Effects of fermentation temperature on red wine composition In this column, Peter Godden concludes a series examining the effects of winemaking variables on red wine composition, by examining fermentation temperature. Background at the University of California, had ethanol and certain volatile compounds established in 1887 that the maximum with increasing temperature are also During tastings of the AWRI’s extraction of colour occurred before common, largely attributed to increased winemaking treatment trial wines held that of tannins, and that maximum volatilisation during fermentation. Small with winemakers around Australia, colour was obtained earlier at higher increases in wine pH are also reported, the red wines produced with increased temperatures. presumably due to increased extraction fermentation temperature were almost of potassium from grape skins at higher universally the most preferred. This Not all phenolics are extracted at the temperature. column examines how a relatively small same rate during fermentation, and while winemaking change can result in a large the rate of extraction of some compounds The effects of higher difference in wine composition and increases with increasing fermentation temperature on wine phenolics temperature, the final concentrations sensory properties. in the AWRI red winemaking may be unaffected. For instance, Lerno What happens to red wine et al. (2015) found that increased treatment trials phenolic profiles when fermentation temperature increased The changes observed in wine phenolics fermentation temperatures the rate of extraction but not the final between two fermentation temperatures increase? concentration of skin-derived phenolics, in the AWRI’s trials are presented whereas for seed-derived phenolics in Table 1 and show increases in all The contribution of grape-derived both the rate and final concentration phenolic measures for all varieties. The phenolics to the colour, tannin increased. It was also concluded that percentage increases with Pinot Noir concentration, overall quality and ageing must temperature was more important were less than those seen for Shiraz potential of red wines has been established than the cap temperature in determining and Cabernet Sauvignon, which might by numerous studies. While the initial the extraction of phenolics. be accounted for by a lower initial concentration of phenolic compounds concentration of phenolic compounds in in grapes has some relationship to the Is the non-phenolic the grapes, as well as a smaller difference final phenolic composition of wine, composition of red wines in fermentation temperatures. The fermentation temperature and the affected by fermentation largest changes in phenolic composition extent and duration of cap management temperature? were seen with the Shiraz wines, with have been shown to strongly influence The effect of increasing temperature total phenolics increasing by 42% phenolic extraction during winemaking, on the concentration of several yeast- and tannins by 107%, when the mean and the phenolic composition of wines synthesised wine components was fermentation temperature was increased over time. examined by Rollero et al. (2015). from approximately 25°C to 33.5°C. In Studies on the extraction of phenolics Increases in some esters were found, general, the percentage increases in wine during red winemaking were conducted including isoamyl acetate (‘fruity’, phenolics seen in these three sets of at the University of California, Davis, ‘banana’, ‘pear’) and ethyl octanoate wines are larger than reported in many in the 1950s and 1960s by Maynard (‘cherry’), with the production of studies. One possible explanation is that Amerine and Cornelius Ough. However, succinic acid and glycerol also positively the starting concentration of phenolics as reported by Casassa and Harberstson correlated with increasing fermentation in the grapes might have been higher (2014), Eugene Hilgard, also working temperature. Lower concentrations of than for grapes used in other studies. 50 Grapegrower & Winemaker www.winetitles.com.au July 2021 – Issue 690 Free SO2 is just the beginning. As world leaders in biosensor technology, our reputation is built on precision. That’s why you can trust the SentiaTM hand-held wine analyzer to accurately measure free SO2 levels in your post- fermentation wine. No sample preparation. No reagent preparation. No calibration. No special training required. Just reliable test results in less than a minute, wherever and whenever you need them. And with more key wine analysis tests on the way, free SO2 is just the beginning. The SentiaTM hand-held wine analyzer is available now through Grapeworks and Grapeworks New Zealand. THE POWER OF A LAB IN THE PALM OF YOUR HAND. AUSTRALIA: Call (03) 9555 5500 or email: [email protected] NEW ZEALAND: Email: [email protected] Table 1. Comparison of phenolic composition of Pinot Noir, Shiraz and Cabernet Sauvignon wines fermented at different temperatures in AWRI winemaking treatment trials Pinot Noir (2016) Shiraz (2017) Cabernet Sauvignon (2018) Control Warm Control Warm Control Warm ferment ferment ferment ferment ferment ferment % % % Phenolic measure 24 - 26°C, 24 - 32°C, 24 - 26°C, 32 - 35°C, 24 - 26°C, 32 - 34°C, increase increase increase 10-day 7-day 12-day 10-day 14-day 10-day ferment fermenta ferment fermentb ferment fermentc Total phenolics (AU) 22 23 4.5% 31 44 41.9% 44 55 25.0% Total anthocyanins (mg/L) 115 121 5.2% 415 556 34.0% 476 508 6.7% Tannin (mg/L) 480 641 33.5% 576 1192 106.9% 1,336 2,167 62.2% Non-bleachable pigments 0.36 0.42 16.7% 1.35 1.83 35.6% 2.7 3.7 37.0% (AU) a One additional pump-over was performed each day compared to the control, so that both the control and warm ferment received approximately the same amount of pumping-over in total. b, c Additional plunging was performed so that both the control and warm ferment received approximately the same amount of plunging overall. What are the practical Conclusion References considerations and potential Other articles in this series have Casassa, L. F,. Harbertson, J.F. 2014. risks? discussed techniques which also increase Extraction, evolution, and sensory impact Increased fermentation temperature red wine phenolics, including pre- of phenolic compounds during red wine maceration. Ann. Rev. Food Sci. Technol. 5: increases the rate of fermentation, ferment cold maceration, post-ferment 83-109. thereby further increasing temperature extended maceration and saigneé. While in a positive feedback loop. each of those treatments confer different Hilgard. E. W. 1887. The extraction of color Consequently, there is a greater risk of sensory properties, if the primary aim and tannin during red-wine fermentation. fermentations becoming uncontrollable Univ. Calif. Agric. Exp. Stn. Bull. 77. at higher temperature if insufficient is to increase the concentrations of total cooling capacity is available or if the phenolics, anthocyanins and tannin, Lerno, L., Reichwage, M., Ponangi, R., fermentations are not actively cooled, increasing fermentation temperature to Hearne, L., Block, D. E., Oberholster, A. 2015 and this can result in undesirable sensory between 30°C and 32°C is a simple, Effects of cap and overall temperature on phenolic extraction in Cabernet Sauvignon characters. Pumping the fermenting relatively low risk and cost-effective liquid though a heat exchanger and fermentations. Am. J. Enol. Vitic. 66:4, 444 method of achieving that aim compared – 453. distributing the cooled liquid over the to other methods. cap is the most effective way of cooling Rollero, S., Bloem, A., Camarasa, C., Sanchez, a ferment. In addition, while pumping Acknowledgements I., Ortiz-Julien, A., Sablayrolles, J-M., Dequin, over, rack-and-return, and to a lesser S., Mouret, J-R. 2015. Combined effects of Anne Lord and Damian Espinase degree plunging may all help to dissipate nutrients and temperature on the production heat, they also introduce oxygen which Nandorfy are thanked for assistance of fermentative aromas by Saccharomyces may stimulate yeast and result in an provided during preparation of cerevisiae during wine fermentation. Appl. increased fermentation rate. this article. Microbiol. Biotechnol. 99: 2291 – 2304. www.winetitles.com.au Wine Industry news at your fingertips Delivered to your inbox daily*. * excludes weekends and public holidays Subscribe for FREE Wherever you go, we’re with you! 52 Grapegrower & Winemaker www.winetitles.com.au July 2021 – Issue 690.