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Biomedical subjects

D Y Fung

Publications and source records attributed to D Y Fung.

At least 19 recordsLinked to original sources
PubMed1996

Alkaline-fermented foods: a review with emphasis on pidan fermentation.

Alkaline-fermented foods constitute a group of less-known food products that are widely consumed in Southeast Asia and African countries. They can be made from different raw ingredients. For instance, Japanese natto, Thai thua-nao, and kinema are made from cooked soybeans, dawadawa from African locust beans, ogiri from melon seeds, ugba from African oil beans, kawal from fresh legale leaves, owoh from cotton seeds, and pidan from fresh poultry eggs. In alkaline-fermented foods, the protein of the raw materials is broken down into amino acids and peptides; ammonia is released during the fermentation, raising the pH of the final products and giving the food a strong ammoniacal smell. Most alkaline fermentations are achieved spontaneously by mixed bacteria cultures, principally dominated by Bacillus subtilis. In other cases, pure cultures can be used. For example, Japanese natto is inoculated with a pure culture of B. subtilis var natto. Pidan is a special example of alkaline fermentation. Instead of using microorganisms, pidan is made using an alkali-treated fermentation. Sodium hydroxide (NaOH) is produced from the reaction of sodium carbonate (Na2CO3), water (H2O), and calcium oxide (CaO) of pickle or coating mud. NaOH penetrates into the eggs, causing the physicochemical changes, color changes, and gelation. The appearance of pidan differs from fresh eggs in that the white becomes a semitransparent tea-brown color, and the yolk is solid or semisolid with a dark-green color. The nutritional value of pidan is slightly decreased compared with fresh eggs, but pidan has an extremely long shelf life and a pleasant, fragrant taste that is preferred by most people in Southeast Asian countries. In a small-scale laboratory study conducted by the authors, B. subtilis was not found in pidan. Four Staphylococcus spp. (S. cohnii, S. epidermidis, S. haemolyticus, and S. warneri) and two strains of Bacillus spp. (B. cereus and B. macerans) were isolated from pidan. Staphylococcus spp. did not contribute to the fermentation and were considered contaminants.

Africa↗
PubMed1995

Microbiology of fresh and restructured lamb meat: a review.

Microbiology of meats has been a subject of great concern in food science and public health in recent years. Although many articles have been devoted to the microbiology of beef, pork, and poultry meats, much less has been written about microbiology of lamb meat and even less on restructured lamb meat. This article presents data on microbiology and shelf-life of fresh lamb meat; restructured meat products, restructured lamb meat products, bacteriology of restructured meat products, and important foodborne pathogens such as Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes in meats and lamb meats. Also, the potential use of sodium and potassium lactates to control foodborne pathogens in meats and restructured lamb meat is reviewed This article should be of interest to all meat scientists, food scientists, and public health microbiologists who are concerned with the safety of meats in general and lamb meat in particular.

Animals↗
PubMed1995

Salmonellae and food safety.

Salmonella is one of the most important foodborne pathogens around the world. The knowledge that very low numbers of Salmonella cells can be infectious emphasizes the need for stringent food safety measures Traditional methods for isolating and identifying Salmonella in food rely on preenrichment, selective enrichment in selective and differential media, biochemical tests, and serological confirmation. Recent advances in diagnostic technology have considerably altered testing methods for foodborne Salmonella. Many commercial assay systems and kits that use newer technologies are available to facilitate the identification of Salmonella in foods. These systems include miniaturized biochemical tests, new media formulations, automated instrumentation, DNA/RNA probes, antibody-dependent assays, and polymerase chain reaction. The technologies used for these systems are described, and the various kit formats are compared. Among the limitations of detection methods in terms of food safety are timeliness, limits of detection, and differentiation of virulent and nonvirulent isolates. Current efforts of prevention measures and strategies at different links of the food chain such as consumer education and hazard analysis and critical control point (HACCP) programs are reviewed, Global approaches to food safety are needed..

Consumer Product Safety↗
PubMed1993

Five-tube most-probable-number method using the Fung-Yu tube for enumeration of Listeria monocytogenes in restructured meat products during refrigerated storage.

The survival of Listeria monocytogenes in cooked, chopped hams stored at 5 degrees C for 5 weeks was studied. Slices of chopped ham (25 g) were inoculated with a three-strain mixture of L. monocytogenes (LM 101M, LM 103M, and Scott A) at levels of < or = 350 cfu/25 g and packaged in Stomacher bags. Prior to inoculation, L. monocytogenes cells were subjected to either heat-injury (56 degrees C, 30 min) or freeze-injury (-18 degrees C, 14 days). The organisms were detected by a five-tube most-probable-number (MPN) technique using the motility enrichment Fung-Yu tube, and the direct plating method. After storage at 5 degrees C for 1 week, there was a one log10 reduction in counts. Thereafter, Listeria recovered and heat- and freeze-injured cells grew to 10(7) and 10(8) within 5 weeks, respectively. Similar results were obtained from both methods. However, direct plating could not recover L. monocytogenes at low levels (< or = 100/25 g), whereas MPN counts were obtained at these low levels. The pH (6.22 +/- 0.10) of the chopped hams remained constant throughout the study. These results indicated that low numbers of L. monocytogenes surviving sublethal heat- or freeze-injury could initiate growth after recovery in chopped hams. The five-tube MPN method using the Fung-Yu tube was effective in enumerating both low and high levels of L. monocytogenes in food.

Animals↗
PubMed1993

Tempeh: a mold-modified indigenous fermented food made from soybeans and/or cereal grains.

A variety of indigenous fermented foods exist today; however, tempeh has been one of the most widely accepted and researched mold-modified fermented products. Tempeh is a traditional fermented food made from soaked and cooked soybeans inoculated with a mold, usually of the genus Rhizopus. After fermentation has occurred, the soybeans are bound together into a compact cake by dense cottony mycelium. An important function of the mold in the fermentation process is the synthesis of enzymes, which hydrolyze soybean constituents and contribute to the development of a desirable texture, flavor, and aroma of the product. Enzymatic hydrolysis also may decrease or eliminate antinutritional constituents; consequently, the nutritional quality of the fermented product may be improved. Current technology and new scientific advancements have enabled researchers to examine specific strains of Rhizopus and new substrates such as cereal grains. Because Kansas produces numerous cereal grains, production of a fermented tempeh-like product using wheat, sorghum (milo), oats, rye, barley, corn, and triticale is a definite possibility for generating a Kansas Value-Added Product. In this study, several different tempeh-like products were produced using various cereal grains inoculated with Rhizopus oligosporus NRRL 2549 or R. oligosporus NRRL 2710. Grains used included hard red winter wheat, triticale, yellow sorghum (milo), and red sorghum (milo). The grain source as well as the strain of R. oligosporus used influenced the product's appearance, flavor, and patty integrity. Results showed that R. oligosporus NRRL 2549 produced more mycelium at a more rapid rate than did the R. oligosporus NRRL 2710 strain. The combination of red sorghum and R. oligosporus NRRL 2549 yielded a product with good patty texture, aroma, and appearance. Furthermore, the red sorghum fermented product was well suited for slicing. On the other hand, yellow sorghum inoculated with either R. oligosporus NRRL 2549 or R. oligosporus NRRL 2710 failed to produce an organoleptically suitable product. Triticale also was found to be an unacceptable substrate for the production of a tempeh-like product. Although the fermented wheat product had a desirable aroma and flavor, it lacked patty integrity and crumbled when sliced. Further research is needed to evaluate the economic significance and industrial applications of these tempeh-like products.

Edible Grain↗
PubMed1991

New aniline blue dye medium for rapid identification and isolation of Candida albicans.

Organic dyes have long been used in diagnostic microbiology to differentiate species by color reactions. We studied the ability of a new noninhibitory medium, YM agar containing 0.01% aniline blue WS dye, Colour Index 42780 (YMAB), to identify Candida albicans among 1,554 yeast specimens obtained from seven clinical laboratories. Appropriate American Type Culture Collection and other characterized strains served as controls. A total of 487 of the clinical strains were identified as C. albicans. The remainder were other Candida species and non-Candida yeasts. Clinical isolates and controls were grown on Sabouraud agar for 18 h at 30 degrees C and then transferred to YMAB. Plates were incubated for 12 to 18 h at 30 degrees C, and colonies were observed for yellow-green fluorescence under long-wave UV light (A365). All control strains of C. albicans and Candida stellatoidea fluoresced, as did 480 of the 490 isolates designated as C. albicans (which included 3 strains of C. stellatoidea). Cells of C. albicans grown on YMAB produced germ tubes in serum. Only five of the other 1,062 non-C. albicans yeasts fluoresced. The sensitivity and specificity were 98.0 and 99.5%, respectively, with a predictive value of 99.1%. A fluorescent metabolite was found in cell wall particulate fractions of C. albicans sonic extracts grown on YMAB but not in non-C. albicans yeasts. This metabolite showed the same spectral curve as those of metabolites from whole cells in a recording spectrofluorometer when it was excited at 400 nm and scanned from 420 to 550 nm. Thus, growth on YMAB generates the production of a fluorescent moiety that can be used to specifically identify C. albicans within 12 to 18 h.

Aniline Compounds↗
PubMed1990

Aeromicrobiology--a review.

This article reviews the presence of microorganisms in air and their sources, the relation of airborne dust and endotoxin, the sources of atmospheric microbial contamination in food-processing plants, the mechanisms of airborne particle deposition, the importance of airborne microbes, the survival of microorganisms in air, methods of air sampling, airborne microbial populations in food-processing plants, control of airborne microorganisms in food-processing plants, and the general issue of microorganisms in air and their impact on food safety. The purpose was to bring together scattered information about airborne microorganisms and review their importance in food protection and sanitation.

Air Microbiology↗
PubMed1987

Conventional and rapid methods for yeast identification.

Identification of yeasts depends on data obtained from morphological features and physiological characteristics. This article reviews the commonly used conventional methods for the identification of yeast to set the stage for a critical review of rapid systems for yeast identification. Comparative analyses of percentage agreement of API 20C, Uni-Yeast Tek, Minitek, Mycotube, Micro-Drop, Auxodisk, Iatron, Autobac 1, AMS, Abbott MS-2, and Abbott Quantum 11 against the conventional method and, in some cases, against each other are tabulated. Gas liquid chromatography method, enzyme method, MUG, and the Fung's mini-system are also mentioned as possible rapid methods for yeast identification. The purpose of this review is to update the rapidly expanding information concerning diagnostic kits and systems for yeast identification and analyze some of the advantages, disadvantages and potential uses of rapid systems of yeast identification.

Mycology↗
PubMed1986

Off-flavors in milk.

This report is a review of off-flavors encountered in fluid milk. It includes sections on transmitted, microbial, lipolyzed, heated, light-activated, oxidized, and miscellaneous flavors. Finally, the flavor of ultrahigh temperature (UHT) milk is reviewed. Most of the literature cited for different off-flavors covers the period since a comprehensive review was done of milk flavors by Strobel et al. (1953). In addition to causative agents and volatile materials associated with off-flavors, methods for control of each of the off-flavors are presented. This report is designed to serve the dairy production and processing industry, students and faculty of food science curricula, dairy product evaluation students, regulatory people, and fieldmen.

Animal Feed↗
PubMed1986

Critical review of water activities and microbiology of drying of meats.

The drying of meat is one of the least expensive and most effective ways to preserve meat. This article reviews the influence of intrinsic and extrinsic parameters of foods in relation to the drying of meat and the role of microbial activities in the drying and storage of meat. The critical role of water activity and its relationship with other physical and chemical parameters and microbial survival in the drying of meat is also reviewed in detail. This article ends with a description of the various methods to measure water activity in foods. The conclusion is that the drying of meat is a highly complex phenomenon which is influenced by the composition of meat, its water holding capacity, the processing of meat, and various microorganisms found on meat before and after the drying process. There is no doubt that the drying of meat is an effective preservation process, but attention should be placed on the possible survival of microorganisms in the process in order to prevent spoilage and food-borne diseases.

Animals↗
PubMed1985

Effect of phenolic antioxidants on microbial growth.

Antioxidants belong to a class of compounds used to retard oxidation of chemicals in foods. These compounds, such as BHA, BHT, TBHQ, PG, etc. are approved to be used in foods by government agencies. In the past 10 years considerable interest has been directed to the antimicrobial properties of these compounds due to the observations by various scientists that many of these compounds can suppress the growth of viruses, protozoa, bacteria, yeast, and molds and their subsequent production of toxic materials in foods. Thus, the dual purpose usage of these compounds (i.e., antioxidation and antimicrobial) has been the subject of many research papers. This review is designed to summarize major publications on this subject as well as present some detailed studies on the effect of major antioxidants on bacteria and mold generated in the laboratory of the author in recent years.

Animals↗
PubMed1982

The effect of microwaves on nutrient value of foods.

Microwave cooking has gained considerable importance as an energy-saving, convenient, and time-saving cooking method. This article reviews the state of the art of microwave cooking and the existing publishing data on the effects of microwave cooking on nutritive values of moisture, protein, carbohydrate, lipid, minerals, and vitamins. Most reports indicated that microwave cooking resulted in higher moisture losses compared with conventional methods. Overall, the nutritional effects of microwaves on protein, lipid, and minerals appear minimal. There is no report on the effects of microwaves on carbohydrate fraction in foods. A large amount of data is available on the effects of microwaves on vitamins. It is concluded that there are only slight differences between microwave and conventional cooking on vitamin retention in foods. In conclusion, no significant nutritional differences exist between foods prepared by conventional and microwave methods. Any differences reported in the literature are minimal.

Animals↗
PubMed1977

The excretion of enterotoxin B from nongrowing cells of Staphylococcus aureus 4916.

The physiological conditions for the excretion of staphylococcal enterotoxin B (SEB) by nongrowing cells have been determined. In general, SEB excretion appears to be best when amino acids serve as sources of carbon, nitrogen, and energy. Little toxin was produced in a nitrogen-free medium with glucose as the sole carbon source. Inhibitor studies have shown that most of the toxin excreted by nongrowing cells was the result of de novo protein synthesis. Optimum toxin excretion was also obtained under conditions of aeration, and at or near optimum growth temperature, those conditions at which the cells are metabolically and biosynthetically most active. Levels of cell-associated SEB decreased during toxin excretion. However, these levels of toxin could not account for the high levels of toxin released during excretion. Glucose and several other rapidly fermentable carbohydrates inhibited toxin excretion by as much as 80% under conditions of uncontrolled decrease in pH: however, when the pH was kept at either 6.2 or 7.5 a stimulation of toxin excretion was observed. Protoplast studies have suggested that SEB production does not take place in the absence of an intact cell wall.

Air↗
PubMed1977

Acriflavine violet red bile agar for the isolation of Klebsiella.

A medium for the isolation and detection of Klebsiella is described. It contains 0.06% Acriflavine in Violet Red Bile agar (Difco). Klebsiella appeared as 5 to 7 mm mucoid (24 h at 37 degrees C) golden-yellow colonies. Pseudomonas aeruginosa and Enterobacter spp. appeared as small, brown to dark brown colonies. Escherichia coli as well as many other gram negative organisms and gram positive organisms did not grow on this medium.

Acridines↗
PubMed1976

The occurrence of cell-associated enterotoxin B in Staphylococcus aureus.

Cell-associated enterotoxin B was detected in lysates of cells of Staphylococcus aureus S-6 and 4916 disrupted by sonication or lysostaphin treatment. As much as 67% of this total cell-associated toxin was surface-bound, located outside the cytoplasmic membrane, and was released during protoplasting of this organism by lysostaphin treatment in hypertonic medium. The remainder of the cell-associated toxin was termed cytoplasmic and was released during osmotic lysis of the protoplasts. Levels of cell-associated toxin as a function of the age of the cells showed a rapid increase in both surface-bound, cytoplasmic, and total cell-associated toxin levels during the period of active toxin synthesis (late exponential phase of growth). These cell-associated toxin levels then reached a peak as the culture entered stationary phase, at a time corresponding to a decrease in the rate of toxin synthesis, and decreased slowly thereafter.

Cell Membrane↗
PubMed1973

Effect of dyes on bacterial growth.

A rapid screening procedure was used to test the effect of 42 dyes on growth of 30 bacteria on solid media. The results indicated that many readily available dyes might have potential application for selective isolation of specific bacterial groups as well as value in differentiating between closely related bacterial taxa. Separation of Enterobacter from Escherichia, Salmonella from Shigella, and Staphylococcus from Micrococcus by selected dyes was also evaluated.

Coloring Agents↗