THE ANTIMICROBIAL ACTIVITY OF PHENOLIC ANTIOXIDANTS IN FOODS: A REVIEW1

Phenolic antioxidants such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and monotertiary butylhydroquinone (TBHQ) are hindered phenols with antimicrobial activity. The antimicrobial activity of phenolic antioxidants appears to depend on the presence of a hydroxyl group on the molecule, the lipid solubility of the compound and the degree of steric hindrance. The use of phenolic antioxidants in food products is regulated by federal agencies. In general, these compounds are permitted in concentrations up to 200 ppm, based on the fat or oil content of the food product. Certain food products have special regulations. The antimicrobial activity of phenolic antioxidants has been studied in meat and its products, poultry and its products, milk and its products, seafood, rice, applesauce and food ingredients. The antimicrobial activity of phenolic antioxidants is modified by at least 10 factors such as microbial species/strain, stressed microorganisms, type and concentration of phenolic antioxidants, concentration of microbial challenge, combination of phenolic antioxidants, combination of phenolic antioxidants with other antimicrobials, combination of phenolic antioxidants with temperature and food additives, food components, carriers of phenolic antioxidants and the mode of addition of phenolic antioxidants. The antimicrobial activity of phenolic antioxidants in foods has been examined against growth and by-products of bacteria (gram positive and negative, spore and nonspore formers, spoilage and pathogenic), molds and yeasts. The concentration of phenolic antioxidants that had antimicrobial activity in food products was in the range of 30–10,000 ppm. The mechanism of inhibition by phenolic antioxidants has been found to affect the function and composition of the cellular membrane, the synthesis of DNA, RNA, protein and lipid, and the function of the mitochondrion.     

INDIRECT ANTIMICROBIAL EFFECTS IN FOODS: PHOSPHATES

This review supplements the review by Hargreaves et al. (1972). Phosphate selection in the U.S. continues to be based upon achieving specific functional objectives other than microbial control. Current federal regulations limit the addition of phosphates to those levels which will achieve functionality. One notable exception is shelf stable pasteurized process cheese, cheese food, and cheese spreads. Adding relatively high levels of phosphates for emulsification coincidentally provides microbiological stability; however, the minimum levels for stability remain uncertain.
It is becoming increasingly evident that phosphates, under certain conditions, have potential value for enhancing the microbial safety and stability of foods. Certain phosphates or mixtures of phosphates are clearly more effective than others. Through future research, it should be possible to further exploit the potential value of phosphates. This review offers direction for such research.     

ANTIMICROBIAL EFFECTS OF SPICES1

There is a renewed interest in the antimicrobial properties of spices. In vitro activities of several ground spices, their water and alcohol extracts, and their essential oils have been demonstrated in culture media. Studies in the last decade confirm growth inhibition of gram positive and gram negative food borne bacteria, yeast and mold by garlic, onion, cinnamon, cloves, thyme, sage and other spices. Effects in foods are limited to observations in pickles, bread, rice, and meat products. In general, higher spice levels are required to effect inhibition in foods than in culture media. Fat, protein, and water contents in foods affect microbial resistance as does salt content. Very few studies report on the effect of spices on spores, and on microbial inhibition in conjunction with preservatives and food processes. Of the recognized antimicrobial components in spices, the majority are phenol compounds with a molecular weight of 150 to 160 containing a hydroxyl group. Eugenol, carvacrol and thymol have been identified as the major antimicrobial compounds in cloves, cinnamon, sage and oregano.     

RHEOLOGY OF LIQUID FOODS - A REVIEW1

Liquid foods are classified and their properties discussed under various types of rheological behavior: Newtonian, pseudoplastic, shear thickening, thixotropic, and viscoelastic. Rheological data on selected liquid foods are summarized in either tabular form or in the form of equations. Wherever possible the influence of temperature, constituents, and structure on the rheological behavior is detailed. Because many foods are suspensions, the measurement of flow properties of suspensions and factors influencing their rheological behavior are also covered. Finally, the relationship between the flow behavior and the sensory evaluation of mouth feel and viscosity is discussed.     

WHOLESOMENESS OF IRRADIATED FOODS: A REVIEW

The major findings in the wholesomeness studies on irradiated foods are reviewed. It is concluded that this process is ready for industrial applications and could be effectively regulated for the benefit of the consumer.     

INSTRUMENTAL MEASUREMENT OF STICKINESS OF DOUGHS AND OTHER FOODS

Stickiness is a difficult attribute to measure. It can be defined as simply the force of adhesion when two surfaces are contacted with each other. In most food systems, the adhesion force is a combination of an adhesive force and a cohesive force. It is when the adhesive force is high and the cohesive force is low that material is perceived as being sticky. Cohesive properties can be measured by rheological techniques. To measure adhesive properties it is imperative to have a clean separation at the probe-material interface.     

SIGNIFICANCE OF RESIDUAL ORGANISMS IN FOODS AFTER SUBSTERILIZING DOSES OF GAMMA RADIATION: A REVIEW1

The nature of the flora surviving substerilizing irradiation of foods is dependent on the dose applied and the conditions of applications as well as the microenvironment of the food. At a dose level low enough to preserve acceptable sensory properties of fresh food, few if any of the common contaminants of public health significance survive irradiation. Survivors are weakened and present no unique problem of acquired resistance through recycling. Those bacteria surviving a low dose treatment of a relatively contaminated product like ground beef can grow under normal storage conditions and cause obvious sensory spoilage. Thus, low dose irradiation extends the shelf-life of fresh foods and reduces public health hazards, but foods so treated require normal care in production and distribution.     

食品中伏马菌素的污染及污染控制

伏马菌素（Fumonisin）是20世纪80年代末期发现的一类由串珠镰刀菌产生的真菌毒素.伏马菌素分布广泛且毒性较大,因此它在食品安全中的意义越来越受到人们的重视.本文叙述了产伏马菌素的真菌,综述了中国不同地区、不同食品中伏马菌素污染的情况,以及各种降低伏马菌素污染的方法,综述了关于伏马菌素的立法.     

INHIBITION OF SPOILAGE AND PATHOGENIC BACTERIA ASSOCIATED WITH FOODS BY COMBINATIONS OF ANTIMICROBIAL AGENTS

The antibacterial activity of combinations of lysozyme, monolaurin (ML), triglycerol 1,2 laurate (TGL) and butylated hydroxyanizole (BHA) against 7 Gram-positive and 8 Gram-negative bacteria was studied at different pH, NaCl and EDTA concentrations by the spiral gradient end point test. The inhibitory effect of lysozyme in combination with ML was slightly greater for Gram-positive than for Gram-negative bacteria, but their combined effect was not markedly more inhibitory than ML alone. Lysozyme and TGL together were only inhibitory at low pH and high NaCl concentrations in the presence of EDTA. There was an increase in inhibition when lysozyme and BHA were combined. For Gram-positive bacteria, inhibition by ML and BHA together was more marked than when either was present singly. However, ML decreased the antibacterial activity of BHA against Gram-negative bacteria. Similarly, TGL was antagonistic to BHA action against both Gram-positive and Gram-negative bacteria. In general, the inhibition produced by all combinations was greater as the pH decreased and the NaCl concentration increased, especially in the presence of EDTA .     

EFFECTS OF OVEN HUMIDITY ON FOODS BAKED IN GAS CONVECTION OVENS1

Bread, cakes, and cookies were baked in direct‐ and indirect‐gas fired, foodservice style convection ovens. Oven humidity was varied by including different numbers of perlite and water dummy loads during baking. Oven, product, and dummy temperatures were continuously recorded during baking, as was oven humidity. The properties of the finished baked foods were measured. Increased oven humidity resulted in products with higher yield, greater volume or spread, lighter color, and reduced firmness.     

A REVIEW: ENZYMATIC CROSS-LINKING OF PROTEINS APPLICABLE TO FOODS

The functional properties of food proteins may be changed by the use of specific enzymes. Enzymatic reactions can be carried out under relatively mild conditions and, because of the specificity of the reactions, are not likely to lead to toxic products. Among the several reactions catalyzed by enzymes, some lead to the intra- and intermolecular cross-linking of proteins. In this review, we briefly describe the reactions catalyzed by transglutaminase, lipoxygenase, lysyl oxidase, protein disulfide reductase, protein disulfide isomerase and sulfhydryl oxidase and the feasibility of using these enzymes for cross-linking of food proteins. Very little data are available on the efficiency of cross-linking and the effect on functional and nutritional properties of the proteins.     

A REVIEW ON PREDICTING FREEZING TIMES OF FOODS

Heat transfer during freezing of a food material involves a complex situation of simultaneous phase transition and changing thermal properties. Models for predicting freezing times range from relatively simple analytical equations based on a number of assumptions and approximations, to the more versatile numerical methods which require the use of a sophisticated computer. The necessity for having a consistent definition for freezing time, the nature of the freezing process, different prediction models and thermo-physical properties of importance are discussed in view of the mathematics of freezing time computations. In this review, attention has been focused on established analytical models which can be solved without resorting to computer techniques. The review points out the need for further refinement of the existing Plank-type models to facilitate accurate freezing time estimations under a wide range of practical conditions.     

INHIBITION OF LISTERIA MONOCYTOGENES AND OTHER BACTERIA BY SODIUM DIACETATE

Growth and survival patterns of Listeria monocytogenes strain Scott A were studied in brain heart infusion broth containing sodium diacetate. Minimum inhibitory concentrations decreased with decrease in temperature, from 35 and 32 mM at 35C and 20C, respectively, to 28 mM at 5C. Broth pH containing 35, 32, and 28 mM sodium diacetate was 5.25, 5.40 and 5.60, respectively. Sodium diacetate was more effective than acetic acid alone in inhibiting the organism over the pH range of 5.0-6.0. Addition of 21 mM (0.3%) sodium diacetate to ground beef or beef slurry suppressed total aerobic counts during refrigerated storage. Although the meat pH decreased from 5.6 to 5.2 by the addition of the compound, a major part of the antimicrobial effect was attributed to the diacetate and not just pH. Sodium diacetate suppressed growth of three additional L. monocytogenes strains and strains of Escherichia coli, Pseudomonas fluorescens, Salmonella enteriditis and Shewanella putrefaciens. P. fragi, Yersinia enterocolitica, Enterococcus faecalis, Lactobacillus fermentis and Staphylococcus aureus were insensitive to the compound. Sodium diacetate has potential for use in controlling growth of listeriae in meat, poultry and fish products and suppressing growth of certain Gram-negative spoilage and pathogenic microorganisms.     

CORRELATION AMONG METALLIC IONS,PHENOLIC COMPOUNDS AND ANTIMICROBIAL ACTION IN MEDICINAL PLANTS EXTRACTS

ABSTRACT

The extracts of three different medicinal plants –Calendula officinalis L., Maytenus ilicifolia Martius ex Reissek and Cymbopogon citratus (DC) Stapf – obtained with 70% and 95% v/v ethanol had their antimicrobial activity tested against five pathogenic microorganisms. A quantitative analysis of total phenols, flavonoids and mineral species was performed on the extracts using UV‐vis spectroscopy and atomic absorption spectroscopy. Klebsiella pneumoniae showed the greatest sensibility to the extracts tested. The mineral content of the medicinal herbs varied according to the type of plant (Cu = not detected to 10.90; Zn = 0.85 to 10.04; Na = 24.94 to 153.62; Al = 90.04 to 420.39; Mg = 9.62 to 1,129.15; Ca = 7.15 to 167.27 and K = 913.85 to 9,578.94 µg/g); however, the concentration of heavy elements (Pb, Cd and Cr) was null in the extracts. The concentrations of flavonoids ranged from 13.55 to 41.54 mg/g and 92.35 to 518.28 mg/g for phenolic acids.

PRACTICAL APPLICATIONS

The use of plants with pharmacological activities has increased significantly because of their functional properties in the diet for the promotion of human health and antimicrobial effects. Moreover, medicinal herbs play an important role in public health, especially in developing countries. In Brazil, the use of plant extracts in the treatment of certain diseases is very common. This habit can be explained, at least in part, by the belief that herbs with therapeutic effects do not have toxic effects on the organism. In this paper, ethanolic extracts of three medicinal plants, widely cultivated and used by the population of Brazil and worldwide, had their levels of metals ions and total phenolic compounds determined. Antimicrobial activity of the extracts was evaluated against foodborne pathogens or food spoilage organisms or clinically isolates microorganisms.