Current status and future prospects of sensory and consumer research approaches to gluten-free bakery and pasta products.

Sensory and consumer research performs a pivotal role in gluten-free (GF) food research and development due to consumer dissatisfaction about currently available products, despite the continued growth of this market and promising research developments. Nowadays, almost half of the original articles about GF products include sensory analysis. A current overview is needed to help both food scientists and industry indentify current trends and forward-looking approaches. This current review has gathered information concerning sensory and consumer research for GF bakery and pasta products, from studies published in the last decade, and then discusses future challenges in the light of recent advances. Among the promising approaches, projective techniques that collect data using social media can provide quick, spontaneous and direct opinions from GF consumers. They can also be used to evaluate trends and cross-cultural or global insights. Participatory methods have highlighted the importance of label information and may further explore the behavior of GF consumers in more realistic environments, as well as to evaluate the intrinsic GF food factors in GF consumer opinions, emotions, behavior and choices. This review details current issues occurring in sensory analysis of GF products, which still need to be resolved. The combination of affective and analytical methods allows for a better characterization of the samples and such sensory analysis of GF products in the future could guide product development and quality control, overcoming technological, nutritional, and shelf-life issues.

Nutrient depletion may trigger the Yersinia pestis OmpR-EnvZ regulatory system to promote flea-borne plague transmission.

The flea's lumen gut is a poorly documented environment where the agent of flea-borne plague, Yersinia pestis, must replicate to produce a transmissible infection. Here, we report that both the acidic pH and osmolarity of the lumen's contents display simple harmonic oscillations with different periods. Since an acidic pH and osmolarity are two of three known stimuli of the OmpR-EnvZ two-component system in bacteria, we investigated the role and function of this Y. pestis system in fleas. By monitoring the in vivo expression pattern of three OmpR-EnvZ-regulated genes, we concluded that the flea gut environment triggers OmpR-EnvZ. This activation was not, however, correlated with changes in pH and osmolarity but matched the pattern of nutrient depletion (the third known stimulus for OmpR-EnvZ). Lastly, we found that the OmpR-EnvZ and the OmpF porin are needed to produce the biofilm that ultimately obstructs the flea's gut and thus hastens the flea-borne transmission of plague. Taken as a whole, our data suggest that the flea gut is a complex, fluctuating environment in which Y. pestis senses nutrient depletion via OmpR-EnvZ. Once activated, the latter triggers a molecular program (including at least OmpF) that produces the biofilm required for efficient plague transmission.

Complex synergistic amino acid-nucleotide interactions contribute to the specificity of NagC operator recognition and induction.

NagC is a transcription factor that represses genes involved in N-acetylglucosamine catabolism in Escherichia coli. Repression by NagC is relieved by interaction with GlcNAc6P, the product of transport of GlcNAc into the cell. The DNA-binding domain of NagC contains a classic helix-turn-helix (HTH) motif, but specific operator recognition requires, in addition, an adjacent linker sequence, which is thought to form an extended wing. Sequences in the linker region are required to distinguish NagC-binding sites from those of its paralogue, Mlc. In investigating the contribution of the HTH to operator recognition, we have identified mutations in the first two positions of the recognition helix of the DNA-binding motif of NagC, which change NagC from being a repressor, which binds in the absence of the inducing signal (GlcNAc6P), to one whose binding is enhanced by GlcNAc6P. In this case GlcNAc6P behaves as a co-repressor rather than an inducer for NagC. The NagC mutants exhibiting this paradoxical behaviour have basic amino acids, arginine or lysine, at two critical positions of the recognition helix. Introducing a third amino acid change converts NagC back to a protein, which represses in the absence of GlcNAc6P. The triple mutant also effectively represses a modified NagC operator that is not repressed by wild-type NagC, showing that this form of NagC is a more promiscuous DNA binder. Specific recognition of the NagC operator thus involves a modulation of basic amino acid-DNA interactions, which affects the ability to discriminate against other permissive sites.