Département des Sciences des aliments, Institut sur la nutrition et les aliments fonctionnels (INAF), Université Laval, Québec, Québec, G1V 0A6, Canada.
Département de Biologie, Département de Biochimie, Microbiologie et Bio-informatique, PROTEO, Centre de recherche en données massives and Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec, Québec, G1V 0A6, Canada.
Sci Rep. 2018 Oct 2;8(1):14658. doi: 10.1038/s41598-018-32940-y.
Maple sap is a complex nutrient matrix collected during spring to produce maple syrup. The characteristics of sap change over the production period and its composition directly impacts syrup quality. This variability could in part be attributed to changes in tree metabolism following dormancy release, but little is known about these changes in deciduous trees. Therefore, understanding the variation in sap composition associated with dormancy release could help pinpoint the causes of some defects in maple syrup. In particular, a defect known as "buddy", is an increasing concern for the industry. This off-flavor appears around the time of bud break, hence its name. To investigate sap variation related to bud break and the buddy defect, we monitored sap variation with respect to a dormancy release index (S) and syrup quality. First, we looked at variation in amino acid content during this period. We observed a shift in amino acid relative proportions associated with dormancy release and found that most of them increase rapidly near the point of bud break, correlating with changes in syrup quality. Second, we identified biological processes that respond to variation in maple sap by performing a competition assay using the barcoded Saccharomyces cerevisiae prototroph deletion collection. This untargeted approach revealed that the organic sulfur content may be responsible for the development of the buddy off-flavor, and that dormancy release is necessary for the appearance of the defect, but other factors such as microbial activity may also be contributing.
枫糖浆是在春季采集的一种复杂的营养基质，用于生产枫糖浆。树液的特性在生产过程中会发生变化，其成分直接影响糖浆的质量。这种可变性部分归因于休眠解除后树木代谢的变化，但对落叶树的这些变化知之甚少。因此，了解与休眠解除相关的树液成分变化，有助于找出枫糖浆一些缺陷的原因。特别是一种称为“buddy”的缺陷，越来越受到行业的关注。这种异味出现在萌芽期前后，因此得名。为了研究与休眠解除和 buddy 缺陷相关的树液变化，我们监测了与休眠解除指数（S）和糖浆质量相关的树液变化。首先，我们观察了这段时间内氨基酸含量的变化。我们观察到与休眠解除相关的氨基酸相对比例的变化，发现它们中的大多数在萌芽期附近迅速增加，与糖浆质量的变化相关。其次，我们通过使用带有条形码的酿酒酵母原生质体缺失库进行竞争测定，鉴定了对枫糖浆变化有响应的生物学过程。这种非靶向方法表明，有机硫含量可能是导致 buddy 异味产生的原因，休眠解除是缺陷出现的必要条件，但微生物活性等其他因素也可能起作用。
