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

Bioprocessing technology to exploit organic palm date (Phoenix dactylifera L. cultivar Siwi) fruit as a functional dietary supplement

Date fruit (Phoenix dactylifera L.) is a suitable raw matrix for manufacturing of functional ingredients. The aptitude of selected autochthonous lactic acid bacteria for manufacturing of freeze-dried powder from fermented date fruits puree as dietary supplement with health-promoting features was investigated. Fermentation of date fruits puree with selected Lactobacillus plantarum strains allowed the highest concentration of γ-amino butyric acid, conjugated fatty acids, and insoluble dietary fibers. The highest Trolox equivalent antioxidant activity was also induced. Lactic acid fermentation affected the profile of phenolic acids and flavonoids, enriching date fruits puree in phenolic derivatives with high human bioavailability. Fermented date fruits puree was also capable to modulate positively in vitro the growths of several cultivable gut microbial taxa, and enhanced the synthesis of short chain fatty acids. In conclusion, the lactic acid fermentation of date fruits is a suitable tool to achieve a standardized and marketable functional dietary supplement

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