Articles scientifiques

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02 juillet 2007

Partial demineralization of maple sap by electrodialysis: impact on syrup sensory and physicochemical characteristics

Auteurs : Laurent Bazinet, Hélène Gaudreau, Darie Lavigne et Nathalie Martin.

Cet article est disponible seulement en anglais (Journal of the Science of Food and Agriculture, Volume 87, Issue 9, July 2007, pages 1691–1698). Le numéro de référence (Digital Object Identifier (DOI)) est le : 10.1002/jsfa.2890.

In this project, samples of osmosed maple saps were demineralized to 12.5 and 25% levels by electrodialysis (ED). The effect of this treatment on the composition and the physicochemical and sensory properties of maple syrups obtained from demineralized maple sap was evaluated. The ED technology was efficient to decrease levels of malic acid and calcium in osmosed maple saps. Effectively, 38% and 24% decreases in malic acid and calcium respectively were reached for ED with a demineralization level of 25% without any changes in the other measured components of osmosed maple saps. The demineralization process had no effect on the yield of syrups produced and on their characteristics: no significant difference was observed during sensory analysis and viscosity. Moreover, the percentage of light transmission of syrups produced from demineralized osmosed saps was higher than for the control. This work suggests that ED could be a potential technology to decrease or avoid sugar sand formation during maple syrup production. Copyright © 2007 Society of Chemical Industry.

15 octobre 2006

Biofilm Formation and Biocides Sensitivity of Pseudomonas marginalis Isolated from a Maple Sap Collection System

Auteurs : Lagacé, L., Jacques, M., Mafu, A. A. et D. Roy.

Cet article est disponible seulement en anglais (Journal of Food Protection, Vol. 69, No 10, October 2006, pp. 2320-2566, pp. 2411-2416(6)).

The susceptibility of planktonic and biofilm cells of Pseudomonas marginalis toward four commonly used biocides at different temperatures (15 and 30°C) and biofilm growth times (24 and 48 h) was assessed. Using the MBEC biofilm device, biofilm production in maple sap was shown to be highly reproducible for each set of conditions tested. Biofilm formation was influenced by growth temperature and time. A temperature of 15°C and incubation time of 24 h yielded fewer CFU per peg and showed fewer adhered cells and typical biofilm structures, based on scanning electron microscopy observations as compared with other conditions. Minimal biofilm eradication concentration values for P. marginalis were significantly greater (P < 0.001) than were MBCs for planktonic cells and for every biocide tested, with the exception of minimal biofilm eradication concentration values for peracetic acid at 15°C and 24 h. Sodium hypochlorite and peracetic acid sanitizers were able to eliminate P. marginalis biofilms at lower concentrations as compared with hydrogen peroxide- and quaternary ammonium-based sanitizers (P < 0.001). According to the results obtained, sodium hypochlorite and peracetic acid sanitizers would be more appropriate for maple sap collection system sanitation.

01 mai 2006

Compositions of maple sap microflora and collection system biofilms evaluated by scanning electron microscopy and denaturing gradient gel electrophoresi

Auteurs : L. Lagacé, M. Jacques, A. A. Mafu et D. Roy.

Cet article est disponible seulement en anglais (International Journal of Food Microbiology, Volume 109, Issues 1–2, 25 May 2006, Pages 9–18). Le numéro de référence (Digital Object Identifier (DOI)) est le : 10.1016/j.ijfoodmicro.2006.01.004.

The bacterial microflora of maple sap and biofilms in collection system tubing were studied through the use of bacterial counts, scanning electron microscopy (SEM) of surfaces and the analysis of 16S rRNA gene by denaturing gradient gel electrophoresis (DGGE). Samples were taken at five times during the 2002 and 2003 seasons in order to follow the changes in the microflora of this complex ecosystem. Bacterial counts showed the growth of bacterial populations as the season advanced. These populations were mainly composed of psychrotrophic bacteria and Pseudomonas spp. SEM results confirmed the suspected presence of biofilms on the inner surfaces of tubing samples. Bacterial colonization and biofilm formation progressively increased during the season for both lateral and main line surfaces, and biofilms were mainly composed of rod shape bacteria. The bacterial microflora profiles obtained for sap and corresponding biofilm by DGGE showed up to 12 major bands. The Shannon-Weaver index of diversity (H) calculated from DGGE bands were statistically higher for sap samples compared to biofilm. The diversity index was relatively stable or increasing for lateral line sap and biofilm samples during the season while the diversity index for sap and biofilm samples of the main line showed a decreasing profile as the season progressed. Sequence analysis of major DGGE bands revealed the predominance of bacteria from the genera Pseudomonas, Rahnella and another, unidentified genus. The results describe the composition of sap collection system microflora as well as the formation of biofilms and will be useful for further studies on factors affecting maple product quality.

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