Antibacterial action of an aqueous grape seed polyphenolic extract

The potential of a polyphenolic grape seed extract for use as a natural antibacterial agent was evaluated. Pure catechin (CS) and a previously LC-MS characterized grape seed phenolic extract (PE) were evaluated as antibacterial agents against Escherichia coli and Brevibacterium linens on solid and in liquid culture media. After 48 h incubation on solid medium, PE had a bactericidal effect on the gram positive B. linens and a reduction of the microbial growth for E. coli. The antibacterial agents tested were effective against E. coli for 13 h, after 7 h incubation, but ineffective against B.linens in liquid medium. CS and PE both had an antibacterial effect depending on incubation time.Key words: Catechin, polyphenolic extract, antibacterial activity, Brevibacterium linens, Escherichia coli B41

Monitoring Lactic Acid Fermentation in Media Containing Dandelion (Taraxacum officinale) by FTIR Spectroscopy

Fourier-transform infrared (FTIR) spectroscopy is considered to be a comprehensive and sensitive method for detection of molecular changes in cells and media. In the present study, FTIR spectroscopy was employed as an easy, rapid and reliable technique to evaluate the lactic fermentation of Lactobacillus casei on a model de Man, Rogosa and Sharpe (MRS) medium with or without the addition of dandelion extract (DE). Dandelion, due to its high content in fructans, can be used as an additional carbon source in lactic fermentation. Lactic fermentation in a dandelion extract, using the FTIR fingerprint as a qualitative and semi-quantitative assay for lactic acid production was monitored. Specific bands of carbohydrates in the fingerprint region (1200-900 cm-1) and their shifts indicated the hydrolysis and metabolism during fermentation. The band at 1336 cm-1 may be considered a sensitive marker for the identification of L. casei during fermentation, while the dandelion extract showed a unique characteristic peak at 1436 cm-1. The results proved that the species were detectable and that significant spectral differences existed between fermented samples in media with or without dandelion addition. Representative peaks of bacteria and dandelion appeared in the spectra of a mixture of bacteria and dandelion. The peaks were evident in the samples taken using the model MRS media from the beginning of fermentation as opposed to at the end of fermentation

Study of the cheese salting process by dielectric properties at microwave frequencies

[EN] The salting process involves complex phenomena that affect the overall quality of cheese due to its effect on water activity and induced biochemical changes. The permittivity of cheese was analysed throughout the cheese salting treatment in order to relate it to water and salt transport. The salting treatment was carried out using 25% (wily) sodium chloride brine at 4 degrees C. The samples were immersed in a vessel containing the osmotic solution with continuous stirring, for 0, 10, 20, 30, 40, 50, 60, 90, 120, 180, 240, 360, 480, 720, 900 and 1440 min. Samples were subsequently equilibrated in an isothermal chamber at 4 degrees C for 24 h. Mass, volume, surface water activity, moisture, ion content and permittivity were determined in fresh and salted samples. Permittivity was measured from 500 MHz to 20 GHz, using an openended coaxial probe connected to a Vector Network Analyser. The results showed that measurements at 20 GHz explain the water loss and water flux in the overall product. The state of the electrolytes in cheese can be followed using the ionic conductivity at 500 MHz. A coupled measurement of permittivity at 20 GHz and 500 MHz can predict the chemical species involved in the cheese salting process, and its structural changes. In conclusion, the measurement of permittivity in the microwave range can be used to monitor the salting cheese process. (C) 2018 Elsevier Ltd. All rights reserved.The authors acknowledge financial support from the Spanish Ministerio de Economia, Industria y Competitividad, Programa Estatal de I+D+i orientada a los Retos de la Sociedad AGL2016-80643-R. Author J. Velazquez-Varela thanks the Consejo Nacional de Ciencia y Tecnologia (CONACyT) of Mexico for its support. This paper was published under the frame of the European Social Fund, Human Resources Development Operational Programme 2007-2013, project no. POSDRU/159/1.5/S/132765.Velazquez-Varela, J.; Castro Giraldez, M.; Cuibus, L.; Tomás-Egea, JÁ.; Socaciu, C.; Fito Suñer, PJ. (2018). Study of the cheese salting process by dielectric properties at microwave frequencies. Journal of Food Engineering. 224:121-128. https://doi.org/10.1016/j.jfoodeng.2017.12.024S12112822