of Thermally Tempered Glass Plates

An earlier theory of contact-induced strength degradation of brittle materials is extended to include plates in residual surface compression. The scale of the strength-controlling flaw is predicted by indentation fracture mechanics, with the modifying effect of the residual field incorporated into both indentation and strength equations. Experimental verification of the predictions is obtained from diamond-pyramid indentation tests on thermally tempered glass plates. As with untempered plates, the theory accounts for the load dependence of the strength loss; it also explains the insensitivity of the degradation characteristics to initial flaw distribution and identifies toughness as the controlling material parameter. Most significant, however, is the demonstration that surface strengthening can produce dramatic improvements in degradation resistance. The possibility of obtaining all parameters necessary for a complete degradation analysis of a given tempered inaterial entirely by routine indentation/strength testing is discussed.     

Failure Mechanisms in Ceramic-Fiber/Ceramic-Matrix Composites

Mechanisms of failure in a unidirectional Sic-fibe/glass-ceramic composite are investigated using in situ observations during tensile and flexural loading. These experiments show that failure in tension occurs in several stages (similar to certain other brittle fiber composites): multiple matrix cracking, followed by fiber fracture and pullout. In flexural loading the failure process is more complex. Consequently, the flexural test cannot be used for measurement of tensile strength (although it can be used for measurement of the stress for matrix cracking). The application of conventional fracture mechanics to describe tensile failure is discussed. The in situ observations provide direct indication of the importance of frictional bonding between the matrix and fibers. Some novel methods for measuring the frictional forces and residual stresses are investigated, and the influence of surface damage on strength is assessed.     

Process capability analysis—a robustness study

The robustness of two popular process capability ratios, C_p and C_pk, when the random process being observed departs from normality is analysed. The distributions of estimated process capability ratios are derived and used as a basis for validation of large-scale simulation studies in an examination of departures from normality. The simulation studies and analytical results provide a basis for recommended procedures. It is recommended that the impact of process distributions be considered before using popular process capability indexes, due to the lack of robustness when departures from normality are ecountered. As an extension of our findings, we consider the Taguchi loss function as a generalization to process capability analysis regardless of the underlying population distribution.     

Fermentation of specially formulated milk with single strains of bifidobacteria

A number of strains of bifidobacteria have been used to ferment milk to a yoghurt-like product. The milk used for fermentation was fortified with whey protein and threonine. It was prepared by mixing skimmed milk and cheddar cheese whey which had been concentrated using ultrafiltration membranes which allowed lactose to permeate. A 2 percent inoculum was used, and fermentation was carried out at 37° C overnight. The resulting products resembled voghurt, having good consistency. 'walnutty' aroma (acetaldehyde). and pleasant acidity.     

Remote sensing applications in the Australian Bureau of Meteorology

Abstract

The space age for the Bureau of Meteorology arrived in December 1963 with the first direct receipt in Australia of visual images of clouds from the US TIROS-8 satellite. Since that time, the successful application of advances in satellite data, products and services has brought dramatic improvements to most aspects of the Bureau's operations and research. This paper documents the developments of the past 25 years by describing the Bureau's current national infrastructure for the reception, processing and dissemination of meteorological satellite data and the way in which satellite data and systems are used to improve the Bureau's services. The meteorological satellite has emerged not only as a highly cost-effective primary observation platform, providing an increasingly diverse range of meteorological data, but also as a vital communications medium for both general meteorological information and the interrogation of complementary observational systems. The prospects for further major advances in the application of satellite information within the Bureau are very high. During the early 1990s and beyond, the next generation of active remote sensing technology will replace the current passive sensor technology deployed in the international meteorological satellite network. As a result, further improvement in the ability of the Australian meteorological community to describe quantitatively the dynamic and thermodynamic structure of the atmospheric and marine environment is confidently predicted.     

Starter cultures for milk fermentation and their characteristics

This paper reviews the different types of fermented milks and their microflora and includes recent work on yogurt, soft cheese and buttermilks, kefir and koumiss. There is considerable interest in the 'new' health promoting products which are now available. These are also discussed in the light of some recent findings on the ability to lower the blood cholesterol concentration and stimulate the immune response. Biotechnology techniques are being developed for many of the lactic acid bacteria involved in dairy fermentations, and in the final section some potential improvements are briefly reviewed.