1. University of Agronomic Sciences and Veterinary Medicine of Bucharest
Faculty of Horticulture
International Student Symposium “Hortus Academicus”
March 29, 2019, Bucharest, Romania
COMPARATIVE STUDY OF SENSORY INFLUENCES INDUCED BY SEVERAL TREATMENTS USED FOR COLOUR AND TARTARIC SALTS STABILIZATION IN YOUNG RED WINES
Authors,
MSc. student Vlad Adrian GIHAC
MSc. student eng. Ionel NICULAE
Coordinator Professors:
Professor PhD Arina Oana ANTOCE
Lecturer PhD George Adrian COJOCARU
International Student Symposium "Hortus Academicus“ March 29, Bucharest, Romania

2. INTRODUCTION
Wine stabilization is a very important stage in wine production industry;
Wine with the potential to precipitate tartrates is classified as wine with tartaric instability;
Many problems can occur in young red wines released soon on the market because of their high potential to precipitate colour matter and tartaric acid salts;
There are necessary some stabilization treatments that are generally done by the wine makers;
International Student Symposium "Hortus Academicus“ March 29, Bucharest, Romania

3. MATERIALS AND METHODS
This study was carried out on a young red wine produced in 2018 from a Romanian grape variety Negru de Dragasani.
Once the malolactic fermentation finished, the wine was racked off sediments and sulphited. In order to stabilize the colour matter and potassium bitartrate, the wine was treated first for colour matter precipitation and after 7 days, the wine samples were racked off lees and then treated for potassium bitartrate stabilization. After 20 days it was bottled in 0.75 liter, leaving behind eventually formed sediment. All the experimental variants were prepared in two sets and in triplicate. Immediately ahead bottling, all samples were sulphited to prevent oxidation.
The main parameters of the resulted wine are: 13.83% vol. alc.; 5.9 g/l total acidity as tartaric acid; pH = 3,65; 0.18 g/l volatile acidity as acetic acid; 28.1 g/l non-reducing extract; 1,6 mg/l free SO2; 17,6 mg/l bound SO2; 0,26 g/l malic acid; 1,39 g/l lactic acid; TSAT = 20.2 (very unstable wine in relation to potassium bitartrate). Sulphited with 60 mg/l SO2 using 10% m/v K2S2O5 solution.
International Student Symposium "Hortus Academicus“ March 29, Bucharest, Romania

4. MATERIALS AND METHODS
The bottles were stored for two months, first set was kept at cellar temperature of 12-16°C to perform a professional sensorial session and the second set at 4°C in order to assess the stability in relation to colour matter and potassium bitartrate loss.
The sensorial session was accomplished with a team of five tasters which analysed taste and mouth feel characteristics of the treated wines (sweetness, sour, bitter, astringency and body of wine) on a scale from 0 to 5.
The second set of wines, cold stored, was inspected for sediments, and if they were present, was placed in a centrifuge and a drying balance, a gravimetric determinations of the dry weight sediment.
The reported results are expressed as g/l dry weight sediment.
They were gravimetrically evaluated by using a drying balance (KERN MLB 50-3N), after being separated by centrifugation (Hettich Mikro 220R centrifuge, with 50 ml tubes, set for 10 minutes at 6000 rpm). The drying balance was set at 120°C and reading done after the automatic shutoff, for a change of weighing value <1 mg within 60 seconds.
International Student Symposium "Hortus Academicus“ March 29, Bucharest, Romania

5. RESULTS AND DISCUSSIONS
Table 1. Experimental variants and detailed treatments for colour and potassium bitartrate stabilization
Codification
Technological approaches for colour matter stabilization
Technological approaches for potassium bitartrate stabilization
Control
cold stabilization treatment 14 days at 0°C
V1_AG_MP1
30 g/hl arabic gum, ®Araban Spray Dry, Vason
20 g/hl mannoprotein, ®Mannostab, Laffort
V2_AG_KPA
10 g/hl potassium polyaspartate, ®Zenith Uno, Enartis
V3_AG_MP2
20 g/hl mannoprotein, ®MPA, Vason
V4_TAN_MP1
10 g/hl mixture of ellagic, gallic, catechinic and procyanidic tannins, ®Premium Color SG, Vason
V5_TAN_KPA
V6_TAN_MP2
V7_ALBU_MP1
20 g/hl micro-granulated egg albumin, ®Albuclar SG, Vason
V8_ALBU_KPA
V9_ALBU_MP2
International Student Symposium "Hortus Academicus“ March 29, Bucharest, Romania

6. RESULTS AND DISCUSSIONS
Arabic gum treatment in combination with mannoproteins and polyaspartate (Figure 1) had the greatest sensory effect. The two types of mannoproteins (MPs) behaved differently, MP1 reducing the bitterness and astringency, while MP2 increased these perceptions as compared to control sample. The body of wine felt increased in all samples treated with arabic gum. Sour taste decreased and sweetness increased slightly in samples with polyaspartate (PA).
Figure 1: Sensorial changes of experimental variants induced by stabilization treatments: arabic gum in combination with mannoproteins and polyaspartate;
International Student Symposium "Hortus Academicus“ March 29, Bucharest, Romania

7. RESULTS AND DISCUSSIONS
Tannins in combination with MPs or PA (Figure 2) make wine less bitter with less or moderate astringency and increased body. Tannins with PA provide a better body structure, a more complex mouth feel, lowering the sourness, bitterness and astringency.
Figure 2: Sensorial changes of experimental variants induced by stabilization treatments: tannin mixture in combination with mannoproteins and polyaspartate;
International Student Symposium "Hortus Academicus“ March 29, Bucharest, Romania

8. RESULTS AND DISCUSSIONS
The fining treatments with egg albumin (Figure 3) lead to simple wines, with similar characteristics as the control wine. Even in this case, PA seems to be beneficial for the mouthfeel and wine structure.
Figure 3: Sensorial changes of experimental variants induced by stabilization treatments: egg albumin in combination with mannoproteins and polyaspartate;
International Student Symposium "Hortus Academicus“ March 29, Bucharest, Romania

9. RESULTS AND DISCUSSIONS
One Way ANOVA applied for dry weight of sediment (Figure 4) indicates that there are certain significant differences (p<0.05) among experimental variants. Although both colour and tartaric acid stabilization treatments were combined in each variant the statistical analyses were run only for the treatment combination, thus independent treatment effects were not evaluated. Even so, the results are highly suggestive that, as compared to other treatments, tannin with MPs may lead to increased stability, at least for a short period of time as the one from our study.
Figure 4: Measured dry weight of sediment (potassium bitartrate and colour matter)
International Student Symposium "Hortus Academicus“ March 29, Bucharest, Romania

10. CONCLUSIONS AND RECOMMENDATIONS
Arabic gum is beneficial for the wine body and structure.
Tannin intensifies the colour and the structure, but generally reduces the olfactory sensation and increases the roughness of wines, which may require longer maturation periods.
Egg albumin is not recommended because is reducing the colour and body structure, highlighting the acidic and vegetal sensations, also reducing the overall complexity.
International Student Symposium "Hortus Academicus“ March 29, Bucharest, Romania

11. CONCLUSIONS AND RECOMMENDATIONS
Mannoproteins MP1 and MP2 increase mouthfeel sensations and sweetness of wines, reducing astringency, but not the sour taste perception. Bitterness perceptions depended on the type of mannoprotein and on other treatments combined with tem.
Polyaspartate is providing a better body structure, a more complex mouthfeel, lowering the sour and astringency perceptions. It gives the best results in combination with tannins.
International Student Symposium "Hortus Academicus“ March 29, Bucharest, Romania