Biomedical subjects

G M Heard

Publications and source records attributed to G M Heard.

7 recordsLinked to original sources

PubMed2006

Lactic acid bacteria associated with wine grapes from several Australian vineyards.

AIMS: The detection and isolation of lactic acid bacteria by enrichment methods from wine grapes cultivated in vineyards located in New South Wales, Australia. METHODS AND RESULTS: Enrichment cultures in de Man, Rogosa and Sharpe (MRS) broth, MRS + ethanol (5%), MRS broth supplemented with 15% (v/v) tomato juice (MRST), pH 5.5 and 3.5 and autoenrichment in grape juice homogenate were used to detect lactic acid bacteria on wine grapes. Bacteria were isolated from enrichment cultures by plating onto MRS and MRST agar and identified by 16S rDNA sequence analysis and phenotypical methods. A molecular method, PCR-denaturing gradient gel electrophoresis (DGGE) was also used to examine the bacteria that developed in enrichment cultures. Species of Lactobacillus, Enterococcus, Lactococcus and Weissella were detected in enrichments by plating and PCR-DGGE. Other bacteria (Sporolactobacillus, Asaia, Bacillus ssp.) were also found in some enrichment cultures. The principal malolactic bacterium, Oenococcus oeni, was not isolated. CONCLUSIONS: The incidence and populations of lactic acid bacteria on wine grapes were very low. Damaged grape berries showed a greater presence of these bacteria than undamaged berries. The diversity of bacterial species isolated from the grapes was greater than those previously reported and represented both lactic acid bacteria and nonlactic acid bacteria. Some of these bacteria (i.e. Lactobacillus lindneri, Lactobacillus kunkeei) could be detrimental to wine production. Oenococcus oeni was not found on grapes, but its recovery could be obscured by overgrowth from other species. SIGNIFICANCE AND IMPACT OF THE STUDY: Lactic acid bacteria are significant in wine production because they conduct the malolactic fermentation and cause stuck or sluggish alcoholic fermentation and wine spoilage. This study investigates wine grapes as a potential source of these bacteria.

Culture Media↗

PubMed2002

Application of nontraditional meat starter cultures in production of Hungarian salami.

Listeria monocytogenes and Escherichia coli O111 have been implicated in several outbreaks of food-borne disease linked to smallgoods products. Traditional meat starter cultures, containing a mixture of lactic acid bacteria (LAB) and staphylococci, are used to maintain safety and sensory properties of Hungarian salami. The present study investigated if nontraditional meat starter (NTMS) cultures can be used for improving the safety of Hungarian salami. Salami batter was inoculated with List. monocytogenes and E. coli and subsequently fermented with NTMS cultures and a commercially available meat starter. A total of 15 NTMS cultures were tested. The salami was monitored for levels of pathogen, LAB and pH. When used in conjunction with the commercial meat starter, 9 NTMS cultures reduced the E. coli O111 count by more than 2.5 log units, whereas 10 of the NTMS cultures reduced List. monocytogenes by more than 2.5 log units. The commercial meat starter alone reduced E. coli and List. monocytogenes by 1.2 and 1.3 log units, respectively. Some NTMS cultures reduced the pathogen count without affecting pH of the salami batter. All NTMS cultures survived in salami throughout fermentation and maturation. It was concluded that NTMS cultures, including Lactobacillus acidophilus LAFTI L10, L. paracasei LAFTI L26, L. paracasei 5119, Lactobacillus sp. L24 and Bifidobacterium lactis LAFTI B94, may be used to increase the safety of Hungarian salami because these cultures gave strong inhibition of both E. coli O111 and List. monocytogenes.

Bifidobacterium↗

PubMed2000

Microbial species associated with different sections of broccoli harvested from three regions in Australia.

The microbial populations associated with the different sections of broccoli harvested from three locations in Australia were studied during storage at 5, 15 and 20 degrees C. Bacterial and yeast populations associated with the outer florets and cut surfaces of the stem were generally 10-fold or more higher than those associated with inner florets or non-cut stems, respectively. The predominating bacterial species varied with the origin of the broccoli. Pseudomonas fluorescens, Ps. corrugata and Ps. viridiflava predominated at populations of 10(5)-10(7) cfu/g on broccoli harvested from Victoria, Ps. fluorescens, Ps. mendocina and Ps. fragii and Arthrobacter spp. (10(-3) 10(6) cfu/g) were prevalent on broccoli harvested from Queensland. Broccoli harvested from New South Wales exhibited a predominance of Ps. fluorescens, Arthrobacter spp. and Enterobacteragglomerans (10(3)-10(5) cfu/g). Most species grew on broccoli during storage. Similar species were found at the different sections of broccoli, although, for some species there was evidence of strain variation at the different locations and for different temperature of storage.

Australia↗

PubMed1997

Evaluation of the Biolog system for the identification of food and beverage yeasts.

The inconvenience of conventional yeast identification methods has resulted in the development of rapid, commercial systems, mainly for clinical yeast species. The Biolog system (Biolog Inc., Hayward, CA, USA) is a new semi-automated, computer-linked technology for rapid identification of clinical and non-clinical yeasts. The system is based around a microtitre tray and includes assimilation and oxidation tests. This paper evaluates the Biolog system for the identification of 21 species (72 strains) of yeasts of food and wine origin. Species correctly identified included Saccharomyces cerevisiae, Debaryomyces hansenii, Yarrowia lipolytica, Kluyveromyces marxianus, Kloeckera apiculata, Dekkera bruxellensis and Schizosaccharomyces pombe. Zygosaccharomyces bailii and Zygosaccharomyces rouxii were identified correctly 50% of the time and Pichia membranaefaciens 20% of the time.

Beverages↗

PubMed1990

A convenient microtitre tray procedure for yeast identification.

Media for yeast identification tests were incorporated into the wells of a microtitre tray. The tests included fermentation and assimilation of carbohydrates, assimilation of nitrogen compounds, growth in vitamin-free medium, resistance to cycloheximide, and observations for cell morphology and sporulation. Results of tests conducted in the trays showed very good agreement with those obtained by conventional methods. Eighteen reference yeasts were correctly identified from tests conducted in the trays. The trays of media could be stored, and provided a convenient system for yeast identification.

Carbohydrate Metabolism↗

PubMed1987

Occurrence and Growth of Killer Yeasts during Wine Fermentation.

Sixteen wine fermentations were examined for the presence of killer yeasts. Killer property and sensitivity to killer action were found in isolates of Saccharomyces cerevisiae but not in isolates of Kloeckera, Candida, Hansenula, and Torulaspora spp. Several killer and killer-sensitive strains of S. cerevisiae were differentiated by colony morphology, and this property was used to monitor their growth kinetics in mixed cultures in grape juice. Killer-sensitive strains died off within 24 to 48 h during mixed-strain fermentation. Killer action was demonstrated at pH 3.0 and pH 3.5 and over the range of 15 to 25 degrees C but depended on the proportion of killer to killer-sensitive cells at the commencement of fermentation. The dominance of killer strains in mixed-strain fermentations was reflected in the production of ethanol, acetic acid, and glycerol.

Journal Article↗

PubMed1985

Growth of Natural Yeast Flora during the Fermentation of Inoculated Wines.

The growth of yeasts that occur naturally in grape juice was quantitatively examined during the fermentation of four wines that had been inoculated with Saccharomyces cerevisiae. Although S. cerevisiae dominated the wine fermentations, there was significant growth of the natural species Kloeckera apiculata, Candida stellata, Candida colliculosa, Candida pulcherrima, and Hansenula anomala.

Journal Article↗