The consumption of red wine, especially wines high in polyphenols, can lead to discolouration of the teeth. There are plenty of almost frightening images on the web of teeth with red wine stains. In addition to staining, wine consumption can lead to tooth decay because the acidity (pH 3.0–3.5) is capable of breaking down the enamel. This in turn can cause tooth sensitivity and gum recession. Geoff Cowey from the Australian Wine Research Institute writing in the Institute’s Technical Review (bit.ly/2JgkvUV) summarises the issues from a winemaker’s perspective. Geoff points out that winemakers and wine judges are possibly most at risk, noting that tasting more than 50 wines a week is considered ‘high risk’. Recommendations about dental care for winemakers are included in Geoff’s article.
So, it was rather intriguing to receive via Sally, our editor, from a reader and occasional columnist of this magazine, a link to an article in ScienceDaily that outlined the potential benefits to dental health from wine polyphenols (bit.ly/2sLkKmS). The 2018 paper (J. Agric. Food Chem. vol. 66, pp. 2071−82) was based on research performed at the Instituto de Investigación en Ciencias de la Alimentación, Madrid, Spain. The group, led by Dr Victoria Moreno-Arribas, is well-known for its work on wine polyphenols and health and this particular project looked at the anti-adhesive capacity of red wine components with respect to bacteria sticking to the gums.
Using an in vitro model of human gingival fibroblasts, a model for gum tissue, the various interactions between three bacteria known to be involved in dental problems, Porphyromonas gingivalis, Fusobacterium nucleatum and Streptococcus mutans, and the phenolic compounds vitaflavan (a grape seed extract), provinols (a red wine extract) as well as the phenolic acids caffeic acid and p-coumaric acid. Some experiments were performed with added Streptococcus dentisani, an oral probiotic. A lot of time was clearly spent culturing and counting colonies!
The results are quite intriguing. While the two phenolic extracts showed considerable influence on P. gingivalis inhibition, there was little effect on the other two bacteria. The two phenolic acids were more effective than the phenolic extracts in ‘cutting back the bacteria’s ability to stick to the cells’, to use the words of the ScienceDaily article (bit.ly/2sLkKmS). Intriguingly, the combination of one or other phenolic acid with S. dentisani increased the inhibition potential against S. mutans. To cap off these new insights in the role of wine compounds in assisting dental health, the authors also observed, using ultra-high performance liquid chromatography coupled with tandem mass spectrometry, some metabolism of the wine phenolic compounds in the oral cavity that could lead to either increase or loss of benefit depending on the extent of metabolism.
The authors do point out that their results are at an early stage in terms of designing a dental health strategy. Critics of the potential benefits of wine consumption may well be sceptical of the in vitro model used. I say this as I have had work rejected for publication when attempting to publish a toxicology study on grain fumigants. On the positive side, the results of the Madrid group’s study form the basis for a more intensive study of the mechanisms of the phenolic compound interactions with the bacteria and what combinations will give the most effective protection.
Not content with examining the relationship between wine phenolic compounds and tooth health, the group from Madrid has extended its work to investigate how wine composition can influence aroma release in the oral cavity (Food Chem. 2018, vol. 243, pp. 125–33). One of the critical roles of the oral cavity is the sensory analysis of material before swallowing. There is now increasing evidence for the creation of an ‘aroma depot’ in the oral cavity due to adsorption of aroma compounds on mucosa, leading to release over time, thereby giving rise to aroma persistence.
The major challenge in this Madrid work was the development of a sampling protocol that allowed the reliable intra-oral assessment of aroma. Three steps were involved. First, 15 millilitres of wine was taken and held in the mouth for 30 seconds to ensure equilibration and after spitting, a two-centimetre SPME fibre was inserted and held in the mouth for two minutes. Finally, the fibre was removed for GC-MS analysis. I cannot imagine how one could bear having the fibre in one’s mouth. The process was repeated three times for each of the 12 wines studied: 36 experiments in one’s mouth. Perhaps it is not surprising that only three volunteers were involved. Phenolic compounds were important in aroma release with, for example, caffeic acid enhancing the release of linalool while anthocyanins decreased the release of ester compounds such as ethyl hexanoate.
Wine phenolic compounds, so long associated with taste sensations, obviously have a major role to play in protection gums for bacterial decay as well as impacting on aroma release. Maybe we might get to the stage of matching our salivary mucosa with a wine’s phenolic profile for the best health and sensory outcomes.