Articles scientifiques

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03 janvier 2005

Compartimentage chez l’érable à sucre

Le compartimentage de l'érable à sucre.

01 avril 2004

Identification of the Bacterial Community of Maple Sap by Using Amplified Ribosomal DNA (rDNA) Restriction Analysis and rDNA Sequencing

Auteurs : L. Lagacé, M. Pitre, M. Jacques et D. Roy.

Cet article est disponible seulement en anglais (Applied and Environmental Microbiology, April 2004, vol. 70, no. 4, 2052-2060). Le numéro de référence (Digital Object Identifier (DOI)) est le : 10.1128/AEM.70.4.2052-2060.2004 .

The bacterial community of maple sap was characterized by analysis of samples obtained at the taphole of maple trees for the 2001 and 2002 seasons. Among the 190 bacterial isolates, 32 groups were formed according to the similarity of the banding patterns obtained by amplified ribosomal DNA restriction analysis (ARDRA). A subset of representative isolates for each ARDRA group was identified by 16S rRNA gene fragment sequencing. Results showed a wide variety of organisms, with 22 different genera encountered. Pseudomonas and Ralstonia, of the {gamma}- and ß-Proteobacteria, respectively, were the most frequently encountered genera. Gram-positive bacteria were also observed, and Staphylococcus, Plantibacter, and Bacillus were the most highly represented genera. The sampling period corresponding to 50% of the cumulative sap flow percentage presented the greatest bacterial diversity according to its Shannon diversity index value (1.1). {gamma}-Proteobacteria were found to be dominant almost from the beginning of the season to the end. These results are providing interesting insights on maple sap microflora that will be useful for further investigation related to microbial contamination and quality of maple products and also for guiding new strategies on taphole contamination control.

01 mai 2003

Level of Endogenous Formaldehyde in Maple Syrup as Determined by Spectrofluorimetry

Auteurs : Luc Lagacé, Stéphane Guay et Nathalie Martin.

Cet article est disponible seulement en anglais (Journal of AOAC International, Volume 86, Number 3, May 2003, pp. 598-601).

The level of endogenous formaldehyde in maple syrup was established from a large number (n = 300) of authentic maple syrup samples collected during 2000 and 2001 in the province of Quebec, Canada. The average level of formaldehyde from these authentic samples was measured at 0.18 mg/kg in 2000 and 0.28 mg/kg in 2001, which is lower than previously published. These average values can be attributed to the improved spectrofluorimetric method used for the determination. However, the formaldehyde values obtained demonstrate a relatively large distribution with maximums observed at 1.04 and 1.54 mg/kg. These values are still under the maximum tolerance level of 2.0 mg/kg formaldéhyde pesticide residue. Extensive heat treatment of maple syrup samples greatly enhanced the formaldehyde concentration of the samples, suggesting that extensive heat degradation of the sap constituents during evaporation could be responsible for the highest formaldehyde values in maple syrup.

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