Effect of oxygen and lipid supplementation on the volatile composition of chemically defined medium and Chardonnay wine fermented with Saccharomyces cerevisiae.

Oxygen or lipids are required to complete stressful alcoholic fermentation. Lack of these nutrients can inhibit sugar uptake and growth, which leads to incomplete or 'stuck' fermentation. Oxygen or lipids supplementation not only restores yeast fermentative activity and also affects formation of yeast volatile metabolites. To clarify the effect of oxygen and lipid supplementation on the formation of flavour active metabolites during wine fermentation, we evaluated the addition of these two nutrients to chemically defined grape juice and filter clarified Chardonnay must. Lipid addition increased the concentration of esters, higher alcohols and volatile acids, whereas oxygen increased the concentration of higher alcohols and altered the proportion of acetate to ethyl esters and the proportion of branch-chain acids to medium-chain fatty acids. Combined addition of lipids and oxygen showed an additive effect on concentration of higher alcohols whereas oxygen suppressed the enhancing effect of lipids on formation of esters and volatile acids. Our results demonstrate the potential of lipid and oxygen supplementation for the manipulation of wine aroma in white wine fermentation.

Influence of fertilisation with foliar urea on the content of amines in wine.

Amines are substances that could cause toxic effects in the consumer. The concentration of amines in wine depends on different factors such as grape variety, vinification conditions and nitrogen fertilisation of the vines. The aim of this work was to study the influence of the application of foliar urea on the concentration of amines in wine. To carry out the study, grapevines of Tempranillo variety were used. These grapevines were treated with foliar urea at two different concentrations: 2 and 4 kg N ha(-1). Treatment with foliar urea significantly increased (p < 0.05) the concentration of histamine in the wines compared with the control sample (65% in the treatment with 2 kg N ha(-1) and 93% in the treatment with 4 kg N ha(-1)), reaching higher concentrations than the threshold level where it could provoke toxic effects in the consumer (8-20 mg l(-1)). On the other hand, treatment with foliar urea did not increase the concentrations of other amines which could be toxic such as tyramine or phenylethylamine, nor amines such as putrescine which could enhance the toxic effect of histamine. In the case of the volatile amines containing secondary amine groups, the concentration of pirrolidine increased by 37% after treatment with 2 kg N ha(-1) and 61% after treatment with 4 kg N ha(-1).

beta-Carboline alkaloids in Peganum harmala and inhibition of human monoamine oxidase (MAO).

Peganum harmala L. is a multipurpose medicinal plant increasingly used for psychoactive recreational purposes (Ayahuasca analog). Harmaline, harmine, harmalol, harmol and tetrahydroharmine were identified and quantified as the main beta-carboline alkaloids in P. harmala extracts. Seeds and roots contained the highest levels of alkaloids with low levels in stems and leaves, and absence in flowers. Harmine and harmaline accumulated in dry seeds at 4.3% and 5.6% (w/w), respectively, harmalol at 0.6%, and tetrahydroharmine at 0.1% (w/w). Roots contained harmine and harmol with 2.0% and 1.4% (w/w), respectively. Seed extracts were potent reversible and competitive inhibitors of human monoamine oxidase (MAO-A) with an IC(50) of 27 microg/l whereas root extracts strongly inhibited MAO-A with an IC(50) of 159 microg/l. In contrast, they were poor inhibitors of MAO-B. Inhibition of MAO-A by seed extracts was quantitatively attributed to harmaline and harmine whereas inhibition by root extracts came from harmine with no additional interferences. Stems and leaves extracts were poor inhibitors of MAO. The potent inhibition of MAO-A by seed and root extracts of P. harmala containing beta-carbolines should contribute to the psychopharmacological and toxicological effects of this plant and could be the basis for its purported antidepressant actions.