Recommendations for the viability assessment of probiotics as concentrated cultures and in food matrices

Due to the fact that probiotic cells need to be alive when they are consumed, culture-based analysis (plate count) is critical in ascertaining the quality (numbers of viable cells) of probiotic products. Since probiotic cells are typically stressed, due to various factors related to their production, processing and formulation, the standard methodology for total plate counts tends to underestimate the cell numbers of these products. Furthermore, products such as microencapsulated cultures require modifications in the release and sampling procedure in order to correctly estimate viable counts. This review examines the enumeration of probiotic bacteria in the following commercial products: powders, microencapsulated cultures, frozen concentrates, capsules, foods and beverages. The parameters which are specifically examined include: sample preparation (rehydration, thawing), dilutions (homogenization, media) and plating (media, incubation) procedures. Recommendations are provided for each of these analytical steps to improve the accuracy of the analysis. Although the recommendations specifically target the analysis of probiotics, many will apply to the analysis of commercial lactic starter cultures used in food fermentations as well.

Enhanced aglycone production of fermented soybean products by Bacillus species

This study evaluated the effect of starter culture and fermentation period on the isoflavone content of protein-rich soybeans variety TG145. Initially, soybeans were washed, soaked in water for 16 h and autoclaved at 121°C for 40min. Three different bacterial starter cultures (~104 CFU/g) namely Bacillus subtilis BEST195, B. subtilis Asaichiban and B. subtilis TN51 were then added and the fermentation was allowed to proceed at 42°C for 24 h (natto-style) and 72 h (thua nao-style). The quantities of six major isoflavones (daidzin, genistin, glycitin, daidzein, genistein, and glycitein) were then determined in these fermented soybean products using reverse phase HPLC technique. Generally, our results clearly showed that the content of total isoflavones in the fermented products prepared by Bacillus starter cultures greatly increased ranging from 43 to 99% compared to that of the unfermented autoclaved soybeans. In addition, a dramatic increase of aglycones was also observed (> 400%) in the soybean products fermented by Bacillus subtilis strain TN51. This present study suggests a promising use of Bacillus starter cultures in improving isoflavone compounds especially the aglycones which would benefit for novel functional food development.

Microbiological, chemical and rheological properties of low fat set yoghurt produced with exopolysaccharide (EPS) producing Bifidobacterium strains.

In this work, the microbiological and physicochemical differences of three types of low fat set yoghurts were studied, as well as the changes taking place during storage at 4 °C for 28 days. The first yoghurt was produced with yoghurt starters and exopolysaccharide (EPS) producing Bifidobacterium longum subsp. infantis CCUG 52486 (CCUGY), the second with yoghurt starters and Bifidobacterium infantis NCIMB 702205 (NCIMBY) and the third with just yoghurt starters (control yoghurt). No significant differences were observed in terms of cell concentrations; for all three yoghurts, similar final cell concentrations were obtained for the yoghurt starter cultures (~7.5 log cfu g−1) and the Bifidobacterium strains (~7.8 log cfu g−1). Both Bifidobacterium survived well during storage, as in both cases the cell viability decreased by less than 0.5 log cfu g−1after 28 days of storage. A decrease in pH followed by an increase in lactic acid was observed during storage for all three yoghurts, which was mostly attributed to the activity of the yoghurt starter cultures. The two yoghurts with the EPS producing Bifidobacterium strains exhibited lower syneresis than the control yoghurt. The lowest was shown by CCUGY, which also exhibited the highest storage modulus and firmness, and a well defined porous web-like structure in cryo-SEM. Examination of the micro-structure of the yoghurts using cryo-scanning electron microscopy (cryo-SEM) indicated that the above observations were due to the interaction between the EPS and the milk proteins. Overall, the results indicated that the EPS producing Bifidobacterium longum subsp. infantis CCUG 52486 is the most promising strain, and can be used with yoghurt starter cultures to manufacture low fat set yoghurt with probiotic activities and at the same time enhanced physicochemical and rheological properties.

Youth/youth cultures

Youth is an embodied social construct attached to people who are too young to be classified as fully adult, and yet older than children. It is a term whose meaning is sociospatially specific and shifting. Youth and young people are often perceived as troubling to society, and the earliest studies of youth were tied to attempts to control unruly young people. Studies of youth cultures often utilized ethnographic research to explore the perspectives of young people. Early youth cultural studies inadvertently reproduced some dominant representations of youth, as male and troubling to society, by focusing upon subcultural groupings, such as Punks and Mods, and by excluding accounts of those other than white, heterosexual males. Recent studies have moved beyond these accounts to consider how youth cultures are porous, differentiated rather than holistic, connected to broader sociospatial processes, and can reproduce powerful social relationships, such as gender, along with teasing out how youth cultures are played out differently in various geographical contexts.

Bridging the two cultures. Commercial archaeology and the study of prehistoric Britain

This paper was given at a meeting of the Society held on 12 January 2006 and it discusses the relationship between academic research and developer-funded archaeology in Britain today, highlighting the strengths and weaknesses of each. It considers the relationship between archaeological theory and practice and discusses the changing roles of academics, fieldworkers and managers. It argues that important issues need to be resolved, including the dissemination of information from recent archaeological fieldwork and the use of ‘grey literature’ in informing more ambitious interpretations of the past.

Pollen ultrastructure in anther cultures of Datura innoxia. III. Incomplete microspore division

During the microspore division in Datura innoxia, the mitotic spindle is oriented in planes both perpendicular (PE) and oblique (OB) to the spore wall against which the nucleus is situated. However, irrespective of polarity, the usual type of hemispherical wall is laid down at cytokinesis and isolates the generative cell from the rest of the pollen grain (type A). In PE spores the vegetative nucleus initially occupies a central position in the pollen grain, whereas in OB spores the vegetative nucleus lies at the periphery of the grain close to the generative cell. In anther cultures initiated just before the microspore division is due to take place, no marked change can be observed in either orientation or symmetry of the mitotic spindle when the spores divide. In some, however, cytokinesis is disrupted and deposition of the hemispherical wall arrested. In the absence of a complete wall, differentiation of the generative cell cannot take place and binucleate pollen grains are formed having 2 vegetative-type nuclei (type B). The 2 nuclei in the B pollens are always situated against the pollen-grain wall, suggesting that the disruption phenomenon is related to the OB spores. The incomplete wall always makes contact with the intine on the intine-side of the spindle. Wall material may be represented merely as short stubs projecting out from the intine into the cytoplasm, in which event the 2 nuclei lie close to each other and are separated by only a narrow zone of cytoplasm. In other grains the wall is partially developed between the nuclei and terminates at varying distances from the tonoplast; in these, the nuclei are separated by a wider zone of cytoplasm. The significance of these binucleate grains in pollen embryogenesis is discussed.

Pollen ultrastructure in anther cultures of Datura innoxia. II. The generative-cell wall.

In young pollen grains of Datura innoxia, a wall of the usual hemispherical type separates the 2 gametophytic cells initially and, in the electron microscope, appears as an electron-translucent matrix which is contiguous with the intine. Before detachment of the generative cell from the intine, the matrix decreases in thickness and in places is dispersed altogether leaving the plasmalemmae on either side of it in close apposition. A particularly prominent zone, triangular in profile, is left where the wall joins with the intine. After detachment of the cell, remnants of the matrix can be seen distributed irregularly around the cell and it is supposed that these are partly derived from material in the triangular zone as the cell is drawn away from the intine. The wall residues persist throughout the maturation phase of the pollen and are considered to be either callose resulting from incomplete digestion of the initial wall, or some other polysaccharide material which is unevenly laid down along the wall and concentrated at the junction with the intine. In pollen induced into embryogenesis by anther culture, wall material is also distributed irregularly around the detached cell in a series of discrete zones, but these are more extensive than in vivo, closer together and in many instances highly dilated. The wall profiles thus have a beaded appearance, the 'beads' being connected together by short links of the 2 apposed plasmalemmae. The contents of the swollen zones have a similar electron density to that of the matrix in vivo but also show traces of a fibrillar component. It is postulated that this unusual swelling is a prelude to dispersal of the wall by disruption of the plasmalemmal links and to the establishment of cytoplasmic continuity between the 2 cells. The significance of such binucleate pollen grains in the formation of non-haploid embryos is discussed.

Pollen ultrastructure in anther cultures of Datura innoxia. I. Division of the presumptive vegetative cell.

Ultrastructural features of embryogenic pollen in Datura innoxia are described, just prior to, during, and after completion of the first division of the presumptive vegetative cell. In anther cultures initiated towards the end of the microspore phase and incubated at 28 degrees C in darkness, the spores divide within 24 h and show features consistent with those of dividing spores in vivo. Cytokinesis is also normal in most of the spores and the gametophytic cell-plate curves round the presumptive generative nucleus in the usual highly ordered way. Further differentiation of the 2 gametophytic cells does not take place and the pollen either switches to embryogenesis or degenerates. After 48-72 h, the remaining viable pollen shows the vegetative cell in division. The cell, which has a large vacuole and thin layer of parietal cytoplasm carried over from the microspore, divides consistently in a plane parallel to the microspore division. The dividing wall follows a less-ordered course than the gametophytic wall and usually traverses the vacuole, small portions of which are incorporated into the daughter cell adjacent to the generative cell. The only structural changes in the vegetative cell associated with the change in programme appear to be an increase in electron density of both plastids and mitochondria and deposition of an electron-dense material (possibly lipid) on the tonoplast. The generative cell is attached to the intine when the vegetative cell divides. Ribosomal density increases in the generative cell and exceeds that in the vegetative cell. A thin electron-dense layer also appears in the generative-cell wall. It is concluded that embryogenesis commences as soon as the 2 gametophytic cells are laid down. Gene activity associated with postmitotic synthesis of RNA and protein in the vegetative cell is switched off. The data are discussed in relation to the first division of the embryogenic vegetative cells in Nicotiana tabacum.