Aroma compounds in sweet whey powder were investigated in this study. Volatiles were isolated by solvent extraction followed by solvent-assisted flavor evaporation. Fractionation was used to separate acidic from nonacidic volatiles. Gas chromatography/mass spectrometry and gas chromatography/olfactometry were used for the identification of aroma compounds. Osme methodology was applied to assess the relative importance of each aroma compound. The most aroma-intense free fatty acids detected were acetic, propanoic, butanoic, hexanoic, heptanoic, octanoic, decanoic, dodecanoic, and 9-decenoic acids. The most aroma-intense nonacidic compounds detected were hexanal, heptanal, nonanal, phenylacetaldehyde, 1-octen-3-one, methional, 2,6-dimethylpyrazine, 2,5-dimethylpyrazine, 2,3-dimethylpyrazine, 2,3,5-trimethylpyrazine, furfuryl alcohol, p-cresol, 2-acetylpyrrole, maltol, furaneol, and several lactones. This study suggested that the aroma of whey powder could comprise compounds originating from milk, compounds generated by the starter culture during cheese making, and compounds formed during the manufacturing process of whey powder.

Mycobacterium avium subsp. paratuberculosis is the cause of Johne's disease in cattle and other ruminants. M. avium subsp. paratuberculosis infection of the bovine host is not well understood; however, it is assumed that crossing the bovine intestinal mucosa is important in order for M. avium subsp. paratuberculosis to establish infection. To examine the ability of M. avium subsp. paratuberculosis to infect bovine epithelial cells in vitro, Madin-Darby bovine kidney (MDBK) epithelial cells were exposed to M. avium subsp. paratuberculosis. It was observed that bacteria can establish infection and replicate within MDBK cells. M. avium subsp. paratuberculosis also has been reported to infect mammary tissue and milk, and we showed that M. avium subsp. paratuberculosis infects bovine mammary epithelial cells (MAC-T cell line). Using polarized MAC-T cell monolayers, it was also determined that M. avium subsp. paratuberculosis crosses apical and basolateral surfaces with approximately the same degree of efficiency. Because M. avium subsp. paratuberculosis can be delivered to the naïve host by milk, it was investigated whether incubation of M. avium subsp. paratuberculosis with milk has an effect on invasion of MDBK cells. M. avium subsp. paratuberculosis exposed to milk entered epithelial cells with greater efficiency than M. avium subsp. paratuberculosis exposed to broth medium or water (P < 0.01). Growth of M. avium subsp. paratuberculosis within MAC-T cells also resulted in augmented ability to subsequently infect bovine MDBK cells (P < 0.001). Microarray analysis of intracellular M. avium subsp. paratuberculosis RNA indicates the increased transcription of genes which might be associated with an invasive phenotype.Mycobacterium avium subsp. paratuberculosis is the etiologic agent of Johne's disease in cattle and other ruminants. It is assumed that M. avium subsp. paratuberculosis infects the young calf by crossing the intestinal barrier. Previous work (3, 26) has indicated that the interaction of M. avium subsp. paratuberculosis with bovine epithelial cells is a complex process which might involve participation of several bacterial and host factors. For example, it has been reported that both in calves and in mice, challenge by the gastrointestinal route results in M. avium subsp. paratuberculosis infecting M cells in the Peyer's patches (23,26). Recently, Secott and colleagues have suggested that the invasion of the intestinal mucosa by M. avium subsp. paratuberculosis is secondary to the binding to fibronectin (26). In addition, Bannantine and colleagues demonstrated a role for a 35-kDa M. avium subsp. paratuberculosis protein in the invasion of cultured bovine epithelial cells (5). The 35-kDa protein is exposed in the outer layer of M. avium subsp. paratuberculosis and has also been associated with Mycobacterium avium invasion of human intestinal cells (22).After M. avium subsp. paratuberculosis crosses the intestinal mucosa, the infection spreads to other organs, leading to the advanced stages of disease. Sever...

Three varieties of Queso Fresco cheese were produced: a control cheese made from raw milk, cheese made from pressure-treated milk, and cheese treated with high pressure after production. Sensory attributes, texture profile analysis, and composition were compared following 1 and 8 d of storage time.High-pressure treatment of cheese (400 MPa, 20 min, 20 °C) did not impart major textural and compositional changes; however, cheese made from pressure-treated milk contained more moisture and was less firm, less crumbly, and more sticky than the control and decreased in firmness during storage. High-pressure processing treatment of cheese can provide an alternative method for producing Queso Fresco-style cheese with acceptable textural attributes.

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