Influence of protein stabilization with aspergillopepsin I on wine aroma composition

Fruit quality in grapes is not well defined but is often depicted as correlating inversely with crop yield. Both fruit yield and composition, however, are made from distinct components that interact in complex ways. Reproductive growth of grapevines extends over two growing seasons. Inflorescences initiated in buds during the previous year differentiate flowers and set and develop berries during the harvest year.

Elemental sulfur is a fungicide used by grape growers to control the development of powdery mildew, caused by the fungus Erysiphe necator. This compound is effective, cheap and has a low toxicity with no withholding period recommended. However, high levels of S0 residues in the harvested grapes can lead to the formation of reductive sulfur compounds that can impart taints and faults to the wine. Hydrogen sulphide (H2S) is a very volatile and unpleasant sulfur compound which formation is connected to high residues of S0 in juice (10 – 100 mg/L).

In recent years, there has been an increase in demand for non-alcoholic wine with an ethanol content of less than 0.5% v/v. The dealcoholization process can take place by various methods, such as vacuum distillation or membrane technologies like osmotic distillation. Compared to distillation, membrane systems often require multiple passes or a combination of multiple separation methods. Complete or almost complete removal of ethanol significantly changes the sensory characteristics of wine.

La topographie du vignoble de Côte Rôtie, la prédominance de la non culture ainsi que la structure très légère des sols amènent les vignerons à s’interroger sur l’entretien du sol, la conduite de la fertilisation de leurs parcelles ainsi que sur le développement racinaire de la vigne.

Certain yeast species belonging to the Pichia genus are known to form a distinctive film on grape must and wine. In a mixed-culture type fermentation, Pichia spp. (P. kluyveri in particular) are known to impart beneficial oenological attributes. In this study, we report on an easy isolation method of Pichia spp. from grape must by exploiting their film-forming capacity on media containing 10% ethanol. We isolated and identified two Pichia species, namely Pichia kudriavzevii and Pichia kluyveri, and subsequently co-inoculated them with Saccharomyces cerevisiae to ferment Gewürztraminer musts. Noteworthy differences included a significant increase in the 2-phenethyl acetate levels with the P. kluyveri co-fermentation and a general increase in ethyl esters with the P. kudriavzevii co-fermentation. Both Pichia co-inoculations yielded higher levels of glycerol in the final wines. Based on all the wine parameters we tested, the P. kluyveri strain that was isolated performed similarly to a commercial P. kluyveri strain.