ANTIMICROBIAL ACTIVITY OF SOME FOOD FLAVORING COMPOUNDS

Of 21 food flavoring compounds tested against 39–40 organisms, 10 were ineffective at 1,000 ppm or 10 mM either at pH 6 or 8 and by either surface plating or in broth. The 11 effective compounds were d- and l-carvone, diacetyl, ethyl vanillin, eugenol, maltol, menthol, phenylacetic acid, phenylacetal-dehyde, 2,3-pentanedione and vanillin; with diacetyl and eugenol being the most effective. All were more effective at pH 6 than at pH 8. With the exception of maltol and phenylacetic acid, each was generally more effective against fungi than bacteria with the lactic acid bacteria being the most resistant. At pH 5.5 and 5°C, diacetyl was inhibitory to Pseudomonas fluorescens and P. geniculata at < 10 ppm. The findings suggest that compounds used in acid foods, ostensibly as flavoring agents, may exert antimicrobial effects when considered in context with all parameters of growth.     

Optical Absorption Spectra of Cr3+ in MgO·Al2O3-MgO·3.5Al2O3 Spinels

Spinel crystals in the system MgO· n Al₂O³:Cr³⁺ (1.04≤ n ≤3.51) were synthesized by flame fusion; their absorption spectra were measured in transmission from 400 to 50,000 cm⁻¹. The O-H band spectra suggest the presence of protons in octahedral site vacancies which appear for n >1. The spectra for Cr³⁺ indicate clearly that these ions occupy only octahedral sites. However, the effective trigonal field, which varies with n , causes the major absorption bands to split in the form of a lower-energy shoulder on a higher-energy component. The red-green transition in these spinels was rationalized and observed to arise from a somewhat different mechanism than that in other oxides in which the site radii and Cr³⁺ concentration vary considerably.     

HEXOSAMINE PRODUCTION BY PSYCHROTROPHIC FOOD-SPOILAGE BACTERIA UNDER VARYING GROWTH CONDITIONS

Four psychrotrophic, gram negative meat isolates were grown at 6 and 22°C with and without aeration, in AOAC synthetic broth with 0.1% glucose and in a basal medium containing 0.1% glucose and 0.5% glycine (BMGG-1). In AOAC broth, three strains produced more hexosamine at 6°C, while the fourth produced more at 22°C. Three of the four strains also produced more slime at 6°C. All four strains grew faster with aeration at both temperatures, but produced less hexosamine. Under all conditions, the growth rate of each strain was inversely proportional to its hexosamine production. During the growth cycle in BMGG-1, medium pH dropped until the log phase was under way and then rose again through the stationary phase. This rise coincided with the depletion of glucose. Hexosamine production first became detectable at the end of the log phase, rose during the stationary phase, and then leveled off. Adjusting pH to prevent the initial drop increased both growth and hexosamine production. Raising the concentration of glucose to 0.5% accelerated growth but decreased hexosamine production. Approximately 95.1% of the hexosamine produced was cell-associated. It consisted primarily of glucosamine polymers with a lesser amount of galactosamine. Only 3.0% of the nitrogen from the BMGG-1 was utilized by the cells. Of this 3.0%, 58% was used for ammonia, 27.2% for hexosamine, and 14.8% for other substances. Of the 40.7% used for total cell production, 63.8% went into hexosamine.     

VACUUM-PUFF FREEZE DRYING OF TROPICAL FRUIT JUICES

SUMMARY— A study was made to develop high Quality juice powders from four tropical fruits. Guava and mango puree, passion fruit and pineapple juice were dehydrated in a vacuum-puff freeze-drying process. Sucrose in amount (25–40%) approximating nectar formulations was mixed with single-strength juice or puree samples, blended 2 min, and frozen. Freezing temperatures of various samples were measured in a constant temperature bath of −21.6°F. Samples initially frozen in blast freezers at −40°F or 0°F with 0.25–1.0 lb/ft² were vacuum-puffed and freeze dried on aluminum trays at 50μ Hg and 120–130°F shell temperature for 6–9 hr to 1–2% moisture. Puffing was affected by (1) rapid freezing of the juice-sucrose mixture; (2) artificially entrapping some gas in the mixture before freezing; (3) changing the pressure or temperature in the chamber to effect gas expansion; and (4) increasing the mixture viscosity to limit bubble sizes. Results of drying over 160 different samples showed that: (1) added sucrose to give a 40° 5° Brix in the mixture resulted in a stable 'puffed' structure; (2) several permissible calcium salts and silica at 0.1–0.5% (w/w) added to the mixture before drying, improve the free-flowing properties of the dried product. Process variables are discussed and typical sample compositions given.     

NaF-KF-K2NbF7 Fused Salt Temperature-Solubility Diagram

Freezing and eutectic temperatures were determined for the NaF-KF-K₂NbF₇ ternary system and the NaF-K₂NbF₇, KFK₂NbF₇, and NaF-KF binary systems. The compound KF-K₂NbF₇ freezes congruently at 770°C; eutectics occur at 708° and 724°C for high- and low-K₂NbF₇ mixtures, respectively. The NaF-K₂NbF₇ eutectic freezes at 658°C. The ternary system has two eutectics, a high-KF mixture and a high-K₂NbF₇ mixture, which occur at 663° and 652°C, respectively.     

ENERGY CONSERVATION IN DRYING OF FRUITS IN TUNNEL DEHYDRATORS

This study reports the energy use and thermal losses associated with tunnel dehydrators and discusses methods of increasing energy efficiency. These dehydrators can operate with an efficiency of water removal greater than 50%. It is shown that energy conservation techniques such as minimizing air leakage, increasing air recirculation, utilizing a furnace heat shield to prevent heat losses, and maximizing input can result in significant energy savings.     

Mechanics of Pressure Slip Casting

The quantitative mechanics of pressure slip casting an aqueous Al₂O₃ slip deflocculated with an organic polyelectrolyte were investigated at 50 to 500 psi. The specific resistance, casting rate, and microstructural characteristics of the resultant cakes were especially sensitive to the electrophoretic mobility of the slip. The mechanochemical action of the polyelectrolyte in effecting deflocculation was somewhat different from that of simple ionic electrolytes.     

Incremental planning using conceptual graphs

Abstract

When performing a planning or design task in many domains it is often difficult to specify in advance what the precise goals are. It is therefore useful to have a system in which the planning process is performed interactively, with the solution approaching the users' intent incrementally through iterations of the planning process. A planning system intended to function in this way must be able to take goal specifications interactively rather than all at once at the beginning of the planning process. The planning process then becomes one of satisfying new goals as they are given by the user, modifying as little as possible the results of previous planning work. Incremental planning is an approach to interactive planning problems that allows a system to create a plan incrementally, modifying a previous plan to satisfy new or more precise goal specifications. In this paper we present an incremental planning system called the general constraint system (GCS) that is based on the conceptual programming environment (CP) developed at New Mexico State University and we show an example of the use of the system for a simple civil engineering design problem