Understanding Wine Astringency Sub-Qualities by Tribology – What Is the Role of Saliva?

Understanding wine astringency sub-qualities by tribology – what is the role of saliva?

Shaoyang Wang1, Sandra Olarte Mantilla1, Jason Stokes2, Paul Smith3, Heather Smyth1 1 Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland 2 School of Chemical Engineering, The University of Queensland 3 Wine Australia

Physical measures Preliminary results Fullness S What is astringency? m R The oral tribology is a physical measure simulating the development of g 90 o in ot RE1 astringency in mouth. This technique simultaneously considers all astringent 80 hne nger Think of your daily experience when taking a sip of black tea stimuli and their interactions in a complex wine matrix. Li s RE3 70 s or red wine. Your mouth dries up with the feelings of RE7 ab 60 RT0.5 roughness and contraction. 50 RT1 D RT2 40 r Defined by American Section of the International Association for Testing ying RA-0.4 [1] 30 Materials , astringency is ‘a complex of sensations due to shrinking, urning RA-0.2 B drawing or puckering of the epithelium as a result of exposure to 20 RA+0.2 substances such as alums or tannins’. RA+0.4 In-mouth lubrication system (a) and tribometer lubrication system RP2 [5] R (b) . Tribometer monitors the friction change when the property e RP5 s r a e RP10 of lubricant (saliva) is altered. liv a ck t u io P n Experiments and results Mouthfeel profiling of redwinewithmodified Rou y matrix compositions Research aim: To develop appropriate tribological techniques, which consider gh Gripp saliva-wine interactions, that allow the drivers for different wine astringency • Higher tannin  Higher Drying/Grippy/Rough  Higher friction & sluggish sub-qualities to be determined. lubricating speed of saliva + wine mixture

Study I: A model wine system with defined levels of • Higher mannoprotein  Lower Drying/Grippy/Rough  Lower dynamic tannin, pH and polysaccharide. friction coefficient of saliva + wine mixture MW3 MW2 (maltodextrin) polysaccharide Adding • Higher ethanol/acidity  Higher Pucker  Higher rate-of-increase of friction High MW3 MW4 MW5 MW6 on salivary pellicle flushed by wine pH MW6 2.0 0.8 Dynamic tribology 1.8 0.7 with salivary pellicle 1.6 Dynamic tribology [2] Equalised chemically 0.6 High ethanol/acidity Possible multimodal mechanisms of astringency perception MW4 MW5 1.4 with bulk saliva 0.5 measured astringency 1.2

MW1 1.0 0.4 (1) Grittiness created by aggregation of salivary proteins. (2) Disruption of salivary film. Sensory Physical Low 0.8 High tannin (3) Reduction of salivary lubrication. (4) Possible exposure of receptors. (5) Nociceptors/ 0.3 Friction coefficient Friction MW1 Paired Tribology: coefficient Friction 0.6 Mechanoreceptors or nerve innervation pH 0.2 Low acidity comparison • Dynamic 0.4 MW2 0.1 High mannoprotein Astringency can be perceived in many foods and is usually characterised as • Drying Bulk saliva 0.2 Salivary film High mannoprotein the ‘backbone’ of food texture. • Rough 0.0 0.0 Low Medium High • Stribeck 0 20 40 60 80 100 120 140 160 180 200 0 20 40 60 80 100 120 140 160 180 200 • Pucker Time (s) Time (s) tannin tannin tannin 1 (0.9 g/L) (2 g/L) (3 g/L) • High tannin/acidity reduces sensorily perceived Fullness/Smoothness 1.8 70 h [6] bc g Tribological protocols 1.6 e d 65 Dynamic tribology Dynamic tribology with a c a bc c bc bc ab a c 1.4 cd f 60 with bulk saliva (DWB) salivary pellicle (DWP) bc c 1.2 55 cde ef bc abcd bc Pre-adsorbed 1.0 bc bc 50 c cdef bc

ab Smoothness bc abcd abcd salivary pellicle 0.8 cde a bc 45

Viscosity (cP) ab Wine 0.6 def 40 Tea Fruits Vegetables Wine a abc Saliva Saliva Fullness / (persimmon) (spinach) 0.4 35 bcd Examples of foods that induce astringency sensations 0.2 ab 30 0.0 25 Alter R RE1 RE3 RE7 RT0.5 RT1 RT2 RA-0.4 RA-0.2 RA+0.2 RA+0.4 RP2 RP5 RP10 Red wine samples entrainment Physically measured viscosity and sensorily perceived Astringency in wine speed (Stribeck) Wine Fullness/Smoothness

For wine, a balanced level of astringency is the requisite of high-quality reds; (a) (b) when in excess the astringency detracts from other components; while with too little, the wines may taste flat, insipid and uninteresting. Important Test friction contributors of wine astringency include:

• Tannin quantity and quality (concentration, degree of polymerisation, Results anthocyanin-tannin ratio, conformation, etc.) Pair Sample N of answers for Dynamic tribology with Which sample is more … 2.0 bulk saliva MW1 • Wine matrix (acidity, polysaccharide, alcohol strength, etc.) Drying Rough Pucker MW2 MW3 Pair 1 MW1 23 26 44* 1.5 MW4 MW5 Various combinations of these factors shape the types of wine astringency MW2 37* 34 16 MW6 Pair 2 MW1 37* 25 42* 1.0 3 g/L perceived (termed astringency sub-qualities). Wine mouthfeel wheels have 3 g/L MW3 23 35 18

been developed to help tasters pick up these subtle sensory differences. coefficient Friction 2 g/L2 g/L 0.5 0.9 g/L Pair 3 MW2 41* 40** 36 2 g/L MW3 19 20 24 Principle component analysis (a) and correlation matrix (b) of 0.0 Pair 4 MW3 38* 33 16 0 100 200 300 400 500 600 mouthfeel sensations linking with instrumental measurements. y0, MW4 22 27 44* Time (s) R0ꞏt r0, A are parameters from modelled friction curves (μ = y0 + Aꞏe ). Stribeck behaviour 2 6 Pair 5 MW3 28 23 12 1.2 MW5 32 37* 48* 1 1.0 Pair 6 MW3 17 18 28 3 g/L 3 Conclusions 3 g/L 5 MW6 43* 42* 32 0.8 2 g/L 4 2 g/L 2 g/L Pair 7 MW1 39* 31 32 0.6 Ranking • Wine astringency sub-qualities can be driven by different matrix components. 0.9 g/L MW5 21 29 28 of Drying Linkages and independence exist among different sub-qualities. 0.4 Pair 8 MW2 30 31 34 coefficient Friction MW6 30 29 26 0.2 • Saliva plays different roles in astringency sub-quality perception. High tannin resulting in poor lubricity of saliva + wine mixture is found to be a driver of 0.0 a b • Chemically equalised astringency are NOT 1 10 100 1000 Drying/Grippy/Rough. sensorily the same in sub-qualities Entrainment speed (mm/s) [3, 4] Mouthfeel wheels of red wine (a) and white wine (b) • Rough seems to be a combination of • High acidity and high ethanol accelerate the collapse of salivary pellicle, 1.2 Dynamic tribology with Drying and Pucker:BothDrying and salivary pellicle which drive Pucker. Pucker can elicit Rough independently 1.0 Measuring wine astringency • Polysaccharide reduces Drying in a low- 0.8 • Mannoprotein can reduce astringency by facilitating the lubrication of saliva + tannin-high-acidity matrix 0.6 wine mixture.

Sensory evaluations Chemical assessments 0.4 Ranking of Pucker Pucker is linked to lower Friction coefficient • Sensorily perceived Fullness/Smoothness does not in line with physically pH and higher rate-of- • Straightforward, able to discern • Tannin spectrometry / protein 1 4 5 0.2 measured wine viscosity. Saliva’s potential role in reshaping wine astringency sub-qualities precipitation methods increase of friction on 2 3 6 0.0 Fullness/Smoothness may need to be considered. • Expensive • Unable to consider all the salivary pellicle 0 200 400 600 800 1000 1200 • Panel fatigue (build-up effect) astringency contributors Adjusted time (s) • Individual variation in the whole wine matrix • Unable to explain astringency Study II: A real wine system spiked with ethanol, tannin, References sub-qualities mannoprotein; adjusted pH levels McGuigan The 1. ASTM (2004). Standard Definitions of Terms Relating to Sensory Evaluation of Materials and Ethanol Tannin Acidity Polysaccharide Plan Malbec Products, E253-18a. R 12.9 % Unchanged Unchanged Unchanged Wine Supernatant Saliva bands 2018 2. Gibbins, H. L. and G. H. Carpenter (2013). Journal of texture studies 44(5): 364-375. + Saliva SDS-PAGE density +1% +0.5 g/L pH ‐0.4 + 2 g/L 3. Gawel, R., Oberholster, A., and Francis, I. L. (2000). Australian Journal of Grape and Wine Research, e +4% +1 g/L pH ‐0.2 + 5 g/L 6(3): p. 203-207. +7% +2 g/L pH +0.2 +10 g/L Sensory profiling 4. Pickering, G. J. and Demiglio, P. (2008). Journal of Wine Research, 19(1): p. 51-67. pH +0.4 + 5. Pictures cited from Laguna, L. and Sarkar A. (2017). Tribology - Materials, Surfaces & Interfaces, RE1 RT0.5 RA‐0.4 RP2 Tribology measures 11(2): 116-123. RE3 RT1 RA‐0.2 RP5 6. Pictures cited from Macakova, L., et al. (2011). Tribology International, 44(9): 956-962. RE7 RT2 RA+0.2 RP10 RA+0.4