Unravelling the contribution of lactic acid bacteria and acetic acid bacteria to cocoa fermentation using inoculated organisms.

Cocoa beans (Theobroma cacao L.) are the raw material for chocolate production. Fermentation of the bean pulp by microorganisms is essential for developing the precursors of chocolate flavour.

Autochthonous yeasts associated with mature pineapple fruits, freshly crushed juice and their ferments; and the chemical changes during natural fermentation.

This study investigated autochthonous yeasts and their functions in the spontaneous fermentation of freshly crushed pineapple juice samples collected from two different areas of both Thailand and Australia. Hanseniaspora uvarum and Pichia guilliermondii were the main yeast species observed on the fruit skins of Thai samples, and also in the fresh juice and ferments of all samples from both countries. P.

Wine yeasts for the future.

International competition within the wine market, consumer demands for newer styles of wines and increasing concerns about the environmental sustainability of wine production are providing new challenges for innovation in wine fermentation. Within the total production chain, the alcoholic fermentation of grape juice by yeasts is a key process where winemakers can creatively engineer wine character and value through better yeast management and, thereby, strategically tailor wines to a changing market. This review considers the importance of yeast ecology and yeast metabolic reactions in determining wine quality, and then discusses new directions for exploiting yeasts in wine fermentation.

Yeasts in foods and beverages: impact on product quality and safety.

The role of yeasts in food and beverage production extends beyond the well-known bread, beer and wine fermentations. Molecular analytical technologies have led to a major revision of yeast taxonomy, and have facilitated the ecological study of yeasts in many other products. The mechanisms by which yeasts grow in these ecosystems and impact on product quality can now be studied at the level of gene expression.

Metabolic profiling as a tool for revealing Saccharomyces interactions during wine fermentation.

The multi-yeast strain composition of wine fermentations has been well established. However, the effect of multiple strains of Saccharomyces spp. on wine flavour is unknown.

Genetic determinants of volatile-thiol release by Saccharomyces cerevisiae during wine fermentation.

Volatile thiols, particularly 4-mercapto-4-methylpentan-2-one (4MMP), make an important contribution to the aroma of wine. During wine fermentation, Saccharomyces cerevisiae mediates the cleavage of a nonvolatile cysteinylated precursor in grape juice (Cys-4MMP) to release the volatile thiol 4MMP. Carbon-sulfur lyases are anticipated to be involved in this reaction.

Degradation of RNA during the autolysis of Saccharomyces cerevisiae produces predominantly ribonucleotides.

Autolytic degradation of yeast RNA occurs in many foods and beverages and can impact on the sensory quality of the product, but the resulting complex mixture of nucleotides, nucleosides and nucleobases has not been properly characterised. In this study, yeast autolysis was induced by incubating cell suspensions of Saccharomyces cerevisiae at 30-60 degrees C (pH 7.0), and at pH 4.

Pesticides as a source of microbial contamination of salad vegetables.

Ten commercially available pesticides (insecticides, herbicides and fungicides), used during the production of vegetable produce, were examined as potential sources of microbial contaminants. As purchased, none of the pesticides showed the presence of viable microorganisms (< 5 CFU/ml). Using an agar plate diffusion assay, they did not inhibit a range of bacteria of spoilage and public health significance on vegetable produce.

Variation in 4-mercapto-4-methyl-pentan-2-one release by Saccharomyces cerevisiae commercial wine strains.

The volatile thiol 4-mercapto-4-methylpentan-2-one (4MMP) is a potent contributor to wine aroma. In grape juice, 4MMP is bound to cysteine as a non-volatile compound and requires the action of yeast during fermentation to release the aroma active thiol. A method was developed to measure 4MMP release from the precursor by headspace solid-phase microextraction and separation by gas chromatography with atomic emission detection to screen the ability of wine yeast to release 4MMP.

Application and evaluation of denaturing gradient gel electrophoresis to analyse the yeast ecology of wine grapes.

The performance of denaturing gradient gel electrophoresis (DGGE) for analysing yeasts associated with wine grapes was compared with cultural isolation on malt extract agar (MEA). After optimisation of PCR and electrophoretic conditions, the lower limit of yeast detection by PCR-DGGE was 10(2) cfuml(-1), although this value was affected by culture age and the relative populations of the species in mixed culture. In mixed yeast populations, PCR-DGGE detected species present at 10-100-fold less than other species but not when the ratio exceeded 100-fold.

Occurrence and significance of Bacillus thuringiensis on wine grapes.

Wine grapes harvested at different stages during cultivation from several vineyards in New South Wales, Australia, harboured Bacillus thuringiensis at viable populations of 10(2)-10(6) cfu/g. Commercial preparations of B. thuringiensis had been sprayed onto the grapes as a biological insecticide.

The microbial ecology of cocoa bean fermentations in Indonesia.

Cocoa beans are the principal raw material of chocolate manufacture. The beans are subject to a microbial fermentation as the first stage in chocolate production. The microbial ecology of bean fermentation (Forastero and Trinitario cultivars) was investigated at three commercial fermentaries in East Java, Indonesia by determining the populations of individual species at 12-h intervals throughout the process.

Yeast interactions and wine flavour.

Wine is the product of complex interactions between fungi, yeasts and bacteria that commence in the vineyard and continue throughout the fermentation process until packaging. Although grape cultivar and cultivation provide the foundations of wine flavour, microorganisms, especially yeasts, impact on the subtlety and individuality of the flavour response. Consequently, it is important to identify and understand the ecological interactions that occur between the different microbial groups, species and strains.

Degradation of DNA during the autolysis of Saccharomyces cerevisiae.

The autolysis of yeast cells has practical implications in the production of fermented foods and beverages and flavourants for food processing. Protein and RNA degradation during yeast autolysis are well described but the fate of DNA is unclear. Yeast cells ( Saccharomyces cerevisiae) were autolysed by incubating suspensions at 30-60 degrees C (pH 7.

Rapid Detection of Salmonellae in Foods Using Immunoassay Systems.

A standard cultural method, radioimmunometric (RIMA) and enzyme immunometric (EIMA) assays were compared for detection of salmonellae in 235 food samples. The immunoassays used titanous hydroxide as the solid-phase, commercial Spicer-Edwards salmonella polyvalent H antisera (SEA) or pooled antisera produced against 10 salmonella flagellins (PFA). Nineteen food samples were positive for Salmonella by the standard cultural method.