Influence of must nitrogen composition on wine and spirit quality and relation with aromatic composition and defects - A review

Abstract

<p style="text-align: justify;">The development of wine-growing practices (reducing of nitrogen supply, grass cover) in order to improve the production control and environment protection lead to nitrogen deficiencies in must. Many fermentation problems appeared : stuck and sluggish fermentation, aromatic deviation. In opposite, it was underscored that must with high nitrogen content could lead to wine containing potentially dangerous molecules for human health, like amine and ethyl carbamate.</p><p style="text-align: justify;">Many studies related the nitrogen fertilisation and grass cover effects on vine and must composition, but just a few works were done about their consequences on wine and spirit quality.</p><p style="text-align: justify;">The quantitative aspects of alcoholic fermentation are now well know as the yeast nitrogen requirements (140 à 160 mg/l N). But yeast has also qualitative requirement (amino acids, vitamins, fatty acids), in relation with the medium (t°, O<sub>2</sub>, turbidity).</p><p style="text-align: justify;">In case of nutrient lack, even slight, yeast produce volatile acidity, H<sub>2</sub>S and many sulphur compounds (origin of aromatic defects), and fermentation rate is slowed, sometime stopped. The yeast strains play an important role because of genetic differences and specific nutrient requirements. On the other hand, the possibility of enhancing wine aroma appears with the control of the nitrogen content of must which induce mainly ester and higher alcohols formation. Furthermore, it must keep in mind that large amount of must nitrogen (> 1,000 mg/l) could also lead to problems with wine composition.</p><p style="text-align: justify;">Sensory analyses show correlations between must nitrogen content and soil management with wine quality. It seems that must with medium nitrogen give the better wines.</p><p style="text-align: justify;">The aim of this study was to resume the actual experimental knowledge on this subject.</p>

Differential expression of thiamine biosynthetic genes in yeast strains with high and low production of hydrogen sulfide during wine fermentation

“…2008). Current strategies to prevent these undesirable effects in wine aroma aim at prevention of its formation rather than to remove it from the must (Ferrari 2002), being yeast strain choice one of the intervening variables. Despite growing knowledge on the factors that affect H 2 S production during wine fermentation, many aspects remain still unclear.…”

“…These data impel most cellars to add routinely diammonium phosphate (DAP) to the fermenting must, even in musts with enough FAN content to allow complete fermentations. On the other hand, an excess of available nitrogen may favour growth of contaminant yeast or bacteria and increase ethyl carbamate production (Ferrari 2002), besides other considerations, including regulatory ones. Therefore, there is a delicate balance between adding extra nitrogen to avoid nitrogen depletions and H 2 S production and increasing FAN above the level of producing other undesirable side effects (Jiranek et al 1996;Ferrari 2002;Vilanova et al 2007;Ugliano et al 2009).…”

“…Solving these still unknown aspects of yeast sulfur metabolism is central in the process of implementing fermentation protocols to reduce or eliminate the production of undesirable compounds during wine production. The aim of this work is to find tools that can predict the production of H 2 S during fermentation and minimize its production to obtain a clean wine without off-flavours, as well as to facilitate genetic selection of H 2 S low producer strains (Ferrari 2002;Moreira et al 2002;Beltran et al 2006).…”

“…On the other hand, an excess of available nitrogen may favour growth of contaminant yeast or bacteria and increase ethyl carbamate production (Ferrari 2002), besides other considerations, including regulatory ones. Therefore, there is a delicate balance between adding extra nitrogen to avoid nitrogen depletions and H 2 S production and increasing FAN above the level of producing other undesirable side effects (Jiranek et al 1996;Ferrari 2002;Vilanova et al 2007;Ugliano et al 2009). Our knowledge of the genetic make-up of wine strains has increased enormously in last years (Dunn et al 2005;Borneman et al 2008;Carreto et al 2008;Jimenez-Marti and del Olmo 2008).…”

“…Most of it is removed from the fermenting must, as it dissipates along with the carbon dioxide originated during alcohol fermentation. However, even small remains of H 2 S or of some of its derivatives can be detrimental to wine aroma (Ferrari 2002; Moreira et al. 2002; Carrau et al.…”