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The ability of various dietary fibers to impede lipase-catalyzed hydrolysis of tributyrin was studied in vitro. Conditions (temperature, kind and concentration of constituents, pH, agitation) were chosen to mimic, as closely as possible, those prevailing in the human duodenum. Lipolysis was monitored at pH 6.0 and 37 degrees C using a constant pH titrimeter. Some fibers inhibited lipolysis (red wheat bran, white wheat bran, oat bran and sugarbeet fiber), whereas most did not (psyllium seed, pectin LM 12CG, carrageenan, carboxymethylcellulose, gum arabic, and pectin slow set). Water extracts of the fibers accounted for 32-41% of the inhibitory effect of the two wheat brans on lipolysis and 100% of the inhibitory effect of oat bran.

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Various lipids, present as thin films on polar filter paper supports, were evaluated for resistance to the transmission of water vapor (rH2O) and oxygen (rO2). Beeswax exhibited the largest r(H2O), followed in order by fully-hydrogenated soy-rapeseed oil, stearyl alcohol, acetylated monoglycerides, hexatriacontane, tristearin, and stearic acid. Most of the lipids exhibited negative activation energies, E, for resistance to transmission of water vapor and positive Es for resistance to transmission of oxygen. The type of lipid support (hydrophobic or hydrophilic) also influenced E for resistance to water vapor transmission. Differences in r(H2O) for the various lipids, comparative r(H2O) and r(O2) values, and the temperature dependence of these values can be explained, in part, by the degree of hydrophilicity of the lipid molecule. Tempering at 48 degrees C of stearyl alcohol caused a substantial decrease in its permeability to oxygen and water vapor. The polymorphic form of a blend of fully-hydrogenated soybean and rapeseed oil had a moderate influence on its permeability to oxygen and water vapor. This information will be useful for formulating lipid-containing films with controlled barrier properties to the passage of water vapor and oxygen.

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The quality and safety of foods are affected by the environment, and the quality and safety of the environment are, in turn, affected by foods and food processing. To explore these interrelationships, as they might exist in the twenty-first century, one must speculate regarding future changes in foods and food processing. Several trends in food processing seem likely to predominate into the twenty-first century, and they will be, for the most part, evolutionary in nature and of low consumer visibility. These trends are greater use of foods marketed in a refrigerated state, greater use of irradiation and combination processes, greater automation and optimization of processes, and greater use of biotechnology. It is also reasonable to assume that food products of the following types will increase in importance, namely, those that are convenient (includes eating away from home), those that are tailored to specific dietary needs, those containing chemically modified components such as altered proteins and carbohydrates, and fabricated foods. If these trends in foods and food processes prevail then concern must be directed to the following areas: Microbiological concerns--refrigerated foods; food service operations; new or altered procedures for processing, handling and storing foods; and new foods or food formulations; attention must be given both to controlling known pathogens as well as newly perceived pathogens. Chemical concerns--toxicants occurring naturally in foods; contaminants; chemicals developing in foods during processing, handling and storage; chemicals used in fabricated foods; and chemicals of newly perceived importance, especially those having adverse, covert effects. Several of these chemical concerns are influenced in seriousness by composition of the food environment.

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The use of food additives originated in ancient times but did not engender controversy until the early 1800s, when intentional food adulteration became appallingly common in some countries. Problems with intentional food adulteration continued until about 1920, when regulatory pressures and effective methods of food analysis reduced the frequency and seriousness of food adulteration to acceptable levels in the United States. Since 1920 the use of legally sanctioned food additives has become common. However, for the last several decades the regulation of food additives has been a matter of controversy. Explanations for this controversy, which is likely to continue, are not difficult to identify and are discussed in the text.

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Solutions of glucose-3-phosphate dehydrogenase (GPD) and pectin methylesterase (PME) were exposed to various anesthetics and dichlorodifluoromethane (F-12) to determine the abilities of these chemicals to inhibit enzyme activity. An aqueous solution of PME was exposed to saturation levels of the test chemicals for 30 min at 21 degrees. All test chemicals were inhibitory (measured after release of the test chemical) with propane being most inhibitory followed in order by F-12, cyclopropane, Ethrane (F2HCOF2CCHClF) and halothane (CF3CHClBr). GPD was exposed to various concentrations of F-12 and halothane for various times at 0 degrees and 33 degrees. Halothane at 33 degrees and a saturation concentration reduced the initial reaction velocity of GPD to zero after a 10-min exposure period. F-12 was somewhat less inhibitory than halothane, but inhibition in all instances was irreversible. Halothane was found to affect the circular dichroism and optical rotary dispersion spectra of GPD, with the magnitude of the changes generally increasing with treatment time. The observed changes were believed to arise from side-chain transitions of GPD.

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Three anaesthetics (halothane, CF3CHClBr; Ethrane, F2 HCOF2CCHClF; cyclopropane) and one other halogenated, short-chain hydrocarbon (F-12, Cl2F2C) were tested under various conditions to determine their effects on the viability of cells of Escherichia coli and the activities of some of its enzymes. When any of the test chemicals were applied for 60 min at concentrations slightly in excess of saturation, the number of surviving cells decreased substantially, with halothane being the most biocidal of the four chemicals and F-12 the least. Three enzymes (malate dehydrogenase, MD; NADH dehydrogenase; glyceraldehyde-3-phosphate dehydrogenase, GPD) were tested for activity after treatment of E. coli with the test chemicals. In all instances, GPD was least resistant to inactivation and MD was most resistant. Halothane was most inhibitory followed in order by Ethrane, cyclopropane and F-12. Treatment of E. coli with halothane for 60 min at 23 degrees C and a concentration slightly in excess of saturation, resulted in nearly complete inhibition of all three enzymes.

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Cells of Escherichia coli ML30 in a mineral salts medium were exposed to dichlorodifluoromethane (f-12), cyclopropane, halothane, or Ethrane at concentrations of 1.25, 0.2, 0.04, and 0.008 X saturation for times up to 1,200 min, and at temperatures in the range of 2 to 37 C. When any of these anesthetics were applied for 300 min at 1.25 X saturation, a substantial decrease in number of survivors occurred. Halothane was most bactericidal, cyclopropane and Ethrane were moderately bactericidal, and t-12 was least bactericidal. At saturation values of less than 1.0, none of the four anesthetics had an appreciable effect on viability of E. coli. Greatest increases in cell permeability occurred when anesthetics were used at saturation values of 1.25, and permeability changes generally decreased as the concentrations of the chemicals were reduced. In many instances, anesthetics in the vapor state caused significant increases in cell permeability but little or no loss of viability. This indicated that a close relationship did not exist between loss of viability and increased permeability. All four anesthetics caused E. coli to lose substantial and similar amounts of compounds absorbing at 260 nm. Release of compounds absorbing at 260 nm generally increased as the saturation value of a given chemical was increased. Halothane, Ethrane, and cyclopropane but not f-12 caused lysis of E. coli ML300. Considering all results, E. coli ML30 was damaged more by halothane or cyclopropane than by f-12 or Ethrane. When f-12 was applied at a saturation value of 1.25, the bactericidal effect on E. coli was much greater at 37 or 22 C than at 12 or 2 C.

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Cultures of Escherichia coli H52 were treated with liquid dichlorodifluoromethane (fluorocarbon-12 [f-12]) for 2 h at 22 C and then examined microscopically. Treated cells tended to clump, and their cytoplasms were generally less dense and less uniform in appearance than those of control cells. E. coli ML30 was exposed to f-12 at a concentration of 1.25 X saturation for times up to 1,200 min at 22 C. Cells were examined for changes in viability (plate count), permeability (as measured by exit of alpha-[14-C]methylglucoside or uptake of omicron-nitrophenyl-beta-D-galactopyranoside), release of compounds absorbing at 260 nm, and lysis (changes in absorbance at 420 nm). Large losses of alpha-methylglucoside and of percentage of viability occurred after brief exposure to f-12. Release of compounds absorbing at 260 nm occurred more slowly than the aforementioned events, possibly because these molecules are larger than alpha-methylglucoside. During 1,200-min exposure to f-12, the number of survivors decreased from 10-9 to 10-4 organisms/ml, the loss of compounds absorbing at 260 nm amounted to 50 percent, and 32 percent lysis occurred. Most of these changes occurred during the first 300 min of treatment. Loss of alpha-methylglucoside was almost complete after 1-min exposure to f-12. These results suggest that death of the cell involves several stages, with a change of permeability, occurring first, followed by leakage of compounds of increasing size and, finally, lysis.

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Saccharomyces cerevisiae was incubated in aerosol cans containing YM broth and dichlorofluoromethane (f-21). The presence and number of viable cells were determined by inoculating (1% vol/vol) YM broth and by the plate count procedure (YM agar). Inactivation of the yeast was greater or more rapid when: (i) the thermodynamic activity (saturation value) of f-21 became greater through increasing the concentration of chemical from 0.5 to 1.5% (wt/wt) in a given volume (20, 40, or 80 ml) of broth, or by holding the concentration of chemical constant but increasing the volume of broth in the test vessel, (ii) the temperature of treatment was increased (7, 22, 37, and 47 C), (iii) samples with 1.5% (wt/wt) f-21 were agitated, (iv) young (8 h) rather than old (36 h or 10 days) cells were treated, and (v) cells were grown in YM broth without, rather than with, glucose. Adjusting the pH (6.3 to 4.0) of broth before treatment, pretreating the substrate with f-21, or distilling the chemical before use had no effect on viability of cells when treated with f-21. Yeast cells inactivated by f-21, chlorine, or heat were more resistant to disruption by sonic treatment than were viable cells.

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