EFFECT OF FILMS OF DIFFERENT OXYGEN TRANSMISSION RATE ON TOXIN PRODUCTION BY CLOSTRIDIUM BOTULINUM TYPE E IN VACUUM PACKAGED COLD AND HOT SMOKED TROUT FILLETS

Studies were done to determine the effect of film oxygen transmission rate (OTR) on the time to toxicity in vacuum packaged cold and hot smoked rainbow trout fillets challenged with C. botulinum type E (10² spores/g) and stored at refrigerated conditions (4C), and under mild (8C) and moderate (12C) temperature abuse conditions. While no samples were toxic at 4C, toxin was detected within 28 days at 8C for cold smoked trout fillets vacuum packaged in films with high OTR. Toxin was also detected for most vacuum packaged hot smoked trout fillets within 14–28 days at 8C, with the exception of trout fillets packaged in films with an OTR > 10,000 cc/m²/day. In most cases at 8C, spoilage, based on odor/color scores, preceded or occurred simultaneously with toxigenesis. At 12C all cold and hot smoked trout were toxic after 14–21 days and samples packaged in films with an OTR <5000 cc/m²/day became toxic before, or at the same time as, samples became spoiled. This study has shown that vacuum packaging of trout fillets in low gas barrier films, ranging in OTR from approximately 3,000 to approximately 10,000 cc/m²/day at 24C and 0% relative humidity (RH), did not prevent the growth and toxin production by C. botulinum in vacuum packaged cold and hot smoked trout fillets at 12C. Additional barriers, other than the OTR of the packaging film, need to be considered to ensure the safety of vacuum packaged trout fillets, particularly at mild to moderate temperature abuse storage conditions.     

FROM TOXIC TOURS TO GROWING THE GRASSROOTS: TENSIONS IN CRITICAL PEDAGOGY AND COMMUNITY DEVELOPMENT

ABSTRACT: Structural inequalities in American public education are inextricably tied to deep‐seated patterns of racial and economic segregation. Children in poor neighborhoods are less likely to have the household resources, neighborhood institutions, or school amenities necessary for a good, challenging education. In response, a growing number of organizations have launched initiatives to simultaneously revitalize neighborhoods and improve public education, emphasizing youth participation as an essential component in their efforts. We draw upon ethnographic data from two such organizations to examine their practice of place‐based critical pedagogy in community development. We focus on how they engage marginalized, “hard‐to‐reach” youth via (1) experiential learning, to counter high‐stakes testing models and cultivate a sense of ownership in the local community, and (2) empowered deliberative action, in contextualized ways. The tensions embedded in these organizations’ complex efforts have implications for other groups of marginalized youth engaged in community development, especially in their attempts to help students gain concrete outcomes in community development and achieve long‐term sustainability.     

EFFECT OF HEADSPACE OXYGEN AND FILMS OF DIFFERENT OXYGEN TRANSMISSION RATE ON TOXIN PRODUCTION BY CLOSTRIDIUM BOTULINUM TYPE E IN RAINBOW TROUT FILLETS STORED UNDER MODIFIED ATMOSPHERES

Studies were conducted to determine the effect of various levels of headspace oxygen (0–100%, balance CO₂) or film oxygen transmission rate (OTR) on the time to toxicity in modified atmosphere packaged (MAP) fresh trout fillets challenged with C. botulinum type E (10² spore/g) and stored under moderate temperature abuse conditions (12C). In all cases, trout were toxic within 5 days, irrespective of the initial levels of oxygen in the package headspace. However, spoilage preceded toxigenesis. Packaging of trout fillets in low gas barrier films, with OTRs ranging from 4,000 to 10,000 cc/m²/day at 24C and 0% relative humidity, also had no effect on time to toxicity in all MAP trout fillets. All fillets were toxic within 4–5 days and spoilage again preceded toxigenesis. This study has shown that the addition of headspace O₂, either directly to a package or indirectly by using a low gas barrier film, had no influence on the time to toxigenesis or spoilage. Additional barriers, other than headspace O₂ or film transmission rate, need to be considered to ensure the safety of MAP trout fillets, particularty at moderate temperature abuse conditions.     

Mathematical Characterization of the Compressive Stress-Strain Relationships of Spongy Baked Goods

The compressive stress-strain relationships of selected breads, English muffins and sponge cake were determined with a Universal Testing Machine and described mathematically in terms of a three-parameter empirical model. These parameters gave account of the overall mechanical resistance of the sponge, the existence of a shoulder in its stress-strain curve and the strain level at which densification of the sponge becomes the dominant deformation mechanism. They were also sensitive indicators of the changes that were observed in the stress-strain relationship as a result of successive compression and could be used to distinguish between the deformation patterns of the various products.     

A RESEARCH NOTE UNIAXIAL COMPRESSION OF DOUBLE LAYERS OF SOLID FOODS 1

The compressive force deformation relationships of various foods, that included breads, cheeses and sausages, were described by a two parameter power model. To predict the behavior of double layered arrays of some foods, their model parameters were incorporated into an equation that describes the relationships between the force and the total deformation of the array for a given cross-sectional area and any initial thickness of each of the two layers. Construction of the force-deformation relationships of the double layered array was done by numerical solution of this equation for various levels of deformation. The force deformation relationships predicted in this way were found to be in good agreement with experimental relationships. This was irrespective of whether the force deformation curve of the components had a concave upward or downward shape.     

Emulsifying Effects of Food Macromolecules In Presence of Ethanol

The influence on droplet size of ethanol present during homogenization was investigated for emulsions stabilized by macromolecular emulsifiers: sodium caseinate, whey protein isolate, gelatin and gum arabic. Emulsions produced with polysaccharide gum arabic had increasing droplet size as ethanol concentration increased, in contrast to the protein-stabilized emulsions which had decreasing droplet size (up to 20 % ethanol for gelatin and 30 % ethanol for the milk proteins), followed by increasing droplet size with increasing ethanol concentration. Interfacial tension measurements indicated that the emulsifying property of the macromolecules depended on adsorption at the oil-water/alcohol interface during emulsification.     

TEM and AES investigations of the natural surface nano‐oxide layer of an AISI 316L stainless steel microfibre

The chemical composition, nanostructure and electronic structure of nanosized oxide scales naturally formed on the surface of AISI 316L stainless steel microfibres used for strengthening of composite materials have been characterised using a combination of scanning and transmission electron microscopy with energy‐dispersive X‐ray, electron energy loss and Auger spectroscopy. The analysis reveals the presence of three sublayers within the total surface oxide scale of 5.0–6.7 nm thick: an outer oxide layer rich in a mixture of FeO.Fe₂O₃, an intermediate layer rich in Cr₂O₃ with a mixture of FeO.Fe₂O₃ and an inner oxide layer rich in nickel.     

The yeast flora of stored ready-to-use carrots and their role in spoilage

Spoilage of ready-to-use grated raw carrots packaged in polymeric films and stored at 10°C was investigated for involvement of yeasts. Cryptococcus albidus was only isolated during the first 3 days of storage, increasing to levels of 10⁵–10⁶g^-1. Candida lambica was more commonly isolated after 3–7 days of storage, and reached 10⁷–10⁸g^-1 after 12 days. Candida sake was present throughout storage, increasing from 10⁵–10⁶ after 3 days to 10⁷–10⁸ after 12 days. In some samples, Candida parapsilosis and Candida tropicalis were also isolated at levels similars to C. sake . All the yeasts isolated at the end of storage were fermentative species and their metabolism was characterized with a Warburg apparatus. Neither the number of yeasts nor the composition of the yeast flora were related to the deterioration of the product. Although Candida lambica inoculated on grated carrots caused spoilage after 12 days at 10°C, the high O₂ permeable film was most effective in reducing exudate.