Rafael D. Chaves

Differential attraction of drosophilids to banana baits inoculated with Saccharomyces cerevisiae and Hanseniaspora uvarum within a Neotropical forest remnant

Background Yeasts are a necessary requisite in the diet of most Drosophila species that, in turn, may vector their dispersal in natural environments. Differential attractiveness experiments and the isolation of yeasts consumed by Drosophila may be informative for characterizing this association. Hanseniaspora uvarum is among the most common yeast species isolated from Drosophila crops, with high attractiveness to drosophilids. Saccharomyces cerevisiae has been widely used to collect flies, and it allows broad sampling of almost all local Drosophila species. Pronounced differences in the field concerning Drosophila attractivity to baits seeded with these yeast species have been previously reported. However, few explicit generalizations have been set. Since late fifties, no field experiments of Drosophila attractivity were carried out in the Neotropical region, which is facing shifts in abiotic and biotic factors. Our objective is to characterize preference behavior that mediates the interaction in the wild among Neotropical Drosophila species and yeasts associated with them. We want to set a broad generalization about drosophilids attracted to these yeasts. Here we present the results of a differential attractiveness experiment we carried out in a natural Atlantic Rainforest fragment to assess the preferences of Drosophila species groups to baits inoculated with H. uvarum and S. cerevisiae. Methods Both yeast species were cultured in GYMP broth and separately poured in autoclaved mashed banana that was left fermenting. In the field, we collected drosophilids over five arrays of three different baits: non-inoculated autoclaved banana and banana inoculated with each yeast. In the laboratory the drosophilids were sorted to five sets according to their external morphology and/or genitalia: tripunctata; guarani; willistoni; exotic; and the remaining flies pooled in others. Results and Conclusions Uninoculated banana baits attracted virtually no flies. We found significant departures from random distribution over the other two baits (1:1 proportion) for all sets, except the pooled others. Flies of the sets willistoni and exotic preferred H. uvarum over S. cerevisiae, while the remaining sets were more attracted to S. cerevisiae. Previously, various authors reported similar patterns in attraction experiments with S. cerevisiae and H. uvarum. It is also noteworthy that both yeast species have been isolated from natural substrates and crops of Drosophila species. Taken together, these results suggest that the preferences among Drosophila species groups may be reflecting deep and stable relations with yeast species in natural environments. They can be summarized as: forest dwelling species from subgenus Drosophila (such as tripunctata and guarani groups) are attracted to banana baits seeded with S. cerevisiae; while exotic (as D. melanogaster) and subgenus Sophophora species are preferentially attracted to baits seeded with H. uvarum.

FRUITS AND VEGETABLES | Fruit and Vegetable Juices

Microorganisms present on or below the fruit–vegetable surface potentially may contaminate juices. Most juices are acidic beverages (pH 3–4) with high sugar content (11–15 °Brix), but juices with pH close to neutrality may offer more risk of pathogens. Lactic acid bacteria are the primary spoilage bacteria in fresh, unpasteurized fruit beverage while fungi that tolerate high-osmotic pressure and low pH and grow at refrigeration temperature may spoil the processed products, which have received thermal treatment to reduce enzymatic activity and the number of viable microorganism. Heat-resistant molds may survive thermal processes and may be mycotoxigenic. Alicyclobacillus may also produce off-flavor. This chapter includes tools to adequate juice process design and organisms control.

Fungi in cake production chain: Occurrence and evaluation of growth potential in different cake formulations during storage

This study aimed to determine the prevalence and populations of fungi in cake production chain. Besides, the growth potential of twelve fungal strains in different cake formulations was evaluated. Raw materials from two different batches (n=143), chocolate cakes (n=30), orange cakes (n=20), and processing environment air samples (n=147) were analyzed. Among the raw materials, wheat flour (3.2±0.3 log CFU per g) and corn meal (3.8±0.8 log CFU per g) belonging to batch #1 showed significant higher fungal counts (p<0.05). The fungal counts in the processing environment air reached up to 2.56 log CFU per m3 (p<0.05). The predominant fungi species in the industrialized cakes were Aspergillus flavus (28.15%), Penicillium citrinum (18.45%), Penicillium paxilli (14.56%), and Aspergillus niger (6.8%), which were also detected in the raw materials and processing environment air. Only Penicillium glabrum and Penicillium citrinum showed visible mycelium (>3mm) in the free of preservative cake formulation at 19th and 44th days of storage at 25°C, respectively. Revealing the biodiversity of fungi in ingredients, air and final products, as well as challenging final products with representative fungal strains may assist to implement effective controlling measures as well as to gather data for the development of more robust cake formulations.

Salmonella and Listeria monocytogenes in ready-to-eat leafy vegetables

Abstract Changes in dietary habits have pushed the inclusion of numerous ready-to-eat products in the market. Among them, minimally processed vegetables are of great importance because of their convenience, freshness, and nutritional values. The increasing demand for these foods has led to a rise in the association of these foods with disease outbreaks. The concerns with the occurrence of these outbreaks are related to the associated morbidity and mortality rates. Producers also suffer from losses in crops, food products, and corporate image. Leafy vegetables can carry potentially pathogenic microorganisms that may impact public health. This chapter focuses on the aspects related to the occurrence and importance of Salmonella spp. and Listeria monocytogenes in leafy vegetables. The main outbreaks associated with the consumption of leafy vegetables contaminated by these pathogens and the measures to prevent their transmission are discussed.