Development of Potential Yeast Protein Extracts for Red Wine Clarification and Stabilization

Abstract

Recently, new technologies have been combined to improve quality and sensorial diversity of wine. Several fining agents were developed to induce flocculation and sedimentation of particulate matter in wine, enhancing its clarification, and stabilization. The fining agents most commonly used are animal proteins, such as milk casein or egg albumin. However, its use is being related to food intolerance. To overcome this issue, alternative sources should be explored for use in industrial processes. In previous studies performed by our consortium, the potential of yeast protein extracts (YPE) in white wine clarification, stabilization, and curative processes was identified. Thus, the main objective of the present work is to select YPE with the potential to develop fining agents for red wine, without health risk to consumers. Therefore, five yeast strains were selected from a diversified collection of oenological yeasts, in order to produce protein extracts. Along with the fining trials, a vinification assay was performed to evaluate the maceration effect of the obtained YPE. The previously selected yeast strains were also screened for the production of the usual enzymatic activities found in commercial maceration preparations, namely polygalacturonase, cellulase, protease, and ß-glucosidase activities, in order to evaluate its potential effect on wine. Our results indicate that YPE, particularly BCVII 1, BCVII 2, and BCVII 5 were able to promote a significant brilliance increase, along with a turbidity reduction and final color improvement. In the vinification assay, BCVII 2 stands out with better results for color intensity and phenolic compounds content improvement. In what refers to enzymatic activities, BCVII 2 shows advantage over the other YPEs, due to its protease and β-glucosidase activity. We demonstrate that the selected YPEs, with emphasis on BCVII 2, may represent an efficient alternative to the commonly used fining products.

Keywords: color; fining agents; turbidity; vinification; wine.

FIGURE 1

Protein molecular weight profile. Protein samples of the fining agents tested in this study by Coomassie-stained SDS-PAGE. BioRad Precision Plus Protein^TM as the protein weight standard. VP, vegetable protein.

FIGURE 2

The aspect of lees after 48 h of treatment by the application of the referenced fining products and the selected yeast protein extracts. NT, not treated wine.

FIGURE 3

Final turbidity of wine after 48 h of fining trials. NT, non-treated wine; VP, vegetable protein; BCVII 1 to BCVII 5, treated wine samples. Bars indicate mean ± SD (n = 3), ^∗ denote significant differences at p < 0.05, ^∗∗ denote significant differences at p < 0.01.

FIGURE 4

Chromatic characterization using the CIELab system. (A) Saturation (C^∗) and Brilliance (L^∗). (B) Red (a^∗) and Yellow (b^∗) values. Results were obtained before and after treatment of red wine with the reference fining products and YPE.

FIGURE 5

Color intensity (CI) of wine after the vinification assay. NT, non-treated wine; CMP, commercial maceration preparation; VP, vegetable protein; BCVII 1 to BCVII 5, treated wine samples. Bars indicate mean ± SD (n = 3), ^∗ denote significant differences at p < 0.05, ^∗∗ denote significant differences at p < 0.01.

FIGURE 6

Phenolic compounds index of wines (Folin-Ciocâlteu method) after the vinification assay. NT, non-treated wine; CMP, commercial maceration preparation; VP, vegetable protein; BCVII 1 to BCVII 5, treated wine samples. Bars indicate mean ± SD (n = 3), ^∗ denote significant differences at p < 0.05, ^*⁣*⁣** denote significant differences at p < 0.0001.

FIGURE 7

Positive results for cellulase production. Zone of clearance in (A) P. anomala BCVII 1. (B) M. pulcherrima BCVII 2, (C) L. thermotolerans BCVII 4. (D) S. cerevisiae BCVII5 on agar plate after incubation at 30°C and Coomassie Brilliant Blue R-250 coloration.

FIGURE 8

Positive results for protease and β-glucosidase activity in M. pulcherrima BCVII 2. (A) Zone of clearance showing protease production on agar plate after incubation at 30°C. (B) Brown colonies showing β-glucosidase activity on agar plate after incubation at 30°C.