Search

Now that energy has become a world problem, cheap, effective chemical preservation is critical. This discussion forwards a new concept in food preservation. The concept is based on a 'systems' approach, using three common foodstuffs: monolaurin, food-grade phenolics and chelator, three multifunctional food materials, whose history as potential preservatives is reviewed. Although monolaurin (Lauricidin) is a Generally Recognized As Safe chemical, its use as part of a 'preservative system' is new. Comparisons of its germicidal activity by investigators have shown it to be more effective than proprionates, benzoates and even sorbic acid. The common antioxidants, tert-butylhydroxytoluene (BHT) or tert-butylhydroxyanisole (BHA) have been shown since 1967 to affect a number of different microorganisms, including viruses. The chelator ethylenediamineacetate (EDT A) has weak biocidal activity on its own but can potentiate the effect of the first two biocidal agents, particularly against gram-negative bacteria. The three common food chemicals therefore become part of a 'preservative system'. The amount and ratio of one to the other is determined by the specific need for microbiological protection.

A new family of surfactants, aminimides, has been screened forin vitro antimicrobial activity. These compounds are active against both bacteria and yeast, activity being a function of chain length. Maximum activity for acetimide and acrylimide amine derivatives was extablished with chain lengths of C14–C16. Homologous compounds with lower or higher chain lengths were less active. While showing low antimicrobial activity against gram negative bacteria, mixtures containing C12 and C16 gave good activity against gram negative strains without losing gram positive activity. Aminimides gave low acute LD50’s (200–400 mg/kg) when tested in mice by intraperitoneal injection.

The LD50 oral ingestion values for the common commercial fatty acids are in the range which are considered nontoxic; 24 hour primary skin irritation is considered positive for octanoic acid but negative for decanoic acid and upwards; 4 hour skin corrosivity is considered positive for decanoic acid and lower, negative for lauric acid and higher; eye irritation is considered positive for lauric acid and lower, negative for myristic acid and higher. Among the fatty acid derivatives that have well recognized bacteriocidal and fungicidal properties are undecanoic acid and its salts, sodium and zinc particularly, (athlete’s foot fungus), fatty amine quaternary salts, (general bacteriocide properties), fatty amide derivatives, and sodium salts of common fatty acids. The highly purified monoglyceride prepared from high C-12 fatty acid has unprecedented activity and sanitizing properties.

The structural relationships of 30 straight-chain fatty acids and derivatives and their bactericidal properties were studied with 8 gram-negative and 12 grampositive organisms. Chain length, unsaturation ( cis, trans ), and functional group were all variables considered in this study. Our data indicate that C 12 (lauric acid) is the most inhibitory saturated fatty acid against gram-positive organisms. Monoenoic acid (C 18:1 ) was more inhibitory than saturated fatty acid, but was less active than dienoic derivatives (C 18:2 ). Other unsaturated compounds were less active than C 18:2 . Alcohols and glyceryl esters were active only against gram-positive organisms. In general, esterification of the carboxyl group led to a compound which was less active; monoglycerides were the sole exception. Amine derivatives, contrary to results with fatty acids, esters, and amides, showed activity against both gram-positive and gram-negative organisms.

A broth dilution method was used to determine the minimal inhibitory concentration of a series of fatty acid esters of polyhydric alcohols against gram-negative and gram-positive organisms. Gram-negative organisms were not affected. Gram-positive organisms were inhibited as follows. Of the monoglycerol esters, monoglycerol laurate was the most active. Esters of polyglycerols (tri-, hexa-, and decaglycerol esters) were generally active when the fatty acid had chain lengths of 8 to 12 carbon atoms. Sucrose esters, when active, except for laurate, are more active than the free fatty acid. The spectrum of antimicrobial action of esters of polyhydric alcohols is narrower when compared with the free acids.

The newest member of the aminimide family of surfactants was screened for antimicrobial activity. The present report supports past conclusions that chain lengths of C14 or C16 gave maximum activity to the aminimide derivative. When a number of hexadecane compounds with different polar groups were compared, the aminimide exhibited wide spectrum antimicrobial activity. Although the functional group was important, the length and character of the acyl chain also help to determine antimicrobial activity. A new amide antibiotic, Cerulenin, with a 4-keto-2-enyl chain, was more active than the unsaturated isomer. Thus, both the functional grup as well as the chain length contribute to biocidal activity.

Aminimides are a new class of surface active agents which have antimicrobial activity. These bipolar compounds have activity against both gran-positive and yeast organisms. Their activity against gram-negative organisms is low or absent. The acyl derivatives tested showed maximum activity at chain lengths of C14 and C16. Fatty acid derivatives, shorter ( C16), were less active. Unsaturation was an important factor contributing to aminimide activity. Their low toxicity and wide spectrum of antimicrobial activity make aminimides ideal candidates for further investigation.

Monolaurin alone and monolaurin with tert-butylhydroxyanisole (BHA), methylparaben, or sorbic acid were tested for in vitro virucidal activity against 14 human RNA and DNA enveloped viruses in cell culture. At concentrations of 1% additive in the reaction mixture for 1 h at 23°C, all viruses were reduced in infectivity by >99.9%. Monolaurin with BHA was the most effective virucidal agent in that it removed all measurable infectivity from all of the viruses tested. The compounds acted similarly on all the viruses and reduced infectivity by disintegrating the virus envelope.

Aminimides, a new class of surfactants, have been screened for in vitro antimicrobial activity. Greatest activity against gram (+) and yeast organisms is achieved when a chain length of C16 is reached. This generalization is true whether or not the chain length is joined to the imide or amine group. The type of functional group associated with the surfactant is less important than chain length. Gram (-) organisms do not fit this generalization, since shorter (

Contrary to the limited effects of alkyl amides and their corresponding N -derivatives, alkyl amines affected both gram-positive and gram-negative organisms. As with other alkyl derivatives the most sensitive gram-negative bacteria were usually more resistant than the most resistant gram-positive bacteria. Compounds with a chain-length of 11 to 15 are most active. Although some of the general properties relating the activity of fatty acids to their antimicrobial action are similar to those of amine compounds, the amines are unique in that monounsaturation does not increase compound activity. The possible modes of action of these compounds are discussed.

A new instrument is described for evaluating electrophoretograms on various media. The same densitometer can be used to evaluate spots on chromatographic strips and for colorimetric analysis of solutions. The versatility of this instrument makes it a useful adjunct to any analytical laboratory.

During the past decade, our laboratory has been involved in studying the biosynthesis of brain cholesterol under various conditions. As a result of these studies, we feel that the hypothesis of metabolic stability of cholesterol in adult life is untenable. Our data suggest that there are several compartments of sterol metabolism ranging from extremely fast to metabolically very slow. It is our hypothesis that (a) brain function is more nearly associated with fast turnover compartments than with metabolically slow ones; (b) these compartments can be altered by a variety of stress conditions.