Sourdough authentication: quantitative PCR to detect the lactic acid bacterial microbiota in breads.

No national legislation anywhere in the world regulates and protects traditional/typical sourdough breads. Sourdough fermentation is firmly associated with a century-old tradition, and with sensory and nutritional quality of breads. A well-defined cell density of lactic acid bacteria has to be reached at the end of fermentation, and be indirectly detectable in baked breads. A Quantitative PCR (qPCR) method was developed to discriminate between breads made with and without sourdoughs. Universal primers targeting an approximately 178-bp fragment of the 16S rRNA-encoding gene of lactic acid bacteria were designed, covering the known diversity of sourdough lactic acid bacteria and excluding commonly encountered flour bacterial contaminants. A total of 191 breads either made with traditional type I and dried sourdough and baker's yeast, or by a chemical leavening method were shown to be accurately discriminated by means of qPCR. Discriminating values of gene copy number were only weakly correlated with pH values, and with lactate and acetate concentration, thus questioning the validity of these latter indirect indices. The use of sourdough has to be guaranteed to meet both bakery and consumer expectations, and to fulfil legal requirements; our work presents a reliable authentication method providing a suitable tool to satisfy such requirements.

Exploitation of Leuconostoc mesenteroides strains to improve shelf life, rheological, sensory and functional features of prickly pear (Opuntia ficus-indica L.) fruit puree.

Strains of Leuconostoc mesenteroides were identified from raw prickly pear (Opuntia ficus-indica L.). Five autochthonous strains were selected based on the kinetics of growth and acidification on prickly pear fruit juice, and the capacity to synthesize exo-polysaccharides. All selected Leuc. mesenteroides strains showed an in vitro mucilage-degrading capability. A protocol for processing and storage of fermented prickly pear fruit puree (FP) was set up. Unstarted FP and chemically acidified FP were used as the controls. Starters grew and remained viable at elevated cell numbers during 21 days of storage at 4 °C. Contaminating Enterobacteriaceae and yeasts were found only in the controls. Viscosity and serum separation distinguished started FP compared to the controls. Colour parameters, browning index, sensory attributes, antimicrobial activity, vitamin C and betalains levels were positively affected by lactic acid fermentation. Increase of free radical scavenging activity in ethyl acetate soluble extract suggested an effect of selected strains on phenolic profiles. Started FP markedly inhibited the inflammatory status of Caco-2/TC7 cells, and also contributed to maintaining the integrity of tight junctions. Started FP scavenged the reactive oxygen species generated by H2O2 on Caco-2 cells. All selected strain variously affected the immunomodulatory activity towards anti- and pro-inflammatory cytokines.

Yogurt-like beverages made of a mixture of cereals, soy and grape must: microbiology, texture, nutritional and sensory properties.

Cereal (rice, barley, emmer and oat) and soy flours and concentrated red grape must were used for making vegetable yogurt-like beverages (VYLB). Two selected strains of Lactobacillus plantarum were used for lactic acid fermentation, according to a process which included the flour gelatinization. All VLYB had values of pH lower than 4.0 and both selected starters remained viable at ca. 8.4 log cfu/g throughout storage. All VLYB showed high values of apparent viscosity and water holding capacity. During fermentation, lactic acid bacteria consumed glucose, fructose, and malic acid, which was supplied with grape must. Compared to control vegetable yogurt-like beverages (CVYLB), without bacterial inoculum, an increase of total free amino acids (FAA) was found during fermentation and storage. Also the concentration of polyphenolic compounds and ascorbic acid (ASC) was higher in VLYB compared to CVYLB. This was reflected on the antioxidant activity. As determined by Solid Phase Micro-Extraction/Gas-Chromatography/Mass-Spectrometry analysis, several volatile compounds were identified. Beverages made with the mixture of rice and barley or emmer flours seemed to possess the best combination textural, nutritional and sensory properties.