Predicting maple syrup grade . . .
tamination classes showed zero or very low concentrations of in- tion has serious implications for the commercial value of maple
vert sugar, resulting in syrups of extra-light or light color. This can syrup and hence for the maple industry at large.
be explained in part by the fact that sap with a high contamina-
References
tion level was collected and processed so rapidly that sucrose hy-
drolysis could not take place. This type of situation is likely to oc-
cur mid-season, when the weather is favorable for both microbial
growth and high sap flow, and the storage period is not long.
AOAC. 1984. Bacterial population of maple sap. In: Williams S, editor. Official
Methods of Analysis of the Association of Official Analytical Chemists. Arling-
ton, VA. U.S.A. Association of Official Analytical Chemists. p 600.
Bautista DA, Sprung DW, Barbut S, Griffiths MW. 1997. A sampling regime based
on an ATP bioluminescence assay to assess the quality of poultry carcasses at
critical control points during processing. Food Res Int 30:803-809.
Branger A, Cuvillier I, Rabhi L. 1995. Dosage de l’ATP microbien pour l’estimation
de la flore totale du lait cru. Lait 75:295-299.
ATP versus syrup flavor
Sap contamination also has an impact on the organoleptic
characteristics of syrup, as shown in Figure 4. In this figure, most
of the syrups in the low sap contamination classes were found to
be superior or standard in taste in sensory evaluation, while most
of the syrups grouped in the higher sap contamination classes
exhibited off-flavors. These results show that sap microorga-
nisms contribute to the degradation of syrup organoleptic char-
acteristics to some extent. The off-flavor attributes of maple syr-
up comprised characteristics such as intense caramel flavor or
foreign flavor. Figure 5 also reveals the effect of sap contamina-
tion on maple syrup flavor by showing the presence of acetic acid
in syrups made from sap with a higher level of microbial contami-
nation. Acetic acid is not normally present in syrup made from
sap with a lower level of microbial contamination, and this can be
seen in Figure 5. The presence of acetic acid gives maple syrup
an undesirable taste.
In general, microbial contamination of maple sap giving bi-
oluminescence levels (log RLU/mL) lower than 5.5 will yield a syr-
up with acceptable color and flavor characteristics, whereas sap
with levels higher than 5.5 will predominantly result in syrups
with lower color and flavor grades. These results indicate that the
commercial value of maple syrup is highly dependent on the ex-
tent of microbial contamination of maple sap. Hence, this factor
deserves considerable attention.
Edson HA. 1912. Micro-organisms occurring in maple sap and their influence
on the color, flavor and chemical composition of sirup. In: Micro-organisms of
maple sap. Hills JL, editor. Univ Vt Agric Exp Sta Bull. 167:333-418.
Fabian FW, Buskirk HH. 1935. Aerobacter aerogenes as a cause of ropiness in
maple sirup. J Ind Engin Chem 27:349-350.
Gouvernement du Québec, 1998. Les produits de l’érable et leur succédanés. In:
Règlement sur les aliments. Ch. 8. Éditeur Officiel du Québec, Québec. p 86-91.
Graumlich TR. 1985. Estimation of microbial populations in orange juice by
bioluminescence. J Food Sci 50:116-117.
Griffiths MW. 1993. Applications of bioluminescence in the dairy industry. J Dairy
Sci 76:3118-3125.
Holgate KC. 1950. Changes in the composition of maple sap during the tapping
season. NY State Agr Exp Sta Bull. 742:1-14.
Kissinger JC. 1969. Modified resazurin test for estimating bacterial population
in maple sap. JAOAC 52:714-716.
Kissinger JC. 1974. Collaborative study of a modified resazurin test for estimat-
ing bacterial count in raw maple sap. JAOAC 57:544-547.
Littel KJ, LaRocco KA. 1985. Bioluminescent standard curves for quantitative
determination of yeast contaminants in carbonated beverages. J Food Prot 48:
1022-1024.
Morselli MF, Whalen ML. 1991. Aseptic tapping of sugar maple (Acer saccharum)
results in light color grade syrup. Can J For Res 21:999–1005.
Murphy SC, Kozlowski SM, Bandler DK, Boor KJ. 1998. Evaluation of adenosine
triphosphate-bioluminescence hygiene monitoring for trouble-shooting flu-
id milk shelf-life problems. J Dairy Sci 81:817-820.
Naghski J, Willits CO. 1957. Maple sirup. XI. Relationship between the type and
origin of reducing sugars in sap and the color and flavor of maple sirup. Food
Res 22:567–571.
Phillips JD, Griffiths MW. 1985. Bioluminescence and impedimetric methods for
assessing shelf-life of pasteurized milk and cream. Food Microbiol 2:39-51.
Reybroeck W, Schram E. 1995. Improved filtration method to assess bacteriolog-
ical quality of raw milk based on bioluminescence of adenosine triphosphate.
Netherlands Milk & Dairy J 49:1-14.
Sheneman JM, Costilow RN. 1958. Identification of micro-organisms from ma-
ple tree tapholes. Food Res 24:146-151.
Siragusa GR, Cutter CN. 1995. Microbial ATP bioluminescence as a means to
detect contamination on artificially contaminated beef carcass tissue. J Food
Prot 58:764-769.
Siragusa GR, Cutter CN, Dorsa WJ, Koohmaraie M. 1995. Use of a rapid microbial
ATP bioluminescence assay to detect contamination on beef and pork carcass-
es. J Food Prot 58:770-775.
Sutherland AD, Bell C, Limond A, Deakin J, Hunter EA. 1994. The biotrace meth-
od for estimating bacterial numbers in milk by bioluminescence. J Soc Dairy
Technol 47:117-120.
Conclusions
N THE PRESENT STUDY, WHICH INVOLVED THE APPLICATION OF ATP BI-
I
oluminescence as a method of measuring maple sap microbial
contamination, the values obtained were found to correlate with
total aerobic count. This method is easier and gives quicker re-
sults than both the standard plate count method and the modi-
fied resazurin method. In view of this, ATP bioluminescence rep-
resents a useful method for improving sanitation procedures
and predicting maple syrup characteristics. According to our
findings, ATP bioluminescence of sap gave an adequate assess-
ment of maple syrup color and flavor, keeping in mind that other
factors besides the microbial contamination level of sap can af-
fect the characteristics of maple syrup. One such factor is the
control of the evaporation process. In most cases, maple sap with
ATP bioluminescence values greater than 5.5 log RLU/mL result-
ed in maple syrup with a lower grade color and flavor. This situa-
MS20010374 Submitted 7/23/01, Accepted 9/13/01, Received 9/17/01
The authors are grateful to the maple producers who participated in the project by supply-
ing the samples of sap and syrup needed for the experiments and to the regional maple
advisor with the Quebec Department of Agriculture, who supervised the sampling. Thanks
go also to J. Lefebvre of Biocontrole (supplier of the Charms Sciences Inc. products) for
technical advice and to M. Cournoyer, C. Charron and R. Gaudy for their technical work.
Authors Lagacé, Girouard, and Dumont are with Centre de Recherche, de
Development et de Transfert Technologique Acéricole Inc, 3600 Casavant Blvd
West, St-Hyacinthe, Que, Canada. J2S 8E3. Authors Fortin and Roy are with
the Food Research and Development Centre, Agriculture and Agri-Food
Canada, 3600 Casavant Blvd West, St-Hyacinthe, Que., Canada J2S 8E3.
Direct inquiries to author Lagacé (E-mail: luclagace@centreacer.qc.ca).
1854 JOURNAL OF FOOD SCIENCE—Vol. 67, Nr. 5, 2002