The aim of the study was to compare the efficacy of vegetable protein fining agents to traditional proteinaceous fining agents in the reduction of wine astringency (mostly tannins). One of the motivations behind this project is the increased demand for vegetarian / vegan friendly wines, with traditional fining agents often being from animal origin.
- Cabernet Sauvignon bag-in-box (2015) from South Australia was used as base wine.
- Base wine with 0.5 g/l grape seed extract (GSE) added to it served as astringent, un-fined control wine.
- Pea, rice, potato and soy protein was compared with gelatine and PVPP.
- Dosages ranged from 15 – 100 g/hl for gelatine and rice protein and 30 – 100 g/hl for the rest of the fining agents.
- Fining agents were all dissolved in water and inoculated into the control wine at different dosages. All samples were prepared in duplicate.
- Samples were allowed to settle for 48 hours at 20°C and then centrifuged.
- 20 additional samples were also prepared for sensory analysis and bigger volumes were used in this case.
- Sensory analysis was conducted by a trained panel (23 – 27 years old).
- Tannin levels were reduced with increasing fining concentrations for all fining agents used.
- Gelatine removed the most tannins followed by potato protein.
- PVPP was the least effective fining agent in removing tannins. This was expected since PVPP only react with smaller polyphenolic compounds, tannins being large compounds.
- All fining agents reduced colour intensity depending on the dosage.
- Gelatine reduced colour intensity the most.
- Potato and soy protein finings affected the hue, changing the wine colour from yellow-red toward more red hue.
- Gelatine, pea, potato and soy proteins decreased stable colour pigments.
- Rice protein did not affect wine colour.
- Only gelatine and potato protein reduced astringency in the sensory analysis even though all fining agents reduced total tannin content. The reason for this observation can be because gelatine and potato protein have higher affinities for higher polymerised tannins than the other fining agents, and therefore more capable of removing the stronger elicitors of astringency.
- No significant differences were detected in overall flavour intensity of all six fining agents used.
SIGNIFICANCE OF THE STUDY:
The study indicated that potato protein can be used as a substitute for gelatine to reduce astringency. Potato protein should be used with caution at higher dosages since it can reduce colour. The study also showed that rice protein can be a possible alternative to PVPP due to a similar mode of action. Rice is a more natural alternative to PVPP and will please those consumers preferring their wines to be produced “as natural as possible.”