Articles scientifiques

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06 juillet 2010

Quantitative assessment of maple syrup properties by means of fluorescence spectroscopy

Auteurs : Alain Clément, Bernard Panneton et Luc Lagacé

Proceedings of the XVIIth World Congress of the International Commission of Agricultural and Biosystems Engineering, Quebec, Canada.

01 avril 2010

Seasonal and regional diversity of maple sap microbiota revealed using community PCR fingerprint and 16S rRNA gene clone librairies

Auteurs : Marie Filteau, Luc Lagacé, Gisèle LaPointe et Denis Roy

Cet article est disponible seulement en anglais (Systematic and Applied Microbiology, Volume 33, Issue 3, April 2010, Pages 165–173). Le numéro de référence (Digital Object Identifier (DOI)) est le : 10.1016/j.syapm.2010.02.003.

An arbitrary primed community PCR fingerprinting technique based on capillary electrophoresis was developed to study maple sap microbial community characteristics among 19 production sites in Que´bec over the tapping season. Presumptive fragment identification was made with corresponding fingerprint profiles of bacterial isolate cultures. Maple sap microbial communities were subsequently compared using a representative subset of 13 16S rRNA gene clone libraries followed by gene sequence analysis. Results from both methods indicated that all maple sap production sites and flow periods shared common microbiota members, but distinctive features also existed. Changes over the season in relative abundance of predominant populations showed evidence of a common pattern. Pseudomonas (64%) and Rahnella (8%) were the most abundantly and frequently represented genera of the 2239 sequences analyzed. Janthinobacterium, Leuconostoc, Lactococcus, Weissella, Epilithonimonas and Sphingomonas were revealed as occasional contaminants in maple sap. Maple sap microbiota showed a low level of deep diversity along with a high variation of similar 16S rRNA gene sequences within the Pseudomonas genus. Predominance of Pseudomonas is suggested as a typical feature of maple sap microbiota across geographical regions, production sites, and sap flow periods.

01 mars 2010

Assessment of maple syrup physico-chemistry and typicity by means of fluorescence spectroscopy

Auteurs : Alain Clément, Luc Lagacé et Bernard Panneton

Cet article est disponible seulement en anglais (Journal of Food Engineering, Volume 97, Issue 1, March 2010, Pages 17–23).  Le numéro de référence (Digital Object Identifier (DOI)) est le : 10.1016/j.jfoodeng.2009.08.029.

Maple syrup is a natural sweetener obtained from the transformation of maple sap collected mostly from sugar maple (Acer saccharum Marsh) in North America. At present, simple physico-chemical tests are used for routine quality control. Inspectors also taste all batches on the market to ensure authenticity. Because of the presence of various aromatic compounds in sap and syrup, intrinsic fluorescence was tested as a means to characterize the physico-chemistry and typicity of maple syrup. Two hundred samples of sap and their corresponding syrup were obtained from various farms in 2003 and 2004. They were analysed by conventional physico-chemical tests and by fluorescence spectroscopy. Two major regions of fluorescence were found, which were mostly the same for sap and syrup. The first one was at 320 nm, excited at 275 nm, and the second one at 460 nm, excited at 360 (syrup) or 370 nm (sap). The first peak diminishes as harvesting season progresses, while the second peak increases, making it possible to predict the harvesting period of syrup from its spectra (r2 = 0.88 in 2003 and 0.81 in 2004). Color of syrup (r2 = 0.91 and 0.88) and bacterial counts in sap (r2 = 0.75 and 0.78) were also predicted from syrup spectra. Results show that sap spectra are related to syrup spectra and could potentially be used as predictor of quality prior to transformation. Discriminant analysis revealed that between 71% and 95% of syrup samples were correctly classified according to the farm of origin in 2003, and between 78% and 100% in 2004. Proximity was not always a factor of explanation of misclassification, suggesting that precise farm location, rather than the broad region of production is the major factor of typicity.

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